{"@context":{"@language":"en","Affiliation":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","AggregatedSourceRepository":"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider","Campus":"https:\/\/open.library.ubc.ca\/terms#degreeCampus","Creator":"http:\/\/purl.org\/dc\/terms\/creator","DateAvailable":"http:\/\/purl.org\/dc\/terms\/issued","DateIssued":"http:\/\/purl.org\/dc\/terms\/issued","Degree":"http:\/\/vivoweb.org\/ontology\/core#relatedDegree","DegreeGrantor":"https:\/\/open.library.ubc.ca\/terms#degreeGrantor","Description":"http:\/\/purl.org\/dc\/terms\/description","DigitalResourceOriginalRecord":"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO","FullText":"http:\/\/www.w3.org\/2009\/08\/skos-reference\/skos.html#note","Genre":"http:\/\/www.europeana.eu\/schemas\/edm\/hasType","GraduationDate":"http:\/\/vivoweb.org\/ontology\/core#dateIssued","IsShownAt":"http:\/\/www.europeana.eu\/schemas\/edm\/isShownAt","Language":"http:\/\/purl.org\/dc\/terms\/language","Program":"https:\/\/open.library.ubc.ca\/terms#degreeDiscipline","Provider":"http:\/\/www.europeana.eu\/schemas\/edm\/provider","Publisher":"http:\/\/purl.org\/dc\/terms\/publisher","Rights":"http:\/\/purl.org\/dc\/terms\/rights","RightsURI":"https:\/\/open.library.ubc.ca\/terms#rightsURI","ScholarlyLevel":"https:\/\/open.library.ubc.ca\/terms#scholarLevel","Supervisor":"http:\/\/purl.org\/dc\/terms\/contributor","Title":"http:\/\/purl.org\/dc\/terms\/title","Type":"http:\/\/purl.org\/dc\/terms\/type","URI":"https:\/\/open.library.ubc.ca\/terms#identifierURI","SortDate":"http:\/\/purl.org\/dc\/terms\/date"},"Affiliation":[{"@value":"Science, Faculty of","@language":"en"},{"@value":"Chemistry, Department of","@language":"en"}],"AggregatedSourceRepository":[{"@value":"DSpace","@language":"en"}],"Campus":[{"@value":"UBCV","@language":"en"}],"Creator":[{"@value":"Altus, Kristof","@language":"en"}],"DateAvailable":[{"@value":"2022-08-31T21:13:24Z","@language":"en"}],"DateIssued":[{"@value":"2022","@language":"en"}],"Degree":[{"@value":"Doctor of Philosophy - PhD","@language":"en"}],"DegreeGrantor":[{"@value":"University of British Columbia","@language":"en"}],"Description":[{"@value":"Within this thesis, the syntheses of novel Pt\u207d\u1d35\u1d35\u207e complexes that show reactivity towards carbon-hydrogen and carbon-halogen bonds is explored. Understanding the nuances of fundamental reactivity is important for catalyst design. These nuances allow for the development of novel systems capable of tackling challenging reactions such as alkane activation and functionalisation. Chapter 1 gives an overview of the current understanding of the mechanisms for C-H activation of alkanes and how the communities understanding has changed over the last 20 years. In chapter 2 the intermolecular oxidative addition of aryl halides to Pt\u207d\u1d35\u1d35\u207e complexes is presented. The work in chapter 2 forms part of a proposed catalytic cycle for methane functionalisation, using aryl halides as oxidants. The oxidative addition of aryl halides to Pt\u207d\u1d35\u1d35\u207e  complexes has so far only been reported for aryl halides that are tethered to the ligand backbone. The work in chapter 2 therefore constitutes a significant advance in the reactivity of aryl halide chemistry with platinum. Novel ligand design and synthesis of new platinum complexes targeted towards small molecule activation is presented in chapter 3. The new ligands provide an entry into the synthesis of (hetero)bimetallic complexes that could show activity in cascade or tandem reactions. The use of bimetallic complexes is important for tailoring the reactivity of two catalysts simultaneously in the same molecule allowing for a higher degree of control over a reaction or multiple reactions in the same flask. The C-H activation of pyridine via the formation of Pt-Pt bonded bimetallic species is shown in chapter 4. Furthermore, a detailed computational and experimental study into the donor-acceptor nature of the Pt-Pt bond shows how bimetallic complexes of platinum could be used in challenging C-H activation reactions. Chapter 5 provides a summary of the work in this thesis and gives new avenues for the continued development of new platinum compounds for small molecule activation reactions.","@language":"en"}],"DigitalResourceOriginalRecord":[{"@value":"https:\/\/circle.library.ubc.ca\/rest\/handle\/2429\/82637?expand=metadata","@language":"en"}],"FullText":[{"@value":"    i  SYNTHESIS AND CHARACTERISATION OF PLATINUM(II) METHYL COMPLEXES AND THEIR REACTIVITY TOWARDS CARBON-HYDROGEN (C-H) AND CARBON-HALOGEN BONDS (C-X)  by  Kristof Altus  B.Sc., London Metropolitan University, 2015 M.Sc., University of Bristol, 2016  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemistry)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)   August 2022  \u00a9 Kristof Altus, 2022ii   The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the dissertation entitled: SYNTHESIS AND CHARACTERISATION OF PLATINUM(II) METHYL COMPLEXES AND THEIR REACTIVITY TOWARDS CARBON-HYDROGEN (C-H) AND CARBON-HALOGEN BONDS (C-X)  submitted by Kristof Altus in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry  Examining Committee: Jennifer Love, Professor, Chemistry,  University of Calgary Co-supervisor  Jason Hein, Associate Professor, Chemistry, UBC Co-supervisor  Chris Orvig, Professor, Chemistry, UBC University Examiner Mark Thachuk, Associate Professor, Chemistry, UBC University Examiner Richard Puddephatt, Professor, Chemistry, Western University External Examiner  Additional Supervisory Committee Members: Laurel Schafer, Professor, Chemistry,  UBC Supervisory committee member Glenn Sammis, Associate Professor, Chemistry, UBC Supervisory committee member    iii  Abstract Within this thesis, the syntheses of novel Pt(II) complexes that show reactivity towards carbon-hydrogen and carbon-halogen bonds is explored. Understanding the nuances of fundamental reactivity is important for catalyst design. These nuances allow for the development of novel systems capable of tackling challenging reactions such as alkane activation and functionalisation. Chapter 1 gives an overview of the current understanding of the mechanisms for C-H activation of alkanes and how the communities understanding has changed over the last 20 years. In chapter 2 the intermolecular oxidative addition of aryl halides to Pt(II) complexes is presented. The work in chapter 2 forms part of a proposed catalytic cycle for methane functionalisation, using aryl halides as oxidants. The oxidative addition of aryl halides to Pt(II) complexes has so far only been reported for aryl halides that are tethered to the ligand backbone. The work in chapter 2 therefore constitutes a significant advance in the reactivity of aryl halide chemistry with platinum. Novel ligand design and synthesis of new platinum complexes targeted towards small molecule activation is presented in chapter 3. The new ligands provide an entry into the synthesis of (hetero)bimetallic complexes that could show activity in cascade or tandem reactions. The use of bimetallic complexes is important for tailoring the reactivity of two catalysts simultaneously in the same molecule allowing for a higher degree of control over a reaction or multiple reactions in the same flask. The C-H activation of pyridine via the formation of Pt-Pt bonded bimetallic species is shown in chapter 4. Furthermore, a detailed computational and experimental study into the donor-acceptor nature of the Pt-Pt bond shows how bimetallic complexes of platinum could be used in challenging C-H activation reactions. Chapter 5 provides a summary of the work in this thesis and gives new avenues for the continued development of new platinum compounds for small molecule activation reactions. iv  Lay Summary Sustainability in chemistry is becoming more important with concerns over climate change in today\u2019s society. Developing chemical reactions which can turn greenhouse gasses, such as methane, into useful molecules is an endeavour to the global community. A fundamental understanding of the intricacies of these reactions must first be established before developing reactions involving methane. In this thesis, new reactivity based on platinum catalysts are developed and discovered that provide context and new ideas for the potential application towards upscaling methane.     v  Preface All contents of this thesis were written by myself with the supervision of Prof Jennifer Love. All experimental data collection and experimental design were performed by myself with input from Prof. Jennifer Love. Chapter 1. All contents of this chapter were written by me. A version of this Chapter has been published: Altus, K. M. & Love, J. A. The continuum of carbon\u2013hydrogen (C\u2013H) activation mechanisms and terminology. Commun. Chem. 4, 1\u201311 (2021). Chapter 2. The design of experiment, synthesis, and characterisation of all complexes in this chapter were carried out by me at the University of British Columbia. Computational calculations were carried out by Dr. Eric Bowes, a former PhD student in the Love group. Collection and refinement of all crystallographic data was conducted by Dr. Dawson Beattie, a former PhD student in the Love group. A version of this chapter has been published: Altus, K. M., Bowes, E. G., Beattie, D. D. & Love, J. A. Intermolecular Oxidative Addition of Aryl Halides to Platinum(II) Alkyl Complexes. Organometallics 38, 2273\u20132277 (2019). Chapter 3.  All contents relating to design of experiment, synthesis and characterisation of compounds was conducted by myself at the University of British Columbia and the University of Calgary. Collection and refinement of all crystallographic data was conducted by Dr. Benjamin Gelfand at the University of Calgary. Chapter 4. All experimental synthesis and characterisation were completed by me at the university of British Columbia and the University of Calgary. Calum Patel was responsible for the isolation and growing of suitable crystals for X-ray analysis of 4.2. Collection and refinement of all crystallographic data was conducted by Dr. Benjamin Gelfand at the University of Calgary. All computational studies regarding the reaction coordinate and charge decomposition analyses were carried out by collaborators Prof. Pierre Kennepohl and Xing Tong. Design of experiments were conducted in collaboration with Prof. Jennifer Love, Prof. Pierre Kennepohl and Xing Tong. Time course data was collected with assistance from Wade White of the NMR facilities at the University of Calgary. Modelling of the time course data in COPASI was carried out by me with advice from Prof. Jason Hein and Dr Pedro Mendes.   vi  Table of Contents Abstract .............................................................................................................................................................. iii Lay Summary .................................................................................................................................................... iv Preface ................................................................................................................................................................. v Table of Contents ............................................................................................................................................. vi List of Tables ..................................................................................................................................................... ix List of Figures .................................................................................................................................................... x List of Schemes .............................................................................................................................................. xix List of Symbols ...............................................................................................................................................xxii List of Abbreviations ..................................................................................................................................... xxiii Acknowledgements ........................................................................................................................................ xxv Dedication ...................................................................................................................................................... xxvii Chapter 1: Introduction .................................................................................................................................. 28 1.1 Mechanisms of C-H activation for alkanes. ................................................................................................ 29 1.1.1 C-H Activation vs Functionalisation ..................................................................................................... 31 1.1.2 Sigma and agostic complexes .............................................................................................................. 31 1.1.3 Mechanisms of C-H activation .............................................................................................................. 32 1.2 Historical context of the use of platinum in C-H activation reactions. .................................................... 44 1.3 Proposed catalytic cycle for the functionalisation of methane using aryl halides as oxidants. .......... 50 Chapter 2: Intermolecular Oxidative Addition of Aryl Halides to Platinum(II) Alkyl Complexes....... 53 2.1: Introduction .................................................................................................................................................... 53 2.2: Synthesis and reactivity of Me2Pt(IMes)(L) and MePt(IMes\u2019)(L) (IMes\u2019 = cyclometallated IMes, L = SMe2 or pyridine) with phenyl halides. .............................................................................................................. 54 2.3 Alternative ligands for OA of PhI to platinum (II) alkyl complexes. ......................................................... 69 2.4 Possible mechanisms for observed product distribution in oxidative addition of phenyl iodide to platinum(II) phosphine complexes ..................................................................................................................... 75 2.5 Summary ......................................................................................................................................................... 77 Chapter 3: Synthesis of a tridentate (C,N,N) N-heterocyclic carbene diamine ligand: complexation and reactivity with platinum and boron ....................................................................................................... 78 3.1 Introduction ..................................................................................................................................................... 78 3.1.1 Abnormal N-heterocyclic carbenes...................................................................................................... 78 vii  3.1.2 Diazaboryl ligands .................................................................................................................................. 80 3.2 Synthesis and characterisation of C,N,N tridentate imidazolium ligands.  ................................... 83 3.3 Attempted insertion of boron into the diamine backbone of 3.13 to form an NHC-NHB ligand ................................................................................................................................................................................. 88 3.4 Synthesis and characterisation of normal and abnormal carbene platinum complexes  ......... 95 3.5 Reactivity of abnormal carbene platinum complex 3.28  ................................................................ 103 3.6 Summary ....................................................................................................................................................... 110 Chapter 4: Mechanistic investigation into the ortho C-H activation of pyridine via the formation of a Pt-Pt bonded bimetallic intermediate. .................................................................................................... 112 4.1 introduction ................................................................................................................................................... 112 4.2 Reaction discovery and characterisation of isolable complexes involved in the C-H activation of pyridine. ................................................................................................................................................................ 117 4.2.1 1H NMR spectroscopic analysis and solid characterisation of side product ................................ 128 4.3 Time course analysis of the C-H activation of 4.1 ................................................................................... 137 4.3.1 Time course analysis of the C-H activation of 4.1 at 30 \u00b0C and excess pyridine experiments . 139 4.3.3 Time course analysis of the C-H activation of 4.1 at 50 \u00b0C ........................................................... 144 4.3.4 Time course analysis of the C-H activation of 4.1 at 60 \u00b0C ........................................................... 145 4.3.5 Attempted modelling of time course data. ........................................................................................ 147 4.3.6 Kinetic isotope (KIE) and para substituent effects. ......................................................................... 154 4.4 DFT analysis ................................................................................................................................................. 161 4.4.2 Charge decomposition analysis (CDA) ............................................................................................. 167 4.5 Reactivity of complex 4.2 ............................................................................................................................ 169 4.5.1 Ligand exchange .................................................................................................................................. 169 4.5.2 Reactivity of adamantane carboxylic acid (ACA) with 4.2. ............................................................. 171 4.5.3 Reactivity of PhI with 4.2. .................................................................................................................... 174 4.6 Summary ....................................................................................................................................................... 176 Chapter 5: Overview and Future Work ...................................................................................................... 177 5.1 Overview ....................................................................................................................................................... 177 5.2 Future Work .................................................................................................................................................. 178 Bibliography ................................................................................................................................................... 184 Appendices ..................................................................................................................................................... 199 CREATE Sustainable synthesis ....................................................................................................................... 199 Appendix A. Experimental ................................................................................................................................. 199 A 1. General considerations ......................................................................................................................... 199 A 2. Experimental data for Chapter 2 .......................................................................................................... 202 A 3. Experimental data for chapter 3 ........................................................................................................... 239 A 4. Experimental data for chapter 4 ........................................................................................................... 274 Appendix B. Crystallographic data ................................................................................................................... 293 viii  B 1. Crystallographic tables for chapter 2 ................................................................................................... 293 B 2. Crystallographic tables for chapter 3 ................................................................................................... 298 Appendix C. Computational details .................................................................................................................. 312 C 1. Computational details for chapter 2 .................................................................................................... 312 C 2. Computational details for chapter 4 .................................................................................................... 318  ix  List of Tables  Table 3.1 Attempted conditions for the insertion of Boron into the diamine backbone of 3.13 ..................... 89 Table 3.2 Conditions for the attempted insertion of Me2Sn into the diamine backbone of 3.13 ................... 92  Table 4.1 Rate constants at each temperature interval for the first and second C-H activation as described in Scheme 4.7. ............................................................................................................................. 152 Table 4.2 showing the net charge transfer between platinum atoms on going from reactant to  transition state and the relative activation barrier. ..................................................................................... 168  Table B1 Crystallographic data for compounds 2.1 and 2,4 ............................................................................ 295 Table B2 Crystallographic data for compounds 2.6 and 2.8 ............................................................................ 296 Table B3 Crystallographic data for compounds 2.3 and 2.4 ............................................................................ 297 Table B4 Crystallographic data for the compound 2.18 .................................................................................... 298 Table B5 Crystallographic data for compounds 3.13......................................................................................... 299 Table B6 Crystallographic data for compound 3.28........................................................................................... 301 Table B7 Crystallographic data for compound 3.29........................................................................................... 302 Table B8 Crystallographic data for compound 3.22........................................................................................... 303 Table B9 Crystallographic data for compounds 3.23......................................................................................... 304 Table B10 Crystallographic data for compound 4.1 ........................................................................................... 305 Table B11 Crystallographic data for compound 4.4 .......................................................................................... 307 Table B12 Crystallographic data for compound 4.2 .......................................................................................... 308 Table B13 Crystallographic data for compound 4.1-CF3 .................................................................................. 309 Table B14 Crystallographic data for compound 4.1-NMe2 ............................................................................... 310 Table B15 Crystallographic data for compound 4.6 .......................................................................................... 311  Table C1. Summary of charge decomposition analysis results 319 x   List of Figures Figure 1.1 Representation of the continuum of charge transfer in C-H activation reaction pathways. ........ 31 Figure 1.2 Examples of sigma and agostic complexes.a: First methane sigma complex fully  characterised in situ. b: Agostic complex featuring two agostic interactions........................................... 32 Figure 1.3 Electrophilic mechanisms. a: Three most common transition states found in electrophilic  C-H activation. b: simplified depiction of the AMLA(6) mechanism. c: DFT calculated mechanism  for the C-H activation of methane at (NHC)2Pd(II) via the  AMLA(6)\/CMD transition state. ...................................................................................................................... 34 Figure 1.4 Calculated transition states for the C-H activation of methane at Pd(II). All energies  are relative to sigma complex 1.1, Figure 1.3. Pd-H red dashed lines in A and B do not  represent an interaction, instead are representative of distance to the metal. ....................................... 37 Figure 1.5 Oxidative addition mechanism. a: simplified depiction of the oxidative addition mechanism.  b:  Concerted oxidative addition of an alkane to an unsaturated Iridium(I) PCP complex. .................. 38 Figure 1.6 Sigma bond metathesis mechanisms. a: transition states encountered during the different sigma bond metathesis mechanisms; green dots represent the ring critical  points of the interaction which show the point of minimum electron density in the interaction.67  b: simplified reaction mechanism for MA\u03c3BM reaction. c: Hartwig\u2019s alkane borylation reaction pathway. ............................................................................................................................................................ 40 Figure 1.7 1,2-Addition mechanism.  a: simplified reaction pathway. b: Reaction pathway  showing the transition state of the 1,2-addition of a C-H bond to a titanium alkylidyne complex. Alkylidene and imido complexes follow the same transition state. ........................................................... 43  Figure 2.1 Sterically bulky N-heterocyclic carbenes commonly used in stoichiometric and  catalytic reactions to stabilise reactive intermediates ................................................................................. 54 Figure 2.2 Stacked 1H NMR spectra (C6D6, 400 MHz, 25 \u00b0C) of the aliphatic region of 2.1 with PhI  after two hours at 60 \u00b0C (top\/blue) and independently synthesised complexes 2.5 (middle\/green) and2.3 (bottom\/red) to show the formation of the platinum complexes during the reaction shown above. ................................................................................................................................................................ 56 Figure 2.3 A. Control experiments that probe the reaction between PhI and 2.1, 2.3 and 2.5. B.  Reaction of 2.3 with PhI showing no further reaction. C. Cyclometallation of 2.1 into 2.4 .................... 57 Figure 2.4 Comparison between 1H NMR spectra of reactions of 2.1 and PhI (top\/green) and  2.1 and PhI-d5 (bottom\/red) showing the toluene signals are no longer visible during the reaction when using deuterated PhI. ............................................................................................................................ 58 Figure 2.5 Observation of Pt(II) intermediates throughout the reaction between 2.6 and PhI  after 16 hours at room temperature. Spectra from top to bottom: 1H NMR spectrum of  reaction mixture as depicted in reaction scheme above. 1H NMR spectrum of 2.9\/2.9a.  1H NMR spectrum of 2.7. 1H NMR spectrum of 2.8. 1H NMR spectrum of 2.6. ...................................... 60 Figure 2.6 Stacked 1H NMR spectra (C6D6, 300 MHz, 25 \u00b0C) of the reaction between 2.4 with  PhBr at 75\u00b0C over 68 hours. ........................................................................................................................... 62 Figure 2.7 Stacked 1H NMR spectra of the reaction between 2.6 and PhI in the presence of 5  equivalents of pyridine at 60 \u00b0C over a period of 48 hours. Red\/bottom spectrum  corresponds to the reaction prior to heating. Middle\/green corresponds to the reaction  after 24 hours. Top\/blue spectrum corresponds to the reaction after 48 hours. ..................................... 64 Figure 2.8 DFT calculated pathway for the OA of PhI to 2.4. An expanded view of the Pathway  be seen in supporting information. ................................................................................................................ 66 Figure 2.9 DFT calculated pathway for the OA of PhI to 2.1. An expanded view of the Pathway  can be seen in supporting information. ......................................................................................................... 67 Figure 2.10 Reaction scheme of 2.21 and PhI at 60 \u00b0C and stacked 1H NMR spectrum (C6D6,  400 MHz, 25 \u00b0C) of the reaction between phosphine complex 2.21 and PhI at 60 \u00b0C. Bottom\/green xi  spectrum, is the reaction before heating. Top\/red spectrum is the reaction  after 16 hours at 60 \u00b0C. Bottom inset features an expansion of the aliphatic region.  Top inset features an expansion of the aromatic region. ........................................................................... 71 Figure 2.11 Left: 1H-31P HMBC NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) showing the correlation  between Pt-phosphine and Pt-methyl resonances. Right: Stacked  31P{1H} NMR (C6D6, 400 MHz,  25 \u00b0C) spectrum of the reaction between 2.21 and PhI after 16 hours at 60 \u00b0C  showing the new Pt-Phosphine signal with characteristic large Pt-P coupling indicating a trans  iodine ligand. .................................................................................................................................................... 72 2.12 Rection scheme of 2.22 with PhI at 100 \u00b0C in C6D6. Stacked 1H NMR spectra showing the  reaction between 2.22 with PhI at 100 \u00b0C for 16 hours. Bottom\/ red spectrum shows the reaction mixture before heating. Top\/green spectrum shows the reaction mixture after heating for 16  hours at 100 \u00b0C. Bottom inset shows an expansion of the aliphatic region. Top inset shows and expansion of the aromatic region. .................................................................................................................. 73 Figure 2.13 1H-31P HMBC NMR spectrum of the reaction between 2.22 and PhI after 16 hours at  100 \u00b0C showing the 3JP-H correlation between the new Pt-phosphine signal and new  Pt-methyl signal. ............................................................................................................................................... 74  Figure 3.1 Selection of NHCs with wing tip heteroatom functionalisations. ..................................................... 78 Figure 3.2 Select examples of aNHC metal complexes bearing C-2 H atoms. C-2, C-4 and C-5 carbon atoms are labelled for clarity. ......................................................................................................................... 79 Figure 3.3 Select examples of (hetero)bimetallic complexes ............................................................................. 80 Figure 3.4 11B NMR spectrum (dcm-d2, 192 MHz, 25 \u00b0C) of 3.18 ..................................................................... 91 Figure 3.5 ORTEP depiction of the solid-state structure of complex 3.27  (ellipsoids are set at 50% probability, minor portions of disorder have been omitted for clarity). ........ 97 Figure 3.6 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C) showing the 3JPt-H coupling  between Pt and the imidazolium proton........................................................................................................ 97 Figure 3.7 1H-1H NOESY NMR spectrum (Acetone-d6, 600 MHz, 25 \u00b0C) showing the NOE  interaction between imidazolium proton and adjacent Pt-Me resonance. .............................................. 98 Figure 3.8 ORTEP depiction of the solid-state molecular structure of 3.28  (ellipsoids are set at 50 % probability, minor portions of disorder have been omitted for clarity) ........ 99 Figure 3.9 1H-1H NOESY NMR spectrum (Acetone-d6, 600 MHz, 25 \u00b0C) showing the NOE interactions between C4\/5 backbone protons in 3.28. ..................................................................................................... 99 Figure 3.10 ORTEP depiction of the solid-state structure of complex 3.29  (ellipsoids are set at 50% probability) ......................................................................................................... 101 Figure 3.11 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) showing the change in  symmetry of the  CH2 backbone protons as well as the equivalent dimethyl sulfide ligand relative to 3.29. .................. 103  Figure 4.1 A. Yu and co-workers meta C-H functionalisation of pyridine with olefins. B.  Alb\u00e9niz and co-workers C-H functionalisation of pyridine with aryl halides. ......................................... 112 Figure 4.2 Select examples of C-H activated pyridine metal complexes. ...................................................... 113 Figure 4.3 Examples of Pt-Pt bimetallic complexes featuring the bis-phosphinomethane core. ................ 115 Figure 4.4 Examples of Pt-Pt bimetallic complexes featuring O,O and N,O bridging ligands. .................... 116 Figure 4.5 Examples of Pt-Pt bimetallic complexes featuring \u00b5-bridging ligands. ........................................ 116 Figure 4.6 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) of 4.2 showing the signal assignment to  each proton environment. ............................................................................................................................. 118 Figure 4.7 Stacked 1H NMR spectrum (MeCN-d3, 400 MHz, 25 \u00b0C) of the reaction between 4.1  and MeCN-d3 before heating (bottom) and after heating for 1 hour at 50 \u00b0C (top). ............................. 120 Figure 4.8 1H NMR spectrum (400 MHz, 25 \u00b0C) of 4.1 in toluene-d8 and acetone-d8 at room  temperature. Inset shows the formation of the intermediate in both solvents. ...................................... 121 xii  Figure 4.9 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C) of the aliphatic region 4.1 in  acetone-d6 after heating for one hour at 50 \u00b0C, showing the primary and secondary Pt-CH3 couplings. ........................................................................................................................................................ 122 Figure 4.10 1H NMR spectrum  of the aromatic region of 4.1 in acetone after one hour of  heating ............................................................................................................................................................. 123 Figure 4.11 Proposed methyl agostic complex 4.5. ........................................................................................... 123 Figure 4.12 A. Pt-Pt bonded intermediate 4.4 and Puddephatt\u2019s Pt-Pt bonded complex with the diphenylphosphino methane core. B. ORTEP depiction of the solid-state structure of 4.4  (ellipsoids are set 50% probability) .............................................................................................................. 124 Figure 4.13. 1H NMR spectrum (Tol-d8, 400 MHz, 25 \u00b0C) of the aromatic region of reaction of  4.1 in toluene-d8 after two hours at 50 \u00b0C followed by removal of all volatiles. Inset shows  full spectrum................................................................................................................................................... 125 Figure 4.14 1H-1H NOESY NMR spectrum (Tol-d8, 400 MHz, 25 \u00b0C) of the aliphatic region of a  reaction mixture of containing 4.4, 4.1 and 4.2 .......................................................................................... 126 Figure 4.15 1H-1H NOESY NMR spectrum (tol-d8, 400 MHz, 25 \u00b0C) of the aliphatic and aromatic  regions of a reaction mixture containing 4.4, 4.1 and 4.2. ....................................................................... 127 Figure 4.16 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) of 4.2 and the side product. The region  between 2.00 ppm and 6.00 has been removed for clarity (Bottom spectrum). The full spectrum  trace is shown on top. .................................................................................................................................... 129 Figure 4.17 Stacked 1H NMR spectra (tol-d8, 400 MHz, 25 \u00b0C) of 4.2, 4.4 and the side product  over time. ........................................................................................................................................................ 130 Figure 4.18 1H-1H COSY NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) of a mixture containing 4.2  and 4.6. ............................................................................................................................................................ 131 Figure 4.19 1H NMR spectra (pyridine-d5, 400 MHz, 25 \u00b0C) of 4.2 and 4.6 in pyridine-d5 at room temperature (bottom) and the same mixture after heating at 40 C for 18 hours (top). ........................ 132 Figure 4.20 1H NMR spectrum (pyridine-d5, 600 MHz, 25 \u00b0C) of the aromatic region of 4.2  and 4.6. Full spectrum above. ..................................................................................................................... 133 Figure 4.21 1H-1H NOESY NMR spectrum (Pyridine-d5, 600 MHz, 25 \u00b0C) of the aromatic region  of 4.2 and 4.6. ................................................................................................................................................ 134 Figure 4.22 1H-1H NOESY NMR spectrum (pyridine-d5, 600 MHz, 25 \u00b0C) showing NOE  correlation between the aliphatic Pt-Me resonances and the aromatic pyridine  resonances. ..................................................................................................................................................... 135 Figure 4.23 ORTEP depiction of the solid-state structure of 4.6  (ellipsoids are set 50% probability). ............................................................................................................. 136 Figure 4.24 Time course data for the consumption of 4.1 over eight hours at 30-60 \u00b0C (top left).  Time course data for the formation and consumption of 4.4 over eight hours at 30-60 \u00b0C  (top right). Time course data for the formation of 4.2 over eight hours at 30-60 \u00b0C  (bottom). .......................................................................................................................................................... 138 Figure 4.25 Reaction schematic showing the overall stoichiometry of the reaction, excluding  the side product 4.6. Time course data for the reaction in the above scheme at 30 \u00b0C  (Run 1, top left). Time course data for the reaction in the above scheme at 30 \u00b0C  (Run 2, top right). Time course data for the reaction in the above scheme at 30 \u00b0C  (Run 3, bottom) ............................................................................................................................................... 140 Figure 4.26 Reaction schematic of 4.1 in the presence of 1.5 equivalents of pyridine in C6D6 at  60 \u00b0C over 48 hours. Stacked 1H NMR spectra of the reaction between 4.1 and 1.5  equivalents of pyridine at 60 \u00b0C over 48 hours. ......................................................................................... 142 Figure 4.27 Reaction scheme for the reaction of 4.1 at 40 \u00b0C. Time course data for the reaction  at 40 \u00b0C (Run 1, top left). Time course data for the reaction at 40 \u00b0C (Run 2, top right).  Time course data for the reaction at 40 \u00b0C (Run 3, bottom) .................................................................... 144 xiii  Figure 4.28 Reaction scheme for the reaction of 4.1 at 50 \u00b0C. Time course data for the reaction  50 \u00b0C (Run 1, top left). Time course data for the reaction at 50 \u00b0C (Run 2, top right).  Time course data for the reaction at 50 \u00b0C (Run 1, bottom) .................................................................... 145 Figure 4.29 Reaction scheme for the reaction of 4.1 at 60 \u00b0C.Time course data for the reaction  60 \u00b0C (Run 1, top left). Time course data for the reaction at 60 \u00b0C (Run 2, top right). Time course data for the reaction at 60 \u00b0C (Run 1, bottom) ........................................................................................... 146 Figure 4.30 Parameter estimation plot for the time course data of the C-H activation of 4.1 at  30 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine. ........................................................................ 149 Figure 4.31 Parameter estimation plot for the time course data of the C-H activation of 4.1 at  40 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine. ......................................................................... 150 Figure 4.32 Parameter estimation plot for the time course data of the C-H activation of 4.1 at  50 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine, [side] = 4.6 .................................................... 151 Figure 4.33 Parameter estimation plot for the time course data of the C-H activation of 4.1 at  60 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine, [side] = 4.6 .................................................... 152 Figure 4.34 Eyring plots for the formation of 4.4  from 4.1 (left) and formation of 4.2 from 4.4  (right) ................................................................................................................................................................ 153 Figure 4.35 Time course data for the consumption of 4.1 vs 4.1-d10 (left) and time course data  for the formation of 4.4 vs 4.4-d15 ( right) and ........................................................................................... 155 Figure 4.36 Parameter estimation plot for the time course data of the C-H activation of 4.1-d10   at 30 \u00b0C [SM] = 4.1-d10, [2-int] = 4.4-d15, [p] = 4.2-d20, ............................................................................ 156 Figure 4.37 Time course data for the C-H activation of 4.1-CF3 at 30 \u00b0C (top left). Time course  data for the consumption of 4.1 vs 4.1-CF3 (top right). Time course data for the formation  of 4.4 vs 4.4-CF3 (bottom left). Time course data for the formation of 4.2 vs 4.2-CF3  (bottom right) ................................................................................................................................................... 158 Figure 4.38 Reaction schematic showing the products of C-H activation of 4.1-NMe2.  Stacked 1H NMR spectra (Tol-d8, 400 MHz, 25 \u00b0C) of the C-H activation reaction of  4.1-NMe2 over 18 hours (Bottom: rt, middle: after one hour heating at 60 \u00b0C, top:  after 18 hours heating at 60 \u00b0C). .................................................................................................................. 159 Figure 4.39 Calculated transition state for the sigma bond metathesis mechanism for the C-H  activation of pyridine. Calculated using the DLPNO-CCSD functional and def2-TZVP  basis set ........................................................................................................................................................... 165 Figure 4.40 Calculated transition states for the First C-H activation (4.11-TS and 4.14-TS) and  second C-H activation (4.18-TS) broken into 4 separate fragments a-d. ............................................. 168 Figure 4.41 Reaction schematic of 4.2 and IMes. Stacked 1H NMR spectra of the aromatic  region from the reaction between 4.2 and IMes at 60 \u00b0C over 16 hours. .............................................. 170 Figure 4.42 ORETP depiction of the solid-state molecular structure of 4.23 ................................................. 170 Figure 4.43 Stacked 1H NMR spectra of the aliphatic region from the reaction between 4.2  and IMes at 60 \u00b0C over 16 hours. ................................................................................................................ 171 Figure 4.44 Stacked 1H NMR spectra of the reaction between 4.2 and adamantane carboxylic  acid over 45 mins at 60 \u00b0C. ........................................................................................................................... 173 Figure 4.45 Stacked 1H NMR spectra (C6D6, 400 MHz, 25 \u00b0C) of the reaction between 4.2 and  PhI at room temperature after one and three hours. ................................................................................ 175  Figure 5.1 Proposed new Pt-Pt bimetallic species using existing general Pt-Pt bimetallic  structures with new hemilabile P,N ligands. ...................................................................................... 182  Figure A1 2.1, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) ........................................................................... 202 Figure A2 2.1, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C) .................................................................. 203 Figure A3 2.1, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) ............................................... 203 xiv  Figure A4 2.1, HSQC NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) .................................................................... 204 Figure A5 2.3, 1H NMR spectrum (C6D6, 400 MHz, 35\u00b0C) ................................................................................ 205 Figure A6 2.3, 13C{1H} NMR (C6D6, 100 MHz, 35\u00b0C) ......................................................................................... 206 Figure A7 2.3, HSQC NMR spectrum (C6D6, 400\/100 MHz, 35 \u00b0C) ................................................................ 206 Figure A8 2.3, 1H-13C HMBC NMR spectrum (C6D6, 400\/100 MHz, 35 \u00b0C) ................................................... 207 Figure A9 2.3, 1H-1H NOESY NMR spectrum (C6D6, 400 MHz, 35 \u00b0C) .......................................................... 207 Figure A10 2.4, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C)......................................................................... 208 Figure A11 2.4, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C) ................................................................ 209 Figure A12 2.4, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) ............................................. 210 Figure A13 2.4, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) .......................................................... 210 Figure A14 2.4, 1H-1H NOESY NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) .................................................. 210 Figure A15 2.5, 1H NMR spectrum (C6D6, 400 MHz, 55 \u00b0C) ............................................................................ 212 Figure A16 2.5, 13C{1H} NMR spectrum (C6D6, 100 MHz, 55 \u00b0C) .................................................................... 212 Figure A17 2.5, HSQC NMR spectrum (C6D6, 400\/100 MHz, 55 \u00b0C) ............................................................. 213 Figure A18 2.5, 1H-13C HMBC NMR spectrum (C6D6, 400\/100 MHz, 55 \u00b0C) ................................................. 213 Figure A19 2.5, 1H-1H NOESY NMR spectrum (C6D6, 400 MHz, 55 \u00b0C) ........................................................ 214 Figure A20 2.5, region showing NOE between SMe2 and aryl C-H (C6D6, 400 MHz, 55 \u00b0C)...................... 214 Figure A21 2.6, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C)......................................................................... 215 Figure A22 2.6, 13C{1-H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C) ............................................................... 216 Figure A23 2.7, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C), peak at 2.1 corresponds to acetone  from recrystallisation. ..................................................................................................................................... 217 Figure A24 2.7, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C), peaks at 31ppm and 206ppm correspond to acetone. .................................................................................................................................. 218 Figure A25 2.7, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) .......................................................... 218 Figure A26 2.7, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) ............................................. 219 Figure A27 2.8, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C)......................................................................... 220 Figure A28 2.8, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C) ................................................................ 221 Figure A29 2.8, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) .......................................................... 221 Figure A30 2.8, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) ............................................. 222 Figure A31 2.9 and 2.9a, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) ........................................................ 224 Figure A32 2.9 and 2.9a, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C) ................................................ 224 Figure A33 2.9 and 2.9a, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) ......................................... 225 Figure A34 2.9 and 2.9a, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) ............................ 225 Figure A35 2.9 and 2.9a, 1H-1H NOESY NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) ................................... 226 Figure A36 2.18, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C). * Acetone from recrystallisation ............. 227 Figure A37 2.18,13C{1H} NMR spectrum (100 MHz, CD2Cl2, 25 \u00b0C). * Acetone from  recrystallisation ............................................................................................................................................... 228 Figure A38 2.18, HSQC NMR spectrum (400\/100 MHZ, CD2Cl2, 25 \u00b0C) ....................................................... 228 Figure A39 2.18, 1H-1H NOESY NMR spectrum (400 MHz, CD2Cl2, 25 \u00b0C) .................................................. 229 Figure A40 2.21, 1H NMR spectrum (C6D6, 300 MHz, 25 \u00b0C) .......................................................................... 230 Figure A41 2.21, 13C{1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C) .................................................................. 231 Figure A42 2.21, 31P{1H} NMR spectrum (C6D6, 121 MHz, 25 \u00b0C) .................................................................. 231 Figure A43 2.21, HSQC NMR spectrum (C6D6, 300\/100 MHz, 25 \u00b0C) ........................................................... 232 Figure A44 2.21, 1H-13C HMBC NMR spectrum (C6D6, 300\/100 MHz, 25 \u00b0C) .............................................. 232 Figure A45 2.22, 1H NMR spectrum (C6D6, 600 MHz, 25 \u00b0C) .......................................................................... 233 Figure A46 2.22, 13C{1H} NMR spectrum (C6D6, 150 MHz, 25 \u00b0C) .................................................................. 234 Figure A47 2.22, 31P NMR spectrum (C6D6, 162 MHz, 25 \u00b0C) ......................................................................... 234 Figure A48 2.22, 19F NMR spectrum (C6D6, 282 MHz, 25 \u00b0C) ......................................................................... 235 Figure A49 2.23, 1H NMR spectrum (C6D6, 600 MHz, 25 \u00b0C) .......................................................................... 236 xv  Figure A50 2.23, 13C{1H} NMR spectrum (C6D6, 150 MHz, 25 \u00b0C) .................................................................. 237 Figure A51 2.23, 31P{1H} NMR spectrum (C6D6, 121 MHz, 25 \u00b0C) .................................................................. 237 Figure A52 2.23, HSQC, NMR spectrum (C6D6, 600\/150 MHz, 25 \u00b0C) .......................................................... 238 Figure A53 2.23, COSY NMR spectrum (400 MHz, C6D6, 25 \u00b0C) ................................................................... 238 Figure A54 3.3, 1H NMR spectrum (CDCl3, 300 MHz, 25 \u00b0C) ......................................................................... 240 Figure A55 3.3, 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C) .................................................................. 240 Figure A56 3.4, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C) .......................................................................... 242 Figure A57 3.4, 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C) .................................................................. 242 Figure A58 3.5, 1H NMR spectrum (CD3CN, 400 MHZ, 25 \u00b0C) ....................................................................... 244 Figure A59 3.5, 13C{1H} NMR spectrum (CD3CN, 100 MHZ, 25 \u00b0C) .............................................................. 244 Figure A60 3.5, 31P NMR spectrum (CD3CN, 121 MHZ, 25 \u00b0C) ...................................................................... 245 Figure A61 3.5 19F NMR spectrum (CD3CN, 376 MHz, 25 \u00b0C) ........................................................................ 245 Figure A62 3.6, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C) .......................................................................... 247 Figure A63 3.6, 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C) .................................................................. 247 Figure A64 3.6, 31P NMR spectrum (CDCl3, 161 MHz, 25 \u00b0C) ......................................................................... 248 Figure A65 3.6, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C) ......................................................................... 248 Figure A66 3.7, !H NMR spectrum (CDCl3, 400 MHZ, 25 \u00b0C) .......................................................................... 250 Figure A67 3.7, 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 \u00b0C) .................................................................. 250 Figure A68 3.7, 31P NMR spectrum ( CDCl3, 161 MHz, 25 \u00b0C) ........................................................................ 251 Figure A69 3.7, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C) ......................................................................... 251 Figure A70 3.8, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C) .......................................................................... 253 Figure A71 3.8 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C) ................................................................... 253 Figure A72 3.8, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C) ......................................................................... 254 Figure A73 3.8, 31P NMR spectrum (CDCl3, 161 MHz, 25 \u00b0C) ......................................................................... 254 Figure A74 3.9, 1H NMR spectrum (CDCl3, 300 MHz, 25 \u00b0C) .......................................................................... 255 Figure A75 3.10, 1H NMR spectrum (CDCl3, 300 MHz, 25 \u00b0C) ........................................................................ 257 Figure A76 3.11, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C) ........................................................................ 259 Figure A77 3.11, 13C{1H} NMR spectrum (CDCl3 100 MHz, 25 \u00b0C) ................................................................ 259 Figure A78 3.11, HSQC NMR spectrum (CDCl3, 100\/400 MHz, 25 \u00b0C) ......................................................... 260 Figure A79 3.12, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C) ........................................................................ 262 Figure A80 3.12, 13C{1H} NMR spectrum (CDCl3 100 MHz, 25 \u00b0C) ................................................................ 262 Figure A81 3.12, HSQC NMR spectrum (CDCl3, 100\/400 MHz, 25 \u00b0C) ......................................................... 263 Figure A82 3.13, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C) ........................................................................ 265 Figure A83 3.13, 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 \u00b0C) ............................................................... 266 Figure A84 3.13,  31P NMR spectrum (CDCl3, 161 MHz, 25 \u00b0C ....................................................................... 266 Figure A85 3.13, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C) ....................................................................... 267 Figure A86 3.13, 1H NMR spectrum (CD3CN, 400 MHZ, 25 \u00b0C) ..................................................................... 267 Figure A87 3.27, 1H NMR spectrum (Acetonitrile-d3, 400 MHz, 25 \u00b0C) .......................................................... 269 Figure A88 3.27, 13C{1H} NMR spectrum (acetonitrile-d3, 100 MHz, 25 \u00b0C) .................................................. 269 Figure A89 3.27, 19F NMR spectrum (Acetonitrile-d3, 376 MHz, 25 \u00b0C) ......................................................... 270 Figure A90 3.27, 31P NMR spectrum (Acetonitrile-d3, 161 MHz, 25 \u00b0C) ......................................................... 270 Figure A91 3.22, 1H NMR (Acetone-d6, 600 MHz, 25 \u00b0C) ................................................................................ 272 Figure A92 3.22, 19F NMR spectrum (Acetone-d6, 376 MHz, 25 \u00b0C) ............................................................. 272 Figure A93 3.22, 31P NMR spectrum (Acetone-d6, 241 MHz, 25 \u00b0C) ............................................................. 273 Figure A94 4.1, 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) ............................................................................ 276 Figure A95 4.1, 13C{1H} NMR spectrum (C6D6 , 100 MHz, 25 \u00b0C) ................................................................... 276 Figure A96 4.1-CF3, 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) .................................................................... 279 Figure A97 4.1-CF3, 13C {1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C) ........................................................... 279 Figure A98 4.1-CF3, 13C {1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C) ........................................................... 280 xvi  Figure A 99 4.1-CF3, 19F NMR spectrum (C6D6, 376 MHz, 25 \u00b0C) .................................................................. 281 Figure A100 4.1-NMe2, 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C) .................................................... 283 Figure A101 4.1-NMe2, 13C{1H} NMR spectrum (Acetone-d6, 100 MHz, 25 \u00b0C) ............................................ 283 Figure A102 4.2, 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) .......................................................................... 285 Figure A103 4.2, 13C{1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C) .................................................................. 285 Figure A104 Stacked 1H NMR spectra (tol-d8, 400 MHz, 30 \u00b0C) for time course data of 4.1 at  30 \u00b0C run 1 ...................................................................................................................................................... 286 Figure A105 Stacked 1H NMR spectra (Tol-d8, 400 MHz, 30 \u00b0C) for the time course data of 4.1  at 30 \u00b0C run 2 .................................................................................................................................................. 286 Figure A106 Stacked 1H NMR spectra (tol-d8, 400 MHz, 30 \u00b0C) for the time course data of 4.1  at 30 \u00b0C run 3 ................................................................................................................................................. 287 Figure A107 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1  at 40 \u00b0C run 1 .................................................................................................................................................. 287 Figure A108 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1  at 40 \u00b0C run 2 .................................................................................................................................................. 288 Figure A109 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1  at 40 \u00b0C run 3 .................................................................................................................................................. 288 Figure A110 Stacked 1H NMR spectra (tol-d8, 400 MHz, 50 \u00b0C) for the time course data of 4.1  at 50 \u00b0C run 1 .................................................................................................................................................. 289 Figure A111 Stacked 1H NMR spectra (tol-d8, 400MHz, 50 \u00b0C) for the time course data of 4.1  at 50 \u00b0C run 2 .................................................................................................................................................. 289 Figure A112 Stacked 1H NMR spectra (tol-d8, 400 MHz, 50 \u00b0C) for the time course data of 4.1  at 50 \u00b0C run 3 .................................................................................................................................................. 290 Figure A113 Stacked 1H NMR spectra (tol-d8, 400 MHz, 60 \u00b0C) for the time course data of 4.1  at 60 \u00b0C run 1 .................................................................................................................................................. 290 Figure A114 Stacked 1H NMR spectra (tol-d8, 400 MHz, 60 \u00b0C) for the time course data of 4.1  at 60 \u00b0C run 2 .................................................................................................................................................. 291 Figure A115 Stacked 1H NMR spectra (tol-d8, 400 MHz, 60 \u00b0C) for the time course data of 4.1  at 60 \u00b0C run 3 .................................................................................................................................................. 291 Figure A116 Stacked 1H NMR spectra (tol-d8, 400 MHz, 30 \u00b0C) for the time course data of 4.1-CF3  at 30 \u00b0C ........................................................................................................................................................... 292 Figure A117 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1-d10  at 40 \u00b0C ........................................................................................................................................................... 292   Figure B1 ORTEP depiction of the solid-state molecular structure of complex 2.1 and 2.4 (ellipsoids are set at 50% probability; H atoms have been omitted for clarity). Selected  bond lengths (\u00c5) and angles (\u00b0) 2.1: Pt-C1 2.059(2), Pt-C2 2.088(2), Pt-C3 2.039(3), Pt-S 2.367(1), S-Pt-C3 91.73(9), C2-Pt-C1 88.03, C1-Pt1-C3 88.42, S1-Pt1-C2 91.98. 2.4: Pt-C1 2.103(1), Pt-C2 2.010(5), Pt-C7 2.063(6), Pt-S1 2.351(3), C1-Pt1-C7 90.11, S1-Pt1-C2 94.60,  C2-Pt1-C7 82.66, C1-Pt-1-S1 92.63. ......................................................................................................... 294 Figure B2 ORTEP depiction of the solid-state molecular structure of complex 2.6 and 2.8 (ellipsoids are set at 50% probability; H atoms have been omitted for clarity). Selected  bond lengths (\u00c5) and angles (\u00b0) 2.6: C1-Pt1 2.049(3), C2-Pt1 2.084(2), C3-Pt1 2.027(2),  N1-Pt1 2.126(2), C1-Pt1-C2 88.8(1), C2-Pt1-N1 88.28(9), C3-Pt1-C1 90.11(9), N1-Pt1-C3  92.77(8). 2.8: C1-Pt1 2.079(2), C2-Pt1 2.021(2), C7-Pt1 2.045(2), N1-Pt1 2.102(2), C1-Pt1-N1 88.57(7), C2-Pt1-C7 83.49(8), C7-Pt1-C1 90.07(8), N1-Pt1-C2 97.83(7). ............................................ 296 Figure B3 ORTEP depiction of the solid-state molecular structure of complex 2.3 and 2.5  (ellipsoids are set at 50% probability; H atoms have been omitted for clarity).  Selected bond lengths (\u00c5) and angles (\u00b0) 2.3: Pt1-C1 2.064(2), Pt1-C2 1.972(2),  Pt1-S1 2.3941(5), Pt1-I1 2.6631(5), C1-Pt1-C2 87.69(7), C2-Pt1-S1 91.69(5), S1-Pt1-I1 92.31(1), xvii  I1-Pt1-C188.44(5). 2.5: Pt1-C1 1.972(2), Pt1-C6 2.068(2), Pt1-I1 2.6350(4), Pt1-S1 2.3871(6),  S1-Pt1-C1 94.66(6), C1-Pt1-C6 81.61(8), C6-Pt1-I 90.21(6), I1-Pt-1-S1 93.53(2). ............................. 296 Figure B4 Ortep depiction of the solid-state molecular structure of complex 2.18 (ellipsoids  are set at 50% probability; H atoms and three acetonitrile molecules have been omitted for clarity). The complex is substitutionally disordered at C1 (0.8) and I1 (0.8), with the alternate positions of iodide (cis to NHC) and methyl (cis to phenyl) holding occupancies of (0.2). Selected bond lengths (\u00c5) and angles (\u00b0) angle and lengths the same across both isomers except for C1  and I1: C1-Pt 2.161(6), C1a-Pt 2.20(2), C2-Pt1 2.015(3), C23-Pt1 2.076(3), C7-Pt1 2.083(3),  I1-Pt1 2.6849(6), I1a-Pt 2.649(1) ,N1-P1 2.164(2), C2-Pt1-N1 100.4(1), C23-Pt1-N1 79.1(1),  C2-Pt1-C7 82.4(1), N1-Pt1-I1 86.19(7). ...................................................................................................... 297 Figure B5 ORTEP depiction of the solid-state molecular structure of 3.13 (ellipsoids are set at  50% probability; H atoms and minor portions of disorder been omitted for clarity). ............................. 298 Figure B6 Figure S3.1 ORTEP depiction of the solid-state molecular structure of 3.28  (ellipsoids are set at 50% probability, H atoms, PF6 anion and 2 molecules of acetone  along with minor portions of disorder have been removed for clarity). Selected bond  lengths (\u00c5) and angles (\u00b0): Pt-C2 1.968(3), Pt-C1 2.044(3), Pt-N3 2.147(3), Pt1-N4 2.146(2).  C2-Pt-N3 94.3(1), C2-Pt1-C1 90.9(1), N3-Pt1-N4 81.38(9), N4-Pt1-C1 93.5(1). ................................. 300 Figure B7 ORTEP depiction of the solid-state molecular structure of complex 3.29 (ellipsoids  are set at 50% probability; two molecules of acetone and a PF6 anion have been omitted  for clarity). Selected bond lengths (\u00c5) and angles (\u00b0): Pt1-C1 2.039(2), Pt1-C2 1.945(2),  Pt1-N3 2.166(2), Pt1-N4 2.128(2). C1-Pt1-C2 94.7(1), C1-Pt1-N4 92.63(9), C2-Pt1-N3 89.69(9),  N3-Pt1-N4 82.97(8)........................................................................................................................................ 301 Figure B8 ORTEP depiction of the solid-state molecular structure of 3.22 (ellipsoids are set at  50% probability, H atoms, PF6 anion and portions of minor disorder have been removed  for clarity). Selected bond lengths (\u00c5): C1-Ag1 2.069. Selected Angles (\u00b0):  C1-Ag1-C26 180.00. ...................................................................................................................................... 302 Figure B9 ORTEP depiction of the solid-state molecular structure of 3.23 (ellipsoids are  set at 50% probability, another molecule of 3.23 and minor portions of disorder have  been omitted for clarity). Selected bond lengths (\u00c5): C1_1-Pt_1 2.082(3),  S1_1-Pt_1 2.108(3), N3_1-Pt_1 2.2555(9), C8_1-Pt_1 2.059(3). Selected angles (\u00b0).  C1_1-Pt_1-N3_1 86.7(1), C8_1-Pt_1-S1_1 90.53(9), S1_1-Pt_1-C1_1 91.8(1), N3_1-Pt_1-C8_1 90.9(1). ............................................................................................................................................................. 303 Figure B10 ORTEP depiction of the solid-state molecular structure of 4.1 (ellipsoids are set at  50% probability, H atoms and another molecule of 4.1 has been omitted for clarity).  Selected bond angles (\u00c5): C1-Pt1 2.040(4), C2-Pt1 2.034(4), N1-Pt1 2.129(3),  N2-Pt1 2.126(3). Selected bond angles (\u00b0): C1-Pt1-C2, C1-Pt1-N1, N1-Pt1-N2, N2-Pt1-C2. ............ 305 Figure B11 ORTEP depiction of the solid-state molecular structure of 4.4 (ellipsoids are set at  50% probability and H atoms have been omitted for clarity). Selected bond lengths (\u00c5): C1-Pt1 2.028(5), C2-Pt1 2.035(4), N1-Pt1 2.142(3), N2-Pt1 2.103(3), Pt1-Pt2 2.6998(6), C8-Pt2 2.033(3), N3-Pt2 2.107(4), C9-Pt2 1.958(4). Selected bond angles (\u00b0):C1-Pt1-C2 88.3(2),  C1-Pt1-Pt2 86.6(1), C2-Pt1-N1 90.7(2), C2-Pt1-Pt2 108.4(1), N1-Pt1-N2 89.9(1), N1-Pt1-Pt2 97.66(9), N2-Pt1-C1 91.4(2), N2-Pt1-Pt2 67.78(9), C8-Pt2-C9 94.5(2), N3-Pt2-Pt1 100.52(9),  C9-Pt2-Pt1 74.0(1),C8-Pt2-N3 90.9(1) . ...................................................................................................... 306 Figure B12  ORTEP depiction of the solid-state molecular structure of 4.2 (ellipsoids are set  at 50% probability, H atoms, two molecules of THF and a second molecule of 4.2 have  been removed for clarity). Selected bond lengths (\u00c5): Pt1-C24 2.062(4), Pt1-C30 1.971(4),  Pt1-N6 2.119(3), Pt1-N7 2.107(3), Pt02-C23 2.060(4), Pt02-C25 (1.982(4)), Pt02-N5 2.122(3),  Pt02-N8 2.107(3). Selected bond angles (\u00b0): C24-Pt02-C25 89.1(2), C24-Pt1-C30 88.1(2),  C25-Pt02-N5 92.0(1), C30-Pt1-N6 92.2(1), N5-Pt02-N8 88.9(1), N6-Pt1-N7 89.1(1), N7-Pt1-C24 90.5(2), N8-Pt02-C23 90.1(1)....................................................................................................................... 307 xviii  Figure B13 ORTEP depiction of the solid-state molecular structure of 4.1-CF3 (ellipsoids are  set at 50% probability, H atoms and minor portions of disorder have been removed for clarity). Selected bond lengths(\u00c5): C1-Pt1 2.034(3), C2-Pt1 2.039(4), N1-Pt1 2.119(3),  N2-Pt 2.118(2). Selected bond angles (\u00b0): N1-Pt1-N2 91.85(8), N2-Pt1-C2 89.9(1),  C2-Pt1-C1 88.3(1), C1-Pt1-N1 89.9(1). ...................................................................................................... 308 Figure B14 ORTEP depiction of the solid-state molecular structure of 4.1-NMe2 (ellipsoids  are set at 50% probability, H atoms have been removed for clarity). Selected bond lengths (\u00c5): Pt1-N1 2.127(2), Pt1-C1 2.040(5), Pt1-C2 2.033(3), Pt1-N2 2.128(3). Selected bond angles  (\u00b0): N2-Pt1-N1 91.0(1), N1-Pt1-C1 90.7(1), C1-Pt1-C2 87.9(2), C2-Pt1-N2 90.6(1). ........................... 309 Figure B15 ORTEP depiction of the solid-state molecular structure of 4.6 (ellipsoids are set at  50% probability, H atoms, and five molecules of benzene along with minor portions of disorder  have been omitted for clarity) Selected bond lengths (\u00c5): C23-Pt3 2.038(8), N5-Pt3 2.112(5),  N3-Pt3 2.113(6), Pt3-Pt2 3.0634(4), C18-Pt3 1.976(5), C12-Pt2 2.037(6), C13-Pt2 1.988(7),  N4-Pt2 2.120(4), N2-Pt2 2.099(5), C7-Pt1 1.962(7), Pt2-Pt1 2.7109(4), C1-Pt1 2.052(5),  C7-Pt1, N1-Pt1 2.105(5). Selected bond angles (\u00b0): N5-Pt3-N3 90.8(2), N3-Pt3-C18 90.8(2),  C18-Pt3-C23 89.6(2), C23-Pt3-N5 89.6(2), N5-Pt3-Pt2 113.7(1), N3-Pt3-Pt2 63.1(1),  C18-Pt3-Pt2 67.1(2), C23-Pt3-Pt2 114.5(2), C13-Pt2-C12 89.5(3), C12-Pt2-N2 90.2(2),  N2-Pt2-N4 89.9(2), N4-Pt2-C13 90.4(2), N1-Pt-C1 91.7(2), C1-Pt1-C7 94.8(2), C7-Pt1-Pt2  73.6(2), Pt2-Pt1-N1 99.9(1). ........................................................................................................................ 310 Figure B16 Reaction coordinate for Csp2-I oxidative addition starting from the Pt(II) dimethyl complex  2.1.................................................................................................................................................................... 314 Figure B17 Reaction coordinate for Csp2-I oxidative addition starting from cyclometallated complex  2.4.................................................................................................................................................................... 315 Figure B18 Transition states for Csp2-I OA showing higher energies when Pt-alkyl groups  are in a mutally trans configuration. Relative energies reported relative to 2.1 for 2.15TS  and 2.15_transalkylTS, relative to 2.4 for 2.11TS and 2.11_transalkylTS. ................................................. 316 Figure B19 Csp2-I OA transition state geometries. ............................................................................................ 317  xix  List of Schemes Scheme 1.1 representative example of the H\/D exchange in aromatic compounds reported by  Garnett and Hodges using K2PtCl4 as a catalyst......................................................................................... 45 Scheme 1.2 Simplified catalytic cycle of the Shilov system for the C-H activation  of methane by K2PtCl4. .................................................................................................................................... 46 Scheme 1.3 Catalytic cycle for the Catalytica system showing the oxidation of methane  to methylbisulfate. ............................................................................................................................................ 47 Scheme 1.4 Oxidation of methane reported by Strassner employing a Bis-NHC platinum complex  using K2S2O8 as oxidant in trifluoroacetic acid as reaction medium. ........................................................ 48 Scheme 1.5 Proposed catalytic cycle for the oxidation of methane by trifluoroacetic acid ........................... 49 Scheme 1.6 Proposed catalytic cycle for the functionalisation of methane by aryl halides using a Pt(II)\/Pt(IV) redox cycle. .................................................................................................................................. 51  Scheme 2.1 Intramolecular oxidative addition of aryl halides to a Pt(II) dimethyl complex ........................... 53 Scheme 2.2 Synthesis of NHC-Pt(II) complexes 2.1 and 2.2 ............................................................................ 55 Scheme 2.3 A. Synthesis of platinum pyridine analogues of 2.1 and 2.4. B. Reaction of 2.6 with  PhI and the resulting product distribution. ................................................................................................... 59 Scheme 2.4 Reaction of independently synthesised cyclometallated complexes 2.4 and 2.8 with  phenyl iodide at 60 \u00b0C in C6D6. ...................................................................................................................... 61 Scheme 2.5 Equilibrium between 2.6 and its trans isomer ................................................................................. 65 Scheme 2.6 Attempted trapping of a Pt(IV) intermediate using the sterically bulky 2,4,6-trimethylphenyliodide. ...................................................................................................................................... 68 Scheme 2.7 A. Oxidative addition of chelating aryl halide to trap the cyclometallated Pt(IV) complex  2.18. B. ORTEP depiction of the solid-state structure of 2.18 (thermal ellipsoids  are set at 50% probability, solvent molecules have been removed for clarity). The crystal shows substitutional disorder with respect to the methyl and iodide positions, the  structure shown is the major occupancy isomer (0.8:0.2). ......................................................................... 68 Scheme 2.8 Reaction between 2.19 and PhI showing the reported reaction from Kistner et al. .................. 69 Scheme 2.9 Synthesis of Mono (2.21 and 2.22) and bisphosphine complexes (2.23) .................................. 70 Scheme 2.10 Possible mechanisms for the observed products in the reactions between phosphine complexes 2.21\/2.22 and PhI. ........................................................................................................................ 76  Scheme 3.1. A: structures of an NHC and diazaboryl anion. B: Synthesis of a diazaboryllithium compound. ......................................................................................................................................................... 80 Scheme 3.2. Halogen abstraction from a Pt(II) boryl complex showing the formation and stabilisation  of an unsaturated T-shaped complex .......................................................................................................... 81 Scheme 3.3. C-H borylation of Csp2-H bonds via a chiral diazaboryl iridium catalyst ................................... 82 Scheme 3.4. Proposed general structure of an NHC-NHB ligand precursor and the proposed  NHC-NHB metal complex. .............................................................................................................................. 83 Scheme 3.5 Retrosynthetic analysis of the target NHC-NHB ligand via different fragmentation  patterns. ............................................................................................................................................................. 84 Scheme 3.6. Synthesis of compounds 3.1-3.8 ..................................................................................................... 85 Scheme 3.7. Synthesis of compounds 3.7-3.14 ................................................................................................... 86 Scheme 3.8. ORTEP depiction of the solid-state stricture of compound 3.13 (ellipsoids are set  50% probability, minor portions of disorder have been omitted for clarity) .............................................. 87 Scheme 3.9 General depiction of the synthesis of an NHC-NHB precursor ligand and  coordination to platinum. ................................................................................................................................. 88 xx  Scheme 3.10 Scheme for the insertion of PhCl2B into the diamine backbone of 3.13 and  1 H NMR spectra of 3.13 (CDCl3, bottom), reaction mixture (dcm-d2, middle) and crystals obtained from the reaction mixture (dcm-d2, top). ....................................................................................................... 90 Scheme 3.11 General schematic for the Intended method of coordination of the  NHC-NHB ligand to platinum. ......................................................................................................................... 92 Scheme 3.12 Synthesis of Silver dicarbene complex 3.22. Attempted insertion of Me2SnCl2  into the diamine backbone of the silver dicarbene complex 3.22. 1H NMR spectrum  (Toluene-d8, 400 MHz, 25 \u00b0C) of the reaction mixture after 18 hours at 80 \u00b0C....................................... 93 Scheme 3.13 Control experiment showing the effect of NH4Cl on the silver dicarbene complex 3.22. Stacked 1H NMR spectra of the reaction mixture between 3.22, Me2SnCl2 and NEt3 (bottom)  and the control experiment between 3.22 and NH4Cl (top) ...................................................................... 94 Scheme 3.14 H2 activation at a ruthenium NHC diamine complex. .................................................................. 95 Scheme 3.15. 1H NMR spectrum (acetone-d6, 400 MHz, 25 \u00b0C) of the reaction mixture  between 3.13 and Me4Pt2(SMe2)2 after 18 h at 55 \u00b0C. ............................................................................... 96 Scheme 3.16 Synthetic scheme for the synthesis of tridentate C-2 bound complex 3.29 from  3.22 and PtClMe(SMe2)2 and AgPF6. 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C) of the reaction between 3.22 and PtClMe(SMe2)2 after 2 hours at 50 \u00b0C. ........................................................ 101 Scheme 3.17 Deprotonation of 3.29 by KHMDS to give the amido complex 3.30. ...................................... 102 Scheme 3.18 Attempted double C-H activation of 3.13 to give a bimetallic platinum complex bridged  by an imidazolium core ................................................................................................................................. 104 Scheme 3.19 Attempted C-H activation of the C-2 proton of 3.28 with (py)2PtMe2 to give  bimetallic complex 3.32 ................................................................................................................................ 104 Scheme 3.20 Deprotonation of 3.28 with NaH or KOtBu in benzene-d6 or THF-d8 to give  bimetallic complex 3.31\/32 ........................................................................................................................... 105 Scheme 3.21 PEPPSI like synthesis of bimetallic platinum complexes. ........................................................ 106 Scheme 3.22 Reaction scheme for the deprotonation of 3.28 with KOtBu in toluene-d8.  1H NMR spectrum (Toluene-d8, 400 MHz, 25 C) showing the disappearance of the downfield  shifted C-2 proton. Some amount of complex 3.29 was carried over from the previous step  but did not react .............................................................................................................................................. 107 Scheme 3.23 Representation of the deprotonation equilibrium of 3.28 by one equivalent of  KHMDS in THF-d8. 1H NMR spectrum (THF-d8, 400 MHz, 25 \u00b0C)  showing the broadened  signals of the CH2 backbone and C-2 protons. .......................................................................................... 108 Scheme 3.24 Deprotonation of 3.28 with 2.2 equivalents of KHMDS in THF-d8 showing the  multiple deprotonations have occurred to form a platinate complexes. 1H NMR  spectrum (THF-d8, 400 MHz, 25 \u00b0C) showing the backbone CH2 protons characteristic of N-H deprotonation. ................................................................................................................................................. 109 Scheme 3.25 synthesis of (hetero)bimetallic complexes 3.40 ......................................................................... 110  Scheme 4.1 C-H activation of 4-methylpyridine by an early-late heterobimetallic  cobalt-zirconium complex. ............................................................................................................................ 114 Scheme 4.2 Attempted oxidative addition of phenyl iodide to 4.1 ................................................................... 117 Scheme 4.3 synthesis of 4.1 and 4.2 and ORTEP depictions of the solid-state structures  of 4.1 and 4.2. ................................................................................................................................................. 118 Scheme 4.4 Reported synthesis of 4.1 by Appleton and co-workers. ............................................................ 119 Scheme 4.5 Reaction between 4.1 and MeCN-d3 ............................................................................................. 119 Scheme 4.6 Reaction of 4.1 to give 4.4 and 4.2. ............................................................................................... 138 Scheme 4.7 Reaction showing the dissociation of pyridine to form the T-shaped complex 4.7 ................. 141 Scheme 4.8 Reaction steps used to describe the COPASI model. ................................................................ 148 Scheme 4.9 Synthesis of deuterated analogue 4.1-d10..................................................................................... 154 xxi  Scheme 4.10 Synthesis of para substituted platinum pyridine complexes, 4.1-CF3 and  4.1-NMe2 .......................................................................................................................................................... 157 Scheme 4.11 Reaction coordinate showing the dissociation of pyridine from 4.1 to give  complexes 4.7 and 4.8 with subsequent reaction to complexes 4.9 and 4.9\u2019. Calculations  performed with the DLPNO-CCSD functional and def2-TZVP basis set. .............................................. 162 Scheme 4.12 Reaction coordinate showing calculated intermediates 4.10-4.13 and transition  states 4.11-TS and 4.12-TS. Calculations performed with the DLPNO-CCSD functional and  def2-TZVP basis set ...................................................................................................................................... 163 Scheme 4.13 Reaction coordinate showing the higher energy pathway for the formation of  4.4. Calculations performed with the DLPNO-CCSD functional and def2-TZVP basis set ................. 164 Scheme 4.14 Reaction coordinate showing the two possible pathways for the C-H activation  of 4.4 -> 4.2. Calculations were carried out using the DLPNO-CCSD functional and  def2-TZVP basis set ..................................................................................................................................... 166 Scheme 4.15 Reaction between 4.2 and adamantane carboxylic acid to give compound 4.24 ................. 172 Scheme 4.16  Proposed equilibrium between k1 and k2 coordination of the adamantane carboxylate ligand ................................................................................................................................................................ 174 Scheme 4.17 Proposed reactivity of aryl halides with 4.2 to give complexes 4.26 and 4.27. ..................... 174  Scheme 5.1 Reaction showing the two Pt(IV) aryl complexes detected in solution by 1H NMR spectroscopy. .................................................................................................................................................. 179 Scheme 5.2 Reaction between para substituted phenyl iodide and para substituted pyridine  Pt(II) NHC complexes .................................................................................................................................... 179 Scheme 5.3 Reaction showing two different possible pathways to access a chelating  NHC-NHB platinum(II) complex. ................................................................................................................. 180 Scheme 5.4 C-H activation of the ligand precursor 3.14 to give a 5:1 mixture of 5.10 (aNHC)  and 5.11 (NHC). ............................................................................................................................................. 181 Scheme 5.5 Deprotonation of complex 5.10 to give carbanion 5.12, followed by salt  metathesis with a metal salt to give (hetero)bimetallic complex 5.13 .................................................... 181 Scheme 5.6  Representation of the sequential C-H activation to form polymeric chain of  platinum and pyridine. ................................................................................................................................... 183     xxii  List of Symbols  \u00b0 Angle (degrees) \u03c3* Anti-bonding sigma orbital \u00b5 Bridging ligands \u0394H\u2021 Change in enthalpy (transition state) \u0394S\u2021 Change in entropy (transition state) \u0394G\u2021 Change in Gibbs energy (transition state) COPASI COmplex PAthway SImulator \u00b0C Degrees Celsius \uf04b Denticity d doublet (spectroscopy); d-orbital > Greater than \uf0544 Index for tetrahedral or square planar geometry \uf0545 Index for square based pyramidal or < Less than \u03c0 Orbital; backdonation; p p-orbital \u03c3 Sigma orbital; sigma bond   xxiii  List of Abbreviations aNHC Abnormal N-Heterocyclic Carbene AMLA Assisted Metal Ligand Activation B2Pin2 Bis(pinacolato)diboron BDE  Bond Dissociation Energy  CMD Cyclometallation deprotonation CT1 Charge Transfer 1 CT2 Charge Transfer 2 CP Cyclopentadienyl ligand CP* pentamethyl cyclopentadienyl ligand DFT Density Functional Theory Dipp 2,6-diisopropylphenyl ESI-MS Electron Spray Ionization Mass Spectrometry ES Electrophilic Substitution E2 Elimination, bimolecular EMAC Extended Metal Atom Chain FMOC-Cl 9-Fluorenylmethyloxycarboyl chloride FMOC Fluorenylmethyloxycarbonyl FLP Frustrated Lewis Pair GC-MS Gas Chromatography Mass Spectrometry HBPin pinacol borane IPr 1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene IMes 1,3-Bis(2,4,6-trimethylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene MA\u03c3BM Metal Assisted sigma Bond Metathesis Mes 2,4,6-trimethylphenyl xxiv  NHC N-Heterocyclic Carbene NHC-NHB N-Heterocyclic carbene-N-Heterocyclic boryl NMR Nuclear Magnetic Resonance  NOE Nuclear Overhauser effect NOESY Nuclear Overhauser effect spectroscopy OA Oxidative Addition OATS Oxidative Addition Transition State OHM Oxidative Hydride Migration PCP Tridentate Phosphorus-carbon-Phosphorus ligand PEPPSI Pyridine-enhanced Precatalyst Preparation stabilisation and initiation PhI Phenyl Iodide POCOP Tridentate Phosphorus-oxygen-Carbon-Oxygen-Phosphorus ligand Py Pyridine RE Reductive Elimination SBM Sigma Bond Metathesis \u03c3-CAM sigma Complex Assisted Metathesis SN2 Substitution nucleophilic, bimolecular TRIR Time Resolved Infrared Spectroscopy TS Transition State TON Turn Over Number Xs excess xxv  Acknowledgements First and foremost, I want to thank my advisor Prof. Jennifer Love for giving me the opportunity to embark on my PhD journey. You have given me the space to develop not only as a scientist but also a person and for that I am truly thankful. You trusted me to be creative in my science and to discover things I thought were worthwhile pursuing. I always felt that you had my back, which is reassuring when dealing with the pressures of grad life. You supported me when I needed it. Thank you. To my supervisory committee Prof. Laurel Schafer, Prof. Jason Hein, and Prof. Glenn Sammis. I cannot express enough how crucial each of you have been in helping me to the end. It truly takes a village and your friendly and caring natures have made this difficult journey possible, and for that I will be forever grateful. I will have fond memories of our chats about chemistry and everything in between.  I want to thank those who took the time to read my thesis: Dr. Eric Bowes, Dr. Dawson Beattie, Dr. Weiling Chiu, Ben Nadeau and Prof Jennifer Love. Writing is something I struggle with and each of you have helped make this thesis better. To the Love group members of old and new, I thank you for being good people, you have taught me much and I couldn\u2019t have gotten to this point without you. Special thanks go to Dr. Weiling Chiu, Nan Zhang, Ben Nadaeu, Cal Patel, Ruvini Kirihettiliyanage and Dr Maximillian Marx.  To Dr Eric Bowes, I thank you for being a good friend and mentor. I came into the group not knowing anything about platinum chemistry and you helped me get up to speed. You helped me publish my first paper and made sure it was a piece of work I could be proud off. I will always remember our climbing sessions at the aviary and look forward to going climbing together again soon.  To Dr Dawson Beattie, I will always be grateful to you for pushing me to be better and to think creatively and most importantly to laugh. You helped me through hard times, and I knew I could always count on you for friendship and advice. I will always remember the hilarious moment in the aviary climbing gym\u2026 Clipping!... NOPE! To Braulio Puerta, Alex Harrison, Devon Lowe, and Prof. Roland Roesler. You made me feel incredibly welcome when I joined UofC and I have immensely enjoyed discussing chemistry together along with sharing the occasional beer. You will be greatly missed. xxvi  I would like to thank the facilities personnel at both UBC and UofC that have allowed me to carry out my science with little interruption. A special thanks go to the NMR staff Dr. Maria Erzhova, Dr. Michelle Forgeron and Wade White, I am truly indebted to you for all your teaching and expertise that have been crucial to the progress of my science. I also like to thank Dr Benjamin Gelfand and Dr. Brian Patrick who collected and refined crystallographic data throughout my PhD. I would like to thank Mark Toonen and Nelzon Cruz for all their help with setting up our new lab at UofC.  I am appreciative to both UBC and UofC for access to great facilities, thankful to NSERC CREATE for funding as well as the opportunity to the develop myself as a chemist in industry. I thank Everyone at NOVA chemicals for a great eight-month internship which I will not forget and is certainly one my favourite experiences over the last 5 years. Finally, I want to thank all my friends, particularly those in the climbing community, that I have met since coming to Canada, you truly made me feel at home. To my mum Susan and my brother Seb, I couldn\u2019t have done this without you. Your unwavering belief in my ability to complete the PhD kept me motivated and focused to achieve all that I wanted.    xxvii  Dedication To Angus and Simone Reid   I will not be able to celebrate my achievement with you, but I hope that you went with the knowledge of the profound impact you left on my life.28  Chapter 1: Introduction The development of methods for the transformation of hydrocarbons, specifically methane, into more valuable molecules such as methanol are an important target within the industrial and academic setting. With ever growing concerns about global warming, a means to convert gaseous hydrocarbons such as methane are becoming more important than ever. Methane emissions are largely a result of human activity and is dominated by the agricultural as well as the fossil fuel industry. While methane made up 14% of green-house gas emissions in 2004, the atmospheric impact of methane is about 25 times greater than CO2 over a 100-year period.1  Currently about 2% (146 billion cubic metres) of global methane emissions from the fossil fuel industry are flared into the atmosphere as CO2.2 A significant proportion of the remaining methane budget is attributed to 50% of the worlds production of H2 via the steam-methane reformation reaction.3 Although, this process forms useful dihydrogen, which can be used in a variety of applications. The process is energy intensive and produces CO and CO2 as byproducts leading to further greenhouse gas emissions. Other than steam methane reformation very few other chemical processes rely on methane as a feedstock. This can be attributed to the high energetic cost required for breaking the C-H bond in methane. Not only is the C-H bond in methane difficult to break it is generally only achieved with the use of expensive and rare noble metals such as Ir, Rh, Pt and Pd. Furthermore, the products from methane reactions also pose a challenge in that they are usually more reactive than methane itself, this has the effect of requiring high pressures and temperatures as well as harsh reaction conditions to force the reaction towards products. However, over the past 20 years significant advancements have been made in both the fundamental and application-based understanding of homogenous reactions involving methane and higher order hydrocarbons. The following sections outline the current understanding of C-H activation mechanisms for alkanes, a brief historical overview of the use of platinum in reactions pertinent to methane functionalisation and, a brief description of a proposed catalytic cycle for methane functionalisation.  29  1.1 Mechanisms of C-H activation for alkanes. As a rapidly growing field across all areas of chemistry, C-H activation\/functionalisation is being used to access a wide range of important molecular targets. Of particular interest is the development of a sustainable methodology for alkane functionalisation as a means for reducing hydrocarbon emissions.  The replacement of a hydrogen atom in a carbon-hydrogen (C-H) bond by another element or functional group brings together collaborations from all areas of chemistry. The replacement of the hydrogen atom in methane is so important that it has been highlighted as one of the grand challenges of chemistry.4,5 The interest stems from the high atom economy these transformations provide along with the potential environmental benefits of using alkanes as chemical building blocks. The two main challenges regarding these reactions are (1) poor selectivity, due the abundance of C-H bonds with similar bond dissociation energies and reactivity, and (2) the chemical inertness of hydrocarbon C-H bonds, often due to the inherent low polarity. Furthermore, the potential atom economy of C-H activation\/functionalisation reactions remains limited by the need for stoichiometric reagents, such as oxidants, which are critical in most reactions and hamper uptake by industry. Notwithstanding these challenges, the field has thrived in the last 20 years, with a considerable number of new methods being developed for the activation and functionalisation of a wide variety of C-H bonds. Several reviews covering reactivity tailored towards complex target molecules have been published.6\u201314 Although significantly less well understood, the increasing usage of Earth-abundant metals in catalyst development has not escaped the C-H functionalisation community and reviews highlighting their importance are available.15\u201318 Early transition metals have also proven effective in C-H bond activation and functionalisation.19\u201321 Developments towards water-stable reactivity,22 as well  as electrochemical reactions, are also prevalent.23 Furthermore, a myriad of computational work regarding the breaking of C-H bonds has also been described.24 Since Labinger and Bercaw reviewed the mechanisms of C-H activation in 2002,25 there have been significant developments in C-H activation, including new mechanisms (e.g., ambiphilic metal ligand activation (AMLA) and concerted metalation deprotonation (CMD)), breakthroughs in the isolation of \u03c3C-H complexes, catalytically relevant examples of hydrocarbon functionalisation, and an expanded understanding of these reactions and their mechanisms. Based on the work of many researchers outlined in the text below, it can be argued that C-H activation should not be categorised based on metal\/ligand combinations, but rather the degree 30  of net charge transfer between the fragments involved in the transition state (electrophilic, ambiphilic, nucleophilic, Figure 1.1).  While C-H bond reactivity covers a large variety of C-H bonds with differing bond dissociation energies (BDEs), the focus will be on processes involved in breaking C-H bonds of alkanes and the nuances that govern their reactivity. Then a discussion on the major differences in the mechanisms of C-H activation, which can be classified as ambiphilic metal-ligand activation or concerted metallation deprotonation (AMLA or CMD), oxidative addition (OA), sigma bond metathesis and 1,2-addition will be presented. Furthermore, the use of terminology, such as the differences between functionalisation and activation as well as sigma vs agostic interactions will also be discussed. The  classical representations of the mechanisms will be used to break down the transition states involved in each mechanism, to maintain clarity and ease of understanding. Although it is important to realise that a continuum of reactivity is a more accurate descriptor of how to categorise the mechanisms, although it is not the most intuitive, especially without the use of computational methods.  Ess, Goddard, and Periana challenged the conventional classification of C-H activation mechanisms in a computational study.26 The authors deconstructed the classical perception that C-H activation reactions are segregated into specific mechanisms based on the type of metal (i.e. late or early), the ligands, and the number of atoms involved in the transition state. They provided a detailed energy decomposition analysis of the transition states and reaction pathways involved in C-H activation reactions. This showed that the factor dictating the mechanism is the overall degree of charge transfer from a metal d\u03c0-orbital to the C-H \u03c3*-orbital (CT1, reverse charge transfer, Figure 1.1) and the charge transfer from the C-H \u03c3-orbital to a metal d\u03c3-orbital (CT2, forward charge transfer, Figure 1.1). A key conclusion is that instead of segregated mechanisms, a continuum of reactivity exists ranging from electrophilic, through ambiphilic to nucleophilic in character. The traditional mechanisms can therefore be categorised on this scale by the overall difference in charge transfer during the transition state and not, for example, the overall charge of the complex or formal oxidation state of the metal involved. This concept had loosely been applied by Cundari, Macgregor and Davies some years prior (Figure 1.1).27,28  31   Figure 1.1 Representation of the continuum of charge transfer in C-H activation reaction pathways. 1.1.1 C-H Activation vs Functionalisation Terminology is an important part of chemistry and defines the way that chemists converse with each other effectively. Within the field of C-H bond cleavage, both the terms \u201cactivation\u201d and \u201cfunctionalisation\u201d are becoming increasingly popular in the literature, and in some cases are being used inconsistently. It is important to distinguish the two definitions for the sake of continuity in the following text.  C-H Activation \u2013 A specific mechanistic step that involves the direct cleavage of a C-H bond that occurs due to an interaction with a transition metal, where the result is a new carbon-metal bond.  C-H Functionalisation \u2013 A process involving the replacement of a C-H bond by another element or functional group but where the functionalisation is most often preceded by a C-H activation event.  It is also noteworthy that in the context of breaking a C-H bond the term \u201cactivation\u201d should not refer to the elongation or change in polarity of a C-H bond upon coordination to a transition metal. This could be misconstrued, as the word \u201cactivation\u201d implies that the C-H bond is in an altered state. While this statement is true, the new carbon-metal fragment that is generated upon cleavage can also be described as an \u201cactivated\u201d state. It is this definition that has become the accepted convention within the organometallic field. 1.1.2 Sigma and agostic complexes Sigma and agostic interactions have been established as the principle step prior to C-H bond activation.29 It must be recognised that in almost all cases these interactions are crucial for activating a C-H bond by stabilising high energy metal intermediates and polarising the C-H bond to allow for cleavage to occur. Both terms describe the same interaction: the donation of electron density from the \u03c3-orbital of a C-H bond into an empty d-orbital on a transition metal. The difference, however, is in the connectivity of the molecule undergoing the interaction. Sigma 32  complexes are classified as C-H bonds undergoing this interaction through an intermolecular approach. An agostic complex, a term coined by Brookhart and Green,30 is therefore classified as an intramolecular approach by a C-H bond that is held in the coordination sphere of the metal due to another primary metal-ligand interaction.31,32 Sigma interactions are weak and as such these complexes are generally not isolable. However, time-resolved infrared spectroscopy (TRIR) has been used to show the existence of such species.33\u201335 In 2009 the first methane sigma complex was fully characterised in solution by Goldberg and co-workers in what was then an extremely rare example (Figure 1.2 a).36 Multiple sigma and agostic interactions have also been reported, notably by Ball and co-workers.37 one example of a multiple agostic interaction is the nickel complex shown by Beattie and co-workers (Figure 1.2 b).38 Further reports of methane and longer (cyclo)alkanes forming sigma complexes have since been shown and supported with kinetic, computational and X-ray experiments.37,39\u201342 A detailed collection on the characterisation of sigma complexes has been published.29   Figure 1.2 Examples of sigma and agostic complexes.a: First methane sigma complex fully characterised in situ. b: Agostic complex featuring two agostic interactions. 1.1.3 Mechanisms of C-H activation C-H Activation processes have historically been separated into three or four different classical mechanisms. Each mechanism can be described by a variety of factors such as whether the metal is an early or late transition metal, whether the formal oxidation state of the metal changes, if a ligand is involved during the transition state of the bond cleaving event and or the type of ligand involved. As discussed above, and highlighted by Ess et al,  the notion of separating the mechanisms is changing as more and more examples are discovered that contradict these descriptors 26  The mechanistic nuances that will be covered are based on activation of alkanes and will be grouped according to the historical four categories: electrophilic, oxidative addition, sigma bond metathesis and 1,2-addition mechanisms. The mechanisms are grouped under these historical 33  categories for clarity and to maintain focus on the steps involved in the breaking of the C-H bond in each respective mechanism.  The electrophilic mechanisms, namely substitution\/CMD\/AMLA, generally occur at electropositive late transition metal complexes. In these systems the oxidation state of the metal does not change during the C-H activation step. Typically, carboxylate ligands are used as an intramolecular base to deprotonate the alkane. Oxidative addition, one of the most studied fundamental transformations in organometallic chemistry, is generally reserved for low valent electron rich metal complexes featuring strongly donating L-type (L = neutral) ligands, such as those often seen in dehydrogenation chemistry. In this mechanism the C-H bond breaks and two M-X (X = C, H) bonds are formed, increasing the metal\u2019s oxidation state and coordination number by two.   Sigma bond metathesis (SBM) generally involves the early transition metals when d electrons are not available for oxidative addition. A four-centred transition state is operative in which the H atom from a C-H bond is transferred to an existing M-C bond. The H atom acceptor normally dissociates from the metal complex upon acceptance of the H atom. In sigma bond metathesis systems, the oxidation state does not change throughout the reaction. The receiving ligand is generally another hydrocarbyl or hydride fragment but can also be a main group substituent such a boryl or silyl. 1,2-Addition across a multiple bond is generally associated with early transition metals. In this mechanism, the hydrogen atom from the C-H fragment adds across a double or triple bond, thereby reducing the atom bound to the metal and forming a new M-C bond in the process. These reactions are most often seen in metals such as Zr and Ti, featuring multiply bonded carbon or heteroatoms. 34  1.1.3.1 Electrophilic (ES and AMLA\/CMD)   Figure 1.3 Electrophilic mechanisms. a: Three most common transition states found in electrophilic C-H activation. b: simplified depiction of the AMLA(6) mechanism. c: DFT calculated mechanism for the C-H activation of methane at (NHC)2Pd(II) via the AMLA(6)\/CMD transition state. The electrophilic mechanism of C-H activation first came to light with the pioneering work of Shilov, which was later expanded upon by Bercaw, Labinger and many others.43\u201345 The guiding requirement for a C-H activation to be considered as an electrophilic mechanism is the abstraction of a proton by an available lone pair on a neighbouring heteroatom during the transition state (Figure 1.3a). This key feature also distinguishes the electrophilic substitution (ES) mechanism from the sigma bond metathesis mechanisms, which also have a four centred transition state but no lone pair involvement. In electrophilic systems the formal oxidation state of the metal remains constant throughout the process. Generally, the formation of a ring that includes the metal, the C-H fragment and the heteroatom is present during the transition state (Figure 1.3c). However, examples without ring formation have also been calculated as possible pathways.46  The current classifications related to alkane C-H activation mechanisms are the electrophilic substitution, the AMLA(4) and AMLA(6)\/CMD mechanisms (Figure 1.3a), which have been reviewed by Goddard, Ess and Periana.47 A couple other mechanism have also been reported 35  that could be considered subsets of the electrophilic mechanisms but as of yet no alkane C-H activation has been reported to proceed via them and will therefore not be covered.48,49  Arguably the most important sub field of C-H activation for transformations related to pharmaceutical and agrochemical molecules are AMLA, coined by Macgregor and Davis50, and CMD, coined by Fagnou.51 Both terms describe the base assisted cleavage of a C-H bond, a strategy that has become increasingly useful in the quest for a homogenous catalytic process for the activation of alkanes.46,52 During AMLA\/CMD, a late transition metal (Ir, Pd, Pt etc) forms a sigma bond with an alkane (Figure 1.3c, 1.1).46 The formation of the sigma complex polarises the C-H bond, thereby increasing the acidity of the proton. This allows for a weak base, classically a carboxylate ligand, to deprotonate the hydrocarbon leading to a new metal-carbon bond and a carboxylic acid (Figure 1.3c, 1.2 \u2192 1.3).  Computational studies have been instrumental in teasing apart the smallest of details regarding C-H activation. For example, while a significant proportion of complexes studied for AMLA\/CMD have been some variation of an electropositive Ir(III) metal complex, many of the transition states have been assigned as ambiphilic in character (to be both electrophilic and nucleophilic). This seems counter intuitive, but the net transfer of electrons between the metal, the internal base and the C-H bond is small, and it is this balance of charge density that has resulted in the term AMLA being assigned to this process. Further calculations have also shown that the energy associated with distorting the geometry of the metal complex upon approach of the C-H bond (distortion energy) dictates whether the AMLA(4) or AMLA(6) transition state will be favourable.47 Another factor dictating the mechanism is the M-H interaction: as it becomes more pronounced, the transition state becomes increasingly more oxidative in character, showing the continuum between the electrophilic and oxidative addition mechanisms.28 Consequently, the main difference between the AMLA and CMD mechanisms refers to where they fall on the continuum with respect to each other. AMLA can be viewed as more ambiphilic whereas CMD is more nucleophilic or oxidative. Another important difference lies in the number of transition states with AMLA processes possessing two transition states and CMD only one. A review by Macgregor and Davies explores some of these differences.53 As more details are revealed by computational studies, ligand design becomes increasingly more relevant. With the understanding of charge transfer and geometrical constraints within the transition state, more elaborate and finely tuned ligands can be designed that address potential 36  shortcomings. For instance, the Strassner group has for the better part of two decades been describing the activation of methane and other small alkanes by employing a chelating bis-N-heterocyclic carbene palladium complex that operates under the AMLA\/CMD mechanism (Figure 1.3C, 1.1).52,54,55 Considering the classical descriptions for C-H activation reactions, one could expect this complex to be susceptible to oxidative addition due to the strongly donating carbenes which impart considerable sigma donation with little backdonation increasing the electron density on the metal.56,57 However, the oxidative addition pathway was calculated to be 28.3 kcal\/mol higher in energy than the AMLA(6) mechanism (AMLA(4) not calculated). A third transition state involves the C-H bond being deprotonated by a trifluoroacetato group in an intermolecular fashion; the authors describe this transition state as intermolecular neutral and it was calculated to be 8.3 kcal\/mol higher in energy than the AMLA(6) mechanism (Figure 1.4). Interestingly, the three calculated transition states further illustrate the mechanistic continuum. From the calculated bond distances, it can be seen that moving between the transition states and as they become more oxidative in character, the M-H distance gets smaller until a M-H bond is formed (Figure 1.4a: 2.16\u00c5 > b: 2.08\u00c5 > c: 1.57\u00c5). Similarly, the O-H interaction between the carboxylate oxygen and the C-H bond also decreases towards the oxidative addition transition state until the interaction becomes negligible. Charge transfer stabilisation energies have not been calculated on these transition states and can therefore not be given a specific position on the continuum. Although the differences in energy between the transition states in Figure 1.4 are large and indicate a preference for the AMLA\/CMD mechanism, caution must be used when assigning a mechanism to a process that has not undergone extensive kinetic and or computational modelling. From this example alone we can see the diversity of potential mechanisms at play and these three mechanisms could easily be closer in energy with modified ligands or different metals. 37    Figure 1.4 Calculated transition states for the C-H activation of methane at Pd(II). All energies are relative to sigma complex 1.1, Figure 1.3. Pd-H red dashed lines in A and B do not represent an interaction, instead are representative of distance to the metal. Further developments from the Strassner group have included the activation and functionalisation of propanes to a variety of products which was hampered by poor selectivity.58,59 Ligands containing charge-shift bonding may provide improvements in the activity for C-H activation of alkanes as shown in calculations by Ma and Zhang.60 The charge-shift bonding motif in the 2-borabicyclo [1.1.0] but-1(3)-ene ligand scaffold imparts more electron density onto the palladium centre compared to the bis-NHC scaffold and results in a smaller M-C contact during the transition state which in turn lowers the barrier to terminal C-H activation in propane. The electrophilic mechanisms, especially AMLA\/CMD, have been shown to be involved in many C-H activation processes. Active efforts in this area continue and may lead to an industrial process capable of functionalising methane and higher order alkanes in an efficient manner. 38  1.1.3.2 Oxidative addition (OA)   Figure 1.5 Oxidative addition mechanism. a: simplified depiction of the oxidative addition mechanism. b:  Concerted oxidative addition of an alkane to an unsaturated Iridium(I) PCP complex. Oxidative addition is one of the most studied fundamental mechanistic steps in inorganic chemistry. In this mechanism, the formal oxidation state and the coordination number of the metal is increased by two units. It has long been believed that oxidative addition reactions are exclusive to electron rich late transition metals. However, that notion has changed significantly over the last 20 years. Examples of oxidative transition states and intermediates have been calculated for cationic and electron deficient complexes such as those in Shilov type systems.45,61 A recent study, following up on calculations initially carried out by Cundari has shown that strong sigma donor ligands trans to the site of activation increase the barrier to oxidative addition of alkanes versus weakly sigma donating and strongly \u03c0-donating ligands.27,62 It has also been shown that the oxidative addition mechanism is closely linked to that of the sigma bond metathesis mechanism, a mechanism that has been considered to occur exclusively in early transition metals. The findings highlight that the alkyl hydride intermediate for oxidative addition mechanisms can serve as a transition state during some sigma bond metathesis) reaction pathways where a temporary M-H (oxidative addition) interaction exists.63  The concerted mechanism shown in Figure 1.5b (TS 1.5) is the most common pathway for the activation of C-H bonds via oxidative addition. The development of the PCP\/POCOP pincer ligands have revolutionised dehydrogenation chemistry of alkanes and many groups have contributed to this field. Excellent reviews on the intricacies of ligand design and catalytic methods are available.64,65 An example of this dependency can be seen in the chemistry 39  reported by the Goldman group, which shows that steric control enables the fine tuning of energetic barriers to C-H activation.66 Reduction of the steric environment in the active site lowers the activation barrier to C-H activation. However, insufficient steric crowding can lead to multinuclear cluster formation, inhibiting catalysis. The C-H activation barrier was lowered by about 5 kcal\/mol when a single tert-butyl group was replaced with a methyl group. The bulky tert-butyl groups on the phosphines are important for creating an open coordination site trans to the phenyl position allowing for alkane coordination and activation (1.5, Figure 1.5). The alkane can then orientate itself in one of two directions, towards the methyl substituent or towards the tert-butyl with the former being 3 kcal\/mol lower in energy. Subsequent substitution of the tert-butyl groups for methyl substituents does not lower the activation barrier any further but could increase the amount of multinuclear cluster formation.  The transition metal complexes bearing carbon monoxide (CO) ligands have become crucial in understanding oxidative addition reactions of C-H bonds. Photolysis can be used to readily dissociate a CO ligand to create an open coordination site which allows for the binding of a cycloalkane via a sigma complex. Nano-second time-resolved infrared spectroscopy (TR-IR) has been key in determining experimental numbers for oxidative addition of C-H bonds to support the ever-growing catalogue of computationally derived data. George and co-workers have been at the forefront of this effort  using TR-IR to show that the oxidative addition of cycloalkanes is a process which has many mechanistic features. For example, once coordinated via a sigma complex the C-H bonds around a cycloalkane become chemically inequivalent. This has a particularly interesting effect when considering cycloalkanes with a ring size greater than 8, whereby the isomerisation between sigma complexes becomes more favourable than oxidative addition of the C-H bond.35 Furthermore, lower barriers to oxidative addition occur when the sigma complex is formed from the interaction of an equatorial C-H bond rather than an axial one. George and co-workers suggest this occurs as a result of lowered steric congestion. However, equatorial bonds are shorter than axial ones which leads to higher barriers of sigma complex formation and is due to less efficient donation of the electrons to the metal centre.35 Although isomerisation between \u03c3-complexes of cycloalkanes can impact the rate at which C-H activation occurs this phenomenon does not affect smaller ring sizes such as cyclopentane and cyclo hexane. In general, some conclusions that can be made regarding the activation of alkane C-H bonds are that if primary C-H bonds exist they are activated more favourably compared to secondary C-H despite their higher BDE. The influence of the spectator ligands, such as Cp and Cp* have 40  a significant effect on the activation barriers of straight chain alkanes as well as cycloalkanes making ligand design and choice an important variable. 1.1.3.3 Sigma bond metathesis (SBM\/MA\u03c3BM\/OATS\/OHM\/\u03c3-CAM)   Figure 1.6 Sigma bond metathesis mechanisms. a: transition states encountered during the different sigma bond metathesis mechanisms; green dots represent the ring critical points of the interaction which show the point of minimum electron density in the interaction.67 b: simplified reaction mechanism for MA\u03c3BM reaction. c: Hartwig\u2019s alkane borylation reaction pathway. Traditionally sigma bond metathesis reactions of hydrocarbons occur between two hydrocarbyl fragments, a hydrocarbyl and metal hydride or a hydrocarbyl and main group element at early transition metals, lanthanide and actinide metals.68,69 Much of the ground breaking work has been carried out by Watson and Bercaw.70\u201373 While early metals are commonly associated with this mechanism, late transition metals have also been found to operate via similar transition states.64 The simplistic picture of this mechanism is the transfer of a hydrogen atom between hydrocarbyl or hydride units in a 4 centre transition state (Figure 1.6, SBM). However, the reality is more complicated, and several mechanisms exist which can be differentiated from each other based on the geometry of the atoms involved in the transition state. Akin to the ES\/CMD\/AMLA mechanisms, the sigma bond metathesis mechanisms are fundamentally similar and can be seen as a being a part of a continuum. Although a sigma complex is normally required for the 41  activation of a C-H bond prior to the actual cleavage event, the sigma bond metathesis mechanisms do not necessarily have to proceed through one.74  The transition states of the sigma bond metathesis reaction path are somewhat convoluted and several groups have found differences in the degree of \u201coxidation\u201d of the metal during the transition state (Figure 6A).67 These examples range from having no metal hydrogen interaction (SBM coined by Bercaw), some degree of metal hydrogen interaction, that is metal assisted sigma bond metathesis (MA\u03c3BM coined by Hall and Hartwig)75,76, \u03c3-complex assisted metathesis (\u03c3-CAM coined by Perutz)77,78 and oxidatively added transition state (OATS coined by Lin)79; to a full metal hydride during the transition state, called oxidative hydrogen migration (OHM coined by Oxgaard)80. Vastine and Hall provided an excellent in depth breakdown of the transition states of each.67 C-H activation reactions involving the sigma bond metathesis mechanism are a highly active area of research, with many researchers publishing in depth computational studies of the diverse range of transition states and pathways these reactions proceed through. It is noteworthy to mention that without computational means, the difference between these mechanisms can be difficult to discern with experimental techniques.67  While the MA\u03c3BM mechanism is a subset of sigma bond metathesis it has its own nuances.77 Uniquely, it involves a main group element such as boron. Because boron-hydrogen bonds are able to form stable \u03c3-complexes at a variety of transition metals,81 the transfer of the hydrogen atom from an alkane to the boryl becomes facile as the hydrogen is shuttled between the carbon atom and the boron atom through the sigma complexes of each fragment (Figure 1.6, 1.8).  The MA\u03c3BM and \u03c3-CAM mechanisms have common features, but meaningful differences. Both mechanisms utilise sigma complexes during the transition state as well as an interaction of the metal to the hydrogen undergoing activation. However, the difference between the two lies in the interaction of the hydrogen atom with the two pendant fragments which the hydrogen is being transferred to and from. In the case of the \u03c3-CAM mechanism, there is no interaction of the hydrogen atom and the receiving atom in the TS. On the other hand, the MA\u03c3BM mechanism does have an interaction between the transferring hydrogen atom and the receiving atom (Figure 6A, \u03c3-CAM and MA\u03c3BM). The MA\u03c3BM mechanism is involved in one of the most successful alkane functionalisation reactions developed to date: the borylation of unbranched alkanes which have a multitude of uses, including Suzuki cross-couplings.75,82  42  The Hartwig group has been one of the leaders in the development of alkane borylation chemistry for several decades.82\u201385 They followed up on their original reports of stoichiometric and catalytic alkane borylation chemistry with a series of computational and kinetic investigations detailing the mechanism of the process.75,76 They found that B2Pin2 (bis(pinacolato)diboron) reacts faster than HBPin in reactions with alkanes and that the process slowed in the presence of added HBPin. The addition of excess HBPin which slowed the rates of borylation, and the inverse order in HBPin, confirmed that reversible dissociation of HBPin to generate a reactive 16e complex precedes the activation of an alkane.75 However, it must be noted that these results should be considered tentative, as side reactions involving the formation of other rhodium species did occur. Importantly, in this system the C-H bond cleavage is not rate determining and, as such, much information regarding the transition state cannot be acquired from experimental data alone. Here, again, computational studies have proven to be vital in unravelling the smallest of details regarding the mechanism. It was calculated that a MA\u03c3BM mechanism is favoured over other mechanisms which has been reported by other groups as well.86 Furthermore, the empty Bpin p-orbital was shown to be involved in the transition state with regards to either abstraction of the resulting hydride or direct interaction with the C-H bond during cleavage, further supporting the notion of the MA\u03c3BM mechanism being operative.76 This was again supported by a significant degree of B-H bonding in the transition state which helps weaken the C-H bond. More recently in 2016, Sanford and Mindiola independently developed catalytic systems for the borylation of methane utilising similar boryl species.87,88 Although the sigma bond metathesis mechanism holds some resemblance to the carbene\/imido C-H activation mechanisms, and the orbital interactions are similar, the degree of back-bonding for the boryl species is much lower.75 Legzdins and co-workers have also shown that tungsten nitrosyl complexes are active for alkane metathesis with longer alkyl chains being ever more readily activated.89 Increased reactivity was achieved by substituting tungsten for molybdenum.90 Even more promising is the selectivity tungsten nitrosyl complexes show for primary C-H bonds over C-X bonds in the same molecule. Such selectivity might allow for late-stage functionalisation of complex molecules, particularly those often seen in the pharmaceutical and agrochemical sectors.    43   1.1.3.4 1,2-Addition  Figure 1.7 1,2-Addition mechanism.  a: simplified reaction pathway. b: Reaction pathway showing the transition state of the 1,2-addition of a C-H bond to a titanium alkylidyne complex. Alkylidene and imido complexes follow the same transition state. Early metals are also commonly involved in the activation of alkanes through 1,2-addition reactions.91 Wolczanski and Bergman first reported the reaction in the late 1980s.92 Initial binding of the alkane in these systems most often occurs via sigma complex formation to the dz2-orbital (1.10, Figure 1.7). The crucial interaction that results in the cleavage and transfer of the hydrogen atom comes from donation of electron density from the metal-ligand d\u03c0 orbital to the R-H \u03c3*-orbital resulting in the four membered transition state akin to the sigma bond metathesis mechanism (1.11, Figure 1.7). The activation is then driven forward by the overall bond strength of the resulting M-R bond. This reaction mechanism is active for alkylidene, alkylidyne and imido metal complexes. Recent advances reported by Mindiola and Baik, studying the reactions of gaseous hydrocarbons with titanium alkylidenes, appear promising for to the development of a catalytic process. Much of this work was built upon the titanium alkylidene complexes reported by the Mindiola group since 2005.19,20 Even these early analogues were successful in activating benzene and Csp3 groups of alkyl silanes. However, significant progress was made when in 2011 they reported the activation of methane and ethane.93,94 Methane was found to be 44  activated at 310 psi at 31 \u00b0C across the titanium carbon triple bond with 54% conversion. Almost quantitative conversion was seen if the pressure was increased above 1000 psi. Deuterium labelling studies supported their earlier results that there was no significant KIE in these systems and that the rate determining step is the formation of the alkylidyne which precedes the C-H activation of methane.93 Furthermore, CD4 activation studies in these systems can rule out other mechanisms if the resulting deuteron ends up fully incorporated in the alkylidene\/alkylidyne. This is because the deuteron\/proton is shuttled directly to the alkylidene\/alkylidyne without formation of an M-H\/D bond that could scramble it into other ligands. This result has also been corroborated for imido complexes.95  One of the elegant properties of this system is the ability to study both the experimental kinetic component as well as the computational perspective. The kinetic investigation of the reaction shown in Figure 7 has revealed the interplay between intermediates and transition states. While the barrier to C-H activation of methane was found to be <24.7 kcal\/mol, reversible extrusion of methane from 1.12 (Figure 1.7) occurs at a higher barrier of 28.1 kcal\/mol. Furthermore, dehydrogenation of methane can also occur but has a minimum requirement >28.1 kcal\/mol. Further experiments probing these side reactions showed that, while they are feasible, they also face higher barriers with respect to the main C-H activation pathway.96 Ethane C-H activation has, likewise, been studied by Mindiola and Baik, resulting in the first example of an ethane to ethylene reaction that takes place at room temperature. This reaction has been proposed to occur via a 1,2 addition followed by a beta C-H migration.94 Conversion of ethane to ethylene is of critical importance due to the expanding usage of polyethylene worldwide. Currently, ethylene is generated via steam cracking. Although industrially viable, the process is energy intensive and much of the ethane is not converted to ethylene. Furthermore, this mechanism could be looked at favourably for late-stage diversification due the ability to select sp3 C-H bonds over sp2 C-H bonds when the Sp2 bond is less sterically accessible.  1.2 Historical context of the use of platinum in C-H activation reactions. Over the past 20 years significant advancement have been made regarding the nuances of C-H activation mechanisms, mainly from a computational perspective. Although, many different transition metals have been used to C-H activate and functionalise alkanes, many researchers are moving away from the precious metals to focus on the more abundant first row metals. However, the use precious metals such as platinum are still important due to the increased covalent interaction with hydrocarbyl ligands. As a result of the increased covalency many products that result from C-H activation can be stabilised and studied, whereas the lighter 45  second and first row metals tend to be less stable and more reactive. Increasing the chance that reactive intermediates are stable and isolable, the work carried out in this thesis focuses on platinum(II) chemistry with the intent of identifying novel reaction pathways relevant to C-H activation. Since the 1960\u2019s platinum has been at the forefront of research dedicated to C-H activation and functionalisation. Simple platinum salts were first employed by Garnett and Hodges in 1967, they showed that simple arenes as well as cyclohexane could undergo hydrogen\/deuterium exchange in a solution of acetic acid\/hydrochloric acid at 100 \u00b0C (Scheme 1.1).97   Scheme 1.1 representative example of the H\/D exchange in aromatic compounds reported by Garnett and Hodges using K2PtCl4 as a catalyst. This work set the stage for the eventual development of the first C-H functionalisation reactions of methane reported by Shilov. Using the same simple platinum catalyst, K2PtCl4 and the same reaction conditions reported by Garnett and Hodges, the activation and functionalisation of methane to alcohols and alkyl chlorides was achieved. However, for this system to work stoichiometric amounts of Pt(IV) oxidant are required (Scheme 1.2). The chloro-aqua complex, PtCl2(H2O)2 as well as the anionic [PtCl3(H2O)]- are thought to be the most active species involved in the C-H activation. Several proposed mechanisms have been reported by different groups and have been summarised in the following reviews.43,98 46   Scheme 1.2 Simplified catalytic cycle of the Shilov system for the C-H activation of methane by K2PtCl4. Another system that has garnered significant attention is the Catalytica\/Periana system (Scheme 1.3).99 This catalytic reaction is based on the use of a bipyrimidine platinum dichloride complex. One of the advantages of the bipyrimidine catalyst is that the stoichiometric Pt(IV) oxidant is no longer necessary. Instead, the reaction is conducted in fuming sulfuric acid at temperatures over 100 \u00b0C which allows for the oxidation of methane to methylbisulfate in a selective manner. The use of the bipyrimidine ligand also proved vital for reducing the amount of metallic platinum generated in the reaction, ensuring catalytic turnover did not diminish. While this system proved to be impressive in terms of methane conversion (90% based on methane), the use of fuming sulfuric acid as a solvent does pose challenges for transferability into an industrial process.  47   Scheme 1.3 Catalytic cycle for the Catalytica system showing the oxidation of methane to methylbisulfate. In more recent years the Strassner group, as mentioned above in Section 1.1.2, has developed a platinum catalyst for methane oxidation based on a chelating bis N-heterocyclic carbene ligand (NHC) (Scheme 1.4). This reaction uses similar acidic conditions as the catalytica system, employing a mixture of trifluoroacetic acid and its anhydride in the presence of the oxidant K2S2O8 instead of fuming sulfuric acid.54  The platinum catalysts were shown to be active for methane functionalisation, but methane conversion was found to be poor, giving only 0.5% conversion with a turnover number (TON) of 4.1 in the best case. The low conversion rate and poor TON could be a result of the low catalyst 48  loading used in the reaction (0.133 mol%), which must be kept low to observe any reaction at all.    Scheme 1.4 Oxidation of methane reported by Strassner employing a Bis-NHC platinum complex using K2S2O8 as oxidant in trifluoroacetic acid as reaction medium. It is worth mentioning that the analogous palladium complexes show significantly higher efficacy for this reaction.52 The same group also conducted a thorough mechanistic investigation of how the reaction operates. It was found that the C-H activation step proceeds through a CMD\/AMLA transition state and that an oxidative addition mechanism was calculated to be inaccessible (DFT study based on Pd catalyst).60 The importance of K2S2O8 is to generate trace amounts elemental chlorine or bromine from the metal which is later recycled by oxidising the catalyst to induce reductive elimination of the trifluoroacetic acid methyl ester product (Scheme 1.5).100 While the calculations were reported for palladium it stands to reason that a similar mechanism could be operable with platinum. However, the energetic differences between the oxidative addition and CMD pathways may be closer as platinum can achieve the +IV oxidation state more easily than Pd.  49   Scheme 1.5 Proposed catalytic cycle for the oxidation of methane by trifluoroacetic acid    50  1.3 Proposed catalytic cycle for the functionalisation of methane using aryl halides as oxidants. While several methodologies have been reported on the catalytic functionalisation of methane, they have relied on either expensive stoichiometric oxidants (Shilov) or harsh reaction conditions employing strong corrosive acids (Catalytica\/Strassner). Diversifying the possible mechanisms by which methane functionalisation can occur could give more insight into design of new systems that could become more sustainable and industrially viable. Outlined in scheme 1.6 is a proposed catalytic cycle for the functionalisation of methane. This catalytic cycle is based on a combination of historical platinum C-H activation reactions and the abundant reports of C-C cross coupling chemistry that the heavier group 10 metals are known for. The cycle is initiated by the oxidative addition of an aryl halide to a Pt(II) dimethyl complex to give a Pt(IV) species. This Pt(IV) species then reductively eliminates toluene, either by the dissociation of a ligand or via the removal of the halide with a silver salt. Solvation of the resulting unsaturated Pt(II) complex allows for the formation of a methane sigma complex, which in turn weakens or polarises the C-H bond leading to C-H activation. Following C-H activation of methane, the Pt(IV) hydride can be deprotonated by an exogenous base in the reaction mixture to give back the Pt(II) dialkyl complex and completing the catalytic cycle. 51   Scheme 1.6 Proposed catalytic cycle for the functionalisation of methane by aryl halides using a Pt(II)\/Pt(IV) redox cycle. The Love group has previously reported on C-C reductive elimination processes of this catalytic cycle.101 However, one of the challenges encountered in this work is that the aryl halide must be tethered to the ligand scaffold for the oxidative addition to proceed. Several reports have been published focusing on the oxidative addition of aryl halides to Pt(II) complexes, but all examples required the aryl halide to be tethered.102,103 While these ligand systems proved useful in determining the oxidative addition step is possible and that a redox cycle between Pt(II)\/Pt(IV) was accessible, some inherent challenges remain. The requirement to tether the aryl halide to the ligand scaffold does not allow for the functionalised product to dissociate from the metal without an acidic work up effectively halting turnover. Furthermore, the resulting Pt(IV) complex from oxidative addition of the aryl halide is stable to reductive elimination due to being coordinatively saturated. Reductive elimination at Pt(IV) most often occurs at 5-coordinate geometries and must therefore form from either the dissociation of a neutral or ionic ligand. Therefore, in order to develop an efficient and useful catalytic system that mimics the proposed cycle in scheme 1.6, a new ligand system must be developed that can negate the tethering of the aryl halide and if possible, avoid the use of silver salts.  52  Outlined in the subsequent chapters are the efforts towards developing new ligands and catalysts that could be used in the above catalytic cycle for methane activation. We show that existing ligands such as NHCs can be used to successfully oxidatively add aryl halides to a Pt(II) dimethyl complex as required by the catalytic cycle above. Furthermore, the development of a new NHC ligand that leads to bimetallic and heterobimetallic complexes could be employed in C-H and C-X activation reactions. Additionally, a mechanistic investigation into the C-H activation of pyridine is conducted that sheds light on the potential application of Pt-Pt complexes in the C-H activation reactions. 53  Chapter 2: Intermolecular Oxidative Addition of Aryl Halides to Platinum(II) Alkyl Complexes. The work conducted in this chapter has been carried out in collaboration with the Dr Eric Bowes who carried out all the DFT calculations. X-ray diffraction data was collected and refined by Dr Dawson Beattie. The remainder of the work (design of experiments, synthesis, and characterisation) was carried out by me. 2.1: Introduction Oxidative addition (OA) is a fundamental reaction that is a critical step in catalytic processes such as Suzuki-Miyaura coupling,104 Buchwald-Hartwig amination,105 olefin hydrogenation,106 and the Monsanto process.107 The OA of a variety of oxidants to low valent metals is well established and rely on activated species such as carbon-(pseudo)halide (C-X) bonds to electron rich M(0) or M(I) species.108 The OA of alkyl halides to group 10 M(II) species has been well studied stoichiometrically and catalytically.9,107,117,118,109\u2013116 Despite the increasing prevalence of M(II)\/M(IV) (M = Ni, Pd) catalytic processes invoking Csp2-X OA in the literature,119 few well-defined examples of such reactivity have been reported.120\u2013125 While many Pt(II) complexes undergo facile SN2-type Csp3-X OA, these complexes have historically been thought to be inactive toward intermolecular Csp2-X OA which typically occurs in a concerted fashion.126  With the exception of a poorly defined example from 1967,127 efforts to achieve intermolecular C(aryl)-X oxidative addition have necessitated incorporation of the aryl halide into the ligand scaffold, i.e. intramolecularly.102,103,116,124,128\u2013132 The interest in exploring the potential of aryl halides as oxidants comes in part from the proposed process for methane functionalization described in section 1.1.3. Our initial efforts in this area were reliant on a strategy developed by Puddephatt and coworkers, wherein Csp2-X activation is facilitated by tethering an aryl halide to the ancillary ligand scaffold (Scheme 2.1).102,103,124,128\u2013131,133  Scheme 2.1 Intramolecular oxidative addition of aryl halides to a Pt(II) dimethyl complex 54  This approach provides well-defined Pt(IV) intermediates from which C-C reductive elimination (RE) can be induced, but tethering the aryl group prevents product dissociation and facilitates decomposition via ligand C-H activation.101 As intermolecular Csp2-X activation would obviate this problem, it became crucial to develop a Pt(II) system capable of intermolecular oxidative addition of aryl halides. With this in mind, we looked toward traditional cross-coupling catalysts capable of reacting aryl halides as inspiration. One class of ligands that has been used frequently in cross-coupling transformations of aryl halides is N-Heterocyclic carbenes (NHCs, Figure 2.1).134 These carbenes provide steric control around the metal center which can stabilise reactive open coordination sites. Furthermore, the strong \u03c3-donor properties make these ligands primary targets for the synthesis of electron rich metal complexes.57   Figure 2.1 Sterically bulky N-heterocyclic carbenes commonly used in stoichiometric and catalytic reactions to stabilise reactive intermediates 2.2: Synthesis and reactivity of Me2Pt(IMes)(L) and MePt(IMes\u2019)(L) (IMes\u2019 = cyclometallated IMes, L = SMe2 or pyridine) with phenyl halides. A series of Pt(II) dialkyl complexes featuring N-heterocyclic carbene (NHC) ligands were prepared. Complexes bearing either IPr or IMes in addition to dimethyl sulfide were readily synthesised from Pt2Me4(\u00b5-SMe2)2 in benzene (Scheme 2.2). Platinum(II) complexes bearing NHCs have been previously reported by several researchers, most notably the groups of Nolan and Conejero.57,135,136 Platinum complexes bearing methyl groups display 2JPt-H couplings, the magnitude of which can give insight into to the geometry of the complex, particularly the ligand in the trans position to the CH3 group. The coupling constants for complex 2.1 is 2JPt-H = 87 Hz for the methyl trans to the dimethyl sulfide ligand and 2JPt-H = 60 Hz for the methyl trans to the IMes ligand. The coupling constants are in good agreement for other reported platinum(II) dialkyl complexes and, analysing the trans influence strength of both IMes (high trans influence) and dimethyl sulfide (weak trans influence) shows good correlation with the magnitude of the coupling.  55   Scheme 2.2 Synthesis of NHC-Pt(II) complexes 2.1 and 2.2 It was hypothesised that intermolecular Csp2-X OA would be possible with these electron rich Pt(II) complexes giving rise to either a Pt(IV) complex or resulting in the formation of toluene and\/or ethane. Based on the simplicity of the 1H NMR resonances of the IMes ligand, 2.1 was chosen as a starting point with which to test reactions with aryl halides. Heating 2.1 at 60 \u00b0C in the presence of one equivalent of PhI in Benzene-d6 gave rise to new signals with Pt-CH3 satellites. In-situ 1H NMR spectroscopic analysis of the reaction mixture resulted in the detection of toluene and a single new Pt-CH3 signal. The Pt-CH3 coupling constant (2JPt-H = 80 Hz) is consistent with a methyl and an NHC ligand being in a cis configuration. Additionally, another species was identified by the detection of methane in the 1H NMR spectrum which is suggestive of a C-H activation event having occurred, which was confirmed by the presence of diastereotopic methylene resonances characteristic of IMes cyclometallation at the ortho-methyl position (Figure 2.2, 2.5).136,137   56    Figure 2.2 Stacked 1H NMR spectra (C6D6, 400 MHz, 25 \u00b0C) of the aliphatic region of 2.1 with PhI after two hours at 60 \u00b0C (top\/blue) and independently synthesised complexes 2.5 (middle\/green) and 2.3 (bottom\/red) to show the formation of the platinum complexes during the reaction shown above. The independent synthesis and full characterization (1H, 13C{1H} NMR spectroscopy, ESI-MS) of all Pt(II) species detected in the reaction of 2.1 with PhI corroborated our assignments (Figure 2.2). The conversion of PhI to toluene is consistent with a mechanism in which PhI OA to 2.1 is followed by Csp2-Csp3 RE of toluene to provide 2.3, but the mechanism by which 2.5 is formed is less clear. Cyclometallation of organoplatinum(II) NHC complexes via Csp3-H activation and subsequent reductive elimination of methane is well established.136\u2013141 Thus we reasoned that 2.5 was formed either directly from 2.1 via C-H cyclometallation followed by C-I oxidative addition and reductive elimination or via cyclometallation from the less electron-rich product 2.3. 57  To probe these possibilities, product mixtures containing 2.3 and 2.5 were heated for two hours at 100 \u00b0C. No changes in product ratios were observed. Heating an independently prepared sample of 2.3 at 100 \u00b0C for one hour did not afford any conversion to 2.5, nor did heating in the presence of PhI. These results indicate that cyclometallated complexes are formed by an initial C-H activation process at 2.1, followed by PhI OA and reductive elimination of toluene. Gratifyingly, heating 2.1 at 60 \u00b0C for two hours in C6H6 was found to provide cyclometallated complex 2.4 in 71% (Figure 2.3 C, see SI for solid state structures). Comparison of \uf0744 values for 2.1 (0.057) and 2.4 (0.070) shows that both complexes adopt square planar geometries as expected for Pt(II) complexes.142  Figure 2.3 A. Control experiments that probe the reaction between PhI and 2.1, 2.3 and 2.5. B. Reaction of 2.3 with PhI showing no further reaction. C. Cyclometallation of 2.1 into 2.4 Additional evidence for the OA of PhI is provided by the reaction of 2.1 with PhI-d5 which produced toluene-d5 and complexes 2.3 and 2.5. The aromatic signals corresponding to toluene are no longer visible in the experiment with PhI-d5 (Figure 2.4, Inset A). Furthermore, the detection of methane (0.15 ppm) in the NMR spectrum of both experiments (Figure 2.4, inset B) along with the diagnostic doublets at 4.5 ppm provide support for the formation of 2.5. Isotopic labelling of the aryl halide has thus provided evidence that toluene formation is a direct result of the OA of PhI and not from the solvent. Based on the experiments presented above, it can be concluded that the C-H activation from 2.1 \u2192 2.4 is a competitive process, albeit slower compared to the OA of PhI to 2.1.  58    Figure 2.4 Comparison between 1H NMR spectra of reactions of 2.1 and PhI (top\/green) and 2.1 and PhI-d5 (bottom\/red) showing the toluene signals are no longer visible during the reaction when using deuterated PhI. At this stage another analogue of 2.1 was synthesized to verify that the OA of PhI wasn\u2019t specific to the dimethyl sulfide substituted complexes 2.1 and 2.4. We prepared the pyridine analogue of 2.1 from a diethyl ether solution of Me2PtCOD, IMes, and pyridine. The resulting product 2.6 precipitates out of solution after several seconds and is both air and moisture stable. The 2JPt-H = 89 (trans to N) and 60 Hz (trans to C) are analogous to 2.1 (87 and 60 Hz respectively). Further reaction of 2.6 in benzene or toluene also yields the cyclometallated species 2.8 in 78% (Scheme 2.3, A). It is noteworthy that reaction of 2.6 with phenyl iodide gives rise to the same product mixture as the dimethyl sulfide analogue 2.1. However, due to 2.1 with PhI after 1 h at 60 \u00b0C 2.1 with PhI-d5 after 1 h at 60 \u00b0C 59  the lability of the Pt-N bond, the reaction is faster; qualitatively the pyridine complexes undergo near complete conversion of 2.6 into 2.7 and 2.9 and their isomers after only one hour compared to two hours for 2.1 (Scheme 2.3, B).   Scheme 2.3 A. Synthesis of platinum pyridine analogues of 2.1 and 2.4. B. Reaction of 2.6 with PhI and the resulting product distribution. One of the unique features of the pyridine derivatives is the chemical shifts of the ortho-pyridine protons. The resonance of this signal is sensitive to the electronic environment of the platinum centre, as a result, major species can be observed and quantified during the reaction by 1H NMR spectroscopy. These unique resonances allowed for kinetic profiling of reactions by 1H NMR spectroscopy and the identification of the species that were present. The reaction between 2.6 and PhI at room temperature for 16 hours gave rise to a spectrum with several ortho-pyridine resonances. When this spectrum is stacked on top of the 1H NMR spectra of the independently synthesised complexes 2.6, 2.7,2.8 and 2.9\/2.9a the overlap of the signals shows good agreement that each species is being formed throughout the reaction (Figure 2.5). For this reason, the pyridine analogues were favoured compared to the dimethyl sulfide analogues.  60    Figure 2.5 Observation of Pt(II) intermediates throughout the reaction between 2.6 and PhI after 16 hours at room temperature. Spectra from top to bottom: 1H NMR spectrum of reaction mixture as depicted in reaction scheme above. 1H NMR spectrum of 2.9\/2.9a. 1H NMR spectrum of 2.7. 1H NMR spectrum of 2.8. 1H NMR spectrum of 2.6. Next, we opted to study the OA of PhI in isolation with complex 2.4 and 2.8. Removing the possibility of C-H activation from the system should allow for the identification of intermediates that are relevant to PhI OA and not C-H activation. The complexes 2.4 and 2.8 were reacted with one equivalent of phenyl iodide at 60 \u00b0C in C6D6 for one hour. Toluene was observed, forming in 80% and 99% respectively (1H NMR spectroscopic yields) along with the formation of 2.5 and 2.9 and their respective isomers (Scheme 2.4, 2.5a and 2.9a). Although the reaction between 2.4\/2.8 and phenyl iodide gives higher yields of toluene formation over the same period as 2.1\/2.6, there can be no quantitative comparison as to which complex is faster due to the competitive C-H activation that occurs with the non-cyclometallated complexes. However, it is 2.6 + PhI at room temp 61  worth mentioning that 2.8 seems to be more reactive than 2.4 with respect to OA of phenyl iodide at the same temperature and indeed 2.8 can be seen to react slowly even at room temperature whereas 2.4 requires elevated temperatures. Interestingly, the selectivity of reductively eliminated isomer pairs (SMe2: 2.5 & 2.5a and pyridine: 2.9 & 2.9a) between the cis (L = cis to NHC) and trans (L = trans to NHC) are opposite depending on whether the ligand is pyridine (trans) or dimethyl sulfide (cis) (Scheme 2.4).   Scheme 2.4 Reaction of independently synthesised cyclometallated complexes 2.4 and 2.8 with phenyl iodide at 60 \u00b0C in C6D6. While having established the reactivity of phenyl iodides with platinum(II), lower weight halides (Br, Cl, F) have increasingly stronger carbon halogen bonds and are significantly more difficult to cleave in an intermolecular fashion. Activation of the lighter halogens by 2.4 or 2.8 would therefore be of interest. Phenyl bromide was reacted with complex 2.4 in C6D6 at 75 \u00b0C over a period of 68 hours (Figure 2.6). Formation of both toluene and 2.5-br is evidenced by diagnostic shifts at 4.00 and 3.20 ppm for the cyclometallated halide species. However, continued heating at 75 \u00b0C results in decomposition of the starting material. Better results were obtained by using an excess of phenyl bromide (37%; toluene and 2.5-br after 16 h at 60 \u00b0C) and decreasing the temperature to 60\u00b0C. Based on this result it is not surprising that further experiments with chlorobenzene and fluorobenzene failed to give any conversion when reacted with 2.4 or 2.8.  62    Figure 2.6 Stacked 1H NMR spectra (C6D6, 300 MHz, 25 \u00b0C) of the reaction between 2.4 with PhBr at 75\u00b0C over 68 hours. 63  2.2 Experimental and computational investigation into the mechanism of OA of phenyl iodide to Pt(II) alkyl complexes. There is a significant difference in the reactivity between complex 2.4 and 2.8, both complexes undergo the OA of phenyl iodide with relative ease but complex 2.8 gives near complete conversion of PhI into toluene at 60 \u00b0C in one hour, whereas 2.4 requires two hours. One reason for this difference in reactivity can be attributed to the ability of pyridine to stabilize the Pt(IV) oxidation state better than dimethyl sulfide due to the hard-hard interaction of Pt(IV) with pyridine and the mismatch of the soft dimethyl sulfide with Pt(IV). On the other hand, we hypothesised based on literature precedent that the reaction progresses through the dissociation of a ligand to generate an open coordination site that phenyl iodide can bind to and subsequently undergo cleavage of the bond in a concerted manner to give the Pt(IV) phenyl species. Based on this concept the dimethyl sulfide analogues would have a higher barrier to dissociation as the interaction between Pt(II) and sulfur is more favourable than Pt(II) and pyridine. To explore this, the reaction between 2.4 and PhI was performed in the presence of excess dimethyl sulfide at 60 \u00b0C. Ten equivalents of dimethyl sulfide were added and found to inhibit the reaction, affording toluene and 2.5 in only 4% yield over a one-hour period (c.f. 80% yield in the absence of added dimethyl sulfide). A Similar inhibition was observed when 2.6 and PhI were heated in the presence of excess pyridine. We also note that cyclometallation was slowed in this reaction (Figure 2.7).    64    Figure 2.7 Stacked 1H NMR spectra of the reaction between 2.6 and PhI in the presence of 5 equivalents of pyridine at 60 \u00b0C over a period of 48 hours. Red\/bottom spectrum corresponds to the reaction prior to heating. Middle\/green corresponds to the reaction after 24 hours. Top\/blue spectrum corresponds to the reaction after 48 hours.  An unexpected result from this reaction was the observation of a new Pt-CH3 signal with a resonance at 0.16 ppm. This methyl signal has a 2JPt-H = 50 Hz, unusually small for a Pt(II) complex relative to the other complexes that have been observed in this work. Initially, a Pt(IV) complex from oxidative addition of phenyl iodide to 2.6 was proposed based on the decrease in coupling constant normally observed when going from Pt(II) to Pt(IV). However, this was ruled out as no aromatic signals corresponding to a Pt-Ph interaction were observed. Furthermore, addition of AgBF4 did not generate the expected production in toluene or ethane that would result from abstraction of the halide from a Pt(IV) octahedral intermediate. A pyridine signal with 65  platinum coupling was observed in the spectrum that did not correspond to any of the already isolated species and integrated well with the methyl signal in 1:2 ratio. Based on the integration of these signals, as well as their disappearance over the course of the reaction, they were tentatively assigned as the trans-methyl isomer of 2.6-trans. This was further corroborated by observation of the same signal when 2.6 was heated in the presence of excess pyridine without phenyl iodide further ruling out a platinum(IV) intermediate (Scheme 2.5). The trans arrangement of the methyl groups would also account for the small coupling 2JPt-H = 50 Hz that this signal has.  Scheme 2.5 Equilibrium between 2.6 and its trans isomer These observations are consistent with a mechanism in which dissociation of a ligand (pyridine or dimethyl sulfide) creates a coordinative vacancy for interaction with PhI. The steric bulk of NHC ligands is known to stabilize low-coordinate, T-shaped complexes.135,137,138 Furthermore, Crespo and Martinez have shown in several studies that dissociation of a ligand to create a vacant site is a prerequisite for OA of the Csp2-X bond.103,126,133  On this basis, we have tentatively proposed a mechanism in which the ligand (pyridine or dimethyl sulfide) dissociates to facilitate the concerted OA of PhI (Figure 2.8). We turned towards density functional theory as means to support this hypothesis. The calculations establish that a concerted OA process is energetically feasible for both complexes 2.1 and 2.4.  Starting from 2.4, the dissociation of dimethyl sulfide results in the formation of a weak PhI adduct 2.10, 4.9 kcal\u00b7mol-1 uphill in energy due to the relatively weak donor ability of PhI. These interactions have previously been demonstrated.143\u2013145 The oxidative addition barrier (\uf044G\u2021) was calculated to be 14.9 kcal\u00b7mol-1 relative to 2.4 in benzene, which is in general agreement with the experimental observation that this reaction proceeds at 60 \u00b0C. The OA transition state geometry 2.11TS is characterized by a \u2018face-on\u2019 approach of the aryl halide to Pt and a single imaginary frequency corresponding to cleavage of the Ph-I bond. The Csp2-I addition occurs in a manner that positions the Ph group trans to a vacant coordination site in the resultant Pt(IV) 66  complex 2.12, which exhibits a square pyramidal geometry (\uf0745 = 0.04). Toluene reductive elimination from Pt(IV) intermediate 2.12 proceeds through transition state 2.13TS with a barrier of 14.6 kcal\u2219mol-1, accounting for the lack of Pt(IV) intermediates detected experimentally.  Figure 2.8 DFT calculated pathway for the OA of PhI to 2.4. An expanded view of the Pathway be seen in supporting information. Consistent with observed differences in reactivity between 2.1 and 2.4, the Csp2-I OA pathway starting from non-cyclometallated 2.1 proceeds with a significantly higher OA barrier (\uf044G\u2021 =23.1 kcal\u00b7mol-1 relative to 2.1, Figure 2.9) than 2.4. As the free energy (\uf044G) for formation of Pt(IV) intermediates 2.12 and 2.16 is similar in both systems (\uf044G = -10.3 kcal\u00b7mol-1, 2.16 ; -9.0 kcal\u00b7mol-1, 2.12), we attribute the difference in transition state energies to greater steric repulsion between the NHC and PhI in the non-cyclometallated complex. 67   Figure 2.9 DFT calculated pathway for the OA of PhI to 2.1. An expanded view of the Pathway can be seen in supporting information. As a side note it is important to mention that an alternative mechanism involving a metathesis pathway cannot be ruled out. However, the microscopic reverse, Csp2-X RE from Pt(IV), has been demonstrated giving precedence to our hypothesis.146\u2013148 Several experiments were devised to trap and isolate the putative Pt(IV) OA product by controlling both sterics and directing group effects. We started by examining the effect of introducing steric bulk at the ortho position of PhI. It has been shown previously by Goldman that face on arrangement of a phenyl ring with a methyl group must occur for reductive elimination of the two groups to proceed. We employed 2,4,6-trimethylphenyliodide in the hopes that the ortho position steric bulk would inhibit the face on arrangement of the phenyl ring with the methyl group and trap the Pt(IV) product. Unfortunately, using the bulkier phenyl iodide resulted in no reaction at all (Scheme 2.6). Presumably, because additional bulk at ortho positions prevent the cleavage of the C-I bond after coordination of the iodine lone pair to the metal.  68   Scheme 2.6 Attempted trapping of a Pt(IV) intermediate using the sterically bulky 2,4,6-trimethylphenyliodide. We also envisioned that tethering a chelating group to the phenyl iodide would allow for the isolation of the Pt(IV) product via closing of the chelate after oxidative addition of the Csp2-I bond, in turn disfavouring the formation of 5-coordinate Pt(IV) species that undergo C-C RE. To this end, we treated 2.4 with 2-(2-iodophenyl)pyridine in a 1:1 ratio in C6D6 (Scheme 2.7 A). After 36 h at room temperature, octahedral Pt(IV) complex 2.18 was isolated from the reaction mixture. An X-ray crystal structure of 2.18 was obtained, unambiguously confirming oxidative addition of the Csp2-X bond (Scheme 2.7 B). RE from these complexes is likely inhibited by the chelating nature of the phenylpyridine ligand, preventing the formation of a five-coordinate intermediate required for RE.  Scheme 2.7 A. Oxidative addition of chelating aryl halide to trap the cyclometallated Pt(IV) complex 2.18. B. ORTEP depiction of the solid-state structure of 2.18 (thermal ellipsoids are set at 50% probability, solvent molecules have been removed for clarity). The crystal shows substitutional disorder with respect to the methyl and iodide positions, the structure shown is the major occupancy isomer (0.8:0.2). 69  2.3 Alternative ligands for OA of PhI to platinum (II) alkyl complexes. There is only one report providing evidence for intermolecular OA of aryl halides to Pt(II) complexes, reported by Kistner and co-workers in 1967.127  In this paper, a solution of Pt(o-tol)2(pyridine)2 (2.19; o-tol = ortho-tolyl) in neat PhI was reported to produce PtI(o-tol)(pyridine)2 over a period of 6 days at 25 \u00b0C. Limited characterization data were provided for the Pt product, and the formation of the organic product was inferred from that data. It can be reasoned that the formation of the observed PtI(o-tol)(pyridine)2 complex 2.20 (Scheme 2.8) could be attributed to a Csp2-I OA\/Csp2-Csp2 RE process, which would also result in the formation of the presumed organic product. As this would suggest that the intermolecular Csp2-I reaction is generalizable to other electron-rich Pt(II) complexes with labile ligands, we sought to reproduce the reported reactivity. The reaction conditions disclosed by Kistner et al. in their report from 1967, \u201cReacting Pt(o-tolyl)2(pyridine)2 (300 mg) in neat iodobenzene (7 mL) for 6 days\u201d, led to the question whether generation of the resultant PtI(o-tolyl)(pyridine)2 complex could have arisen from formation of iodine\/iodide. No discussion of the reaction or the organic products was given by the authors. With a large volume of phenyl iodide being left for six days in light, generation of a variety of iodine and iodide species may have been responsible for the resultant products. Nevertheless, repeating the experiment in the same manner as reported by Kistner provided 2-methylbiphenyl, which was detected by GC-MS analysis of the reaction mixture (supporting info). Interestingly, the detection of homocoupled product 2,2\u2019-dimethyl-1,1\u2019-biphenyl in the GC-MS trace, shows that reductive elimination of two o-tolyl groups is also possible from this reaction.   Scheme 2.8 Reaction between 2.19 and PhI showing the reported reaction from Kistner et al. Furthermore, the treatment of 2.19 with one equivalent of PhI at 60 \u00b0C in C6D6 afforded 2-methylbiphenyl in 42 % yield (NMR spectroscopy, 2,4,6-trimethoxybenzene internal standard, Scheme 2.8), confirming the hypothesis of the original work conducted by Kistner and showing that a large excess of phenyl iodide is also not necessary.  70  To further establish the generality of this reaction, a series of mono and bisphosphine complexes were prepared featuring both electron donating 2.21, PtMe2(PCy3)(SMe2) and electron withdrawing groups 2.22, PtMe2(P(C6F6)3(SMe2). The bis phosphine complex 2.23, PtMe2(PnBu3)2 was also prepared to investigate whether a labile ligand is necessary for the oxidative addition to occur (Scheme 2.9).   Scheme 2.9 Synthesis of Mono (2.21 and 2.22) and bisphosphine complexes (2.23) 71  Treatment of monophosphine complex 2.21 with one equivalent of phenyl iodide at 60 \u00b0C resulted in the formation of toluene in ~50 % yield (1H NMR spectroscopy, 1,3,5-trimethoxybenzene internal standard) along with ethane (Figure 2.10).    Figure 2.10 Reaction scheme of 2.21 and PhI at 60 \u00b0C and stacked 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) of the reaction between phosphine complex 2.21 and PhI at 60 \u00b0C. Bottom\/green spectrum, is the reaction before heating. Top\/red spectrum is the reaction after 16 hours at 60 \u00b0C. Bottom inset features an expansion of the aliphatic region. Top inset features an expansion of the aromatic region. The reaction of PhI with complex 2.21 is slow relative to the NHC analogues but produces toluene in ~50% yield. Ethane and two new Pt species, which were assigned as 2.24 and 2.25 (Figure 2.10), were also observed. The starting material 2.21 is still present in both the 1H{31P} and 31P{1H} NMR spectra suggesting that longer reaction times are required for complete Toluene Ethane New Me-Pt Toluene Pt-Ph 72  conversion. Ethane was the only gaseous product observed in significant amounts. Furthermore, the new Pt-methyl signal shows Pt-CH3 coupling, 2JPt-H= 75 Hz, consistent with a Pt(II) methyl group. Additionally, the 31P{1H} NMR spectrum shows a new signal with platinum satellites (1JPt-P = 3920 Hz), which is consistent for a phosphine trans to a weak trans influence ligand such as iodide. The corresponding 1H-31P HMBC correlation between the methyl and phosphorous signals gives support to the proposed structure of 2.24 (Figure 2.11).  Figure 2.11 Left: 1H-31P HMBC NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) showing the correlation between Pt-phosphine and Pt-methyl resonances. Right: Stacked  31P{1H} NMR (C6D6, 400 MHz, 25 \u00b0C) spectrum of the reaction between 2.21 and PhI after 16 hours at 60 \u00b0C showing the new Pt-Phosphine signal with characteristic large Pt-P coupling indicating a trans iodine ligand. Structure 2.25 is invoked due to the presence of ethane in the 1H NMR spectrum, although, the only signal that supports this assignment is an aromatic resonance at 7.5 ppm, observed as doublet with Pt satellites (3JPt-H= 54 Hz, Figure 2.10). Oxidative addition of aryl halides to platinum(0) phosphine complexes is a well-studied process. To ensure that the Csp2-I bond cleavage was not being facilitated by a two-step ethane reductive elimination followed by PhI oxidative addition mechanism 2.21 was heated under the reaction conditions without phenyl iodide. However, no change in either 31P{1H) or 1H{31P} NMR spectra was observed, therefore ruling out formation of 2.25 via oxidative addition to a Pt(0) species. The formation of 2.25 must therefore occur from initial oxidative addition followed by either reductive elimination of ethane or methyl transfer. An initial assumption was made that electron rich complexes were necessary for phenyl iodide oxidative addition at platinum(II), however, the reaction between phenyl iodide and complex 2.22 proceeds to complete conversion in 16 hours. A significant amount of metallic platinum is precipitated onto the walls of the NMR tube, suggesting a reductive elimination from 1JPt-P= 3920 Hz 73  platinum(II). Furthermore, 52% toluene is produced at the end of the reaction along with methane and ethane as well as trace amounts of ethylene (Figure 2.12).     2.12 Rection scheme of 2.22 with PhI at 100 \u00b0C in C6D6. Stacked 1H NMR spectra showing the reaction between 2.22 with PhI at 100 \u00b0C for 16 hours. Bottom\/ red spectrum shows the reaction mixture before heating. Top\/green spectrum shows the reaction mixture after heating for 16 hours at 100 \u00b0C. Bottom inset shows an expansion of the aliphatic region. Top inset shows and expansion of the aromatic region. Unlike complex 2.21, no aromatic signals were detected corresponding to the formation of a Pt-Ph complex. The major products from this reaction are metallic Pt and a new Pt-Me complex, 2.26, which shows Pt-CH3 coupling, 2JPt-H= 75 Hz, consistent with a methyl cis to both phosphine and iodide. 31P-1H HMBC provides evidence for the structure via 3J correlation Toluene Toluene Methane New Pt-CH3 Ethane Ethylene 2.22 + PhI before heating 2.22 + PhI after 16 h at 100 \u00b0C 74  between the R3P-Pt and the Pt-CH3 (Figure 2.13). The 31P-1H HMBC shows correlation between three distinct pairs of R3P-Pt-CH3 fragments. Coupling constants for both Pt-P and Pt-CH3 were elucidated from this data as the corresponding 1D spectra were not conclusive. The major signal corresponding to a new Pt-CH3 (~0.8ppm, green) peak showed strong correlation with the major signal in the 31P NMR (26 ppm, green) spectrum. The coupling constants for Pt-P (1JPt-P = 4418 Hz) and Pt-CH3 (2JPt-H = 72 Hz) are indicative of a cis relationship between these two ligands. Furthermore, the large coupling constant of 4418 Hz in the 31P NMR spectrum is suggestive of a weak trans influence ligand, supporting the assignment for complex 2.26.7  Figure 2.13 1H-31P HMBC NMR spectrum of the reaction between 2.22 and PhI after 16 hours at 100 \u00b0C showing the 3JP-H correlation between the new Pt-phosphine signal and new Pt-methyl signal. According to our proposed mechanism, replacement of the labile dimethyl sulfide ligand with a second strongly donating phosphine was expected to inhibit toluene formation. This hypothesis was supported by experiments with bisphosphine complex 2.23, which does not react with PhI at temperatures up to 100 \u00b0C. 75  2.4 Possible mechanisms for observed product distribution in oxidative addition of phenyl iodide to platinum(II) phosphine complexes   The presence of methane, ethane, and ethylene pose an interesting question regarding the mechanism of the oxidative addition of phenyl iodide and the subsequent reductive elimination processes. While the observation of toluene in these systems indicate that oxidative addition of phenyl iodide to 2.21 and 2.22 does occur, it does not give any insight into how the gaseous species, metallic platinum or 2.25 are formed during the reactions.  On the assumption that the initial step after ligand dissociation is the oxidative addition of phenyl iodide to 2.21\/2.22 to give the platinum(IV) complexes 2.27\/2.28 (Scheme 2.10), several pathways can be considered that result in the formation of one or more of the observed products. Firstly, pathway 1 (Scheme 2.10) in which the platinum(IV) intermediate undergoes selective reductive elimination of toluene to give 2.24\/2.26 directly. This alone cannot account for the platinum phenyl complex 2.25 or the presence of ethane. Secondly, in pathway 2 the platinum(IV) intermediate can react with 2.21\/2.22 in a methyl transfer reaction giving rise to platinum(IV) trimethyl complex 2.29 and a new platinum(II) phenyl methyl complex 2.30. Methyl transfer reactions have been studied for high valent platinum complexes bearing both chelating nitrogen and phosphine ligands providing precedent for this pathway.149 The trimethyl platinum(IV) complex can then undergo reductive elimination of ethane to give the product 2.24\/2.26. The platinum(II) phenyl methyl complex, 2.30 can then react in two possible ways, with another equivalent of phenyl iodide or reductively eliminate toluene. The latter results in the formation of metallic platinum and the former would most likely result in the reductive elimination of biphenyl due to the favourable Csp2-Csp2 reductive elimination from Pt(IV).150 As biphenyl was not observed in any of the reactions described above it can be ruled out. Finally, pathway 3 involves the platinum(IV) intermediate undergoing competitive reductive elimination of ethane or toluene to give rise to both observed products 2.24\/2.26 and 2.25. This mechanism is plausible if the energy barriers to reductive elimination of ethane and toluene are comparable. Furthermore, it has been shown that Csp2-Csp3 reductive elimination from platinum(IV) complexes is favoured compared to Csp3-Csp3 when both are possible and could therefore explain the observed product distribution favouring toluene formation over ethane formation.151,152 76  It seems most likely that the reaction between 2.21 and phenyl iodide occurs because of a competitive reductive elimination process. However, the possibility that two or more mechanisms are active in combination cannot be ruled out.   Scheme 2.10 Possible mechanisms for the observed products in the reactions between phosphine complexes 2.21\/2.22 and PhI. The reaction between 2.22 and phenyl iodide produces metallic platinum as mentioned above. This is interesting as it most likely rules out the mechanism involving competitive reductive elimination of toluene and ethane. This is rationalised by the fact that phenyl iodide reductive elimination from Pt(II) to give Pt(0) has no precedence in the literature and that the microscopic reverse is a relatively facile process that has been studied previously.153\u2013155 However, pathway 2 77  does provide a viable pathway to all the observed products. After oxidative addition the methyl transfer occurs giving rise to 2.29 that can reductively eliminate ethane giving 2.26. The platinum(II) complex 2.30 can then reductively eliminate toluene to give platinum metal.  The trace amounts of methane and ethylene can be rationalised by a few pathways. It is possible that methane is generated by the C-H activation of phenyl iodide, followed by Csp2-H RE. The kinetic preference for a C-H bond over a Csp2-X bond has been demonstrated for rhodium and iridium complexes.156,157 However, the resulting rhodium and iridium hydride species are not thermodynamically stable and so reductive elimination of the aryl halide occurs and eventually results in the Csp2-X cleavage to the thermodynamically favoured rhodium and iridium halide species. Alternatively, the C-H activation of ethane and subsequent reductive elimination of methane coupled with a beta hydride elimination of ethane also explains the presence of both gases. 2.5 Summary This chapter describes the first well defined example of intermolecular oxidative addition of aryl halides to platinum(II) dialkyl complexes. It was found that toluene was produced as the sole product when strongly donating NHC ligands are employed but that a mixture of products were generated with phosphines.  Furthermore, the strength of the secondary ligand (pyridine or dimethyl sulfide) plays an important role in the oxidative addition of phenyl iodide, with weaker donors proving more efficient. This was further corroborated by DFT calculation that showed facile ligand loss followed by a concerted oxidative addition mechanism and subsequent reductive elimination of toluene. This work also expands on the literature reported procedures for this type of reaction which had required the tethering of the aryl halide to the ligand scaffold. Additionally, the reaction was expanded to show that both electron withdrawing and electron donating phosphine containing platinum(II) complexes were also suitable for oxidative addition of aryl halides but that one or more different mechanism are operating compared to the selective NHC analogues. The demonstrated generality of these reactions opens avenues towards catalytic reactions involving redox cycles with aryl halides. 78  Chapter 3: Synthesis of a tridentate (C,N,N) N-heterocyclic carbene diamine ligand: complexation and reactivity with platinum and boron The work conducted in this chapter including design of experiments, synthesis and characterisation was carried out by me. X-ray diffraction data was collected and refined by Dr Benjamin Gelfand. 3.1 Introduction N-heterocyclic carbenes (NHCs) have become ubiquitous in modern chemistry since the isolation of the first NHC by Arduengo.158,159 NHC\u2019s and their salt precursors have been employed in a diverse range of applications ranging from organocatalysts,160,161 ligands in homogenous catalysis,134,162\u2013165 ionic liquids166,167 and frustrated Lewis acid base pairs (FLPs).168\u2013170 One feature of NHCs is the relative ease at which they can be functionalised with respect to sterics, electronics and heteroatom incorporation.171 This modular approach has allowed for many different functional groups to be introduced at the side arm of NHCs, some of which include pyridyl,172 amide,173 oxygen,174 sulfur,175 and phosphine containing scaffolds (Figure 3.1).176  Figure 3.1 Selection of NHCs with wing tip heteroatom functionalisations. 3.1.1 Abnormal N-heterocyclic carbenes. Another class of NHC that has been receiving significant interest over the last few decades is abnormal N-heterocyclic carbenes (aNHC) (Figure 3.2). aNHCs are stronger sigma donors due to the decreased population of the sp2 orbital on the carbene carbon relative to normal NHCs.177 The stronger sigma donor effect can have fundamental implications in stabilising highly reactive intermediates as well increasing reactivity of catalysts.178 79   Figure 3.2 Select examples of aNHC metal complexes bearing C-2 H atoms. C-2, C-4 and C-5 carbon atoms are labelled for clarity. Synthesis of aNHCs can be challenging as the C-2 proton is more acidic than the C-4\/5 protons and therefore more reactive towards bases and C-H activation pathways. As a result, many aNHCs are synthesised by blocking the C-2 position of normal NHCs to induce C-H activation of the backbone. Other routes have also been reported that include oxidative addition of a C-I bond at the C-4\/5 position,179 formation of the silver adduct and selective C-H activation of the C-4\/5 position by geometrical constraints of the side arm functional group (Figure 3.2).  What has become apparent in the literature is the lack of examples for the synthesis of aNHC complexes without the protection of the C-2 position. Currently, there are only a handful of examples which selectively form the aNHC over a classical NHC when both the C-2 and C-4\/5 positions bare hydrogen atoms (Figure 3.2). One advantage of a system which can selectively C-H activate the C-4\/5 position over the C-2 position, is the potential to form (hetero)bimetallic species via the formation of another M-C bond at the C-2 position (Figure 3.3). The bimetallic complex could promote dual or cascade reactions if the two metal centres show reactivity toward different processes. However, limited examples of bimetallic species connected via an imidazolium core exist (Figure 3.3).  80   Figure 3.3 Select examples of (hetero)bimetallic complexes 3.1.2 Diazaboryl ligands Isoelectronic to an NHC is the diazaboryl anion which replaces the central C-2 carbon atom in an NHC with a boron anion (Scheme 3.1, A). The diazaboryl anion was first isolated by Nozaki and Yamashita utilising the strongly reducing naphthyl radical anion to give a diazaboryl anion from the corresponding diaminohaloborane (Scheme 3.1, B).180,181   Scheme 3.1. A: structures of an NHC and diazaboryl anion. B: Synthesis of a diazaboryllithium compound. These complexes have interesting properties that are akin to NHCs. The vacant p-orbital on boron acts similarly to the empty sp2 orbital on the C-2 carbon NHC, that is the nitrogen substituents donate their lone pair electron density into the empty orbital stabilising the boryl lone pair making these types of molecules interesting ligands for coordination chemistry with transition metals. However, the degree of \u03c0-backdonation was calculated to be only 4-6% of the 81  total electron density of metal-boron bond, in contrast 11-13% was found for the analogous NHC complexes.182 Furthermore, the strongly donating properties of boryl ligands allow for the generation of electron rich metal complexes that could be employed in redox reactions of late transition metals.183 There has been a significant amount of work dedicated to understanding the interactions of boryl species with platinum catalysts due to the efficacy shown by platinum for the hydroboration of alkenes, which operates through the generation of platinum boryl species. Boryl ligands possess strong trans influence properties, making them ideal for studying unsaturated low coordinate intermediates with respect to platinum mediated C-X and C-H activation reactions.184,185 For example the Braunschweig group has demonstrated how boryl ligands can be used to generate T-shaped complexes with open coordination sites in the trans position to the boryl ligand where no C-H agostic or solvent interactions exist (Scheme 3.2).186,187 T-shaped complexes have been invoked in several redox reactions involving C-H as well as C-X bonds at platinum, but these species have only been isolated as cationic or agostic stabilised complexes.135,137,188 A true neutral platinum T-shaped complex has yet to be isolated, and the diazaboryl motif could provide an entry into this space with several examples providing evidence that these ligands promote stabilisation of open coordination sites during catalysis.189   Scheme 3.2. Halogen abstraction from a Pt(II) boryl complex showing the formation and stabilisation of an unsaturated T-shaped complex The diazaboryl ligand has been receiving great attention with regards towards catalytic borylation of C-H bonds. The Xu and Li groups are developing chiral diazaboryl ligands that are showing great efficacy for the enantioselective borylation of  Csp2-H bonds (Scheme 3.3)189,190 In the work by Ke and Xu, the authors proposed that the active species is an unsaturated Iridium(III) complex with open coordination sites that allow for the control of regioselectivity in the reaction. C-H borylation has been studied extensively (see introduction chapter 1.1.3.3) and calculations of the mechanism have shown the need for open coordination sites due to the 82  required sigma complex formation. Thus, it stands to reason that the strong trans influence of the boryl ligand can promote and stabilise the required open site.  Scheme 3.3. C-H borylation of Csp2-H bonds via a chiral diazaboryl iridium catalyst Furthermore, boryl ligands have also been employed by Yamashita and Nozaki, who leveraged the utility of the diazaboryl ligand and applied it towards novel olefin polymerization catalysts.191 The catalysts showed reactivity similar to other hafnium half sandwich complexes and shows the possibility of expanding on these ligands for further catalyst development in this area. Lastly, Conejero and co-workers have used both NHCs and diazaboryl ligands to show the discrete nature of B-H sigma complex formation that leads to an eventual B-C bond formation with platinum complexes. Using the strongly sigma donating properties and good steric protection of NHCs, with the diazboryl ligand has allowed for the isolation of reactive intermediates invoked in Csp3 borylation reactions at platinum.81 While both mono and bidentate boryl ligands have been made, as described in the above examples, a ligand which incorporates both an NHC as well as a diazaboryl unit has yet to be synthesised (Scheme 3.4). Such a ligand could be of interest to the wider organometallic and main group communities as both a transition metal ligand and\/or as a frustrated Lewis pair (FLP). Additionally, chelating NHCs are amongst the most popular chelating ligands in transition metal catalysed reactions. It therefore stands to reason that an N-heterocyclic carbene \u2013 N-83  Heterocyclic boryl (NHC-NHB) ligand could provide new insights into small molecule activation reactions.   Scheme 3.4. Proposed general structure of an NHC-NHB ligand precursor and the proposed NHC-NHB metal complex.  3.2 Synthesis and characterisation of C,N,N tridentate imidazolium ligands. The design of a viable synthetic route for the synthesis of the NHC-NHB ligand was initiated with a retrosynthetic analysis of the target ligand. Retrosynthesis 1 (Scheme 3.5 A) proved the simplest route with each fragment being easily synthesised in 1-2 steps. Experimentally, both the diazborolidine and mesityl imidazole were successfully synthesised. However, final coupling the diazborolidine with mesityl imidazole was not successful under any conditions. In retrosynthesis 2, the linker is connected to the mesitylimidazole core prior to insertion of the boron, by a proposed SN2 reaction of a diamine with an alkyl halide substituted imidazolium salt (Scheme 3.5 B). Unfortunately, E2 elimination of HCl from the alkyl halide always occurred in the presence of any nucleophile. Finally, retrosynthesis 3 builds upon retrosynthesis 2 by tethering one half of the diamine backbone onto the mesityl imidazole core first. Reductive amination with an aldehyde then then furnishes the target NHC diamine before boron condensation. 84   Scheme 3.5 Retrosynthetic analysis of the target NHC-NHB ligand via different fragmentation patterns. With the syntheses for retrosynthesis 1 and 2 (Scheme 3.5) failing, the synthesis of the NHC-NHB ligand was attempted following the analysis for retrosynthesis 3. The synthesis of the target ligand uses simple organic and inorganic transformations over a series of 10 steps. Isolation and yields are good varying from 60-99% (Scheme 3.6 and 3.7). The imidazole core which features mesityl (3.1) or 2,6-diisopropylphenyl (3.2) groups were synthesised according to literature procedure.192,193 Access to the amine tethered imidazolium salts were attempted via two routes: (i) one, with 2-bromoethylamine.HBr and (ii) one using 2-bromoethylpthalimide followed by hydrazinolysis. Route (i) gave low yields and used excess imidazole (Dipp or Mes), which was inefficient when trying to synthesise larger scales. Route (ii) gave yields upwards of 70% (3.3\/3.4). Quantitative anion exchange from bromide to PF6 was then carried out (3.5\/3.6) Finally, hydrazinolysis was nearly quantitative making this the preferred route even though an additional step is required (3.7\/3.8). 85   Scheme 3.6. Synthesis of compounds 3.1-3.8 After synthesis of the amine tethered imidazolium salt, the remainder of the diamine backbone was synthesised in the steps outlined in (Scheme 3.7). Mesitylaniline was condensed with dimethoxyacetaldehyde to give the imine 3.9 in near quantitative yield. Facile reduction of the imine was carried out using NaBH4 to yield 3.10. Protection of the amine with an acid stable protecting group such as FMOC-Cl is required for the deprotection of the acetal 3.11 to the aldehyde 3.12. Finally, the reductive amination to the diamine was then carried out with NaBH(OAc)3. FMOC deprotection with piperidine then followed to give the imidazolium salts 3.13 (67% yield) and 3.14 (scheme 3.7).  86   Scheme 3.7. Synthesis of compounds 3.7-3.14 Solid state characterisation by single crystals X-ray diffraction was carried out for 3.13 (Figure 3.8). With the ligand in hand, we set out to complete the final boron condensation to yield the target NHC-NHB. Additionally, coordination of 3.13 to platinum was also investigated.  87   Scheme 3.8. ORTEP depiction of the solid-state stricture of compound 3.13 (ellipsoids are set 50% probability, minor portions of disorder have been omitted for clarity)88  3.3 Attempted insertion of boron into the diamine backbone of 3.13 to form an NHC-NHB ligand As discussed in the introduction portion of this chapter the synthesis of platinum boryl species could be of interest for the formation of low valent intermediates relevant to small molecule activation. More specifically, the formation of a vacant or open coordination site must occur to allow for coordination of the molecule being activated. In the case of the oxidative addition of aryl halides, as discussed in chapter 2, the iodine lone pair coordinates to the platinum centre after the dissociation of a neutral ligand. Based on this mechanism the incorporation of a boryl moiety into the ligand scaffold (3.15, Scheme 3.9) could stabilise the open coordination site due to the strong trans-influence that boryl ligands possess (3.16, Scheme 3.9). Therefore, the synthesis of a chelating NHC-NHB ligand could allow for this to occur while maintaining an electron rich environment that has been shown to cleave both C-X and C-H bonds.  Scheme 3.9 General depiction of the synthesis of an NHC-NHB precursor ligand and coordination to platinum. Initial attempts at installing boron into the diamine backbone proved challenging. Traditional condensation methods using BBr3 generally resulted in unidentifiable reaction mixtures regardless of the base or solvent employed (Table 3.1). One of the inherent issues that has been encountered is the solubility of the ligand. Typically, boron condensations with BBr3 are carried out in non-polar solvents such as toluene or hexane with NEt3 as a base, however as 3.13 is a salt and the solubility in alkanes is negligible. In aromatic solvents like toluene, 3.13 is soluble but only at elevated temperatures. The issue of solubility is further exacerbated by the similar solubility profile of the resulting triethylammonium hydrobromide side product, which would render the isolation of the NHC-NHB (3.17) compound exceptionally difficult. Thus, inorganic bases were used, such as NaH and CaH2 to avoid separation issues. However, these bases are also insoluble in most solvents causing slow and ineffective reactivity (Table 3.1).  89   ENTRY BASE SOLVENT TEMP OUTCOME 1 2 NEt3 Toluene RT -> 55 \u00b0C Decomp 2 2 NaH THF\/Toluene (1:1) RT Ring opened THF 3 2 NaH DCM RT Decomp 4  2 NaH Toluene RT Decomp 5 CaH2 Toluene 0 -> RT Decomp Table 3.1 Attempted conditions for the insertion of Boron into the diamine backbone of 3.13 Using THF as the solvent would be beneficial as the solubility of 3.13 is much higher and the by-product salts can then be easily filtered from the reaction mixture. However, THF and BBr3 are incompatible due to the lewis acid activated ring opening of THF (entry 2, table 1). To negate this reactivity BBr3 was substituted with phenyl dichloroborane (PhBCl2) which does not induce C-O bond cleavage of ethers. Fortunately, reaction between 3.13 and PhBCl2 in THF with CaH2 as a base, resulted in the insertion of the boron species into the diamine backbone (Scheme 3.10).  90    Scheme 3.10 Scheme for the insertion of PhCl2B into the diamine backbone of 3.13 and 1 H NMR spectra of 3.13 (CDCl3, bottom), reaction mixture (dcm-d2, middle) and crystals obtained from the reaction mixture (dcm-d2, top). When the 1H NMR spectra of 3.13, the reaction mixture, and a recrystallised sample are stacked together, a characteristic shift of the CH2\u2019s in the diamine backbone occurred. This shift and change in splitting pattern can be attributed to the insertion of the boron and formation of a five membered ring giving rise to 3.18. The formation of the diazaborolidine results in the backbone CH2\u2019s becoming inequivalent due to axial and equatorial positions. Furthermore, three new aromatic signals which correspond to the phenyl group bonded to the boron atom can also be seen. The new aromatic signals integrate well with the remaining signals supporting the insertion of boron. Finally, the 11B 91  NMR spectrum also shows a broad signal around 30 ppm which is characteristic of diazaborolidines (Figure 3.4).  Figure 3.4 11B NMR spectrum (dcm-d2, 192 MHz, 25 \u00b0C) of 3.18  Together the 1H and 11B NMR spectra suggest that insertion of PhBCl2 was successful, and that it is possible for a boron species to be introduced into the diamine backbone. However, one of the challenges that must be overcome is having the correct substituent at boron. The intended method for formation of the Pt-B bond is via an oxidative addition of a B-X (X = halogen) bond to Pt(0) giving a X-Pt(II)-B species (3.19, Scheme 3.11). Deprotonation of the imidazolium salt and chelation to platinum gives the target NHC-NHB complex 3.20 (Scheme 3.11). Therefore, installing a boron species into the diamine backbone which results in B-X bond is critical to the realisation of the desired Pt complex. Whilst the above example in scheme 3.10 shows the possibility of forming the diazaborolidine, the B-Ph bond, would most likely not undergo the required OA reaction to furnish the Pt(II)-B species.  92   Scheme 3.11 General schematic for the Intended method of coordination of the NHC-NHB ligand to platinum. To install a halogen containing boron species, an alternative path was devised using a tin-boron exchange reaction. Installing Sn into the diamine backbone should be less difficult than boron. Reacting Me2SnCl2 with the precursor ligand 3.13 in the presence of base in a variety of solvents did not yield the desired tin product (Table 3.2).    ENTRY SOLVENT BASE TIME TEMP OUTCOME 1 THF\/Toluene CaH2 24 h Rt No reaction 2 Benzene 2 NEt3 24 h 80 \u00b0C No reaction 3 Acetonitrile 2 NEt3 1 h 80 \u00b0C No reaction Table 3.2 Conditions for the attempted insertion of Me2Sn into the diamine backbone of 3.13 While it\u2019s quite surprising that the tin insertion wasn\u2019t successful, it possible that because of the proximity to the imidazolium salt the insertions are somehow affected. To test this hypothesis the silver dicarbene complex 3.22 was synthesised and used in place of 3.13. The coordination of the imidazolium salt to silver protects the C-2 position from unwanted reaction. When 3.22 was reacted with Me2SnCl2 in the presence of four equivalents of NEt3 in toluene at 80 \u00b0C, two new species were detected. However, analysis of the 1H NMR spectrum revealed that one of the set of signals showed characteristics 93  resonances for an imidazolium salt with a proton at the C-2 position (scheme 3.12, green arrows) while the other set only showed the characteristic doublets for the backbone protons of a C-2 bound carbene (Scheme 3.12, red arrows).   Scheme 3.12 Synthesis of Silver dicarbene complex 3.22. Attempted insertion of Me2SnCl2 into the diamine backbone of the silver dicarbene complex 3.22. 1H NMR spectrum (Toluene-d8, 400 MHz, 25 \u00b0C) of the reaction mixture after 18 hours at 80 \u00b0C. One explanation for the protonation of the carbene can come from the resulting NEt3.HCl salt side product after insertion of Me2SnCl2. The presence of the weak acid could 94  protonate one of the carbene ligands off the silver generating an imidazolium salt (3.23) and a mono ligated silver carbene complex (3.24, Scheme 3.13). To test the above hypothesis, a simple control experiment was devised. Compound 3.22 was reacted with excess NH4Cl in toluene-d8 at 80 \u00b0C. Indeed, after several minutes at 80 \u00b0C analysis of the 1H NMR spectrum of the reaction between 3.22 and NH4Cl confirmed the protonation of only one carbene to the imidazolium salt (3.23), leaving half an equivalent of the mono carbene silver complex (3.24). Stacking the 1H NMR spectra of the reaction between 3.22 and Me2SnCl2 as well as 3.22 with NH4Cl shows the resulting products have similar splitting patterns and confirms the proposed products of the reaction between 3.22 and Me2SnCl2.   Scheme 3.13 Control experiment showing the effect of NH4Cl on the silver dicarbene complex 3.22. Stacked 1H NMR spectra of the reaction mixture between 3.22, Me2SnCl2 and NEt3 (bottom) and the control experiment between 3.22 and NH4Cl (top) 95  Although, insertion of the tin was achieved the resulting mixture of the imidazolium salt and silver complex hampers the usefulness of this reaction as separating a mixture of products becomes very challenging. More optimisation is required to effectively install boron or tin into the diamine backbone of 3.13 or 3.22. Due to time constraints no further reactivity could be carried out. However, future work should focus on the optimisation of the boron insertion, specifically with respect to the bases and boron source used. The successful insertion of PhBCl2 into the diamine backbone of 3.13 does gives an indication that BCl3 could a be used to access the correct structure.  3.4 Synthesis and characterisation of normal and abnormal carbene platinum complexes Concurrent to the installation of boron into the diamine backbone of 3.13, the coordination chemistry of 3.13 to platinum was also of interest. Recently, the Glorius group reported on a ruthenium catalyst (3.25, Scheme 3.14) for asymmetric hydrogenations that features both an NHC and a diamine ligand.194 After addition of H2 across the amido ligand the catalyst is then able to hydrogenate various organic molecules (3.26). The potential for the N-H site in 3.13 to act in a similar manner but for C-H activation, made coordination of 3.13 to platinum appealing. Addition of a C-H bond to amido ligands have been extensively utilised in early transition metal 2+1 addition reactions (see chapter 1). Late transition metals often rely on oxidative addition or AMLA\/CMD mechanisms making the use of an amido\/amine ligand for late transition metal mediated C-H activation an interesting approach.  Scheme 3.14 H2 activation at a ruthenium NHC diamine complex.  Initial attempts at complexing 3.13 to platinum via C-H activation with Me4Pt2(\u00b5-SMe2)2 were successful (Scheme 3.15) . The 1H NMR (acetone-d6, 400 MHz, 25 \u00b0C) spectrum of 96  the reaction mixture showed two distinct Pt-Me environments at 0.07 ppm and -0.54 ppm, with platinum satellites (2JPt-H = 80 and 81 Hz, respectively), and were found to be in a 3:1 ratio. Further evidence of imidazolium C-H activation is provided by the detection of methane in the 1H NMR spectrum at 0.17 ppm (Scheme 3.15)   Scheme 3.15. 1H NMR spectrum (acetone-d6, 400 MHz, 25 \u00b0C) of the reaction mixture between 3.13 and Me4Pt2(SMe2)2 after 18 h at 55 \u00b0C. Single crystals suitable for X-ray diffraction were grown from a solution of the reaction mixture in THF and layered with hexane at room temperature. One isomer was unambiguously assigned as the abnormal carbene platinum complex 3.27 (Figure 3.5).  97   Figure 3.5 ORTEP depiction of the solid-state structure of complex 3.27 (ellipsoids are set at 50% probability, minor portions of disorder have been omitted for clarity). Further analysis of the 1H NMR spectrum of the reaction mixture (Figure 3.6), confirmed the major species as the abnormal carbene complex 3.27. This assignment was supported by the observation of platinum satellites for the resonance at 6.7 ppm, which corresponds to the proton at the C-5 position. Furthermore, the resonance at 6.7 ppm also shows through space correlations to the Pt-Me group, which can only be observed when bound via the abnormal carbene motif (Figure 3.7).   Figure 3.6 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C) showing the 3JPt-H coupling between Pt and the imidazolium proton.  3.27 98   Figure 3.7 1H-1H NOESY NMR spectrum (Acetone-d6, 600 MHz, 25 \u00b0C) showing the NOE interaction between imidazolium proton and adjacent Pt-Me resonance.  The structure of the minor product from the above reaction mixture was proposed to be the C-2 bound analogue of 3.28 by 1H 2-D NOESY NMR spectroscopy. The resonances at 7.55 ppm and 7.15 ppm are doublets which is also the case for C-2 bound carbenes such as IMes or IPr. The correlation between these protons was observed in the NOESY spectrum of the reaction mixture (Figure 3.9) and the resonance attributed to the C-2 proton is no longer visible. This evidence leads to the conclusion that the NHC is bound via the C-2 carbon. This assignment was then unambiguously confirmed by X-ray crystallography (Figure 3.8).  99   Figure 3.8 ORTEP depiction of the solid-state molecular structure of 3.28 (ellipsoids are set at 50 % probability, minor portions of disorder have been omitted for clarity)  Figure 3.9 1H-1H NOESY NMR spectrum (Acetone-d6, 600 MHz, 25 \u00b0C) showing the NOE interactions between C4\/5 backbone protons in 3.28. Attempts at forcing a change in the product distribution in favour of either 3.27 or 3.28 was unsuccessful. Changing the solvent, the temperature and or the reaction length always returned the 3:1 product ratio favouring 3.27 over 3.28. Thus, the synthesis of 3.28 was attempted via 3.28 100  transmetallation from silver dicarbene complex 3.22. Transmetallation of the carbene to PtMeCl(SMe2)2 in acetone with one equivalent of AgPF6 gave rise to the new C-2 bound complex 3.29 (Scheme 3.16). Unfortunately, 3.29 is not the desired tridentate C-2 bound NHC complex, but a bidentate C-2 bound complex with a pendent amine group. The assignment was made based on the characteristic resonances of the dimethyl sulfide ligand, which maintains its coordination to platinum. The two dimethyl sulfide methyl groups are not equivalent, presumably because of restricted rotation due to the nearby mesityl substituent. One resonance is clearly observed at 1.7 ppm (3JPt-H = 62 Hz) and integrates to three protons with respect to the methyl resonance at 0.25 ppm (2JPt-H = 53 Hz) . The coupling of the platinum satellites measuring 62 Hz are consistent with a weak trans-influence ligand in the opposing position, i.e. an amino group (Scheme 3.16). The second dimethyl sulfide resonance is buried underneath the mesityl methyl resonances and was therefore not resolved. The structure of 3.29 was confirmed by x-ray diffraction showing the unusual trans-orientation of the methyl and NHC (Figure 3.10). This geometry is unusual due to strong trans-influence of these ligands. Usually, strong trans-influence ligands prefer to be in a cis-orientation, when possible, to lower the overall thermodynamic energy of the complex. Heating of 3.29 in dioxane at 100 \u00b0C for two days showed no change in the coordination environment. Other solvents such as DMSO, and acetonitrile also failed to give the desired complex.   3.29, Pt-SMe2 101   Scheme 3.16 Synthetic scheme for the synthesis of tridentate C-2 bound complex 3.29 from 3.22 and PtClMe(SMe2)2 and AgPF6. 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C) of the reaction between 3.22 and PtClMe(SMe2)2 after 2 hours at 50 \u00b0C.  Figure 3.10 ORTEP depiction of the solid-state structure of complex 3.29 (ellipsoids are set at 50% probability) Chelation of the pendent amine group could be possible after deprotonation of the amine with formation of a neutral amido platinum(II) complex. Therefore, 3.29 was subjected to deprotonation by KHMDS (potassium bis(trimethylsilyl)amide) in toluene at room temperature 3JPt-H = 62 Hz 102  for two days. After two days a dark green solution was found, the 1H NMR spectrum of the reaction mixture provided evidence for the deprotonation of one of the amines (Scheme 3.17).   Scheme 3.17 Deprotonation of 3.29 by KHMDS to give the amido complex 3.30. However, pendent amine deprotonation was not detected, instead deprotonation of the already coordinated amine to the amido ligand was observed. This assignment is based on several characteristic resonances in the 1H NMR spectrum. Firstly, the dimethyl sulfide is still bound to platinum and shows platinum satellites (3JPt-H = 42 Hz). Secondly, the coupling constant between Pt and the protons in the methyl groups of dimethyl sulfide showed a decrease in magnitude from 61 Hz to 42 Hz. This decrease in coupling magnitude is consistent with an increase in trans-influence by the opposing nitrogen ligand, which occurs due to the increased sigma donation on going from a neutral to an anionic ligand. Furthermore, the deprotonation of the coordinated amine to an amido changes the hybridisation of the nitrogen atom from sp3 to sp2 forcing the CH2 groups either side of the nitrogen atom into a planar arrangement. This makes the protons in each CH2 environment equivalent in the 1H NMR spectrum (Scheme 3.11). The complex 3.30 is air sensitive, decomposing in solution after several minutes when exposed to air. 103   Figure 3.11 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) showing the change in  symmetry of the CH2 backbone protons as well as the equivalent dimethyl sulfide ligand relative to 3.29. This series of complexes could have some application towards C-H activation reactions. The pendent amine group could be utilised as a remote intramolecular base for deprotonations, either by abstraction of a hydride or a concerted deprotonation of a C-H bond. Additionally, amido ligands have been used extensively in early transition metals for 1+2 addition C-H activation and complex 3.30 could be leveraged in similar reactions.  3.5 Reactivity of abnormal carbene platinum complex 3.28 One of the advantages of aNHC complexes with a proton in the C-2 position is the possibility of further functionalisation with another metal. As described in section 3.1.1, bimetallic complexes bridged by an imidazolium core have not been extensively explored. Synthesis of bimetallic complexes of 3.28 were therefore attempted. To avoid isolation of 3.28, it was thought possible that a double C-H activation to form the bimetallic complex 3.31 (Scheme 3.18) was possible. However, reacting ligand 3.13 and one equivalent of the dimeric platinum starting material Me4Pt2(\u00b5-SMe2)2 in acetone at 55 \u00b0C did not yield the doubly C-H activated bimetallic species 3.31. Instead, the 3:1 ratio of 104  3.28\/3.29 was observed along with significant amounts of metallic platinum. The presence of metallic platinum can be explained by the decomposition of Me4Pt2(\u00b5SMe2)2 at elevated temperatures in acetone. Changing solvent and temperature of the reaction had no effect on the second C-H activation. Sequential C-H activation reactions at the C-2 position seem more challenging once the imidazole core is bound to platinum at the C-4 position. Further reactivity around the formation of bimetallic species were therefore carried out with isolated 3.28.  Scheme 3.18 Attempted double C-H activation of 3.13 to give a bimetallic platinum complex bridged by an imidazolium core Reacting 3.28 with (py)2PtMe2 did not yield the desired C-H activated bimetallic complexes 3.32 either, suggesting that the C-2 position is not reactive to C-H activation pathways (Scheme 3.19). The steric congestion around the C-2 position could be responsible for the lack of reaction. The steric bulk of the mesityl ring could be inhibiting the C-2 C-H activation by keeping the incoming Pt-Me from approaching.   Scheme 3.19 Attempted C-H activation of the C-2 proton of 3.28 with (py)2PtMe2 to give bimetallic complex 3.32 105  Strategies involving deprotonation of the C-2 position were then considered as an alternative entry point. Reacting 3.28 in the presence of one equivalent of NaH and one equivalent of Me2Pt(py)2 in benzene-d6 at 80 \u00b0C also failed to give any of the desired product (Scheme 3.20). Switching solvent to THF and stirring 3.28 with NaH prior to addition of (py)2PtMe2 gave rise to an unidentifiable mixture by 1H NMR spectroscopy. Due to the low solubility of NaH any deprotonation at the C-2 position would be slow, furthermore, because of the strength of the base there is no guarantee of selectivity between the C-2 position and the N-H sites. As an alternative, the more soluble and weaker base, KOtBu, was used. The strategy being that increasing the solubility of the base would increase reactivity and not require heating of the reaction, which could have deleterious side reactions. Reacting 3.28 with 1.1 equivalents of KOtBu and 0.5 equivalents of Me4Pt2(\u00b5-SMe2)2 turned the reaction mixture yellow immediately. However, analysis of this reaction mixture by 1H NMR spectroscopy showed a complicated spectrum where no characteristic resonances were observed.   Scheme 3.20 Deprotonation of 3.28 with NaH or KOtBu in benzene-d6 or THF-d8 to give bimetallic complex 3.31\/32 Several reactions involving the synthesis of Pd NHC complexes (PEPPSI catalysts) utilise the Pd halide complex along with the imidazolium salt and simple inorganic bases such as Na2CO3 or K2CO3. The weak base can deprotonate small quantities of the imidazolium salt allowing it to coordinate to the metal. Complex 3.28, Na2CO3 and PtCl2(SMe2)2 were stirred in THF at room temperature for two days before removing the solvent and recording the 1H NMR spectrum. Unfortunately, no reaction to the desired 3.33 (Scheme 3.22) was observed and the C2 proton of 3.28 was still intact and observable in the 1H NMR spectrum. 106   Scheme 3.21 PEPPSI like synthesis of bimetallic platinum complexes. Unfortunately, reactions between 3.28 and other metals in presence of bases did not result in the synthesis of bimetallic species. To synthesises the desired bimetallic targets, the deprotonation of the C-2 position of 3.28 was attempted with a variety of bases. Isolation of the deprotonated complex should allow for the coordination of the C-2 position to another metal. The reaction described above with KOtBu gave rise to a yellow colour, indicative of a reaction taking place. To probe this, the reaction was conducted a second time without the presence of the added platinum source. Complex 3.28 was suspended in toluene-d8 and on addition of KOtBu, the solid dissolved immediately and the solution turned a deep yellow. The 1H NMR spectrum revealed that the C-2 proton from 3.28 was no longer visible in the downfield region of the spectrum to give the proposed 3.34 (Scheme 3.23). 107    Scheme 3.22 Reaction scheme for the deprotonation of 3.28 with KOtBu in toluene-d8. 1H NMR spectrum (Toluene-d8, 400 MHz, 25 C) showing the disappearance of the downfield shifted C-2 proton. Some amount of complex 3.29 was carried over from the previous step but did not react Attempts at isolating 3.34 from the reaction mixture were not successful and difficulties removing both tBuOH and KOtBu from the reaction mixture prompted a switch in base. However, the disappearance of the C-2 proton resonance from the reaction mixture suggests that the deprotonation of the C-2 position over the N-H sites is a realistic endeavour.  Another base that has been used extensively in deprotonation reactions of NHCs is the potassium amide base KHMDS. The formation of the silyl amine is irreversible with NHCs and can generally be washed away by hydrocarbon solvents. Furthermore, the good solubility in both polar and non-polar solvents make this base a good alternative to KOtBu systems. When 3.28 was reacted with one equivalent of KHMDS in toluene-d8 the suspension immediately dissolved and turned yellow. The 1H NMR spectrum of this reaction showed a decrease in the intensity as well a broadening of the signals. Furthermore, the backbone CH2 region became broad, and the distinct N-H resonances 108  were no longer observable. This is likely because of partial deprotonation of the C-2 and N-H sites of the complex and is tentatively assigned as an equilibrium between the possible deprotonation of all sites (3.35-3.37, Scheme 3.24).    Scheme 3.23 Representation of the deprotonation equilibrium of 3.28 by one equivalent of KHMDS in THF-d8. 1H NMR spectrum (THF-d8, 400 MHz, 25 \u00b0C)  showing the broadened signals of the CH2 backbone and C-2 protons. 2.2 equivalents of KHMDS were then used to force the equilibrium towards the complex with either two or more deprotonations. After addition of the excess KHMDS the reaction once again turned a deep yellow colour. The 1H NMR spectrum showed a new set of signals that had not been detected previously (Scheme 3.25). Furthermore, the broadened signals were now sharp and resolved. The 1H NMR spectrum of this species looks remarkably similar to that of complex 3.30 (Scheme 3.18). This seems to suggest 109  that at least one of the N-H ligands has been deprotonated to the amido (3.38 or 3.39, scheme 3.25). Furthermore, the absence of the C-2 proton in the spectrum confirms that two sites have been deprotonated and that a platinate complex has been formed (Scheme 3.25). The methyl signal observed at just below 0 ppm has platinum satellites with a coupling constant of 90 Hz. This is consistent with a neutral and low trans influence ligand in the opposing position and is suggestive of an amino ligand and not an amido. This leads to the conclusion that the amine trans to the aNHC has been deprotonated, i.e. structure 3.39 (scheme 3.25)   Scheme 3.24 Deprotonation of 3.28 with 2.2 equivalents of KHMDS in THF-d8 showing the multiple deprotonations have occurred to form a platinate complexes. 1H NMR spectrum (THF-d8, 400 MHz, 25 \u00b0C) showing the backbone CH2 protons characteristic of N-H deprotonation. 110  Due to time constraints no further reactivity of 3.39 was carried out. However, future work should be concerned with the isolation of 3.39 as well as the functionalisation of the C-2 position with other metal complexes. The Synthesis of a diverse series of (hetero)bimetallic complexes should be feasible using a variety of metal halide complexes such as those in scheme 3.26. Bimetallic complexes could be used in cascade or tandem reactions, especially those concerning C-H activation reactions. Furthermore, the C-2 bound complexes 3.29 and 3.30 should also be explored in terms of using the pendant amine group as tethered base in C-H activation reactions.   Scheme 3.25 synthesis of (hetero)bimetallic complexes 3.40 3.6 Summary The tridentate NHC diamine ligand 3.13 was successfully synthesised in this chapter and its reactivity with both boron and platinum explored. Boron insertion into the diamine backbone of 3.13 was successfully achieved with PhBCl2 but the reaction was not optimised and subsequent coordination to platinum was not attempted due to time constraints. Although, the target NHC-NHB ligand was made, the B-Ph bond in 3.18 is unlikely to react via oxidative addition to Pt(0). Thus, optimisation of the boron insertion into 3.13 with different boron sources such as BCl3 or BH3.THF should be carried out.  Additionally, the ligand precursor 3.13 was also subjected to coordination to platinum via C-H activation of the imidazolium ring. C-H activation of the imidazolium ring led to  a mixture of abnormal (3.28) and normal carbene complexes (3.29) in a ratio of 3:1. Reactivity of the abnormal carbene complex 3.28 is of interest due to the possible formation of bimetallic species via deprotonation of the C-2 proton and subsequent coordination to another metal. Studies involving the deprotonation of 3.28 showed that in the presence of 2.2 equivalents of KHMDS, both the C-2 proton and one of the N-H sites are deprotonated to give the proposed platinate 111  complex 3.39. Due to time constraints no further reactivity regarding the formation of bimetallic species was conducted. Future work should be concerned with optimisation of the deprotonation and formation of a series of bimetallic species. 112  Chapter 4: Mechanistic investigation into the ortho C-H activation of pyridine via the formation of a Pt-Pt bonded bimetallic intermediate. The work conducted in this chapter has been carried out in collaboration with the Prof. Pierre Kennepohl and his student Xing Tong. Xing carried out all the DFT calculations as well as the charge decomposition analysis in section 4.4. X-ray diffraction data was collected and refined by Dr Benjamin Gelfand. The remainder of the work (design of experiments, synthesis and characterisation) was carried out by myself. 4.1 introduction N-heteroaromatic functionalization is an important process for the synthesis of diverse bioactive molecules and energy related materials.10 Conventional cross-coupling techniques (e.g. Negishi coupling) have been successfully employed in the functionalisation of N-containing aromatics. However, pre-functionalisation is almost always required in the form of either an organometallic reagent,195,196 (pseudo)halide functionalisation,197 and or protection of the nitrogen atom with Lewis acids.196,198 Similarly, pyridine N-oxides have been used extensively in Pd catalysed (carbon-hydrogen) C-H functionalization since Fagnou showed their utility in 2005.199 C-H functionalisation of N-heteroaromatics, especially quinoline, have been achieved using a variety of directing groups.200 However, C-H functionalisation of un-activated and un-directed N-heteroaromatics remains a challenge due to the inherent Lewis basicity of the nitrogen atom, meaning only a few systems have been developed (Figure 4.1).201,202  Figure 4.1 A. Yu and co-workers meta C-H functionalisation of pyridine with olefins. B. Alb\u00e9niz and co-workers C-H functionalisation of pyridine with aryl halides. 113  Although catalytic processes for direct pyridine C-H functionalisation are scarce, progress has been made with respect to stoichiometric pyridine C-H activation. Mechanistic insights into these processes can shed light not only on the reaction in question but can realise new reaction pathways that can be applied to gain a desired outcome. Bergman and co-workers demonstrated that N-containing heterocycles are activated at a rhodium complex via the formation of an N-heterocyclic carbene intermediate (Figure 4.2). 203,204 The Holland group showed that Fe(I) \u03b2-diketiminate complexes could C-H activate para-functionalized pyridines that result in a pyridine bridged Fe dimer (Figure 4.2).205 Furthermore, several groups have reported on the alpha abstraction of a proton form pyridine with early transition metals, such as the example by Mindiola (Figure 4.2).206\u2013209   Figure 4.2 Select examples of C-H activated pyridine metal complexes. The example by the Holland group which shows a C-H activated pyridine bridging two iron centres is an interesting example of how two metals can be utilised to break C-H bonds. This type of reactivity has been extensively exploited in group 9 (hetero)bimetallic complexes, specifically for the breaking of CO and CO2. The Thomas group have expanded upon this theme by employing an early-late heterobimetallic complex of cobalt and zirconium to activate the ortho position of 4-methylpyridine to give rise to a pyridine bridged Co-Zr bimetallic complex (Scheme 4.1).210 114   Scheme 4.1 C-H activation of 4-methylpyridine by an early-late heterobimetallic cobalt-zirconium complex. The dual metal nature of this complex perfectly masks the challenges of pyridine activation. The favourable coordination to zirconium by the nitrogen atom in 4-methyl pyridine allows for the interaction of the ortho C-H bond into with the more electron rich cobalt metal which is perfectly suited to breaking C-H bonds via oxidative addition. The dual metal reactivity is further enhanced by the donor-acceptor property in the metal-metal bond which allows for easy charge transfer between the two metals, aiding in the oxidative addition of the C-H bond. Platinum-platinum bonded bimetallic complexes have also been synthesised for many decades. The majority of these complexes have exploited the small bite angle chelating bis-phosphinomethane ligand (Figure 4.2).211\u2013216 The small bite angle makes bidentate coordination of the ligand to a single metal challenging and allows for the coordination of two platinum centres. With the exception of the top left example from Figure 4.2 the majority of the examples feature platinum in the +1 oxidation state with electron counts of 16. Most of the complexes are cationic and stabilised by large coordinating anions such as PF6.  115   Figure 4.3 Examples of Pt-Pt bimetallic complexes featuring the bis-phosphinomethane core. Another class of bimetallic platinum complexes that have been prepared feature the chelating O,O or N,O bridging ligands such as acac (acetylacetonate), acetates and pyridonates (Figure 4.4).217\u2013219 These systems have primarily been synthesised to study their solid state structures. Although, the pyridonate complex (middle box Figure 4.4) was synthesised as a potential anti-cancer therapeutic. 116   Figure 4.4 Examples of Pt-Pt bimetallic complexes featuring O,O and N,O bridging ligands. Single atom bridging bimetallic complexes of platinum have also been synthesised but are more scarce than the multi atom chelating examples above (Figure 4.5)  Figure 4.5 Examples of Pt-Pt bimetallic complexes featuring \u00b5-bridging ligands. Reactivity with these complexes has not been extensively studied with respect to small molecule activation and therefore gives an opportunity to look more closely at these reactions. Of particular interest is the Pt-Pt bond which has been hypothesised to have a similar donor-acceptor property as the heterobimetallic complexes mentioned previously. Such properties could give rise to interesting reactivity with respect to challenging bond cleavages. In the following sections, the C-H activation of pyridine is explored via a combined kinetic and DFT study. The donor-acceptor property between platinum centres is further investigated and shows that the activation barrier to C-H oxidative addition can be lowered if the Pt-Pt bond is maintained throughout the transition state.  Furthermore, time course data for the reactions is also collected and then modelled in COPASI (Complex Pathway SImulator), a kinetics modelling software, to obtain experimental reaction parameters.220  117  4.2 Reaction discovery and characterisation of isolable complexes involved in the C-H activation of pyridine.  Platinum C-H activation chemistry has a rich history dating back to the 1960\u2019s with the advent of Shilov and the subsequent Catalytica systems (see Chapter 1.2).43,99 The expansion and further development of platinum catalysts for small molecule activation is important as platinum complexes lend themselves to isolation of reactive intermediates more readily than their second and first row counterparts. While trying to identify such intermediates for the oxidative addition of aryl halides (chapter 2), the dimethyl platinum(II) complex PtMe2(C5H5N)2 (4.1, Scheme 4.2) showed release of methane after being heated in a solution of C6D6 while in the presence of phenyl iodide .   Scheme 4.2 Attempted oxidative addition of phenyl iodide to 4.1 Analysis of the reaction mixture by 1H NMR spectroscopy revealed that two pyridine ligands had undergone C-H activation and subsequent methane release to give rise to the bridged platinum(II) dimer 4.2 (Scheme 4.3). Single crystal x-ray diffraction and 1H NMR spectroscopy (Figure 4.6) confirmed the structure of 4.2. Conducting the reaction without phenyl iodide gave the same product, showing that phenyl iodide has no role in the reaction. 118   Scheme 4.3 synthesis of 4.1 and 4.2 and ORTEP depictions of the solid-state structures of 4.1 and 4.2.  Figure 4.6 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) of 4.2 showing the signal assignment to each proton environment. The discovery of this reaction stems from the original synthesis of 4.1 by Appleton, the authors describe the synthesis of 4.1 from (NBD)PtMe2 (Scheme 4.4) (NBD = norbornadiene) but noted the former undergoes decomposition in solutions of benzene and chloroform.221 The authors did not elaborate on the products of decomposition but mention that decomposition can be slowed 119  in the absence of light and at low temperature in the solid state.  Furthermore, Appleton reported 4.1 as a pale-yellow solid, but under the reaction conditions in scheme 4.3, 4.1 was isolated as a white crystalline solid. However, once 4.1 is dissolved in aromatic solvents such as benzene or toluene a yellow colour is immediately observed. This change in colour does not occur in coordinating solvents such as acetonitrile which prompted observation of the reaction by 1H NMR spectroscopy.   Scheme 4.4 Reported synthesis of 4.1 by Appleton and co-workers. Dissolution of 4.1 in acetonitrile-d3 gave a colourless solution and, upon inspection of the 1H NMR spectrum of this reaction showed that a new species was formed (Figure 4.7). Based on the free pyridine in solution as well as two new Pt-Me signals (2JPt-H = 84 Hz and 90 Hz) in the aliphatic region, the new compound was assigned as the acetonitrile complex 4.3, PtMe2(CD3CN)(C5H5N) (Scheme 4.5). No further reaction of this solution was observed after heating at 50 \u00b0C for one hour and confirms that coordinating solvents inhibit the formation of 4.2  Scheme 4.5 Reaction between 4.1 and MeCN-d3 120   Figure 4.7 Stacked 1H NMR spectrum (MeCN-d3, 400 MHz, 25 \u00b0C) of the reaction between 4.1 and MeCN-d3 before heating (bottom) and after heating for 1 hour at 50 \u00b0C (top). Next, 4.1 was dissolved separately in acetone-d6 and toluene-d8, the two reactions were then followed by 1H NMR spectroscopy at room temperature. A faint yellow hue was observed in both cases and the observation of a new species in the 1H NMR spectrum (Figure 4.8) provided further evidence of a reaction. In both solvents the same species was detected based on the number of new resonances and their splitting patterns, although the resonances appear at different chemical shifts due to the difference in polarity of the two solvents. Methane is also observed in both spectra and can be seen at 0.16 ppm (tol-d8) and 0.17 ppm (acetone-d6).  Heating the acetone-d6 solution at 50 \u00b0C for one hour revealed an increase in the intensity of the signals corresponding to the new species, 4.4 as well as almost equal amounts of 4.2 (Figure 4.9). Platinum satellites are visible (102 Hz and 84 Hz) as well as a smaller doublet (11 Hz and 16 Hz). Integration of these new signals with respect to the platinum methyl signal at 0.3 ppm (2JPt-H = 74 Hz) shows good agreement that they belong to the same molecule and integrate to three protons each. This is indicative of a molecule with three methyl-platinum groups in 121  separate environments. Similar Pt-Me resonances with two sets of Pt coupling been previously reported by Rourke for a t-butyl C-H agostic interaction at a neutral Pt(II) complex.188     Figure 4.8 1H NMR spectrum (400 MHz, 25 \u00b0C) of 4.1 in toluene-d8 and acetone-d8 at room temperature. Inset shows the formation of the intermediate in both solvents. 122   Figure 4.9 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C) of the aliphatic region 4.1 in acetone-d6 after heating for one hour at 50 \u00b0C, showing the primary and secondary Pt-CH3 couplings. Additionally, the aromatic region of the 1H NMR spectrum indicated a more complex change in the signals relative to 4.1. A new set of signals are observed that show Pt satellites characteristic of an aryl-Pt bond (3JPt-H = 27 Hz ) (Figure 4.10). This observation supports the presence of methane in solution as a result of C-H activation of one of the pyridine ligands in 4.1. Furthermore, characteristic resonances for free pyridine are also observed in the 1H NMR spectrum indicating dissociation from 4.1 is facile even at room temperature and is in good agreement with the relative ease of formation of the acetonitrile complex 4.3.  4.1 in acetone-d6 after 1 hour at 50 \u00b0C 4.1 in acetone-d6 after 1 hour at 50 \u00b0C 123  Figure 4.10 1H NMR spectrum  of the aromatic region of 4.1 in acetone after one hour of heating Based on the above observations and the literature precedence for agostic interactions giving multiple Pt-H couplings, an alpha agostic interaction bridging two platinum centres was initially proposed (4.5, Figure 4.11). This would explain both the initial platinum coupling (2JPt-H) to the methyl and the secondary smaller platinum coupling (3JPt-Pt-H).  Figure 4.11 Proposed methyl agostic complex 4.5. However, single crystals suitable for X-ray diffraction grown from this reaction mixture showed the structure of the intermediate as a Pt-Pt bonded species bridged by one C-H activated pyridine (4.4, Figure 4.12A). The Pt-Pt bond distance is 2.700 \u00c5, suggestive of a single Pt-Pt bond and consistent with reported examples.216,222\u2013225 This complex is closely related to the Pt-Pt bimetallic complexes bridged by bis(diphenyl)phosphinomethane ligands described in section 4.1. Furthermore, 4.4 shares its general structure with the complexes described by Puddephatt (Figure 4.12A), both of which have one platinum centre in the square planar geometry and one in the square based pyramidal geometry and connected through a Pt-Pt bond. No Pt-H agostic interactions from methyl or terminal pyridine ligands were observed with the closest Pt-H distance being 3.028 \u00c5.  124   Figure 4.12 A. Pt-Pt bonded intermediate 4.4 and Puddephatt\u2019s Pt-Pt bonded complex with the diphenylphosphino methane core. B. ORTEP depiction of the solid-state structure of 4.4 (ellipsoids are set 50% probability) To confirm whether the connectivity of the solid state structure was the same in solution, 4.1 was heated in toluene at 50 \u00b0C for 2 hours. To the solution was added hexane until a beige solid started to precipitate. The suspension was stirred for one hour before decanting the liquid and drying the solids under reduced pressure. 1H NMR spectroscopic analysis of the solids gave a mixture of 4.1, 4.2 and 4.4. Fortunately, 4.4 was the most concentrated species resulting in a more resolved aromatic region and identification of the signals corresponding to 4.4 (Figure 4.13). 125    Figure 4.13. 1H NMR spectrum (Tol-d8, 400 MHz, 25 \u00b0C) of the aromatic region of reaction of 4.1 in toluene-d8 after two hours at 50 \u00b0C followed by removal of all volatiles. Inset shows full spectrum. With a more resolved aromatic region it is possible to identify the protons belonging to the pyridine ligand which has been C-H activated. The two protons which reside next to the nitrogen atom (ortho HN) and next to the Pt-Caryl bond (ortho HC) have characteristic 3JPt-H satellites, although they are not well resolved, the magnitude of the coupling constants were identified as 27 Hz (ortho HN) and 53 Hz (ortho HC). The difference in magnitude of the coupling is likely due to the shorter Pt-Caryl bond length (1.958 \u00c5) vs the Pt-N bond length (2.103 \u00c5). Furthermore, the HN and Hc signals appear to be similar to the signals corresponding to the same protons in complex 4.2 justifying the assignment. 1H 2-D NOESY NMR spectroscopy was also conducted to distinguish the different methyl signals from each other. NOE interactions between the C-H activated pyridine protons and the three methyl signals in the aliphatic region confirmed the connectivity of the solid state is the same in solution. Looking at the NOE interactions of the three Pt-Me resonances, only two of the three resonances have NOE. Based on the solid-state structure it is possible to see that the two Pt-Me groups ligated to the same platinum are the only methyl ligands that could have NOE. The lone methyl on the adjacent platinum is too far away to interact with either of the other methyl ligands. Therefore, the assignment of the lone methyl can be made as the left most 126  resonance of the three Pt-Me signals (Pt-Me1, Figure 4.14). This signal is also one of the two which has the additional 3JPt-Pt-H coupling.   Figure 4.14 1H-1H NOESY NMR spectrum (Tol-d8, 400 MHz, 25 \u00b0C) of the aliphatic region of a reaction mixture of containing 4.4, 4.1 and 4.2  127    Figure 4.15 1H-1H NOESY NMR spectrum (tol-d8, 400 MHz, 25 \u00b0C) of the aliphatic and aromatic regions of a reaction mixture containing 4.4, 4.1 and 4.2. Looking at the NOE interactions between the methyl and aromatic region shows that all three methyl groups have NOE in common with one other proton resonance. This proton belongs to the ortho position of the terminal pyridine ligand (H1, Figure 4.15) coordinated to the platinum with only one methyl group. As the pyridine molecule has free rotation about the Pt-N bond all three methyl groups within range to observe NOE. The Pt-CH3 interaction with H1 also confirms which of the two ortho pyridine resonances is which. Therefore, the remaining ortho pyridine resonance (H2) can be identified as the terminal pyridine ligand attached to the platinum with two methyl groups. The NOE interactions show that only one methyl resonance has through space interactions with H2 and must correspond to the methyl that is at 90 \u00b0 to H2 (Pt-Me3) as the other methyl signals are either on the opposite side (Pt-Me2) or on adjacent platinum centres (Pt-Me1). This observation confirms that the second resonance with 2JPt-Pt-H coupling is the middle Pt-Me signal (Pt-Me2). This leaves the question why the third signal (Pt-Me3) doesn\u2019t show the additional coupling. Unfortunately, comparing the 1H NMR spectrum of 4.4 to that of Puddephatt\u2019s complex (Figure 4.12A) was not helpful as the two methyl groups were symmetrical and the single resonance correlating to both methyl groups showed the additional 128  coupling, albeit small (6 Hz). Therefore, more spectroscopic and or computational work is required to identify the reason behind the lack of additional coupling to Pt-Me3. 4.2.1 1H NMR spectroscopic analysis and solid characterisation of side product  As described above, heating complex 4.1 gives rise to 4.2 as well the intermediate bimetallic complex 4.4. However, a side reaction was always detected when heating the reaction for extended periods of time and especially at higher temperatures. Trituration of the reaction mixture to isolate 4.2 from the side reaction failed but returned a well resolved mixture of 4.2 and the side product (Figure 4.16). Additionally, the side reaction occurs in a variety of solvents including acetone, benzene, and toluene.  To establish at what point in the reaction the side reaction occurs, 4.1 was heated in toluene at 50 \u00b0C for 2 hours before removing all the volatiles. This mixture was then dissolved in benzene filtered through a glass microfibre filter and layered with hexane at room temperature, where it was left for five days. The resulting mixture of powder and crystals were separated from the solvent, dried and their 1H NMR spectra recorded. The mixture contained both 4.2 and 4.4 in a ratio of 1:0.9 as well as trace amounts of the side product. This mixture containing 4.2, 4.4 and the side product was then subjected to heating at 60 \u00b0C to see whether the side product would grow in over time. The 1H NMR spectrum of this solution was recorded at room temperature, after one and two hours of heating as well as after 20 hours at 60 \u00b0C (Figure 4.17).   129   Figure 4.16 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) of 4.2 and the side product. The region between 2.00 ppm and 6.00 has been removed for clarity (Bottom spectrum). The full spectrum trace is shown on top.   130   Figure 4.17 Stacked 1H NMR spectra (tol-d8, 400 MHz, 25 \u00b0C) of 4.2, 4.4 and the side product over time. Interestingly, the intermediate is fully consumed in this reaction and mostly generates the product 4.2 after two hours at 60 \u00b0C (Figure 4.17). The concentration of the side product does increase and becomes about three times as concentrated over the two hour period. The 1H NMR spectrum after 20 hours at 60 \u00b0C shows no change from the reaction mixture after two hours, with the exception of an increase in the amount of free pyridine. However, the ratio of side product to the complex 4.2 remained the same across both spectra. Noteworthy is that the concentration of the side product stopped increasing once the intermediate was fully consumed which indicates that it could be forming from the intermediate 4.4. Attempts to elucidate the structure of 4.6 by 1H NMR spectroscopy were undertaken. Unfortunately, due to not being able to isolate 4.6 from 4.2, all 1H NMR spectra contain 4.2. The mixture from Figure 4.16 was analysed by 1H-1H COSY NMR spectroscopy to correlate signals which are adjacent to each other. However, only a few signals were identified due to the mostly overlapping signals from 4.2. Most notably, the very downfield shifted peak at 10.5 ppm (doublet J = 5 Hz) shows correlation with a signal at 6.3 ppm and integrates to 2.3 protons relative to the 10.5 ppm signal. Although the signal is overlapping with an adjacent signal and most likely integrates to two protons. Furthermore, the signal at 6.3 ppm also shows correlation to the 20 hours at 60 \u00b0C 2 hours at 60 \u00b0C 1 hour at 60 \u00b0C 131  signal at 6.8 ppm. In turn, the signal at 6.8 ppm shows correlation to the characteristic resonance at 7.8 ppm which has platinum satellites and corresponds to the proton next to the Pt-Caryl bond (ortho HC) of a C-H activated pyridine ring. This together suggest that that these 4 signals correspond to a pyridine ring which is coordinated to at least one platinum centre. However, the integration of 2 for the signal at 6.3 ppm doesn\u2019t align with such a characterisation.     Figure 4.18 1H-1H COSY NMR spectrum (C6D6, 400 MHz, 25 \u00b0C) of a mixture containing 4.2 and 4.6. The mixture containing 4.2 and 4.6 was then dissolved in pyridine-d5 in the hopes that any terminal pyridine ligands would be washed out and replaced by deuterated pyridine ligands leaving any bridging or C-H activated pyridine ligand unchanged. The 1H NMR spectrum was recorded directly after dissolution in pyridine-d5 followed by heating of the solution at 40 \u00b0C 132  overnight, before recording the 1H NMR spectrum again. This resulted in the expected exchange of the terminal ligands in 4.2 as well as one signal in the side product 4.6 (Figure 4.19). Presumably, the other two resonances corresponding to the terminal pyridine ligand in 4.6 are overlapping with signals from 4.2 and were not identified.  Figure 4.19 1H NMR spectra (pyridine-d5, 400 MHz, 25 \u00b0C) of 4.2 and 4.6 in pyridine-d5 at room temperature (bottom) and the same mixture after heating at 40 C for 18 hours (top). This experiment reveals that many of the signals in the side product 4.6 correspond to pyridine ligands which have been C-H activated. Due to the overlap of several signals in the 1H NMR spectrum, same reaction mixture was recorded on a 600 MHz spectrometer for better resolution of the signals. Indeed, the signals were much more resolved and identification of the splitting patterns as well as several other peaks which had been obscured were now revealed (Figure 4.20). Furthermore, it\u2019s now possible to see that every one of the ten signals integrates to one proton each for a total of 10 protons (Figure 4.20).  4.2 + 4.6 in pyridine-d5 after 18 h at 40 \u00b0C 4.2 + 4.6 in pyridine-d5 at rt 133   Figure 4.20 1H NMR spectrum (pyridine-d5, 600 MHz, 25 \u00b0C) of the aromatic region of 4.2 and 4.6. Full spectrum above. A 1H 2-D NOESY NMR experiment was conducted of this same mixture to identify as many signals with NOE as possible. One of the more useful aspects of NOESY NMR spectroscopy is the ability to see through space interactions of signals that are overlapping with each other in the corresponding 1-D spectrum. For example, in Figure 4.20 there were 10 proton environments that could be identified, the 1H NOESY NMR spectrum (Figure 4.21) also shows two additional signals which are buried beneath the more intense signals of 4.2 giving rise to 12 different proton environments for 4.6. This is interesting as it correlates very well with three separate C-H activated pyridine rings which each have four distinct proton environments. 134   Figure 4.21 1H-1H NOESY NMR spectrum (Pyridine-d5, 600 MHz, 25 \u00b0C) of the aromatic region of 4.2 and 4.6. The distinct signal at 8.25 ppm, which is observed as a doublet and integrates to one proton, has apparent NOE with the meta HN\/C resonance at 6.45 ppm. This is not the case as two separate molecules cannot have NOE and the phase of the signal in the 1H-1H NOESY spectrum remains the same so exchange of the two signals can also be ruled out. Therefore, the correlation between the signal at 8.25 ppm and the one at 6.45 ppm must correspond to a signal being hidden by the more intense resonance from 4.2. Similarly, the signal at 7.5 ppm just to the right of the large peak, has apparent NOE with the ortho HC proton from 4.2 but most likely corresponds to a buried signal. Additionally, methyl resonances were also observed in the aliphatic region although they were not well resolved. They do, however, show NOE with some of the resonances in the aromatic region. Most interestingly is one of the methyl resonances which shows NOE to two aromatic signals whilst the other Pt-Me resonances shows only one. However, because the reaction is in pyridine-d5 it can be expected that the terminal pyridine resonances which were washed out by pyridine-d5 would show additional NOE to this methyl resonance. Furthermore, the two methyl resonances did not show any NOE between them, indicating that they likely occupy positions on separate platinum centres. 135   Figure 4.22 1H-1H NOESY NMR spectrum (pyridine-d5, 600 MHz, 25 \u00b0C) showing NOE correlation between the aliphatic Pt-Me resonances and the aromatic pyridine resonances. Lastly, crystals suitable for X-ray diffraction were finally isolated from this mixture by fractional crystallisation of a benzene\/hexane solution. The solid state structure of 4.6 was confirmed to have three C-H activated pyridine ligands but also contained three separate Pt centres (Figure 4.23). Furthermore, Pt-Me ligands indeed occupied separate platinum centres, although there are actually three Pt-Me ligands instead of two suggesting that one of the resonances in the 1H NMR spectrum is buried beneath the larger more intense Pt-Me resonance of 4.2. 136    Figure 4.23 ORTEP depiction of the solid-state structure of 4.6 (ellipsoids are set 50% probability). The identification of 4.6 suggests that the either the intermediate 4.4 or the final product 4.2 reacts with another equivalent of the starting material 4.1 in a third C-H activation reaction. The structure of 4.6 features three platinum environments with square based pyramidal (SBP), pseudo octahedral and square planar geometries. However, the Pt-Pt bond between the SBP and octahedral platinum atoms has a distance of 3.063 \u00c5, which is significantly larger than Pt-Pt bond distance in 4.4 and is likely not a full bond but possibly a weak interaction instead. The isolation of 4.6 does insinuate that further C-H activation reactions are possible and would allow for the synthesis of a chain of platinum atoms. Further work should focus on understanding the conditions required to synthesise such complexes.  137  4.3 Time course analysis of the C-H activation of 4.1 Time course analysis of the reaction was conducted to obtain experimental reaction parameters, which would then be compared to computational calculations to gain a full picture of the reaction mechanism. Concentration vs time data was collected by 1H NMR spectroscopy in triplicate over a temperature range from 30-60 \u00b0C. Each time point was collected by a single 90\u00b0 pulse at five minute intervals to allow for relaxation of all resonances. Each sample was prepared inside the glovebox in the following manner: an NMR tube fitted with a screw cap was loaded with ~ 10 mg of 4.1. To a mass spec vial was added 0.5 mL of a 0.043 M stock solution of trimethoxybenzene (TMB) in toluene-d8. A syringe fitted with a needle was backfilled in the glovebox and the needle capped with a rubber septum to protect the nitrogen atmosphere. The spectrometer was brought to the corresponding temperature, before locking, shimming, and tuning the magnet with a dummy sample containing a mixture of the reaction in toluene-d8. To the NMR tube containing 4.1 was then added all of the stock solution containing the internal standard, TMB. the dummy sample was removed from the spectrometer with the lock still engaged and replaced by the real sample. The sample was shimmed and allowed to equilibrate to the correct temperature for five-minutes before recording the first spectrum. Subsequent data points were then recorded in five-minute intervals over the next eight hours for a total of 94 spectra. Due to the highly reactive nature of 4.1 in all non-coordinating solvents, a stock solution of 4.1 was not possible, therefore the solid was added manually each time. The error in weighing out 4.1 resulted in different starting concentrations for each run. The time course data for each isolable species (4.1, 4.4 and 4.2) across the temperature range 30-60 \u00b0C is shown in the graphs below (Figure 4.24).      138   Scheme 4.6 Reaction of 4.1 to give 4.4 and 4.2.   Figure 4.24 Time course data for the consumption of 4.1 over eight hours at 30-60 \u00b0C (top left). Time course data for the formation and consumption of 4.4 over eight hours at 30-60 \u00b0C (top right). Time course data for the formation of 4.2 over eight hours at 30-60 \u00b0C (bottom). These data give a good overview of the temperature dependence of the reaction and that incremental changes in the temperature give rise to a significant change in the rate of reaction. Furthermore, the time course data allows for the kinetic modelling of the reaction parameters using COPASI, an open source kinetic modelling software.220 From the modelled data the rate constants for the formation of 4.2 from 4.4 were obtained and an Eyring plot generated to give the experimental activation energy barrier for this step. 139  4.3.1 Time course analysis of the C-H activation of 4.1 at 30 \u00b0C and excess pyridine experiments Initial reactions were conducted at 30 \u00b0C to gauge the overall profile of the reaction. The time course data for three separate reactions of 4.1 in toluene-d8 were plotted (Figure 4.25). The concentration of 4.1, 4.2, 4.4 and pyridine could be collected and were plotted against the total mass balance of the reaction (equation 1).   Equation 1   A decrease in the total mass balance of the reaction was observed in all three runs (Figure 4.25), which was attributed to decomposition to metallic platinum. Furthermore, the concentration of pyridine stays slightly higher relative to the concentration of 4.4, which is consistent with decomposition to metallic platinum and release of free pyridine. Small quantities of metallic platinum are observed when the reaction mixture is filtered through a glass microfibre filter. In all cases the initial reaction from 4.1 to 4.4 occurs relatively easily at 30 \u00b0C but the reaction from 4.4 to 4.2 is sluggish and only trace amounts of 4.2 are observed across all three runs. The fast consumption of 4.1 and slow formation of 4.2 is suggestive of a lower activation barrier for the initial C-H activation to form 4.4 and a higher activation barrier for the subsequent C-H activation from 4.4 to 4.2. 140     Figure 4.25 Reaction schematic showing the overall stoichiometry of the reaction, excluding the side product 4.6. Time course data for the reaction in the above scheme at 30 \u00b0C (Run 1, top left). Time course data for the reaction in the above scheme at 30 \u00b0C (Run 2, top right). Time course data for the reaction in the above scheme at 30 \u00b0C (Run 3, bottom) From the time course in Figure 4.25, two distinct regimes can be seen (Box 1 and Box 2) that have different rates. This observation is indicative of a pre-equilibrium possibly due to a reversible dissociation of pyridine in the early stages of the reaction. A reversible dissociation of pyridine could be indicative of the formation of a T-shaped complex with an open coordination site (4.7, Scheme 4.7). To provide support for this theory, the reaction of 4.1 in C6D6 was conducted with 1.5 equivalents of added pyridine.  Box 2 Box 1 141   Scheme 4.7 Reaction showing the dissociation of pyridine to form the T-shaped complex 4.7 The excess pyridine should slow the dissociation of pyridine from 4.1 and the overall reaction. Indeed, in the presence of the added pyridine the reaction was inhibited, showing no signs of 4.4 at room temperature. The reaction was then heated in an oil bath at 60 \u00b0C for one hour. For comparison, when the reaction is carried out at 60 \u00b0C without added pyridine, full consumption of 4.1 and 4.4 is achieved within two hours.  However, as seen in the Figure 4.26 only small amounts of intermediate 4.4 and product 4.2 are formed within the two-hour period. The reaction required heating at 60 \u00b0C for 17 hours to see major consumption of 4.1 and even then, unreacted 4.1 is visible in the 1H NMR spectrum (Figure 4.26). With continued heating at 60 \u00b0C the full consumption of 4.1 was still not complete, indicating that with excess pyridine the reaction is very slow (Figure 4.26 top). 142      Figure 4.26 Reaction schematic of 4.1 in the presence of 1.5 equivalents of pyridine in C6D6 at 60 \u00b0C over 48 hours. Stacked 1H NMR spectra of the reaction between 4.1 and 1.5 equivalents of pyridine at 60 \u00b0C over 48 hours. The slowed reactivity of 4.1 in the presence of added pyridine certainly supports to the notion that dissociation of pyridine is necessary for the reaction to proceed. Additionally, the reaction of 4.1 with acetonitrile-d3 to give complex 4.3 (PtMe2(pyridine)(CD3CN) also shows the lability of pyridine in 4.1.  4.1 + 1.5 pyridine after 48 h at 60 \u00b0C in benzene-d6 4.1 + 1.5 pyridine after 17 h at 60 \u00b0C in benzene-d6 4.1 + 1.5 pyridine after 1 h at 60 \u00b0C in benzene-d6 4.1 + 1.5 pyridine at rt in benzene-d6 143   4.3.2 Time course analysis of the C-H activation of 4.1 at 40 \u00b0C Plotting the time course data for the reaction of 4.1 in toluene-d8 at 40 \u00b0C over a period of eight hours gave similar results when compared to the reaction at 30 \u00b0C. The three triplicate experiments are presented below showing the concentration of all species relative to the mass balance of the reaction. Two distinct rate regimes are observed again (Figure 4.28, Box 1 and Box 2). Overall, the mass balance of the reaction is not conserved but this is likely a result of the formation of metallic platinum throughout the reaction as well as formation of trace amount of the side product 4.6. As expected with the increasing temperature the rate of formation of 4.4 and thus the consumption of 4.1 is faster relative to the reaction at 30 \u00b0C. This observation is also noticeable by the reaction reaching the second rate regime in a shorter period of time (Box 1 and Box 2)  144     Figure 4.27 Reaction scheme for the reaction of 4.1 at 40 \u00b0C. Time course data for the reaction at 40 \u00b0C (Run 1, top left). Time course data for the reaction at 40 \u00b0C (Run 2, top right). Time course data for the reaction at 40 \u00b0C (Run 3, bottom) 4.3.3 Time course analysis of the C-H activation of 4.1 at 50 \u00b0C The reaction at 50 \u00b0C was significantly faster than at 40 \u00b0C and 30 \u00b0C, in these reactions the mass balance change across the time course data is not significant (Figure 4.28); however, at these higher temperatures the formation of the side product was more noticeable. The time course data for the reaction at 50 \u00b0C is shown below (Figure 4.28). Furthermore, the concentration of the side product 4.6 is high enough to allow for integration of the signals in the 1H NMR spectrum and has therefore been plotted alongside the other species and included in the total mass balance. Inclusion of the concentration of 4.6 shows a near constant mass balance in run 2 and 3 (Figure 4.28) which means that decomposition to metallic platinum constitutes only a minor part of the mass balance. This also means that the mass balance difference in the reactions at 40 \u00b0C could be due to the formation of 4.6 but because of the low intensity of the signals corresponding to 4.6 in the 1H NMR spectra they could not be integrated and plotted.  Box 1 Box 2 145      Figure 4.28 Reaction scheme for the reaction of 4.1 at 50 \u00b0C. Time course data for the reaction 50 \u00b0C (Run 1, top left). Time course data for the reaction at 50 \u00b0C (Run 2, top right). Time course data for the reaction at 50 \u00b0C (Run 1, bottom) The observed initial rate regime, which is likely due to the reversible dissociation of pyridine, is significantly faster at 50 \u00b0C than compared to the reactions at 30 \u00b0C and 40 \u00b0C. This is supported by the formation of 4.4 reaching its peak concentration much earlier on and reacting towards the product 4.2 (Figure 4.28, Box 1 and Box 2).  4.3.4 Time course analysis of the C-H activation of 4.1 at 60 \u00b0C The time course data for the reaction at 60 \u00b0C showed similar trends when compared to 50 \u00b0C, with a rapid consumption of 4.1 and fast formation of 4.2. The time course data is shown in the graphs below (Figure 4.29). Box 1 Box 2 146      Figure 4.29 Reaction scheme for the reaction of 4.1 at 60 \u00b0C.Time course data for the reaction 60 \u00b0C (Run 1, top left). Time course data for the reaction at 60 \u00b0C (Run 2, top right). Time course data for the reaction at 60 \u00b0C (Run 1, bottom) Accounting for the formation of 4.6 in the time course data gives a consistent mass balance for runs 1 and 3. However, run 2 still shows a significant decrease in mass balance over the course of the reaction. Although, the trends in the concentration of all the species is the similar across all runs. The two rate regimes are in the reaction at 60 C are now almost indistinguishable from each other as the concentration of 4.4 reaches its peak within the first 3-4 data points before reacting towards the product 4.2 (Box 1 and Box 2, Figure 4.29). This observation is in good agreement with a significantly faster first C-H activation step compared to the slower second step which is accelerated at higher temperatures. Box 1 Box 2 147  4.3.5 Attempted modelling of time course data. With the time course data collected, COPASI was used to model the reaction to obtain experimental parameters, specifically the rate constants so that an Eyring plot could be generated to calculate the transition state energy barriers for C-H activation.  The COPASI model was defined by the model shown in Scheme 4.8 by fitting the rate constants k1, k2, k3 and k4 to two separate experimental data sets from the time course data presented above. Furthermore, due to the instantaneous reaction of 4.1, COPASI was allowed to determine the initial concentration of all modelled species. Concentration of all species were set to an upper bound of 1.0 M and a lower bound of 1e-5 M to allow for quicker function evaluation. No constraints were placed on any parameters allowing COPASI to find the sum of least squares fit of every experimental data set. Attempts at modelling the reaction using a reversible dissociation of pyridine for k1 (scheme 4.8) proved successful for the reactions conducted at lower temperatures. However, modelling a reversible dissociation of pyridine at 60 \u00b0C resulted in the rate constants for k2 being an order of magnitude lower than for k2 in the reactions at 30 \u00b0C and 40 \u00b0C. This observation could be due to the fact that the first time point is collected after 5 minutes, at which point the reaction has already reached the second rate regime which does not allow for modelling of the pre equilibrium. As a result, the model in Scheme 4.7 was chosen to best represent the experimental data at all temperatures. The model describes the reaction as if the reverse binding of pyridine to 4.7 is negligible or that the reaction has already reached the second rate regime. The model in Scheme 4.7 fits the experimental data well across all temperatures for the majority of the reaction; but does not model the early stages of the reaction at 30 \u00b0C well due to the pre-equilibrium. It is important to note that regardless of the model used the rate constants for k3, that is the formation of 4.2 from 4.4 and pyridine, were always consistent across all temperatures.   148   Scheme 4.8 Reaction steps used to describe the COPASI model. Plots of the experimental data with the COPASI fits are shown below along with a table of rate constants for k2 and k3 as well as the sum of squares of the fits. 149   Figure 4.30 Parameter estimation plot for the time course data of the C-H activation of 4.1 at 30 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine. 150    Figure 4.31 Parameter estimation plot for the time course data of the C-H activation of 4.1 at 40 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine.  151   Figure 4.32 Parameter estimation plot for the time course data of the C-H activation of 4.1 at 50 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine, [side] = 4.6 152   Figure 4.33 Parameter estimation plot for the time course data of the C-H activation of 4.1 at 60 \u00b0C. [SM] = 4.1, [2-int] = 4.4, [p] = 4.2, [py] = pyridine, [side] = 4.6 From the modelled time course data, the rate constants for k2, the formation of 4.4 from 4.1, and k3, the formation of 4.2 from 4.4 were obtained (Table 4.1) and the Eyring plots generated (Figure 4.34).  Temp (K) Rate constant k2 (L\u00b7mol-1\u00b7s-1) Rate constant k3 (L\u00b7mol-1\u00b7s-1) Sum of squares  303.15  0.0323 0.000517 1.56E-6 313.15 0.0568 0.00160 6.35E-5 323.15 0.138 0.00579 4.37E-6 333.15 0.365 0.0174 5.38E-5 Table 4.1 Rate constants at each temperature interval for the first and second C-H activation as described in Scheme 4.7.  153    Figure 4.34 Eyring plots for the formation of 4.4  from 4.1 (left) and formation of 4.2 from 4.4 (right) \u0394H\u2021 and \u0394S\u2021 for k2 and k3 were calculated from the Eyring plots shown in Figure 4.34. \u0394G\u2021 was then calculated using the values of \u0394H\u2021 and \u0394S\u2021.  Calculation for the determination of \u0394G\u2021 for the reaction between 4.1 and 4.4 \u0394H\u2021 = - R * Slope = -8.314 * -7897.5 = 65663.6 J\/mol = 15.7 kcal\u00b7mol-1   Equation 2 \u0394S\u2021 = - intercept * R = -6.9892 * 8.314 = -58.1121 J\/mol = -13.9 cal\u00b7mol-1\u00b7K-1 Equation 3 \u0394G\u2021 = \u0394H\u2021 -T\u0394S\u2021          Equation 4 \u0394G\u2021  = 65663.6 \u2013 303.15 * -58.1121 = 83280.3 J\/mol = 19.9 kcal\u00b7mol-1   Equation 5 Calculation for the determination of \u0394G\u2021 for the reaction between 4.4 and 4.2 \u0394H\u2021 = - R * Slope = -8.314 * -11630.2 = 96699.1 J\/mol = 23.1 kcal\u00b7mol-1   Equation 6 \u0394S\u2021 = - intercept * R = 1.2785 * 8.314 = 10.6299 J\/mol = 2.54 cal\u00b7mol-1\u00b7K-1  Equation 7 \u0394G\u2021 = \u0394H\u2021 -T\u0394S\u2021          Equation 8 \u0394G\u2021  = 96699.1 \u2013 303.15 * 10.6299 = 93476.6 J\/mol = 22.3 kcal\u00b7mol-1  Equation 9 The lower activation barrier of 19.9 kcal\u00b7mol-1 for the first C-H activation is in good agreement with a faster first step observed experimentally. Since the model doesn\u2019t account for the very initial stages of the reaction, mainly the change in rate as the concentration of pyridine increases, the activation barrier for the first step is likely to be lower than the 19.9 kcal\u00b7mol-1 calculated above. To address these shortcomings further experimental data is required to be able to model the pre-equilibrium and obtain more accurate values for k2. However, the second C-H activation, that is the reaction from 4.4 to 4.2 was modelled well across all temperatures. The calculated \u0394G\u2021 value of 22.3 kcal\u00b7mol-1 was consistently obtained regardless of the model 154  used to describe the early stages of the reaction and compares well to the DFT calculated value of 24.0 kcal\u00b7mol-1 (see below, section 4.4.1).  4.3.6 Kinetic isotope (KIE) and para substituent effects. The deuterated analogue of 4.1 was synthesised to provide insight into the mechanism of the C-H activation. The synthesis of the deuterated analogue was carried out under the same conditions as 4.1 replacing pyridine with pyridine-d5 (Scheme 4.8).   Scheme 4.9 Synthesis of deuterated analogue 4.1-d10 To probe if both C-H activation steps show a kinetic isotope effect, the kinetics of 4.1-d10 were carried out at 30 \u00b0C. Comparison of the time course data for the reaction of 4.1 and 4.1-d10 at 30 \u00b0C, shows that 4.1-d10 is slower than 4.1 (Figure 4.35). Only trace formation of 4.2-d20 was observed at this temperature and a significant difference in the observed rate is seen.  155     Figure 4.35 Time course data for the consumption of 4.1 vs 4.1-d10 (left) and time course data for the formation of 4.4 vs 4.4-d15 ( right) and  Modelling of the deuterated data in COPASI allowed for the identification of rate constants for both C-H activation steps. The Model was kept the same as the proposed model in Scheme 4.8 to maintain consistency. Two experimental data sets were used to fit the rate constants (k2 and k3). Both experimental data sets were modelled well, with the exception of the very early stages of the reaction (Figure 4.36). The rate constants (k2 and k3) were obtained from this model which showed a positive KIE for both C-H activation steps (equations 10 and 11)  156   Figure 4.36 Parameter estimation plot for the time course data of the C-H activation of 4.1-d10  at 30 \u00b0C [SM] = 4.1-d10, [2-int] = 4.4-d15, [p] = 4.2-d20,  KIE (k2) = kH\/kD = 0.323\/0.0104 = 3.09       Equation 10 KIE (K3) = kH\/kD = 5.17e-4 \/ 3.48e-4 = 1.48       Equation 11 The positive KIE for both steps likely suggests that that C-H activation occurs in the transition state but equilibirum iotope effects are also possible which can lead to positive KIE\u2019s even when the C-H activation is not involved in the transition state. In addition to KIE experiements, the electronic effect of changing the para substituent can also be an effective way of understanding both the electronics of the transition state but also the effect of donor strength on the dissociating pyridine. Two analogues of 4.1 were synthesised with differing para functional groups, 4.1-CF3 and 4.1-NMe2 (scheme 4.10).  157    Scheme 4.10 Synthesis of para substituted platinum pyridine complexes, 4.1-CF3 and 4.1-NMe2 Based on the kinetic data and observations that added pyridine can retard the reaction, the EWG should increase the formation of the intermediate and EDG should decrease the formation of the intermediate relative to just hydrogen in the para position. Indeed, 4.1-CF3 began to immediately react to the C-H activated intermediate at room temperature upon dissolution in C6D6. On the other hand, 4.1-NMe2 was significantly slower, with signs of C-H activation only being detected after three hours at room temperature in C6D6.  Following the consumption of 4.1-CF3 at 30 \u00b0C and plotting the concentration vs time of the formation of 4.4-CF3 revealed that relative to 4.4 about one and half times as much of the intermediate 4.3-CF3 is present during the reaction (Figure 4.37). The increased concentration of 4.1-CF3 supports the notion that dissociation of at least one pyridine ligand is required prior to C-H activation occurring. The increased concentration of intermediate 4.4-CF3 is also suggestive of a lower activation energy for the first C-H activation relative to 4.1. Furthermore, an increase in the rate of formation of the product 4.2-CF3 vs 4.2 is also seen. This is likely because the electron withdrawing nature of the CF3 group weakens the C-H bond strength. 158        Figure 4.37 Time course data for the C-H activation of 4.1-CF3 at 30 \u00b0C (top left). Time course data for the consumption of 4.1 vs 4.1-CF3 (top right). Time course data for the formation of 4.4 vs 4.4-CF3 (bottom left). Time course data for the formation of 4.2 vs 4.2-CF3 (bottom right)  Two rate regimes are once again observed in the time course data (Figure 4.37); however, the second rate regime is reached much faster in the reaction with 4.1-CF3 compared to 4.1 (Box 1 and 2 top right, Figure 4.37). This observation is not unexpected based on the fact that 4.1-CF3 has weaker sigma donor ligands relative to 4.1. Therefore, the equilibrium would be shifted towards the dissociation of the ligand and formation of the intermediate 4.4-CF3.  Unfortunately, time course data for 4.1-NMe2 was not possible to collect due to very low solubility of the complex in all solvents. However, the reaction of 4.1-NMe2 was monitored over a period of 18 hours by 1H NMR spectroscopy which showed that 4.1-NMe2 reacts much slower than the other analogues, 4.1 and 4.1-CF3 (Figure 4.43). After one hour at 60 \u00b0C formation of both 4.4-NMe2 and 4.2-NMe2 was detected. Surprisingly, neither of these species were the most concentrated in solution based on relative intensity of the signals. Instead, the starting material 4.1-NMe2 was still the major species, which follows well with the assignment of an initial dissociative mechanism for the C-H activation of the first pyridine ligand. The increased donor strength of DMAP relative to pyridine and CF3-pyridine means this result is not Box 2 Box 1 159  unexpected and further supports the mechanistic interpretation thus far. Additionally, there is significant formation of product, 4.2-NMe2, after only one hour suggesting that once the intermediate is formed it converts relatively quickly to the product, this is consistent with a mechanism in which association of pyridine to the intermediates 4.4\/4.4-CF3\/4.4-NMe2 is essential for progress along the reaction coordinate to form the final products 4.2\/4.2-CF3\/4.2-NMe2.   Figure 4.38 Reaction schematic showing the products of C-H activation of 4.1-NMe2. Stacked 1H NMR spectra (Tol-d8, 400 MHz, 25 \u00b0C) of the C-H activation reaction of 4.1-NMe2 over 18 hours (Bottom: rt, middle: after one hour heating at 60 \u00b0C, top: after 18 hours heating at 60 \u00b0C). 4.1-NMe2 in tol-d8 after 18 h at 60 \u00b0C 4.1-NMe2 in tol-d8 after 1 h at 60 \u00b0C 4.1-NMe2 in tol-d8 at rt 160  The para substituted analogues of 4.1 clearly show a trend which corresponds well with a mechanism in which initial dissociation of pyridine is required to initiate the C-H activation. Furthermore, the electron deficiency of the pyridine ligands of 4.1-CF3 and the observed increased rate of formation of the intermediate 4.4-CF3 relative to the unsubstituted analogues supports the presence of an initial pre-equilibrium as discussed in section 4.3.1. Additionally, the observation of a very slow reaction of the analogue 4.1-NMe2 also provide further evidence of a dissociative mechanism.  161  4.4 DFT analysis 4.4.1 Reaction Pathway and mechanistic interpretation To supplement the kinetic data on the C-H activation of pyridine from 4.1, DFT analysis of the reaction coordinate was conducted in collaboration with Prof. Kennepohl and Xing Tong. All energies are given as the Gibbs free energy and relative to 4.1.  Based on the observed induction period and relative inhibition observed in presence of excess pyridine, the dissociation of pyridine was calculated as the initial step in the mechanism. Dissociation of one pyridine ligand from 4.1 gave two possible products. Firstly, the T-shaped complex 4.7 was found uphill relative to 4.1 by 14.9 kcal\/mol. Secondly, the toluene bound analogue, 4.8, was also found uphill relative to 4.1 by 12.2 kcal\/mol (Scheme 4.10). Lastly, two intermediates further along the reaction coordinate were found, which were only slightly higher in energy relative to 4.7 and 4.8 and result in the formation of a Pt-Pt bonded intermediate (4.9 or 4.9\u2019). These types of bimetallic complexes have been invoked in methyl for halogen exchange reactions with Pt(II) salts previously.228 The Pt-Pt bonded intermediates are very close in energy to each other and the reactants 4.7\/4.8. However, 4.9\u2019 goes on to react as part of a higher overall energy pathway that is not being considered as a plausible mechanism (see below).   162   Scheme 4.11 Reaction coordinate showing the dissociation of pyridine from 4.1 to give complexes 4.7 and 4.8 with subsequent reaction to complexes 4.9 and 4.9\u2019. Calculations performed with the DLPNO-CCSD functional and def2-TZVP basis set. Progressing through the reaction coordinate the intermediate 4.10 was found at an energy of 25.7 kcal\/mol relative to 4.1 (Scheme 4.11). A second equivalent of pyridine dissociates giving 4.10 as Y-shaped intermediate, presumably to stabilise the unsaturated nature of the metal centre. Y-shaped Pt complexes have been isolated previously and have been invoked as reaction intermediates setting some precedent for calculation of this structure.229 From the unsaturated intermediate 4.10 the reaction progresses forward by formation of the sigma complex intermediate 4.11, which was found at an energy only 1.4 kcal\/mol higher than 4.10. The C-H bond of the sigma complex is then broken via an oxidative addition transition state, 4.11-TS, which occurs at an energy barrier of 34.5 kcal\/mol relative to 4.1 (7.4 kcal\/mol relative to 4.10). The Pt(IV) hydride intermediate, 4.12, is 4.6 kcal\/mol lower in energy than the transition state and easily moves through the reductive elimination transition state, 4.12-TS (32.3 kcal\/mol) which release one equivalent of methane and results in the unsaturated intermediate 4.13. A partial interaction of the methyl protons and the adjacent Pt centre was found, presumably to stabilise the unsaturated nature of this intermediate. Finally, coordination of one molecule of pyridine gives the isolated Pt-Pt bonded complex 4.4.   163   Scheme 4.12 Reaction coordinate showing calculated intermediates 4.10-4.13 and transition states 4.11-TS and 4.12-TS. Calculations performed with the DLPNO-CCSD functional and def2-TZVP basis set A second pathway was also calculated that resulted in an oxidative addition transition state barrier of 41.7 kcal\/mol relative to 4.1 (Scheme 4.12). This pathway is ruled out due to the very high energy transition state; however, there are some notable differences between this pathway and the lower energy pathway in scheme 4.11 that require mentioning. Looking at the two transition states, the main difference lies in the Pt-Pt bond. the lower energy pathway maintains the Pt-Pt bond throughout the transition state whereas in the higher pathway the Pt-Pt bond is broken. The result of this difference is the energy required to reach the transition state from the respective reactants. For examples going from 4.11 -> 4.11-TS requires 7.4 kcal\/mol whereas going from 4.9\u2019 -> 4.14-TS requires 25.8 kcal\/mol. From a qualitative perspective it seems that if the Pt-Pt bond is maintained throughout the transition state, the energy barrier for C-H oxidative addition is significantly lower. This stands to reason the Pt-Pt bond has some effect on C-H bond breaking.   164   Scheme 4.13 Reaction coordinate showing the higher energy pathway for the formation of 4.4. Calculations performed with the DLPNO-CCSD functional and def2-TZVP basis set While late transition metals favour the oxidative addition mechanism for C-H bond activation, the reality is that depending on the degree of electron transfer between the metal, the C-H bond and the ligands, the mechanisms can interchange regardless of metal type (See introduction chapter). An alternative mechanism for the complexes described so far is a sigma bond metathesis mechanism (SBM). A transition state corresponding to a SBM was found but had a relative energy of 41.7 kcal\/mol (Figure 4.44) and so is ruled out as this barrier is inaccessible under the reaction conditions.  While the DFT calculated pathway seems reasonable, these results are not consistent with the observed kinetics and or the experimentally determined \uf044G\u2021 value of 19.9 kcal\/mol. Further DFT modelling is currently being investigated to find a lower energy pathway that does coincide with 165  the experimental data. However, the calculated pathway in Scheme 4.11 is a good first approximation.  Figure 4.39 Calculated transition state for the sigma bond metathesis mechanism for the C-H activation of pyridine. Calculated using the DLPNO-CCSD functional and def2-TZVP basis set Next, the second C-H activation step was calculated from the intermediate 4.4 to the final product 4.2 (Scheme 4.13). Two pathways were calculated as energetically feasible with a slightly lower energy pathway favouring the association of a molecule of pyridine from solution to 4.4 giving transition state complex 4.16-TS (8.8 kcal\/mol). An associative mechanism also agrees with the experimental evidence in section 4.3.6 where early formation of product was observed when the more electron donating DMAP ligand was used in place of pyridine.  Coordination of pyridine then causes an elongation of the Pt-Pt bond until it breaks moving from 4.16-TS to 4.17 giving rise to two square planar platinum centres bridged by one C-H activated pyridine ligand. The intermediate 4.18 (-10.2 kcal\/mol) is slightly downhill by 3.8 kcal\/mol relative to 4.17 (-6.4 kcal\/mol) and has dissociated a pyridine ligand, presumably so that the open coordination site can be generated to allow for the C-H oxidative addition to occur during transition state 4.18-TS. This transition state is 24.0 kcal\/mol higher in energy than the reactant 4.4. This value is in good agreement with the experimentally determined value of 22.3 kcal\/mol calculated above. Much like the higher Pathway in the first C-H activation step (Scheme 4.12), the Pt-Pt bond is not intact during this transition state and results in a higher activation barrier between reactant and product.  166   Scheme 4.14 Reaction coordinate showing the two possible pathways for the C-H activation of 4.4 -> 4.2. Calculations were carried out using the DLPNO-CCSD functional and def2-TZVP basis set 167  It is worth mentioning that a higher energy pathway involving initial dissociation of pyridine and coordination to the adjacent platinum centre was also calculated. This occurs via the intermediate 4.19 (1.8 kcal\/mol) before reaching the transition state 4.19-TS (15.5 kcal\/mol) and converging to the low lying intermediate 4.18.  After the oxidative addition transition state 4.18-TS the Pt(IV) intermediate 4.20, which consists of bridging pyridine and hydride ligands, is reached with an energy of 6.2 kcal\/mol. Again, similar to the first oxidative addition TS (Scheme 4.11), the reductive elimination transition state 4.20-TS  is close in energy to the Pt(IV) intermediate, 4.20, which allows for facile reductive elimination of a molecule of methane to give the intermediate 4.21 (-18.1 kcal\/mol). Coordination of pyridine then completes the square planar geometry and gives the final product 4.2 with an energy of -36.5 kcal\/mol relative to 4.2.  It is worth mentioning that in both the first and second C-H activation steps the resulting Pt(IV) hydride species have energies very close to the reductive elimination transition states, 2.4 and 2.5 kcal\/mol respectively. This coincides well with no detection of any Pt(IV) species throughout the reaction by 1H NMR spectroscopy.  4.4.2 Charge decomposition analysis (CDA) Charge decomposition analysis (CDA) is a useful tool for identifying the movement of electron density between specified fragments in a molecule.230 CDA can show the degree of donation and backdonation in a transition state and give insight into how the coordination environment effects specific process such C-H activation. Of particular interest is the Pt-Pt bond and how it affects the overall C-H bond cleavage. CDA was used to analyse the three transitions states that were calculated in section 4.4.1. Each transition state was divided into four fragments from which the degree of donation and backdonation was calculated (Figure 4.40). 168   Figure 4.40 Calculated transition states for the First C-H activation (4.11-TS and 4.14-TS) and second C-H activation (4.18-TS) broken into 4 separate fragments a-d.  As mentioned previously the energy difference between reactants and transition states was significantly different depending on if the Pt-Pt bond was maintained throughout the transition state. Using CDA, the net degree of electron transfer between the two platinum centres was able to be quantified (Table 4.2). The CDA revealed that when the Pt-Pt bond is intact in the transition state, as in 4.11-TS, a net positive charge transfer from the fragment a to fragment c occurs. This leads to the hypothesis that an increase in charge donation across the platinum bond lowers the relative activation barrier of the C-H activation from reactant to transition state.  Entry Frag a to c net donation change TS energy barrier (kcal\/mol) 4.11 -> 4.11-TS 0.030 7.40 4.8\u2019 -> 4.14-TS -0.056 25.8 4.18 -> 4.18-TS -0.019 23.1  Table 4.2 showing the net charge transfer between platinum atoms on going from reactant to transition state and the relative activation barrier. Being able to synthesise discrete Pt-Pt bonded species with the intent of increasing charge donation across the Pt-Pt bond for C-H activation reactions is an attractive prospect. Activating alkanes such a methane or ethane could be realised with this novel approach but significant research with respect to more stable Pt-Pt bonded species is required and is expanded upon in the future work chapter 5.    169  4.5 Reactivity of complex 4.2 4.5.1 Ligand exchange Initial reactivity of 4.2 centred around ligand exchange of the terminal pyridine ligands with strongly coordinating NHC ligands.  Pyridine is a fairly weak ligand and should therefore exchange easily to give the NHC ligated species, 4.22 (Figure 4.46). Surprisingly, when 4.2 was reacted with two equivalents of IMes no reaction was observed at room temperature. However, heating this solution at 60 \u00b0C for one hour showed signs of free pyridine in solution, suggesting ligand exchange had occurred (Figure 4.45). After 16 hours at 60 \u00b0C nearly complete consumption of 4.2 was observed. identification of the species by 1H NMR spectroscopy proved difficult due to multiple overlapping signals. Furthermore, new species were detected after the 16 hour heating period. The reaction mixture was poured into a vial and hexane was added to induce precipitation. No precipitation occurred so the vial was left at room temperature overnight, which produced yellow as well as colourless crystals. The yellow crystals were suitable for X-ray diffraction which revealed one of the species to be the mono-ligated IMes species, 4.23 (Figure 4.47). The new species observed in Figure 4.45 is tentatively assigned as this complex due to the characteristic ortho pyridine proton shift at 8.6 ppm (labelled new species). 170   Figure 4.41 Reaction schematic of 4.2 and IMes. Stacked 1H NMR spectra of the aromatic region from the reaction between 4.2 and IMes at 60 \u00b0C over 16 hours.  Figure 4.42 ORETP depiction of the solid-state molecular structure of 4.23  The amount of pyridine in solution does increase over time relative to the other signals, which suggests that further substitution reactions of the terminal pyridine ligands is occurring to give the doubly substituted NHC complex 4.22. The aliphatic region of the 1H NMR spectrum of the reaction in Figure 4.48 shows multiple new Pt-Me signals consistent with the initial formation of 4.2 + IMes after 16 h at 60 \u00b0C 4.2 + IMes after 2.5 h at 60 \u00b0C 4.2 + IMes after 1 h at 60 \u00b0C 4.2 + IMes after 30 min at 60 \u00b0C 171  4.23, supported by the presence of two inequivalent methyl signals (Pt satellites of 2JPt-H = 80 and 84 Hz).  Figure 4.43 Stacked 1H NMR spectra of the aliphatic region from the reaction between 4.2 and IMes at 60 \u00b0C over 16 hours. Furthermore, another Pt-Me signal with Pt satellites (83 Hz, Figure 4.47) is consistent with equivalent methyl signals trans to a weak trans influence ligand (i.e., pyridine). These Pt-Me signals are tentatively assigned to complex 4.22. the signal appears to grow in intensity over the course of the reaction along with slow consumption of the Pt-Me signals corresponding to 4.23. The assignment of 4.22 is logical  if the assumption is made that 4.23 is formed first with subsequent formation to 4.22 and that 4.22 is symmetrical. No further reactivity of these complexes was explored, however some further expansion with respect to subsequent reactivity is warranted given the success with Pt-NHC complexes discussed in Chapter 2. In addition to NHCs, phosphines were also reacted with 4.2 but no reactivity was observed at any temperatures with either mono or bisphosphines. 4.5.2 Reactivity of adamantane carboxylic acid (ACA) with 4.2. Next functionalisation of the Pt-Caryl  bond in 4.2 was attempted with a variety of reagents. Protonation of 4.2 to see whether the methyl or pyridyl ligand would be replaced was conducted with two equivalents of adamantane carboxylic acid (ACA) in benzene-d6 at 60 \u00b0C (Scheme 4.2 + IMes after 1 h at 60 \u00b0C 4.2 + IMes after 30 mins at rt 4.2 + IMes after 2.5 h at 60 \u00b0C 4.2 + IMes after 16 h at 60 \u00b0C 172  4.14). No reactivity was observed at room temperature, however heating the solution at 60 \u00b0C showed immediate formation of methane as a result of protonation of one of the methyl groups of 4.2 (Figure 4.49). Continued heating at 60 \u00b0C for another 20 minutes showed almost complete consumption of 4.2. In the aromatic region of the 1H NMR spectrum, two new terminal ortho pyridine proton resonances are observed suggesting a break in symmetry of the molecule. Additionally, two sets of signals corresponding to the bridging pyridine ligands are also observed supporting the notion of a lack of symmetry. A new Pt-Me resonance is observed in the aliphatic region and can be seen to replace the Pt-Me resonance in 4.2 as the reaction continues. When these observations are taken together the new complex is assigned as the adamantane carboxylate complex 4.24 (Scheme 4.14).   Scheme 4.15 Reaction between 4.2 and adamantane carboxylic acid to give compound 4.24  173   Figure 4.44 Stacked 1H NMR spectra of the reaction between 4.2 and adamantane carboxylic acid over 45 mins at 60 \u00b0C. Interestingly, over the course of the reaction small amounts of free pyridine are observed, while this could be due to partial protonation of a pyridyl ligand, it is more likely due to dissociation of a terminal pyridine followed by formation of the k2 carboxylate complex (Scheme 4.15). An equilibrium of \uf06b1 and \uf06b2 carboxylate formation would also rationalise the disparity in integration between the two ortho pyridine resonances of 4.24 which do not integrate to 2:2 as would be expected for the two inequivalent terminal pyridine ligands. Carboxylate complexes of the late transition metals have been extensively used in reactions concerning the C-H activation of inert bonds via the CMD mechanism (see chapter 1). Thus, platinum complexes such as 4.24 and 4.25 could be interesting for application in catalytic or stoichiometric reactions involving C-H activation.   4.2 + ACA after 45 min at 60 \u00b0C 4.2 + ACA after 25 min at 60 \u00b0C 4.2 + ACA at rt 174   Scheme 4.16  Proposed equilibrium between k1 and k2 coordination of the adamantane carboxylate ligand  4.5.3 Reactivity of PhI with 4.2. Building on the work in chapter 2, it was thought possible that 4.2 could be used in oxidative addition reactions with aryl halides. Specifically, the dimeric nature of the complex could inhibit geometrical changes that lead to reductive elimination from reactive Pt(IV) species. Inhibiting reductive elimination would allow for identification of Pt(IV) species directly from Intermolecular oxidative addition of aryl halides but also allow the study of reductive elimination between different hybridised Pt-C bonds. Additionally, if phenyl iodide could oxidatively add to 4.2, it could lead to the synthesis of 2-phenylpyridine which could subsequently coordinate to platinum (4.26, Scheme 4.16) and undergo intramolecular C-H activation to give the bidentate phenylpyridine complex 4.27. Complex 4.27 could then be used in reactions to further functionalise phenyl pyridine with transmetallating reagents such as Grignard reagents or borates. Cascade reactions to form multiple new carbon-carbon bonds would be of interest, especially if they could be achieved with little pre functionalisation.  Scheme 4.17 Proposed reactivity of aryl halides with 4.2 to give complexes 4.26 and 4.27. In the presence of two equivalents of phenyl iodide, 4.2 showed slow reactivity to a new species. After three hours at room temperature new signals in the aromatic region were detected alongside free pyridine (Figure 4.50). Surprisingly, a new Pt-Me signal was detected 175  that exhibited coupling to two platinum centres (2JPt-H = 66 Hz and 3JPt-Pt-H = 8 Hz) characteristic of a Pt-Pt bond, as described above (section 4.2). The identification of this Pt-Pt interaction also rules out the above reaction (scheme 4.16) but provides further support for the utility of Pt-Pt bonded intermediates in redox reactions. Unfortunately, heating of reaction mixture at 60 \u00b0C resulted in an unidentifiable mixture with multiple products. Further analysis of this reaction was not conducted due to time constraints but the identification of the Pt-Pt bond in this reaction means more time should be dedicated to this type of reaction to gain a deeper understanding of the role of the Pt-Pt bond.    Figure 4.45 Stacked 1H NMR spectra (C6D6, 400 MHz, 25 \u00b0C) of the reaction between 4.2 and PhI at room temperature after one and three hours.  176  4.6 Summary The ortho C-H activation of pyridine from 4.1 to form the isolable Pt-Pt bonded bimetallic complex 4.4 which subsequently undergoes a second C-H activation to form 4.2 has been described in this chapter. Bimetallic platinum complexes have not been studied extensively. Furthermore, the formation of bimetallic Pt-Pt species via the C-H activation of a ligand has not been reported as of yet, making 4.4 a rare example. Additionally, the identification of a platinum trimetallic species, 4.7, gives an opportunity to explore the chemistry of coordination polymers via C-H activation of pyridine ligands. The mechanism of the reaction was probed via the analysis of time course data and is suggestive of an initial pyridine dissociation for the first C-H activation event. A complex pre-equilibrium involving the solvent, pyridine and the formation of up to two species with a Pt-Pt bond a are likely responsible for the fast reactivity observed at room temperature. Kinetic modelling of the initial stages of the reaction were not successful and require further investigation before accurate numbers for the activation barrier can be obtained. However, the experimental activation barrier for the second C-H activation, that is the reaction from 4.4 -> 4.2 was found to be 22.26 kcal\/mol which was in good agreement with the DFT calculated value of 24.1 kcal\/mol.  Subsequent analysis of the transition states found an oxidative addition mechanism to be the most favourable for the cleavage of the C-H bond. Alternatively, a SBM transition state was also found  but had an activation barrier of 41.7 kcal\/mol, making this mechanism unlikely. Furthermore, charge decomposition analysis found that a net positive degree of charge transfer between platinum atoms lowered the relative C-H activation barrier compared to when no Pt-Pt bond was present. This finding has implication towards the synthesis of more stable Pt-Pt bimetallic species which could be leveraged towards Intermolecular C-H activation reactions. The reactivity of the product, 4.2, was also explored and showed that at elevated temperature ligand exchange with strongly donating NHC ligands was achieved. Furthermore, carboxylic acids showed preferential protonation of the methyl ligand rather than the pyridyl ligands to give rise to the analogous carboxylate complexes. Finally, reactivity with phenyl iodide did not provide a discrete reaction product but did hint at the formation of a new Pt-Pt bonded bimetallic complex giving further support for the notion that Pt-Pt bimetallic complexes are of high interest in redox reactions of platinum and should be explored further. 177  Chapter 5: Overview and Future Work 5.1 Overview With ever growing concerns regarding sustainability, the effect of greenhouse gasses, and climate change. A wide range of strategies from all areas of society must be undertaken to mitigate global climate change. One strategy is the use of catalysis for the functionalisation of greenhouse gasses such as methane. Catalysis reduces the amount of chemical waste products and increases the atom economy of chemical reactions. Additionally, catalysts lower the energy requirement for a reaction to proceed therefore decreasing the total energy input. Although platinum is a rare metal and concerns about the impact of its mining on the environment exists. Reclamation of the metal from reactions and its use in low concentrations will help mitigate the issues surrounding its mining. This thesis aims to showcase novel mechanisms for the breaking of C-X and C-H bonds at platinum(II) complexes that could be incorporated into the design of new catalytic systems that functionalize methane. Furthermore, the design and synthesis of novel ligand scaffolds opens a new area of organometallic and main group chemistry that has yet to be explored. Chapter 1 gives an overview of the current understanding of the mechanisms of alkane C-H activation and the developments within the C-H activation field over the last 20 years. Additionally, a brief history of the use of platinum in catalytic C-H functionalisation reactions is also given. A novel approach to methane functionalisation is then proposed that builds on the contextual use of platinum in C-H activation reactions that utilises aryl halides as both the oxidant and coupling partner. Chapter 2 builds on a myriad of platinum chemistry developed by Richard Puddephatt in the late 1980\u2019s which concerns the intermolecular oxidative addition of aryl halides to platinum(II) dialkyl complexes.116 The intermolecular oxidative addition of aryl halides to platinum(II) complexes had not been previously shown and was one of the major challenges in the proposed methane functionalisation cycle shown in chapter 1. The introduction of a bulky, strongly \u03c3-donating NHC ligand alongside a weaker \u03c3-donating ligand such as pyridine or dimethyl sulfide was key in realising the aforementioned reactivity. The weaker ligand can dissociate from the metal forming an open coordination site, which allows for the subsequent binding and cleaving of an aryl halide. Furthermore, it was also found that the oxidative addition of aryl halides was more general than expected and worked similarly with platinum(II) phosphine complexes. 178  In chapter 3 the synthesis of a novel tridentate NHC diamine ligand was accomplished with the intent of incorporating boron into the diamine backbone giving rise to an NHC-NHB ligand. Unfortunately, insertion of boron into the diamine backbone proved challenging and the NHC-NHB ligand was not successfully synthesised. However, coordination of the tridentate NHC diamine ligand to platinum was achieved via the C-H activation of the imidazole core which gave rise to a mixture of normal and abnormal carbene complexes. The abnormal carbene isomer can be successfully deprotonated with KHMDS to give a platinate complex that should be able to react with a second metal to form bimetallic complexes. Bimetallic complexes are important as they have shown improved reactivity over their analogous monometallic species in certain catalytic reactions. Furthermore, the potential for cascade or tandem catalysis could be realised with such complexes, opening the door to more complex reactivity. Chapter 4 investigates the sequential C-H activation of the ortho pyridine proton of PtMe2(NC5H5)2, 4.1 to form a rare Pt-Pt bonded bimetallic species 4.4. The bimetallic species then undergoes a second C-H activation of pyridine to form a doubly bridged platinum(II) dimer 4.2. Through a combined experimental and computational study, it was revealed that pyridine dissociation is essential prior to C-H activation and in the formation of the Pt-Pt bond. Furthermore, charge donation across the Pt-Pt bond was found to be responsible for a decrease in the C-H activation barrier between reactant and transition state relative to similar transition states without a Pt-Pt bond. Calculations showed that both C-H activation events occurred via an oxidative addition transition state, with the second C-H activation step occurring at 24 kcal\/mol. The calculated activation barrier of 24 kcal\/mol was supported by experimental determination, which was found to be 22.6 kcal\/mol.  5.2 Future Work The work in chapter 2 features the intermolecular oxidative addition of aryl halides to Pt(II) complexes. Calculations do suggest that a platinum(IV) intermediate is involved, unfortunately, isolation or even detection of a platinum(IV) intermediate was not successful. Ligands that can form chelates and trap the putative Pt(IV) intermediate should be targeted as means to isolate platinum(IV) intermediates. Recent work in the Love group by student Nan Zhang has shown that by tethering the pyridine ligand to the NHC, a platinum(IV) complex results from the oxidative addition of phenyl iodide and can be identified by 1H NMR spectroscopy (Scheme 5.1). An excess of potassium iodide is required as the tethering of the pyridine to the NHC results in a change in mechanism, whereby the pyridine no longer dissociates due to the increased strength of the chelate. The increased chelate strength results in preferential dissociation of iodide to 179  induce reductive elimination of the product.   Consequently, an excess of iodide is required to inhibit the iodide dissociation allowing for the identification of the Pt(IV) aryl intermediates 5.2 and 5.3. Isolation of these Pt(IV) aryl species are currently on going .  Scheme 5.1 Reaction showing the two Pt(IV) aryl complexes detected in solution by 1H NMR spectroscopy. Further work in chapter 2 that should be considered is the effect that para substituted pyridines have on the oxidative addition of aryl halides. The proposed mechanism for phenyl iodide oxidative addition suggests the dissociation of pyridine is facile and results in coordination of the iodine lone pair prior to cleavage. A Hammett plot of para substituted pyridines would be informative as to the intricacies of the initial stages of the reaction. Furthermore, a Hammett plot of para substituted aryl halides would also reveal more about the nuances of the electronics of the calculated transition state (Scheme 5.2). Additionally, with the details uncovered in chapter 4 regarding the reversible dissociation of pyridine at the beginning of the reaction, it might be of interest to probe the initial stages of the oxidative addition of phenyl iodide to see if a similar pre-equilibrium exists.  Scheme 5.2 Reaction between para substituted phenyl iodide and para substituted pyridine Pt(II) NHC complexes Future work in chapter 3 should be focused on optimising the synthesis of the NHC-NHB ligand, 5.6\/5.8 (Scheme 5.3). The proposed NHC-NHB ligand is novel and holds the potential to access challenging C-H and\/or C-X activation reactions. Condensation of the boron into the diamine backbone proved challenging and was only successful with PhBCl2. Alternatively, BCl3 could 180  give the desired insertion product, 5.8, which would then allow for the oxidative addition of the B-Cl bond to Pt(0) to give the platinum(II) compound, 5.9 (Scheme 5.3). Deprotonation of the imidazolium salt with a suitable base would then give the target complex, 5.7. A possible alternative to BCl3 is BH3\u00b7THF, with subsequent coordination of the diazaborolidine via methane elimination from Me4Pt2(\u00b5-SMe2)2 (Scheme 5.3). However, BH3.THF has been used in the formation of NHC-borane adducts and thus presents a problem in terms of selectively inserting the boron into the diamine without formation of the NHC-borane adduct. The method involving BH3\u00b7THF is worth attempting as the coordination to platinum(II) would be less challenging compared to the oxidative cleavage of the B-Cl bond and subsequent deprotonation of the imidazolium salt.  Scheme 5.3 Reaction showing two different possible pathways to access a chelating NHC-NHB platinum(II) complex. Additional work with the precursor ligand 3.14 (Scheme 5.4) should be conducted as preliminary data has shown an increased preference for the C-4 bound abnormal carbene complex 5.10 relative to the Mes derivative 3.15 (5:1 for 5.10 and 3:1 for 3.15 ). An increase in the ratio of abnormal to normal carbene will make separation via fractional crystallisation of the two isomers easier. 181   Scheme 5.4 C-H activation of the ligand precursor 3.14 to give a 5:1 mixture of 5.10 (aNHC) and 5.11 (NHC). Furthermore, deprotonation of the C2 proton of complex 5.10, which has already been achieved with the mesityl analogue 3.15, would allow for the synthesis of a diverse set of (hetero)bimetallic complexes (Scheme 5.5). The reactivity of the imido functionality in complex 5.13, which has been used extensively in early transition metals for 2+1 C-H activation reactions, would be particularly interesting. The (hetero)bimetallic complexes in scheme 5.5 (5.13) are therefore interesting due to the potential C-H activation reactions they could partake in.  Scheme 5.5 Deprotonation of complex 5.10 to give carbanion 5.12, followed by salt metathesis with a metal salt to give (hetero)bimetallic complex 5.13 The work in chapter 4 unravelled some interesting questions regarding the possible utility of Pt-Pt bonds in C-H activation reactions. The charge decomposition analysis showed that with increasing charge transfer across the Pt-Pt bond, a decrease in the relative activation barrier for C-H activation can be achieved. Therefore, the synthesis of a discrete Pt-Pt bonded complex specifically designed for C-H activation reactions involved in Pt(II)\/Pt(IV) cycles should be possible. In particular, the more stable bis-di(phenyl)phosphino methane complexes reported by 182  Puddephatt could serve as a template for this new type of complex. However, the dppm ligand core has two strongly donating phosphine ligands that are unlikely to undergo facile ligand dissociation. The similar 4-membered P,N ligands, however, which were first synthesised by Dr. Eric Bowes in the Love group (Figure 5.1),231 are labile enough to give rise to open coordination sites and could allow for C-H activation reactions to occur. Additionally, the tunability of the Phosphine R groups would allow for the synthesis of a large variety of complexes with different steric and electronic profiles.  Figure 5.1 Proposed new Pt-Pt bimetallic species using existing general Pt-Pt bimetallic structures with new hemilabile P,N ligands.  Lastly, identification of the side product 4.6 in the C-H activation reaction of 4.2 suggests that oligomeric chains of platinum, also known as extended metal atom chains (EMACs),232 are forming via C-H activation (Scheme 5.6). While 4.6 is itself an EMAC, longer chains could be possible but would have to undergo an internal C-H activation to give 5.18 prior to addition of another equivalent of 4.1. The chain is then extended by one unit and the process repeats. While it is likely that 4.6 is formed by the proposed pathway in scheme 5.6, more experimental and computational evidence is required to fully understand this process and if reaction conditions can be influenced to favour longer EMAC formation, as only 4.6 has been detected by 1H NMR spectroscopy thus far. 183   Scheme 5.6  Representation of the sequential C-H activation to form polymeric chain of platinum and pyridine.  EMACs are currently being synthesised and investigated as potential single chain magnets, spin crossover materials as well as molecular wires.232\u2013234 However, one challenge has been the almost ubiquitous use of first row metals in the synthesis of EMACs with very few examples existing with heavier metals.235 Compound 4.6 might therefore constitute a rare example of an organometallic 3rd row transition metal EMAC with properties that could be applicable in nanowires. The design and synthesis of novel platinum based catalysts is an important task for developing new reactivity, whether that be for C-H activation or other classes of reactions. Hopefully, the work presented here has shown that many new avenues for platinum chemistry are yet to be uncovered and pose an exciting challenge.    184  Bibliography  (1)  Reay, D.; Sabine, C.; Smith, P.; Hymus, G. Nature 2007, 446, 727\u2013728. (2)  Methane Guiding Principles. Reducing Methane Emissions: Best Practice Guide - Flaring; 2019. 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(255)  Asgeirsson; Birgirsson; Bjornsson; Becker; Riplinger; Neese; Jonssson (In Prep.). 199  Appendices CREATE Sustainable synthesis  As part of the CREATE sustainable synthesis program, progress towards sustainability in chemistry was an important part of the research conducted in this thesis. The introduction chapter focuses on methods and the mechanisms for the activation of alkanes, in particular methane. Furthermore, the chemistry in chapter 4 also builds on the idea of sustainability by directly activating the C-H bonds of pyridine instead of installation of a more reactive halogen or other reactive functional group prior to subsequent functionalisation reactions. Being able to activate and functionalise C-H bonds directly reduces the amount of chemical waste throughout a synthesis and thus increases both environmental and economic sustainability.  Appendix A. Experimental A 1. General considerations All manipulations were carried out using standard glove box\/Schlenk techniques under an atmosphere of N2 unless otherwise stated. All chemicals that are not described herein were purchased from commercial vendors (Sigma Aldrich, TCI, Strem Chemicals, Alfa-Aesar, Pressure Chemicals and Acros) and used without further purification. Phenyl iodide (PhI) and phenyl bromide (PhBr) were stored over activated 3\u00c5 molecular sieves, PhI and PhBr were stored in the glove box freezer at -35 \u00b0C.  Pyridine was dried over CaCl2 for 48 h before vacuum transferring onto activated 3\u00c5 molecular sieves. 4-(dimethylamino)pyridine (DMAP) was purchased from TCI and used without further purification. 4-(trifluoromethyl)pyridine was purchased from Oakwood, degassed, and used without further purification. Benzene-d6, toluene-d8, acetone-d6 and acetonitrile-d3 were stored over 3\u00c5 molecular sieves for 48 hours prior to use. 3\u00c5 molecular sieves were activated in a vacuum oven (119 torr) at 200 \u00b0C for a minimum of 24 hours. 1H, 1H{31P}, 13C{1H}, 31P, 31P{1H}, 11B and 19F NMR spectra were recorded on 300, 400 or 600 MHz spectrometers. Chemical shifts are reported in ppm and referenced to residual protio-solvent resonance peaks for 1H NMR spectroscopy, and to solvent peaks for 13C{1H} NMR spectroscopy. Multiplicity abbreviations: singlet (s), doublet (d), triplet (t), doublet of doublets (dd), multiplet (m). Coupling constants are designated as nJX-Y for each respective nucleus. The term \u2018Pt satellites\u2019 refers to the doublet observed due to coupling to the 195Pt nucleus, whereas \u2018Pt shoulders\u2019 refers to signals exhibiting coupling to 195Pt where the satellites are not resolved from the parent signal. NMR tubes were cleaned with acetone followed by deionised water and dried in an oven over night at 180 \u00b0C before being cycled into the glove box. NMR characterisation data was recorded by using approximately 5-10 mg of the respective 200  complex and dissolving in 0.6 mL of the appropriate deuterate solvent. All NMR spectroscopic assignments for compounds were made on the basis of 1D and\/or 2D NMR spectroscopic data as well as crystallographic analysis were relevant. Elemental analyses were performed by Analytical Services at the Department of Chemistry at the University of British Columbia. ESI-MS was recorded on waters LCMS. ESI-MS data was recorded by dissolving a sample of the complex in acetonitrile or methanol, in some cases acetonitrile was observed to exchange for dimethyl sulfide\/pyridine and has been specified when observed as the m\/z peak. HRMS data was collected by the analytical services at the department of chemistry at the University of Calgary.   The synthesis of Pt2Me4(SMe2)2\/Pt2(CD3)4(SMe2)2,236 PtMe2COD,237 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene,238 2-(2-iodophenyl)pyridine,196 perdeuterated phenyl iodide239, Pt(o-tolyl)2(pyridine)2240, 2,4,6-trimethylphenyl imidazole,192 and 2,6-diisopropylphenyl imidazole193 were carried out according to literature procedures. Sample preparation for reactivity studies in chapter 2  Reactivity studies were carried out by weighing out 10-15 mg of the appropriate complex along with one equivalent of trimethoxy benzene and one equivalent of phenyl iodide. This mixture was dissolved in C6D6, and 0.6 mL was transferred to J-young tube and the 1H NMR spectrum recorded before and after heating.  Sample preparation for collection of time course data in Chapter 4. In the glove box, complex 4.1 (~10 mg, 0.026 mmol) was added to an oven dried wilmad NMR tube fitted with a pierceable screw cap. A solution of Trimethoxybenzene (TMB) in toluene-d8 (4.37 mg, 0.026 mmol) (0.827 w\/w%, 0.043 M) was weighed out into a mass spec vial with a pierceable screw cap. A syringe was back filled with nitrogen inside the glove box and stuck into a rubber septum to ensure suitable atmosphere. The spectrometer was warmed to the desired temperature at which point a dummy sample containing the reaction mixture at about 50% completion was used to shim the magnet. Keeping the lock engaged the dummy sample was removed. The TMB solution was then added at once to the NMR tube containing complex 4.1. The NMR tube was shaken to dissolve the solid and the NMR tube lowered into the spectrometer. The sample was locked and shimmed while allowing the sample to equilibrate for 5 minutes before acquiring the first spectrum. Each subsequent spectrum was taken at five 201  minute intervals allowing for full relaxation of the trimethoxy benzene signals. A single 90\u00b0 pulse angle was used to irradiate the sample without dummy scans. Concentration vs time data  Concentration data was calculated from 1H NMR spectroscopic integral data of the relevant resonances using the concentration graphing wizard in MestReNova. Time course graphs were generated in excel from the concentration data.  COPASI modelling  Time course data was modelled in COPASI and experimental parameters were acquired using the parameter estimation tool. COPASI models for temperatures at 30 \u00b0C and 40 \u00b0C were modelled as follows: Concentration vs time data of species 4.1, 4.2, 4.4 and pyridine were entered into COPASI as a text tab delimited file. Global optimisation of the concentration vs time data was carried out by \u201cGenetic Algorithm\u201d with 20,000 generations and a population size of 20. A local optimisation was then carried out using the \u201cHooke & Jeeves\u201d algorithm with an iteration limit of 500,000 and a tolerance of 1e-12.  COPASI models for time course data at 50 \u00b0C and 60 \u00b0C were carried out as follows: Concentration vs time data of species 4.1, 4.2, 4.4, 4.6 and pyridine were loaded into COPASI as a text tab delimited file. Global optimisation of the concentration vs time data was carried out by \u201cGenetic Algorithm\u201d with 20,000 generations and a population size of 20. A local optimisation was then carried out using the \u201cHooke & Jeeves\u201d algorithm with an iteration limit of 500,000 and a tolerance of 1e-12.  202  A 2. Experimental data for Chapter 2 PtMe2(IMes)(SMe2) (2.1): To 5-dram vial was added Pt2Me4(SMe2)2 (194 mg, 0.327 mmol), benzene (3 mL) and dimethyl sulfide (48.0 \u00b5L, 0.654 mmol). The solution was stirred for five minutes at room temperature before the addition of IMes (200 mg, 0.654 mmol) which was added as a solution in benzene (10 mL) at once, the solution was then stirred for 10 minutes. The solution was concentrated and the product precipitated with pentane (15 mL). The supernatant was removed and the solid washed further with pentane (2 x 5 mL), it was then dried under vacuum to remove any remaining solvent to give 356 mg of 2.1 as a white powder in 91% yield. 2.1 was stored at -35\u00b0C to prevent thermal decomposition. Colourless X-ray quality crystals were grown from a dilute solution of hexane at -35\u00b0C.  1H NMR (600 MHz, CD2Cl2, 25 \u00b0C) \u03b4 6.99 (s, broad, 6 , 4H), 6.94 (s, 2, 2H), 2.33 (s, 8, 6H), 2.18-2.26 (m, broad, 5, 12H), 1.77 (s, Pt-satellites, 3JPt-H = 24 Hz, 11, 6H), 0.06 (s, Pt satellites, 2JPt-H = 87 Hz, 9, 3H), -0.23 (s, Pt satellites, 2JPt-H = 60 Hz, 10, 3H). 13C{1H} NMR (151 MHz, CD2Cl2, 25 \u00b0C) \u03b4 187.65 (1), 138.73 (7), 137.46 (3), 136.30 (broad, 4), 129.41 (broad, m, 6), 122.47 (s, Pt satellites, 1JPt-C = 25 Hz, 2), 21.36 (8), 19.65 (11), 18.98 (5), -3.52 (s, Pt satellites, 1JPt-C = 596 Hz, 10), -11.61 (s, Pt satellites, 1JPt-C = 763 Hz, 9). Elemental analysis for C25H36N2PtS (C, H, N,): Calculated C, 50.75; H, 6.13; N, 4.73; Found C, 50.70; H, 6.02; N, 4.73. ESI-MS: 576.4 (M-CH3)+.  Figure A1 2.1, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C)  203    Figure A2 2.1, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C)  Figure A3 2.1, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) 204    Figure A4 2.1, HSQC NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) 205  PtIMe(IMes)(SMe2) (2.3): To a 5-dram vial was added 2.1 PtMe2(IMes)(SMe2) (50.0 mg, 0.0860 mmol). The complex was dissolved in C6H6 and followed by addition of methyl iodide as a solution in benzene over one minute (57.3 \u00b5L, 1M, 0.0860 mmol). The solution was stirred for 20 minutes before the volatiles were removed under reduced pressure. The white solid was washed with hexane (2 x 5 mL) and dried under reduced pressure to yield 60.5 mg of 2.3 in 99% yield. X-ray quality crystals were grown from a THF\/pentane layer over a period of three days at room temperature. The solid-state X-ray structure and solution-state structure differ with respect to the positions of the iodide and dimethyl sulfide. The solution-state structure is as shown above which was confirmed by 1H-1H NOESY.  1H NMR (400 MHz, C6D6, 35 \u00b0C) Major Isomer \u03b4 6.81 (s, 6\/9, 2H), 6.75 (s, 6\/9, 2H), 6.19 (s, 2, 2H), 2.66 (s, 5\/11, 6H), 2.22 (s, 5\/11, 6H), 2.05 (S, 8, 6H), 1.79 (s, Pt satellites, 3JPt-H = 33 Hz, 13, 6H), 0.65 (s, Pt satellites, 2JPt-H = 80 Hz, 12, 3H). 13C{1H} NMR (100 MHz, C6D6, 35 \u00b0C) \u03b4 165.9 (Pt satellites not resolved, 1) 138.5 (7), 137.0 (4\/10), 136.8 (3), 134.6 (4\/10), 130.17 (6\/9), 128.9 (6\/9), 122.5 (2), 22.12 (5\/11), 21.80 (13), 21.04 (8), 18.99 (5\/11), -10.69 (12). Minor Isomer peaks were not well resolved. Elemental analysis for C24H34IN2PtS (C, H, N): Calculated C, 40.97; H, 4.73; N, 3.98; Found C, 40.62; H, 4.50; N, 3.90. ESI-MS: 555.2 [M-I]+ - (C2H6S) + (C2H3N).    Figure A5 2.3, 1H NMR spectrum (C6D6, 400 MHz, 35\u00b0C) 206   Figure A6 2.3, 13C{1H} NMR (C6D6, 100 MHz, 35\u00b0C)  Figure A7 2.3, HSQC NMR spectrum (C6D6, 400\/100 MHz, 35 \u00b0C) 207   Figure A8 2.3, 1H-13C HMBC NMR spectrum (C6D6, 400\/100 MHz, 35 \u00b0C)  Figure A9 2.3, 1H-1H NOESY NMR spectrum (C6D6, 400 MHz, 35 \u00b0C) 208  PtMe(IMes\u2019)(SMe2) (2.4): To a flame dried Schlenk flask was added a 2.1 PtMe2(IMes)(SMe2) (102 mg, 0.170 mmol) and benzene (20 mL). The solution was then heated at 60 \u00b0C for 2 hours. The solution was allowed to cool to room temperature where the solvent was concentrated to the point of product precipitation. Hexane was added, and the remaining product immediately precipitates. The supernatant was decanted, and the product washed with hexane (2 x 5 mL) to give 69 mg of 2.4 as a white powder in 71% yield. It is noteworthy that this reaction has a tendency to darken significantly due to Pt(0) formation, Pt(0) was removed by dissolving the solid in THF and adding hexane (half the amount of THF) and leaving at -30 \u00b0C overnight. The solution was then filtered through a glass microfibre filter with celite. X-ray quality crystals were grown from a THF solution layered with hexane.  1H NMR (400 MHz, CD2Cl2, 25 \u00b0C) \u03b4 7.42 (d, 3JH-H = 1.9 Hz, 14, 1H) , 6.99 (s, broad, 18\/21, 1H), 6.97 (s, broad, 18\/21, 1H), 6.89 (s, Pt shoulders, 9, 1H), 6.86 (d, 3JH-H = 1.9 Hz, 2, 1H), 6.73 (s, Pt shoulders, 6, 1H), 2.82 (d, 2JH-H = 9 Hz, Pt satellites; 2JPt-H = 142 Hz, 11a, 1H), 2.33 (s, 17\/23, 6H), 2.33 (s, overlapping, 5, 3H), 2.25 (s, 8, 3H), 2.15 (s, 20, 3H), 2.02 (d, 2JH-H = 9 Hz, Pt satellites; 2JPt-H = 74 Hz, 11b, 1H), 1.71(s, v broad, 13, 6H), 0.14 (s, Pt satellites; 2JPt-H = 62 Hz, 12, 3H). 13C{1H} NMR (101 MHz, CD2Cl2, 25 \u00b0C) \u03b4 187.04 (1), 146.87 (10), 139.37, 137.39, 137.15, 137.09, 136.62, 136.35 (3), 129.25 (18\/21), 129.02 (18\/21), 128.99, 126.76 (Pt satellites, 5JPt-C = 21 Hz, 6), 125.66 (Pt satellites, 3JPt-C = 43 Hz, 9), 121.93 (Pt satellites, 3JPt-C = 30 Hz, 2), 120.30 (Pt satellites, 3JPt-C = 12 Hz, 14), 21.32 (17\/23), 21.20 (8), 20.18 (13), 20.02, 18.96, 18.26 (17\/23), 14.62 (Pt satellites, 1JPt-C = 668 Hz, 11a\/b), -4.41 (Pt satellites, 1JPt-C = 617 Hz, 12). Elemental analysis calculated for C24H32N2PtS (C, H, N): Calculated C, 50.07; H, 5.60; N, 4.87; Found C, 50.08; H, 5.80; N, 4.88. ESI-MS: 560.4 (M-CH3)+.  Figure A10 2.4, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) 209   Figure A11 2.4, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C)   210  Figure A12 2.4, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C)  Figure A13 2.4, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C)  Figure A14 2.4, 1H-1H NOESY NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) 211  PtIMe(IMes\u2019)(SMe2) (2.5\/2.5a): To a 5 dram vial was added 2.4 PtMe(IMes\u2019)(SMe2) (50.0 mg, 0.0860 mmol). this was dissolved in C6H6 and kept stirring while MeI (57.3 \u00b5L, 1M, 0.0860 mmol) was added as a solution in benzene over one minute. The solution was allowed to stir for 20 minutes before the volatiles were removed under reduced pressure. The solid was washed with hexane (2 x 5 mL) and dried to give 59.1 mg of a mixture containing 2.5\/2.5a in 4:1 ratio in 99% yield. X-ray quality crystals were grown from a THF\/hexane diffusion over several days.  1H NMR major isomer (400 MHz, C6D6, 55\u00b0C) \u03b4 7.26 (s, 9, 1H), 6.75 (d, 3JH-H = 2 Hz, Pt satellites, 4JPt-H = 13 Hz, 2, 1H), 6.67 (s, 17\/20, 2H), 6.53 (s, 6, 1H), 6.05 (d, 3JH-H = 2 Hz, Pt satellites, 4JPt-H = 15 Hz, 13, 1H), 4.34 (d, 2JH-H = 10 Hz, Pt satellites; 2JPt-H = 105 Hz, 11b, 1H), 2.91 (d, 2JH-H = 10 Hz, Pt satellites; 2JPt-H = 105 Hz, 11a, 1H), 2.36 (s, 22, 3H), 2.06 (s, overlapping, 16\/19, 3H), 2.06 (s, overlapping, 16\/19, 3H), 2.04 (s, 8, 3H), 1.96 (s, 5, 3H), 1.72 (m, very broad, 12, 6H). 1H NMR minor isomer (400 MHz, C6D6, 55\u00b0C) \u03b4 6.96 (s, 9, 1H), 6.88 (s, 17, 1H), 6.82 (s, 20, 1H), 6.73 (d, 3JH-H = 2 Hz, Pt shoulders, 2, 1H), 6.58 (s, 6, 1H), 6.21 (d, 3JH-H = 2Hz, Pt satellites; 4JPt-H = 15 Hz, 13, 1H),  2.97 (d, 2JH-H = 10 Hz, Pt satellites overlapping, 11a, 1H), 2.51 (s, 22, 3H), 2.47 (d, 2JH-H = 10 Hz, Pt satellites not resolved, 11b, 1H), 2.39 (s, 16, 3H), 2.17 (s, 8, 3H), 2.12 (s, 19, 3H), 1.90 (s, 5, 3H), 1.76 (s, 12, 6H). 13C{1H} NMR major isomer (101 MHz, C6D6, 55 \u00b0C) \u03b4 162.80 (1), 143.34 (10), 139.32 (15\/18), 137.95 (7), 137.76 (21), 136.09 (15\/18), 135.75 (3),135.67 (14), 129.69 (17\/20), 128.70 (17\/20), 127.55 (6), 126.88 (9), 121.97 (13), 119.53 (2), 22.86 (broad, 12), 20.91(8), 20.82 (16\/19), 19.27(5), 19.01 (22), 18.23 (16\/19), 8.03 (11a\/b). 13C{1H} NMR minor isomer (peaks could not be resolved). Elemental analysis calculated for C23H29IN2PtS (C, H, N): Calculated C, 40.18; H, 4.25; N, 4.07; Found C, 40.07; H, 4.38; N, 3.76. ESI-MS: 539.2 [M-I]+ - (C2H6S) + (C2H3N). 212   Figure A15 2.5, 1H NMR spectrum (C6D6, 400 MHz, 55 \u00b0C)  Figure A16 2.5, 13C{1H} NMR spectrum (C6D6, 100 MHz, 55 \u00b0C) 213   Figure A17 2.5, HSQC NMR spectrum (C6D6, 400\/100 MHz, 55 \u00b0C)  Figure A18 2.5, 1H-13C HMBC NMR spectrum (C6D6, 400\/100 MHz, 55 \u00b0C) 214   Figure A19 2.5, 1H-1H NOESY NMR spectrum (C6D6, 400 MHz, 55 \u00b0C)  Figure A20 2.5, region showing NOE between SMe2 and aryl C-H (C6D6, 400 MHz, 55 \u00b0C) 215  PtMe2(IMes)(Pyridine) (2.6): To a 5-dram vial was added PtMe2COD (250 mg, 0.750 mmol), pyridine (118 mg, 1.50 mmol) and IMes (228 mg, 0.750 mmol). This mixture was dissolved in diethyl ether (15 mL) and stirred for 30 minutes at room temperature. The product precipitated after a few seconds and was filtered and washed twice further with Et2O (2 x 5 mL). The solid was dried under reduced pressure to give 373 mg of 2.6 in 81% yield.  1H NMR (400 MHz, CD2Cl2, 25 \u00b0C) \u03b4 7.97 (m, Pt satellites, 3JPt-H = 26 Hz, 11, 2H) 7.49 (t, 13, 1H), 6.96 (s, 6, 4H), 6.92 (m, 12, 2H), 6.85 (s, 2, 2H), 2.38 (s, 8, 6H), 2.07 (s, 5, 12H), 0.07 (s, Pt satellites, 2JPt-H = 89 Hz, 9, 3H), -0.52 (s, Pt satellites, 2JPt-H= 60 Hz, 10, 3H). 13C{1H} NMR (101 MHz, CD2Cl2, 25 \u00b0C) \u03b4 188.49 (1), 152.50 (Pt satellites, 2JPt-C = 15 Hz, 11), 138.63, 137.78, 136.03, 134.70 (13), 129.41 (6), 124.81 (Pt satellites, 3JPt-C= 23 Hz, 12), 122.26 (Pt satellites, 3JPt-C = 25 Hz, 2), 21.40 (8), 18.73 (5), 2.22 (Pt satellites, 1JPt-C = 604 Hz, 10), -26.49 (Pt satellites, 1JPt-C = 755 Hz, 9). Elemental analysis for C28H35N3Pt (C, H, N): Calculated C, 55.25; H, 5.80; N, 6.90; Found C, 55.38; H, 6.06; N, 6.79. ESI-MS: 555.2 [M-CH3]+ - (C5H5N) + (C2H3N).   Figure A21 2.6, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) 216   Figure A22 2.6, 13C{1-H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C) 217  PtIMe(IMes)(pyridine) (2.7): a 5-dram vial was charged with 2.6 PtMe2(IMes)(Pyridine) (39.2 mg, 0.0640 mmol). After dissolving 2.6 in benzene (5 mL), MeI (64.0 uL, 0.0640 mmol, 1M) was then added as a solution in benzene over one minute. A white solid starts to precipitate from the solution, the mixture was kept stirring until all the solid became dissolved (10-15 min). Once dissolved the solvent was evaporated under reduced pressure and pentane (5 mL) was added and subsequently evaporated to remove any remaining volatiles to give 44.6 mg of 2.7 as a white powder in 97% yield.  1H NMR (400 MHz, CD2Cl2, 25 \u00b0C) \u03b4 8.51 (d, 3JH-H = 5.6 Hz, Pt satellites, 3JPt-H = 24 Hz, 13, 2H), 7.60 (t, 3JH-H = 7.8 Hz, 15, 1H), 7.14 (m, 14, 2H), 7.02 (s, broad, 6\/9, 2H), 7.01 (s, broad, overlapping, 6\/9, 2H), 6.98 (s, 2, 2H), 2.44 (s, 5\/11, 6H), 2.37 (s, 8, 6H), 2.25 (s, 5\/11, 6H), 0.25 (s, Pt satellites, 3JPt-H = 84 Hz, 12, 3H). 13C{1H} NMR (101 MHz, CD2Cl2, 25 \u00b0C) \u03b4 157.16 (1), 152.89 (13), 138.83 (7), 137.06 (4\/10), 136.89 (15), 135.47 (3), 129.83 (6\/9), 129.15 (6\/9), 125.11 (Pt satellites, 3JPt-C = 33 Hz, 14), 123.12 (3JPt-C= 46 Hz, 2), 21.57 (5\/11), 21.44 (8), 19.18 (5\/11), -7.03 (Pt- satellites not observed, 12). Elemental analysis calculated for C27H32IN3Pt (C, H, N): Calculated C, 45.01; H, 4.48; N, 5.83; Found C, 45.81; H, 4.76; N, 5.55 (best after three attempts).  ESI-MS: 593.2 [M-I]+.  Figure A23 2.7, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C), peak at 2.1 corresponds to acetone from recrystallisation. 218   Figure A24 2.7, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C), peaks at 31ppm and 206ppm correspond to acetone.  Figure A25 2.7, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) 219   Figure A26 2.7, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C)  220  PtMe(IMes\u2019)(pyridine) (2.8): To a Schlenk flask was added 2.6 PtMe2(IMes)(Pyridine) (215 mg, 0.350 mmol). The solid was dissolved in benzene (25 mL) and heated at 60\u00b0C for two hours. The pale-yellow solution was concentrated to the point of precipitation, at which point a white micro crystalline solid is observed. the suspension was stirred for one day to allow the pure product to precipitate. The white solid was then filtered using a fine glass frit and washed with hexane (5 mL) to give 161 mg of 2.8 as white solid in 78% yield.   1H NMR (400 MHz, CD2Cl2, 25 \u00b0C) \u03b4 8.10 (m, Pt satellites, 3JPt-H = 28 Hz, 13, 2H), 7.42 (d, 3JH-H = 2 Hz, 2\/16 ,1H), 7.41(m, overlapping, 15, 1H) , 6.91-6.97 (m, 9 & 20\/23, 2H), 6.76-6.84 (m, 14 & 6 & 2\/16 ,4H), 6.25 (s, 20\/23, 1H), 3.02 (d, 2JH-H = 9 Hz, Pt satellites; 2JPt-H = 146 Hz, 11a, 1H), 2.50 (s, broad, 19\/25, 3H), 2.36 (s, 5, 3H), 2.28 (s, 8, 3H), 2.20 (s, 22, 3H), 2.01 (d, 2JH-H = 9 Hz, Pt satellites; 2JPt-H = 72 Hz, 11b, 1H), 1.58 (s, broad, 19\/25, 3H), -0.04 (s, Pt satellites, 2JPt-H = 63 Hz, 12). 13C{1H} NMR (101 MHz, CD2Cl2, 25 \u00b0C) \u03b4 189.78 (1), 152.14 (Pt satellites, JPt-C = 18 Hz, 13), 148.34, 138.61, 136.88, 136.63 (3), 136.58, 134.51 (15), 129.25 (20\/23), 128.98, 128.87 (4), 128.71 (20\/23), 126.89 (Pt satellites, 5JPt-C = 21 Hz, 6), 125.80 (Pt satellites, 3JPt-C = 42 Hz, 9), 124.50 (Pt satellites, 3JPt-C= 25 Hz, 14), 120.98 (Pt satellites, 3JPt-C= 30 Hz, 2\/16), 120.07 (Pt satellites, 3JPt-C = 12 Hz, 2\/16), 21.19 (8), 21.15 (22), 20.27 (6),18.89 (19\/25), 17.65 (19\/25), 1.12 (11a\/b), 0.79 (Pt satellites, 1JPt-C  = 619 Hz, 12). Elemental analysis for C27H31N3Pt (C, H, N): Calculated C, 54.72; H, 5.27; N, 7.09; Found C, 54.43; H, 5.28; N, 7.14.  ESI-MS: 498.1 [M-C6H8N]+.  Figure A27 2.8, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) 221    Figure A28 2.8, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C)  Figure A29 2.8, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) 222   Figure A30 2.8, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) 223  PtI(IMes)\u2019(pyridine), (2.9\/2.9a): To a 5 dram vial was added 2.8 (64.0 mg, 0.108 mmol), which was dissolved in benzene (5 mL). MeI (118 \u00b5L, 1M, 0.188 mmol) was added as a solution in benzene to the stirring solution of 2.8 and allowed to stir at room temperature for five minutes. The solvent was removed fully, acetone (5 mL) was then added followed by hexane (5 mL). The supernatant was removed and the remaining solid washed with hexane (2 x 5 mL). Finally, the solid was dried under reduced pressure to yield 72.0 mg of a mixture of 2.9\/2.9a as white solid in 1:1 ratio in 94% yield.  1H NMR (400 MHz, CD2Cl2, 25 \u00b0C) \u03b4 8.72 (d, 3JH-H = 5 Hz, Pt shoulders, 12, 2H), 8.11 (d, 3JH-H = 5 Hz, Pt shoulders, 12), 7.74 (t, 3JH-H = 8 Hz, 14, 1H), 7.55 (d, 3JH-H = 2 Hz, overlapping, 1H), 7.52 (d, 3JH-H = 2 Hz, overlapping, 1H), 7.48 (t, 3JH-H = 8 Hz, 14, 1H), 7.30 (t, 3JH-H = 7 Hz, 13, 2H), 7.05 (s, 3H), 6.95 (s, 2H), 6.87-6.9 (m, 6H), 6.30 (s, 1H), 3.27 (d, 2JH-H = 10 Hz, Pt satellites, 2JPt-H = 108 Hz, 11a, 1H), 2.93 (d, 2JH-H = 10 Hz, Pt satellites, 2JPt-H = 124 Hz, 11b, 1H) 2.77 (d, 2JH-H = 10 Hz, Pt satellites not resolved, 11b, 1H), 2.58 (s, 8\/12, 3H), 2.54 (s, 3H), 2.44 (s, overlapping, 3H), 2.43 (s, overlapping, 3H), 2.37 (s, 3H), 2.31(m, 6H), 2.25 (s, 3H), 2.22 (s, 3H), 1.82 (d, 3JH-H = 10 Hz, Pt satellites, 2JPt-H = 105 Hz, 1b, 1H), 1.47 (s, 18\/24, 3H). 13C{1H} NMR (100 MHz, CD2Cl2, 25 \u00b0C) \u03b4 161.6 (1), 157.21 (1), 152.61 (12), 151.88 (12), 143.80 (10), 142.29 (10), 138.88, 138.50, 137.36, 137.27, 136.78 (14), 136.40, 136.38, 136.10, 135.92, 135.77, 135.63 (14), 135.42, 134.76, 134.05, 129.31, 128.90, 128.80, 128.51, 128.46, 128.25, 127.56, 127.51, 125.20, 124.97 (13), 124.07, 123.85, 123.63, 121.80, 119.64, 119.49, 20.92, 20.70, 20.66, 20.60, 19.52, 19.48, 1937, 18.90, 18.68, 17.27 (18\/24), 16.62 (11a\/b), -4.57 (11a\/b) . Elemental analysis for C26H28IN3Pt (C, H, N): Calculated C, 44.33; H, 4.01; N, 5.96; Found C, 44.48; H, 4.30; N, 5.75 ESI-MS: 577.2 [M-I]+.   224   Figure A31 2.9 and 2.9a, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C)  Figure A32 2.9 and 2.9a, 13C{1H} NMR spectrum (CD2Cl2, 100 MHz, 25 \u00b0C) 225   Figure A33 2.9 and 2.9a, HSQC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C)  Figure A34 2.9 and 2.9a, 1H-13C HMBC NMR spectrum (CD2Cl2, 400\/100 MHz, 25 \u00b0C) 226   Figure A35 2.9 and 2.9a, 1H-1H NOESY NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C) 227  PtIMe(phenyl-pyridine)(IMes\u2019) (2.18): To a 5 dram vile was added 2.4 (100 mg, 0.168 mmol) and 2(2-iodophenyl)pyridine (47.3 mg, 0.168 mmol). This was dissolved in THF (10 ml). After three days a white precipitate had formed. This precipitate was filtered and washed with acetone (2 x 1 mL). All volatiles were removed to yield 51.0 mg of 2.18 as a white powder in 38% yield. X-ray quality crystals were grown from an acetonitrile solution layered with Et2O at -30 \u00b0C. These crystals were obtained by replacing THF with benzene and stirring for 36 h at room temperature. Pentane was added to precipitate a solid which was then recrystallised from acetonitrile\/diethyl ether giving suitable crystals for X-ray diffraction. 1H NMR (400 MHz, CD2Cl2 25\u00b0C): \u03b4 8.55 (d, 3JH-H = 6 Hz, Pt satellites, 3JPt-H = 20 Hz, 22, 1H), 7.60-7.55 (m, , 3H), 7.49 (d, 3JH-H = 8 Hz, , 1H), 7.42 (d, 3JH-H = 8 Hz), 7.22-7.19 (m, , 2H), 7.12-7.04 (m, 21 , 2H), 6.96 (s, , 1H), 6.61 (d, 3JH-H = 2 Hz, Pt satellites, 4JPt-H = 10 Hz, 2\/24, 1H), 6.64 (s, , 1H), 6.00 (s, , 1H), 4.43 (d, 2JH-H = 10 Hz, Pt satellites, 3JPt-H = 89 Hz, 33a\/b, 1H), 3.82 (d, 2JH-H = 10 Hz, Pt satellites, 3JPt-H = 90 Hz, 33a\/b, 1H), 2.40 (s, , 3H), 2.39 (s, , 3H), 2.11 (s, , 3H), 1.61 (s, 11, 3H), 1.06 (s, , 3H), 0.24 (s, Pt satellites, 2JPt-H = 44 Hz, 23). 13C{1H} NMR ( 101 MHz, CD2Cl2, 25 \u00b0C): \u03b4 167.11 (Pt satellites, 1JPt-C = 29 Hz ,1), 162.91 (), 147.08 (Pt satellites, JPt-C = 9 Hz, 22), 146.70 (), 142.23 (), 141.97 (), 138.90 (), 137.03 (), 136.44 (), 135.77 (), 135.01 (), 134.82 (), 132.66 (), 131.93 (Pt satellites, JPt-C = 27 Hz), 129.07 (Pt satellites, JPt-C = 28 Hz, ), 129.05 (), 128.58 (), 128.56 (), 127.25 (), 125.40 (Pt satellites, JPt-C = 24 Hz), 125.23 (Pt satellites, JPt-C = 19 Hz), 123.60 (), 122.76 (Pt satellites, JPt-C = 39 Hz), 121.28 (Pt satellites, JPt-C = 12 Hz), 121.02 (Pt satellites, JPt-C = 23 Hz), 119.70 (Pt satellites, JPt-C = 14 Hz), 20.71 (), 20.55 (), 20.10 (), 17.69 (), 15.77 (), 7.34 (Pt satellites, 2JPt-C = 511 Hz, 33a\/b), -8.05 (Pt satellites not resolved, 23).  Figure A36 2.18, 1H NMR spectrum (CD2Cl2, 400 MHz, 25 \u00b0C). * Acetone from recrystallisation 228   Figure A37 2.18,13C{1H} NMR spectrum (100 MHz, CD2Cl2, 25 \u00b0C). * Acetone from recrystallisation  Figure A38 2.18, HSQC NMR spectrum (400\/100 MHZ, CD2Cl2, 25 \u00b0C) 229   Figure A39 2.18, 1H-1H NOESY NMR spectrum (400 MHz, CD2Cl2, 25 \u00b0C) 230  PtMe2(SMe2)(PCy3) (2.21): To a 5 dram vial was added Pt2Me4(SMe2)2 (47.9 mg, 0.830 mmol) and THF (5 mL). To this solution was added PCy3 (46.8 mg, 0.166 mmol) as a solution in THF (5 mL) at once. After allowing the solution to stir for 30 minutes, the solvents were removed under the reduced pressure and solid suspended in pentane (3 mL), the pentane was then removed along with any remaining volatiles to yield 94.7 mg of 2.21 as a white powder in 99% yield. 1H{31P} NMR (300 MHz, C6D6, 25 \u00b0C) \u03b4 2.22-2.38 (m, 4, 3H), 2.02 (s, Pt satellites, 3JPt-H = 24 Hz, 3, 6H), 1.96 (d, broad overlapping, 2JH-H = 12 Hz, 5, 6H), 1.46-178 (m 5, 6H & 6, 6H & 7, 3H), 1.27 (s, Pt satellites, 2JPt-H = 83 Hz, 2, 3H), 1.14-125 (m, 6, 6H & 7, 3H), 1.10 (s, Pt satellites, 2JPt-H = 66 Hz, 1, 3H). 13C{1H} NMR (101 MHz, C6D6, 25 \u00b0C) \u03b4 32.01 (d, 1JP-C = 20 Hz, Pt satellites, 2JPt-C = 16 Hz, 4), 30.08 (Pt satellites, 3JPt-C = 15 Hz, 5), 28. 08 (d, 3JP-C = 9 Hz, 6), 27.14 (7), 19.43 (d, 3JP-C = 3 Hz, Pt- satellites not resolved, 3), 8.65 (d, 2JP-C = 103 Hz, Pt-satellites not resolved, 2), -7.82 (d, 2JP-C  = 6 Hz, Pt-satellites not resolved, 1). 31P{1H) NMR (121 MHz, C6D6, 25 \u00b0C) \u03b4 22.20 (Pt satellites, 1JPt-P = 1852 Hz). Elemental analysis for C22H45PPtS (C, H, N): Calculated C, 46.54; H, 7.83; Found C, 46.92; H, 7.83. ESI-MS: 531.2 [M-CH3]+ - (C2H6S) + (C2H3N).   Figure A40 2.21, 1H NMR spectrum (C6D6, 300 MHz, 25 \u00b0C) 231   Figure A41 2.21, 13C{1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C)  Figure A42 2.21, 31P{1H} NMR spectrum (C6D6, 121 MHz, 25 \u00b0C) 232   Figure A43 2.21, HSQC NMR spectrum (C6D6, 300\/100 MHz, 25 \u00b0C)  Figure A44 2.21, 1H-13C HMBC NMR spectrum (C6D6, 300\/100 MHz, 25 \u00b0C) 233  PtMe2(SMe2)(P(C6F5)3) (2.22): To a 5 dram vial was added Pt2Me4(SMe2)2 (53.2 mg, 0.0930 mmol) and THF (5 mL). To this solution was added P(C6F5)3 (98.5 mg, 0.185 mmol) as a solution in THF (5 mL) at once. After allowing the solution to stir for 30 minutes, the solvents were removed under reduced pressure to yield a white powder. This complex is soluble in hexane and was therefore dissolved and filtered before the solvent was removed to yield 145 mg of 2.22 as a white powder in 94% yield.  1H NMR (600 MHz, C6D6, 25 \u00b0C) \u03b4 1.78 (s, Pt satellites, 3JPt-H = 26 Hz, 3, 6H), 1.24 (d, 3JP-H = 9 Hz, Pt satellites, 2JPt-H = 74 Hz, 1, 3H), 0.97 (d, 3JP-H = 12 Hz, Pt satellites, 2JPt-H = 83 Hz, 2, 3H). 13C{1H} NMR (151 MHz, C6D6, 25 \u00b0C) \u03b4 147.22 (d, 3JP-C = 250 Hz, 5\/6), 143.26 (d, 1JP-C = 259 Hz, Pt satellites not resolved, 4), 137.78 (d, 2JP-C = 255 Hz, 5\/6), 104.10 (7), 19.35 (d, 3JP-C = 3 Hz, Pt-satellites not resolved, 3), 9.05 (d, 2JP-C = 132 Hz, Pt satellites, 1JPt-C = 719 Hz, 1), 1.38 (silicone grease) -9.00 (Pt satellites, 2JP-C = 2.32 Hz, 1JPt-C = 724 Hz, 2). 31P NMR (162 MHz, C6D6, 25 \u00b0C) \u03b4 -19.55 (Pt satellites, 1JPt-P = 1582 Hz). 19F NMR (282 MHz, C6D6, 25 \u00b0C) \u03b4 -130.15, -146.88 (7), -159.76. Elemental analysis for C22H12F15PPtS (C, H): Calculated C, 32.25; H, 1.48; Found C, 32.40; H, 1.41.   Figure A45 2.22, 1H NMR spectrum (C6D6, 600 MHz, 25 \u00b0C) 234   Figure A46 2.22, 13C{1H} NMR spectrum (C6D6, 150 MHz, 25 \u00b0C)  Figure A47 2.22, 31P NMR spectrum (C6D6, 162 MHz, 25 \u00b0C) 235   Figure A48 2.22, 19F NMR spectrum (C6D6, 282 MHz, 25 \u00b0C) 236  PtMe2(PnBu3)2 (2.23): To a 5 dram vial was added Pt2Me4(SMe2)2 (101.8 mg, 0.177 mmol) which was dissolved in THF (5 mL), to this was added a solution of P(nBu)3 (174 \u00b5L, 0.708 mmol, 4 equiv.) in THF (5 mL) and allowed to stir for 10 minutes before the solvent was removed forming a colourless oil, which under prolonged exposure to vacuum becomes a greasy  white solid, 147.6 mg, 97% yield. The solid was recrystallised from a concentrated acetone solution at -30\u00b0C.  1H NMR (600 MHz, C6D6, 25 \u00b0C) \u03b4 1.72-1.76 (m, 2, 12H), 1.47-1.57 (m, 3, 12H), 1.35 (m, 3JH-H = 7 Hz, 4, 12H), 1.02 (AA\u2019XX\u2019 spin system, 3JP-H = 6 Hz, Pt satellites, 2JPt-H = 66 Hz, 1, 6H), 0.89 (t, 3JH-H = 7 Hz, 5). 13C{1H} NMR (150 MHz, C6D6, 25 \u00b0C) \u03b4 27.09 (t, Pt satellites, 3JPt-C = 18 Hz, 3) 24.81-25.18 (m, Pt and P coupling could not be resolved, 2 & 4), 14.12 (5), 4.33 (dd, cis-2JP-C = 10 Hz, trans-2JP-C = 103 Hz, Pt satellites, 1JP-C = 597 Hz, 1, 6H) .31P{1H} NMR (121 MHz, C6D6) \u03b4 -3.56 (Pt satellites, 1JPt-P = 1821 Hz. Elemental analysis for C26H60P2Pt (C, H): Calculated C, 49.59; H, 9.60. Found C, 49.46; H, 9.28.  Figure A49 2.23, 1H NMR spectrum (C6D6, 600 MHz, 25 \u00b0C) 237   Figure A50 2.23, 13C{1H} NMR spectrum (C6D6, 150 MHz, 25 \u00b0C)  Figure A51 2.23, 31P{1H} NMR spectrum (C6D6, 121 MHz, 25 \u00b0C) 238   Figure A52 2.23, HSQC, NMR spectrum (C6D6, 600\/150 MHz, 25 \u00b0C)  Figure A53 2.23, COSY NMR spectrum (400 MHz, C6D6, 25 \u00b0C) 239  A 3. Experimental data for chapter 3 Synthesis of 3-(2-(1,3-dioxoisoindolin-2-yl)ethyl)-1-mesityl-1H-imidazol-3-ium bromide (3.3)   Procedure adapted from: Martinez Olid, Francisco Jose; Andres Herranz, Roman; De Jesus Alcaniz, Ernesto; Flores Serrano, Juan Carlos, From PCT Int. Appl. (2015), WO 2015197891 A1 20151230. To a teflon sealed Schlenk flask under air was added mesityl imidazole (3.42g, ) and 2-bromoethylpthalimide (4.4g, ) along with technical grade acetonitrile (50 mL). The solution was heated to 80 \u00b0C open to atmosphere, the vessel was then sealed, and the temperature brought to 90 \u00b0C for 48 hours. Caution: Precautions should be taken when heating a reaction past the boiling point of the solvent in a sealed vessel. A protective blast shield should be used to mitigate damage in case of explosion. The solution was cooled to room temperature before transferring to a round bottom flask. Addition of excess diethyl ether (~50-60 mL) under continuous stirring generated a white solid that was filtered via buchner filtration and collected on cellulose paper giving a 3.8 g of a white solid in 82% yield.  1H NMR (CDCl3, 400 MHz, 25 \u00b0C): \u03b4 10.56 (s, 1H), 7.79 (m, 4H), 7.45 (s, 1H), 7.04 (s, 1H), 7.00 (s, 2H), 5.17 (t, 3JH-H = 5 Hz, 2H), 4.36 (t, 3JH-H = 5 Hz, 2H), 2.34 (s, 3H), 2.11 (s, 6H). 13C{1H} NMR (CDCl3, 100 MHz, 25 \u00b0C): \u03b4 167.9, 141.5, 139.09, 134.7, 134.6, 131.7, 130.8, 130.0, 123.8, 123.1, 122.9, 49.81, 39.21, 21.24, 17.78. 240   Figure A54 3.3, 1H NMR spectrum (CDCl3, 300 MHz, 25 \u00b0C)  Figure A55 3.3, 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C) 241  Synthesis of 1-(2,6-diisopropylphenyl)-3-(2-(1,3-dioxoisoindolin-2-yl)ethyl)-1H-imidazol-3-ium bromide (3.4)   Procedure adapted from: Martinez Olid, Francisco Jose; Andres Herranz, Roman; De Jesus Alcaniz, Ernesto; Flores Serrano, Juan Carlos, From PCT Int. Appl. (2015), WO 2015197891 A1 20151230. To a teflon sealed Schlenk flask under air was added 2,6-diisopropylphenyl imidazole (500 mg, 2.19 mmol) and 2-bromoethylpthalimide (556 mg, 2.19 mmol) along with technical grade acetonitrile (5 mL). The solution was heated to 80 \u00b0C open to atmosphere, the vessel was then sealed, and the temperature brought to 90 \u00b0C for 72 hours. Caution: Precautions should be taken when heating a reaction past the boiling point of the solvent in a sealed vessel. A protective blast shield should be used to mitigate damage in case of explosion. The solution was cooled to room temperature before transferring to a round bottom flask. Addition of excess diethyl ether (~20-30 mL) under continuous stirring generated a white solid that was filtered via buchner filtration and collected on cellulose paper giving a 739 mg of a white solid in 70% yield.  1H NMR (CDCl3, 400 MHz, 25 \u00b0C): \u03b4 10.38 (t, J = 1.6 Hz, 1H), 8.08 (d, J = 1.8 Hz, 1H), 7.89 \u2013 7.65 (m, 4H), 7.50 (t, J = 7.8 Hz, 1H), 7.28 (d, J = 7.8 Hz, 2H), 7.15 (t, J = 1.8 Hz, 1H), 5.25 \u2013 5.18 (m, 2H), 4.39 \u2013 4.32 (m, 2H), 2.38 (hept, J = 6.8 Hz, 2H), 1.19 (d, J = 6.8 Hz, 6H), 1.13 (d, J = 6.8 Hz, 6H).13C{1H} NMR (CDCl3, 100 MHz, 25 \u00b0C): \u03b4 167.92, 145.72, 138.61, 134.48, 131.85, 131.75, 130.36, 124.68, 124.15, 124.05, 123.63, 77.48, 77.16, 76.84, 49.61, 39.21, 28.54, 24.55, 24.43. HRMS m\/z calculated for C25H28N3O2 [M+] 402.2176; found: 402.21757  242   Figure A56 3.4, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C)  Figure A57 3.4, 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C)243  Synthesis of 3-(2-(1,3-dioxoisoindolin-2-yl)ethyl)-1-mesityl-1H-imidazol-3-ium hexafluorophosphate (3.5)    To a RBF was added (2.405 g, 5.46 mmol) and water (300 mL) along with KPF6 (1.1 g, 6 mmol). The suspension was heated to 70 \u00b0C and stirred for 1 hour before being vacuum filtered and dried under vacuum to give 2.56 g of a white solid in 92% yield. 1H NMR (CD3CN, 400 MHz, 25 \u00b0C): \u03b4  8.54 (t, J = 1.6 Hz, 1H), 7.82 (s, 4H), 7.73 (s, 1H), 7.42 (s, 1H), 7.12 \u2013 7.03 (m, 2H), 4.71 \u2013 4.36 (m, 2H), 4.30 \u2013 4.00 (m, 2H), 2.32 (s, 3H), 1.94 (s, 6H). 13C{1H} NMR (CD3CN, 100 MHz, 25 \u00b0C): \u03b4168.97, 142.25, 137.70, 135.64, 135.61, 132.82, 131.76, 130.38, 125.29, 124.71, 124.21, 50.04, 38.70, 21.04, 17.30. 31P NMR (CD3CN, 161 MHz, 25 \u00b0C): \u03b4 -144.62 (sep, J = 706 Hz). 19F NMR (CD3CN, 376 MHz, 25 \u00b0C): \u03b4 -72.89 (d, J = 706 Hz). HRMS m\/z calculated for C22H22N3O2 [M+] 360.1707; found: 360.1699   244   Figure A58 3.5, 1H NMR spectrum (CD3CN, 400 MHZ, 25 \u00b0C)  Figure A59 3.5, 13C{1H} NMR spectrum (CD3CN, 100 MHZ, 25 \u00b0C) 245   Figure A60 3.5, 31P NMR spectrum (CD3CN, 121 MHZ, 25 \u00b0C)  Figure A61 3.5 19F NMR spectrum (CD3CN, 376 MHz, 25 \u00b0C)246   Synthesis of 1-(2,6-diisopropylphenyl)-3-(2-(1,3-dioxoisoindolin-2-yl)ethyl)-1H-imidazol-3-ium hexafluorophosphate (3.6)   To a RBF was added (700 mg, 1. 45 mmol) and water (50 mL) along with KPF6 (276 mg, 1.5 mmol). The suspension was heated to 70 \u00b0C and stirred for 1 hour before being vacuum filtered and dried under vacuum to give 730 mg of a white solid in 91% yield. 1H NMR (CDCl3, 400 MHz, 25 \u00b0C): \u03b4 8.84 (d, J = 1.7 Hz, 1H), 7.79 (t, J = 1.8 Hz, 1H), 7.71 (d, J = 1.9 Hz, 3H), 7.53 (t, J = 7.8 Hz, 1H), 7.30 (d, J = 7.9 Hz, 2H), 7.22 (s, 1H), 4.98 \u2013 4.43 (m, 2H), 4.37 \u2013 4.09 (m, 2H), 2.34 (hept, J = 6.8 Hz, 2H), 1.13 (dd, J = 11.6, 6.8 Hz, 11H).  13C{1H} NMR (CDCl3, 100 MHz, 25 \u00b0C): \u03b4 167.94, 145.68, 136.98, 134.48, 131.92, 131.53, 130.00, 124.95, 124.61, 123.96, 123.54, 49.77, 38.25, 28.42, 24.45, 23.90. 31P NMR (CDCl3, 161 MHz, 25 \u00b0C): \u03b4 -144.4 (hept). 19F NMR (CDCl3, 376 MHz, 25 \u00b0C): \u03b4 -71.5 (d). HRMS m\/z calculated for C25H28N3O2 [M+]; 402.2176 found: 402.2179 247   Figure A62 3.6, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C)  Figure A63 3.6, 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C) 248   Figure A64 3.6, 31P NMR spectrum (CDCl3, 161 MHz, 25 \u00b0C)  Figure A65 3.6, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C)249   Synthesis of 3-(2-aminoethyl)-1-mesityl-1H-imidazol-3-ium hexafluorophosphate (3.7)   Procedure adapted from: Martinez Olid, Francisco Jose; Andres Herranz, Roman; De Jesus Alcaniz, Ernesto; Flores Serrano, Juan Carlos, From PCT Int. Appl. (2015), WO 2015197891 A1 20151230. A solution of 3-(2-(1,3-dioxoisoindolin-2-yl)ethyl)-1-mesityl-1H-imidazol-3-ium hexafluorophosphate (2.53 g, 5 mmol) and hydrazine hydrate (1.2 mL (60% w\/w H2O), 20 mmol) in 100 mL of ethanol in a 250 mL flask was heated at 80 \u00b0C overnight. A bulky amorphous white solid formed in the flask. After cooling the flask on ice for 20 minutes, the sticky white solid was filtered on a fritted funnel and the product solution was vacuum filtered into a 250 mL flask; the solid was washed with additional 2 \u00d7 50 mL portions of ethanol. The ethanol was removed on a rotavap, leaving behind the desired product and some residual phthalhydrazide. 30 mL DCM was added to this and the pthalhydrazide filtered once more. The DCM was then removed on a rotavap to give a highly viscous oil in quantitative yield. 1H NMR (CDCl3, 400 MHz, 25 \u00b0C) \u03b4 8.62 (t, J = 1.6 Hz, 1H), 7.68 (t, J = 1.7 Hz, 1H), 7.16 (t, J = 1.8 Hz, 1H), 7.00 (s, 2H), 4.53 \u2013 4.20 (m, 2H), 2.34 (s, 3H), 2.03 (s, 6H), 1.34 (s, Broad, 2H). 13C{1H} NMR (CDCl3, 151 MHz, 25 \u00b0C) \u03b4 141.45, 137.02, 134.60, 130.76, 129.93, 123.73, 123.25, 52.46, 41.39, 21.19, 17.24. 31P NMR (CDCl3, 161 MHz, 25 \u00b0C) \u03b4 -144.4 (septet, J = 712 Hz). 19F NMR (CDCl3, 376 MHz, 25 \u00b0C) \u03b4 . -72.3 (d, J = 712).  250   Figure A66 3.7, !H NMR spectrum (CDCl3, 400 MHZ, 25 \u00b0C)   Figure A67 3.7, 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 \u00b0C) 251   Figure A68 3.7, 31P NMR spectrum ( CDCl3, 161 MHz, 25 \u00b0C)  Figure A69 3.7, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C) 252  Synthesis of 3-(2-aminoethyl)-1-(2,6-diisopropylphenyl)-1H-imidazol-3-ium hexafluorophosphate (3.8)  Procedure adapted from: Martinez Olid, Francisco Jose; Andres Herranz, Roman; De Jesus Alcaniz, Ernesto; Flores Serrano, Juan Carlos, From PCT Int. Appl. (2015), WO 2015197891 A1 20151230. A solution of (730 mg, 1.3 mmol) and hydrazine hydrate (0.540 mL (30% w\/w H2O), 5.2 mmol) in 30 mL of ethanol in a 250 mL flask was heated to reflux overnight. A bulky amorphous white solid formed in the flask. After cooling the flask on ice for 20 minutes, the sticky white solid was filtered on a fritted funnel and the product solution was vacuum filtered into a 250 mL flask; the solid was washed with additional 2 \u00d7 50 mL portions of ethanol. The ethanol was removed on a rotavap, leaving behind the desired product and some residual phthalhydrazide. 30 mL DCM was added to this and the pthalhydrazide filtered once more. The DCM was then removed on a rotavap and the product finally dried on the Schlenk line giving a colourless oil in quantitative yield. Upon leaving the oil at room temperature for several days the oil solidified. This was then used in the next step without further purification.  1H NMR (CDCl3, 400 MHz, 25 \u00b0C) \u03b4 8.72, 7.74, 7.54, 7.31, 7.30, 7.19, 4.44, 3.18, 2.31, 1.16. 13C{1H} NMR (CDCl3, 151 MHz, 25 \u00b0C) \u03b4 145.64, 137.34, 131.93, 130.03, 124.66, 124.12, 123.55, 77.34, 77.02, 76.70, 52.10, 41.18, 28.55, 24.14, 24.06. 31P NMR (CDCl3, 161 MHz, 25 \u00b0C) \u03b4 -144.34 (sept). 19F NMR (CDCl3, 376 MHz, 25 \u00b0C) \u03b4 -72.16 (d). HRMS (ESI) m\/z calculated for C17H26N3 [M]+ 272.21267; Found 272.21304  253   Figure A70 3.8, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C)  Figure A71 3.8 13C{1H} NMR spectrum (CDCl3, 100 MHz, 25 \u00b0C) 254   Figure A72 3.8, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C)  Figure A73 3.8, 31P NMR spectrum (CDCl3, 161 MHz, 25 \u00b0C) 255  Synthesis of N-mesityl-2,2-dimethoxyethan-1-imine (3.9)   Procedure adapted from: Hashmi, A. Stephen K. and Lothschuetz, Christian From U.S. Pat. Appl. Publ., 20120108819, 03 May 2012 To a RBF was added toluene (50 mL), MgSO4 (9.5 g) and mesitylaniline (5 g, 37 mmol). The suspension was stirred for 5 minutes before addition of 2,2\u2019-dimethoxyacetaldehyde (9.54 g, 55.5 mmol, 60% w\/w H2O). The reaction was warmed to 100 \u00b0C and reacted for 4 hours before filtering the MgSO4. Removal of all volatiles then gave quantitative amounts of the product as a yellow solid which was used without further purification. 1H NMR (CDCl3, 300 MHz, 25 \u00b0C): \u03b4 7.50 ( d, 3JH-H = 4.5 Hz, 1H), 6.88 (s, 2H), 4.92 (d, 3JH-H = 4.5 Hz, 1H), 3.55 (s, 6H), 2.28 (s, 3H), 2.11 (s, 6H)  Figure A74 3.9, 1H NMR spectrum (CDCl3, 300 MHz, 25 \u00b0C) 256  Synthesis of N-(2,2-dimethoxyethyl)-2,4,6-trimethylaniline (3.10)   Procedure adapted from: Hashmi, A. Stephen K. and Lothschuetz, Christian From U.S. Pat. Appl. Publ., 20120108819, 03 May 2012 The imine (4.08g, 18.5 mmol) was dissolved in THF\/CHCl3 (30:10 mL). NaBH4 (3 equivs, 1.46 g, 55.5 mmol) was then added and the reaction brough to 75 \u00b0C for 18 h. the reaction was then cooled to room temperature and quenched with water (50 mL) slowly. Chloroform (40 mL) was added to the reaction mixture and the organic layer separated. The aqueous phase was extracted 2 more times with DCM (2 X 50 mL). the combined organic fractions were then washed with NH4Cl (aq) and brine before being dried over Na2SO4 and finally filtered, and solvent removed to give quantitative amounts of the product as a colourless oil which was used in the next step without further purification. 1H NMR ( CDCl3, 300 MHz, 25 \u00b0C) \u03b4 6.82 (s, broad, 2H), 4.46 (t, 3JH-H= 5.5 Hz, 1H), 3.40 (s, 6H), 3.25 (s, broad, 1H), 3.07 (d, 3JH-H= 5.5 Hz, 2H), 2.27 (s, 6H), 2.23 (s, 3H). 257   Figure A75 3.10, 1H NMR spectrum (CDCl3, 300 MHz, 25 \u00b0C) 258   Synthesis of (9H-fluoren-9-yl)methyl (2,2-dimethoxyethyl)(mesityl) carbamate (3.11)  To a RBF was added N-(2,2-dimethoxyethyl)-2,4,6-trimethylaniline (7.50 g, 33.5 mmol) and NaHCO3 (2.81 g, 33.5 mmol), this mixture was suspended in a 1:1 mixture of THF and H2O (60 mL) and taken to 0 \u00b0C. FMOC-Cl (8.68 g, 33.5 mmol) was then added portion-wise to the suspension and left to stir for 5 h at room temperature. The THF was removed under reduced pressure followed by extraction with DCM (3 X 50 mL). the combined organics were washed with brine (50 mL) before drying over Na2SO4 and filtering. Finally, the solvent was removed to give a highly viscous oil. To the oil was added ca 40 mL of hexane and stirred at room temperature, a white precipitate was observed after a few seconds which was filtered after 1 hour of stirring. The hexane was removed from the filtrate to give 13.08 g of a viscous pale-yellow oil in 87% yield which was used in the next step without further purification. Two rotamers are formed in a ratio of 10:1. 1H NMR Major isomer (CDCl3, 400 MHz, 25 \u00b0C) \u03b4 7.67 (dt, J = 7.7, 0.9 Hz, 2H), 7.35 (tt, J = 7.5, 0.9 Hz, 2H), 7.16 (td, J = 7.5, 1.1 Hz, 2H), 7.06 \u2013 6.99 (m, 2H), 6.96 (s, 2H), 4.68 (t, J = 5.4 Hz, 1H), 4.35 (d, J = 7.4 Hz, 2H), 4.00 (t, J = 7.4 Hz, 1H), 3.71 (d, J = 5.4 Hz, 2H), 3.37 (s, 6H), 2.40 (s, 3H), 2.18 (s, 6H).13C{1H} NMR (CDCl3, 101 MHz, 25 \u00b0C) \u03b4 156.04, 143.74, 141.22, 137.06, 137.02, 135.94, 129.29, 127.49, 126.79, 125.09, 119.76, 101.49, 67.64, 53.01, 50.99, 47.05, 21.02, 17.93. HRMS (ESI) m\/z calculated for C28H32NO4 [M+H]+: 446.2326 ; found: 446.2331 1H NMR Minor isomer (CDCl3, 400 MHz, 25 \u00b0C) \u03b4 7.85 \u2013 7.79 (m, 2H), 7.75 \u2013 7.70 (m, 2H), 7.50 \u2013 7.41 (m, 2H), 7.39-7.35 (m, overlapping, 2H), 6.87 (s, 2H), 4.83 (d, J = 5.1 Hz, 2H), 4.29 (t, J = 5.1 Hz, 1H), 4.22 (t, J = 5.3 Hz, 1H), 3.33 (d, J = 5.4 Hz, 2H), 3.10 (s, 6H), 2.27 (s, 3H), 2.08 (s, 6H). 13C{1H} NMR (CDCl3, 101 MHz, 25 \u00b0C) \u03b4 154.82, 143.99, 141.55, 137.33, 259  136.94, 135.61, 129.59, 127.71, 127.18, 124.89, 119.99, 101.87, 66.26, 53.01, 51.08, 47.91, 20.76, 17.78.  Figure A76 3.11, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C)  Figure A77 3.11, 13C{1H} NMR spectrum (CDCl3 100 MHz, 25 \u00b0C) 260   Figure A78 3.11, HSQC NMR spectrum (CDCl3, 100\/400 MHz, 25 \u00b0C)261   Synthesis of (9H-fluoren-9-yl)methyl mesityl(2-oxoethyl)carbamate (3.12)    To a 100 mL RBF was added (9H-fluoren-9-yl)methyl (2,2-dimethoxyethyl)(mesityl) carbamate (13.08 g, 29.3 mmol) which was dissolved in 50 mL of CHCl3, TFA (5 mL, 65.3 mmol) along with a few drops of water were added. The reaction was stirred at room temperature for 4 hours before quenching the remaining TFA with aqueous saturated NaHCO3 solution until no more bubbling was observed. The product was extracted with CHCl3 (2 x 50 mL) and the combined organics were then washed with brine, dried over Na2SO4, and filtered. The solvent was removed to give a highly viscous oil. To the oil was added acetone (5 mL) and hexane (100 mL), the product precipitated as a white powder after several hours of stirring, the suspension was then filtered to give 7.78g of the product as a white analytically pure solid in 78% yield. Two rotamers are formed in a ratio of 6:1  1H NMR Major isomer (CDCl3, 400 MHz, 25 \u00b0C): \u03b4 9.84 (t, br, 1H), 7.65 (d, 3JH-H = 7.5 Hz, 2H), 7.35 (t, 3JH-H = 7.5 Hz, 2H), 7.15 (t, 3JH-H = 7.5 Hz, 2H), 7.05 (d, 3JH-H = 7.5 Hz, 2H), 6.95 (s, 2H), 4.36 (d, 3JH-H = 7.5 Hz), 4.10 (d, 3JH-H = 1 Hz), 4.01 (t, 3JH-H = 7.5 Hz, 1H), 2.38 (s, 3H), 2.17 (s, 6H). 13C{1H} NMR (CDCl3, 100 MHz, 25 \u00b0C): \u03b4 197.9, 156.2, 143.6, 141.3, 137.99, 136.9, 135,7, 129.5, 127.9, 126.9, 125.1, 119.9, 68.22, 59.39, 47.00, 21.10, 18.26. HRMS m\/z calculated for C26H27NO3 [M+H]+: 400.1907; found: 400.1911. 1H NMR Minor isomer (CDCl3, 400 MHz, 25 \u00b0C): \u03b4 9.27 (t, br, 1H), 7.79 (d, 3JH-H = 7.5 Hz, 2H), 7.60 3JH-H = 7.5 Hz, 2H), 7.43 (t, 3JH-H = 7.5 Hz, 2H), 7.35 (t, buried, 2H), 6.85 (s, 2H), 4.78 (d, 3JH-H = 5.0 Hz, 2H), 4,23 (t, 3JH-H = 5.0 Hz, 1H), 3.69 (s, 2H), 2.24 (s, 3H), 2.04 (s, 6H). 13C{1H} NMR (CDCl3, 100 MHz, 25 \u00b0C): \u03b4 197.9, 154.4, 143.7, 141.6, 137.94, 137.3, 135.5, 129.6, 127.9, 127.3, 124.7, 120.1, 66.92, 59.44, 47.79, 20.98, 18.07. 262   Figure A79 3.12, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C)  Figure A80 3.12, 13C{1H} NMR spectrum (CDCl3 100 MHz, 25 \u00b0C) 263   Figure A81 3.12, HSQC NMR spectrum (CDCl3, 100\/400 MHz, 25 \u00b0C) 264   Synthesis of 1-mesityl-3-(2-((2-(mesitylamino)ethyl)amino)ethyl)-1H-imidazol-3-ium hexafluorophosphate (3.13)   Procedure adapted from: Yang W, Chernyshov IY, Schendel RKAvan, Weber M, M\u00fcller C, Filonenko G, et al. Phosphine Ligand Hemilability as a Route Towards Robust and Efficient Hydrogenation with Mn(I) Complexes. ChemRxiv. Cambridge: Cambridge Open Engage; 2020. DOI:10.26434\/chemrxiv.12164262.v1 To a RBF was added 3-(2-aminoethyl)-1-mesityl-1H-imidazol-3-ium hexafluorophosphate (3.15 g, 8.41 mmol) along with dichloromethane (30 mL). (9H-fluoren-9-yl)methyl mesityl(2-oxoethyl)carbamate (3.36g, 8.41 mmol) was added portion-wise at room temperature, the solution was stirred for 30 minutes before addition of NaBH(OAc)3 (4.45 g, 21.0 mmol), the suspension was then stirred for 18 h at room temperature. The reaction was quenched with water (40 mL) and the aqueous phase extracted with DCM (2 x 50 mL). The combined organics were dried over MgSO4, filtered and finally the solvent removed to give a highly viscous oil. Acetonitrile was added (20 mL) to the oil and rotary evaporated at 40 \u00b0C\/ 200 mbar to give a white foamy solid. the foamy solid was dissolved in DCM ( 30 mL) to which piperidine (3 mL) was added in one portion and left to stir at room temperature for 5 hours. NaHCO3 (30 mL) was added, and the organics separated, the aqueous phase was extracted once more with DCM (30 mL). The combined organics were then washed with brine, dried over Na2SO4, filtered and DCM finally removed under reduced pressure to give a yellow pasty solid. To this solid was added diethyl ether (30 mL), the flask swirled to dissolve the deprotected FMOC and decanted. This process was carried out twice ensuring no residual piperidine or deprotected FMOC remains. To the residual yellow oil was added isopropanol (30 mL) heated until full dissolution of the oily 265  material is achieved. The solution was then allowed to cool to room temperature under constant stirring. A white solid is generated as the solution cools, once at room temperature, another portion of Isopropanol (15 mL) was added and the solid filtered under reduced pressure. The solid was washed with isopropanol (2 x 10 mL) and finally diethyl ether ( 2 x 15 mL) to give 3.02g of a white solid in 67% yield. 1H NMR (CDCl3, 400 MHz, 25 \u00b0C): \u03b4 8.64 (t, J = 1.6 Hz, 1H), 7.69 (t, J = 1.7 Hz, 1H), 7.10 (s, 1H), 6.97 (s, 2H), 6.75 (s, 2H), 4.62 \u2013 4.23 (m, 2H), 3.13 \u2013 3.06 (m, 2H), 2.94 (dd, J = 6.5, 5.0 Hz, 2H), 2.79 (dd, J = 6.5, 4.9 Hz, 2H), 2.33 (s, 3H), 2.19 (s, 3H), 2.16 (s, 6H), 2.00 (s, 6H). 13C{1H} NMR (CDCl3, 101 MHz, 25 \u00b0C) \u03b4  143.42, 141.39, 136.85, 134.48, 131.41, 130.71, 129.92, 129.88, 129.48, 123.90, 123.10, 50.21, 49.91, 48.71, 48.37, 21.17, 20.61, 18.28, 17.17. 31P NMR (CDCl3, 162 MHz, 25 \u00b0C) \u03b4 -144.32 (hept). 19F NMR (CDCl3, 376 MHz, 25 \u00b0C) \u03b4 -72.01 (d). HRMS m\/z calculated for C25H35N4 [M+]: 391.2856; found: 391.2860   1H NMR (CD3CN, 400 MHz, 25 \u00b0C) \u03b4 8.66 (t, J = 1.6 Hz, 1H), 7.65 (t, J = 1.8 Hz, 1H), 7.40 (t, J = 1.8 Hz, 1H), 7.09 (m, 2H), 6.88 \u2013 6.61 (m, 2H), 4.58 \u2013 4.16 (m, 2H), 3.25 (s, NH, 1H), 3.06 (t, J = 5.6 Hz, 2H), 2.92 (t, J = 5.9 Hz, 2H), 2.75 (t, J = 5.8 Hz, 2H), 2.34 (s, 3H), 2.16 (t, J = 0.7 Hz, 9H), 2.01 (t, J = 0.7 Hz, 6H), 1.63 (s, NH, 1H).   Figure A82 3.13, 1H NMR spectrum (CDCl3, 400 MHz, 25 \u00b0C) 266   Figure A83 3.13, 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 \u00b0C)  Figure A84 3.13,  31P NMR spectrum (CDCl3, 161 MHz, 25 \u00b0C 267   Figure A85 3.13, 19F NMR spectrum (CDCl3, 376 MHz, 25 \u00b0C)  Figure A86 3.13, 1H NMR spectrum (CD3CN, 400 MHZ, 25 \u00b0C) 268  Synthesis of tridentate C,N,N Abnormal carbene platinum complex 3.27  To a Teflon sealed Schlenk was added 1-mesityl-3-(2-((2-(mesitylamino)ethyl)amino)ethyl)-1H-imidazol-3-ium hexafluorophosphate (410 mg, 0.764 mmol) and Me4Pt2(\u00b5-SMe2)2 (219, mg, 0.382 mmol). To the solids was added 15 mL of dry and degassed benzene. The flask was sealed and heated at 75 \u00b0C for 3 hours. A white solid starts to precipitate after a few hours, the solution was then cooled to room temperature, filtered, and washed with Benzene ( 10 mL) hexane (10 mL) and finally diethyl ether (15 mL). Finally, the solid was dried under reduced pressure to give 464 mg of a white solid in 83 % yield. No noticeable decomposition of the complex was observed when left in air in the solid state after two weeks. Single crystals were grown from a solution of acetone layered with hexane at room temperature. 1H NMR (acetonitrile-d3, 600 MHz, 25 \u00b0C): 13C{1H} NMR (acetonitrile-d3, 150 MHz, 25 \u00b0C) \u03b4.  31P NMR (acetonitrile-d3, 242 MHz, 25 \u00b0C) \u03b4 -143.7 (sept). 19F NMR (acetonitrile-d3, 376 MHz, 25 \u00b0C) \u03b4. ESI-HRMS   269   Figure A87 3.27, 1H NMR spectrum (Acetonitrile-d3, 400 MHz, 25 \u00b0C)  Figure A88 3.27, 13C{1H} NMR spectrum (acetonitrile-d3, 100 MHz, 25 \u00b0C) 270   Figure A89 3.27, 19F NMR spectrum (Acetonitrile-d3, 376 MHz, 25 \u00b0C)  Figure A90 3.27, 31P NMR spectrum (Acetonitrile-d3, 161 MHz, 25 \u00b0C) 271  Synthesis of bis(1-mesityl-3-(2-((2-(mesitylamino)ethyl)amino)ethyl)-2,3-dihydro-1H-imidazol-2-yl)silver(I) Hexafluorophosphate (3.22)   Procedure adapted from: Wang, H. M. J.; Lin, I. J. B. Facile Synthesis of Silver(I)-Carbene Complexes. Useful Carbene Transfer Agents. Organometallics, 1998, 17 (5), 972\u2013975. To  a round bottom flask was added  1-mesityl-3-(2-((2-(mesitylamino)ethyl)amino)ethyl)-1H-imidazol-3-ium hexafluorophosphate (500 mg, 0.93 mmol) with catalytic amounts of NBu4PF6  (5-10 mg). To the solids were added DCM (40 mL) and aqueous NaOH (9 mL, 1 M), the reaction was stirred at room temperature and Ag2O (53.98 mg, 0.23 mmol) was added in one portion. After three days in the dark, water (10 mL) was then added to the reaction and the organic layer separated, dried over MgSO4, and the volatiles removed to give an oily residue. Isopropanol (10-15 mL) was added to the oil and sonicated until a fine white powder was generated, this solid was filtered under reduced pressure and washed with isopropanol (5 mL) and diethyl ether (15 mL) and finally dried under vacuum to give 333 mg of a white solid in 69% yield. Single crystals of the compound were grown from a chloroform\/hexane layered solution.  1H NMR (acetone-d6, 600 MHz, 25 \u00b0C): \u03b4 7.66 (t, J = 1.6 Hz, 2H), 7.34 (t, J = 1.6 Hz, 2H), 7.02 (s, 4H), 6.75 (s, 4H), 4.24 (t, J = 5.9 Hz, 4H), 3.48 (t, J = 7.0 Hz, 2H), 3.04 (t, J = 5.8 Hz, 4H), 2.90 (t, J = 6.0 Hz, 4H), 2.74 (d, J = 5.9 Hz, 4H), 2.38 (s, 6H), 2.18 (s, 12H), 2.16 (s, 6H), 1.84 (s, 12H), 1.6 (t, J = 7.0 Hz, 2H . 13C{1H} NMR (acetone-d6, 150 MHz, 25 \u00b0C) \u03b4.  31P NMR (acetone-d6, 242 MHz, 25 \u00b0C) \u03b4 -143.7 (sept). 19F NMR (acetone-d6, 376 MHz, 25 \u00b0C) \u03b4 \u2013 72.6 (d). ESI-HRMS m\/z calculated for C50H68AgN8 [M]+: 889.4624; Found: 889.4625  272   Figure A91 3.22, 1H NMR (Acetone-d6, 600 MHz, 25 \u00b0C)  Figure A92 3.22, 19F NMR spectrum (Acetone-d6, 376 MHz, 25 \u00b0C) 273   Figure A93 3.22, 31P NMR spectrum (Acetone-d6, 241 MHz, 25 \u00b0C)  274  A 4. Experimental data for chapter 4 Synthesis of Me4Pt2(\u00b5-SMe)2   Procedure adapted from:  Scott, J. D.; Puddephatt, R. J. Organometallics 1983, 2 (11), 1643\u20131648 Methyllithium solution (9.6 mL, 15.4 mmol, 1.6 M in ether) was added dropwise to a suspension of PtCl2(SMe2)2 (2 g, 5.12 mmol) in ether (15 mL) under an atmosphere of N2 at -5 \u00b0C. The solution was stirred for 15-20 minutes at -5 \u00b0C. Keeping the temperature of the reaction below 0 \u00b0C to avoid any decomposition and formation of platinum black. If any yellow PtCl2(SMe2)2 remains, then the reaction should be removed from the ice bath for 5-10 minutes until no more yellow solid is observed. After consumption of the starting material the reaction should be placed back in the ice bath at -5 \u00b0C.  The mixture was then hydrolysed with saturated cold and degassed aqueous ammonium chloride solution (5 minutes nitrogen purge is sufficient; 5 mL drop wise). Water was (5mL) added and the product extracted with diethyl ether (3x40 mL), the fractions were combined and dried over sodium sulfate, filtered, and evaporated under vacuum to give the crude product as an off white solid. The  product was recrystallised from acetone at -30 \u00b0C to yield small fine white\/grey crystals. 89% Notes regarding synthesis and compound properties: The product, while air stable is thermally unstable and will decompose at room temperature. Furthermore, the compound also decomposes under extended periods of time under vacuum. When removing diethyl ether after extraction, a warm water bath should not be used to remove the solvent as this will decompose the product. Loss of product can arise from not using enough diethyl ether during the extraction phase. Some darkening during quenching is normal and doesn\u2019t impact the yield significantly, most of the black particulates can be removed during drying with either sodium or magnesium sulfate and subsequent filtering.    275  Synthesis of Me2Pt(C5H5N)2 (4.1)   To an oven dried Schlenk was added Pt2Me4(\u00b5-SMe2)2 (146 mg, 0.25 mmol), this was dissolved in pyridine (~3 mL) and the solution heated at 50 \u00b0C for 2 hours under a flow of nitrogen. After two hours the reaction was cooled down to room temperature and the pyridine reduced by half, addition of hexane (5 mL) initiated the precipitation of a white solid. the white solid was separated by centrifugation, washed with hexane, and dried under reduced pressure to give 166 mg of the pure product in 84% yield. The solid was stored at -30 \u00b0C, as it decomposed slowly at room temperature over a period of several months. *Dissolution of 2 in any non-coordinating solvent results in C-H activation of one pyridine to give 2-int. Coordinating solvents other than pyridine result in ligand exchange of one or both pyridine ligands. ***NMR data was recorded in the presence of excess pyridine to inhibit C-H activation and has been denoted on spectra.*** 1H NMR (C6D6, 600 MHz, 25 \u00b0C) \u03b4: 8.65 (d, 3JH-H = 6.8 Hz, Pt shoulders, 4H), 6.78 (tt, 3JH-H = 7.6, 1.7 Hz, 2H), 6.38 \u2013 6.35 (m, 4H), 1.58 (s, Pt satellites; 2JPt-H = 85 Hz, 6H).13C{1H} NMR (C6D6, 150 MHz, 25 \u00b0C) \u03b4: 151.14, 134.76, 124.97 (Pt-satellites; 2JPt-C = 18.4 Hz, -19.28 (Pt-satellites; 1JPt-C = 850 Hz).  276   Figure A94 4.1, 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C)  Figure A95 4.1, 13C{1H} NMR spectrum (C6D6 , 100 MHz, 25 \u00b0C) 277  Synthesis of Me2Pt(C5H5N)2 (4.1-d10)    4.1-d10 was synthesised in the same manner as 4.1 using pyridine-d5 instead of pyridine. 4.1-d10 was found as a white crystalline solid in 70% yield. The complex was stored at -30 \u00b0C in the solid state to prevent decomposition.  278  Synthesis of Me2Pt(C6H4F3N)2 (4.1-CF3)    To and oven dried Schlenk flask was added Pt2Me4(\u00b5-SMe2)2 (104.5 mg, 0.18 mmol), this was dissolved in 4-(trifluoromethyl)pyridine (~3 mL) and the solution heated at 50 \u00b0C for 2 hours under a flow of nitrogen. After cooling the reaction to room temperature, the excess 4-(trifluoromethyl)pyridine was removed under reduced pressure to give a yellow solid. To the solid was added hexane (3 mL) and the solid agitated with a spatula. The hexane was then removed under reduced pressure and the solid left to dry giving 181 mg of a yellow solid in  94% yield. The complex was stored in the solid state at -30 \u00b0C. Single crystals were grown from 4-(CF3)pyridine solution layered with hexane at room temperature. ***NMR data was recorded in the presence of excess 4-(trifluoromethyl)pyridine to inhibit C-H activation and has been denoted on spectra.*** 1H NMR (C6D6 , 400 MHz, 25 \u00b0C) \u03b4: 8.57 (d, 3JH-H = 5.3 Hz, Pt shoulders, 4H), 6.56 (d, 3JH-H = 5.6 Hz, 4H), 1.48 (s, 2JPt-H = 86 Hz, 6H). 13C{1H} NMR (C6D6, 100 MHz, 25 \u00b0C) \u03b4: \u03b4 151.88, 136.87 (q, 2JF-C = 34 Hz), 124.37 (q, 1JF-C = 273 Hz), 121.19 (q, 3JF-C = 3.7 Hz), -18.34 (s, Pt satellites; 2JPt-C = 832 Hz)f. 19F NMR (C6D6, 376 MHz, 25 \u00b0C) \u03b4: -64.9. HRMS. EA. 279   Figure A96 4.1-CF3, 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C)  Figure A97 4.1-CF3, 13C {1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C) 280   Figure A98 4.1-CF3, 13C {1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C) Due to the 13C-19F coupling some of the signals are overlapping. The ipso carbon of the 4-(CF3)pyridine seen at 137 ppm should be a quartet for both the complex and the free 4-(CF3)pyridine but are overlapping slightly. The CF3 carbon is also a quartet and the signals seen between 127-122 ppm are 3 of the 4 signals corresponding to this carbon environment with the 4th, for both free 4-(CF3)pyridine and the complex unfortunately overlapping with the meta signal at 119 ppm.  281   Figure A 99 4.1-CF3, 19F NMR spectrum (C6D6, 376 MHz, 25 \u00b0C)282  Synthesis of Me2Pt(C7H11N2)2 (4.1-NMe2)   To a 5 dram vial was added Pt2Me4(\u00b5-SMe2)2 (88 mg, 0.15 mmol) which was suspended in diethyl ether (5 mL), DMAP (73 mg, 0.60 mmol) was weighed into a separate vial and dissolved in diethyl ether (5 mL). The DMAP solution was added in one portion to the vial containing the platinum. the solution was stirred for 1 hour before decanting the solution, washing the white solid with 2 portions of diethyl ether (5 mL) and finally drying under vacuum to give 125 mg of a white solid in 86% yield. Single crystals were grown from benzene solution layered with hexane at room temperature. The product was stored at -30 \u00b0C to avoid decomposition, although decomposition in the solid state is very slow. Signs of C-H activation were seen after 3 hours at room temperature in toluene.  1H NMR (Acetone-d6, 400 MHz, 25 \u00b0C) \u03b4 8.17 \u2013 8.04 (m, Pt shoulders, 4H), 6.55 \u2013 6.47 (m, 4H), 3.00 (s, 12H), 0.42 (s, Pt satellites; 2JPt-H = 86 Hz, 6H). 13C{1H} NMR (Acetone-d6, 100 MHz, 25 \u00b0C) \u03b4 154.28, 150.78 (Pt satellites; 3JPt-C = 12 Hz), 108.20 (Pt satellites; 2JPt-C = 15 Hz) , 39.20, -21.11 (Pt satellites; 1JPt-C = 830 HZ). 283   Figure A100 4.1-NMe2, 1H NMR spectrum (Acetone-d6, 400 MHz, 25 \u00b0C)  Figure A101 4.1-NMe2, 13C{1H} NMR spectrum (Acetone-d6, 100 MHz, 25 \u00b0C) 284  Synthesis of Me2Pt2(C5H5N)2(\u00b5-pyridin-2-yl)2. (4.2)   Me2Pt2(C5H5N)2(\u00b5-pyridin-2-yl)2, 1: To an oven dried Schlenk flask under an atmosphere of nitrogen was added 2 (413 mg, 0.718 mmol) followed by 10 mL of dry pyridine. The reaction was stirred for 2 hours at 50 \u00b0C under a flow of nitrogen. The reaction was cooled to room temperature where the pyridine and any remaining volatiles were completely removed to give a dry white crystalline solid. To the white solid was added dry toluene (10 mL) and the solution heated under a flow of nitrogen at 80 \u00b0C for 2 hours. the toluene was then concentrated until a yellow solid started to precipitate, at which point hexane (10 mL) was added to induce precipitation of the remaining solid. the solid was either filtered on a frit and washed with hexane (5 mL) or separated from the mother liquor via centrifugation.   1H NMR (C6D6, 400 MHz, 25 \u00b0C): \u03b4 9.04 \u2013 8.93 (m, 4H), 8.03 (dd, J = 5.5, 1.1 Hz, Pt shoulders, 2H), 7.98 \u2013 7.82 (m, Pt satellites; 3JPt-H= 48 Hz, 2H), 6.73 (td, J = 7.8, 1.9 Hz, 2H), 6.57 (tt, J = 7.8, 1.6 Hz, 2H), 6.25 (ddd, J = 7.6, 5.0, 1.4 Hz, 4H), 6.09 (ddd, J = 7.1, 5.6, 1.5 Hz, 2H), 1.63 (s, Pt satellites; 3JH-H = 80 Hz, 6H). 13C{1H} NMR (C6D6, 101 MHz, 25 \u00b0C) \u03b4 173.59, 151.91, 149.63, 136.99, 135.37, 131.48, 128.17, 128.05, 127.81, 127.69, 124.58, 117.24, -19.40.  285   Figure A102 4.2, 1H NMR spectrum (C6D6, 400 MHz, 25 \u00b0C)   Figure A103 4.2, 13C{1H} NMR spectrum (C6D6, 100 MHz, 25 \u00b0C) 286  1H NMR spectra for time course data for reaction of 4.1  Figure A104 Stacked 1H NMR spectra (tol-d8, 400 MHz, 30 \u00b0C) for time course data of 4.1 at 30 \u00b0C run 1  Figure A105 Stacked 1H NMR spectra (Tol-d8, 400 MHz, 30 \u00b0C) for the time course data of 4.1 at 30 \u00b0C run 2 287   Figure A106 Stacked 1H NMR spectra (tol-d8, 400 MHz, 30 \u00b0C) for the time course data of 4.1 at 30 \u00b0C run 3  Figure A107 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1 at 40 \u00b0C run 1 288   Figure A108 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1 at 40 \u00b0C run 2  Figure A109 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1 at 40 \u00b0C run 3 289   Figure A110 Stacked 1H NMR spectra (tol-d8, 400 MHz, 50 \u00b0C) for the time course data of 4.1 at 50 \u00b0C run 1   Figure A111 Stacked 1H NMR spectra (tol-d8, 400MHz, 50 \u00b0C) for the time course data of 4.1 at 50 \u00b0C run 2 290   Figure A112 Stacked 1H NMR spectra (tol-d8, 400 MHz, 50 \u00b0C) for the time course data of 4.1 at 50 \u00b0C run 3  Figure A113 Stacked 1H NMR spectra (tol-d8, 400 MHz, 60 \u00b0C) for the time course data of 4.1 at 60 \u00b0C run 1 291   Figure A114 Stacked 1H NMR spectra (tol-d8, 400 MHz, 60 \u00b0C) for the time course data of 4.1 at 60 \u00b0C run 2  Figure A115 Stacked 1H NMR spectra (tol-d8, 400 MHz, 60 \u00b0C) for the time course data of 4.1 at 60 \u00b0C run 3 292   Figure A116 Stacked 1H NMR spectra (tol-d8, 400 MHz, 30 \u00b0C) for the time course data of 4.1-CF3 at 30 \u00b0C  Figure A117 Stacked 1H NMR spectra (tol-d8, 400 MHz, 40 \u00b0C) for the time course data of 4.1-d10 at 40 \u00b0C 293  Appendix B. Crystallographic data B 1. Crystallographic tables for chapter 2 Data for 1.1, 1.3, 1.4, 1.5, 1.6, 1.8, and 1.18 were collected using graphite-monochromated Mo K\u03b1 radiation (\u03bb=0.71073 \u00c5) on a Bruker APEX Duo or X8 diffractometer. This analysis was carried out at the Department of Chemistry, The University of British Columbia by Dr. D. Dawson Beattie. The structures were solved by intrinsic phasing (ShelXT) and refined by full-matrix least-squares procedures on F2 (SHELXL-2013)241 using the OLEX2 interface.242 CCDC 1873760-1873766 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via https:\/\/www.ccdc.cam.ac.uk\/structures Additional Notes on Refinement: Complex 2.18: Two disordered molecules of acetonitrile are found in the unit cell, and were modelled successfully. Additionally, RIGU, SIMU, EADP (2), and SADI (1) restraints were used in the refinement process. All restraints led to improved model statistics. 294    Complex 2.1     Complex 2.4  Figure B1 ORTEP depiction of the solid-state molecular structure of complex 2.1 and 2.4 (ellipsoids are set at 50% probability; H atoms have been omitted for clarity). Selected bond lengths (\u00c5) and angles (\u00b0) 2.1: Pt-C1 2.059(2), Pt-C2 2.088(2), Pt-C3 2.039(3), Pt-S 2.367(1), S-Pt-C3 91.73(9), C2-Pt-C1 88.03, C1-Pt1-C3 88.42, S1-Pt1-C2 91.98. 2.4: Pt-C1 2.103(1), Pt-C2 2.010(5), Pt-C7 2.063(6), Pt-S1 2.351(3), C1-Pt1-C7 90.11, S1-Pt1-C2 94.60, C2-Pt1-C7 82.66, C1-Pt-1-S1 92.63. Compound 2.1 2.4 Empirical formula C31H48N2PtS C24H32N2PtS Formula weight 675.86 575.66 Temperature\/K 100 90 Crystal system monoclinic monoclinic Space group P21\/n P21\/c a\/\u00c5 12.4820(19) 9.3602(8) b\/\u00c5 19.106(3) 14.9581(13) c\/\u00c5 12.859(2) 16.3919(13) \u03b1\/\u00b0 90 90 \u03b2\/\u00b0 90.059(4) 104.308(2) \u03b3\/\u00b0 90 90 Volume\/\u00c53 3066.6(8) 2223.9(3) Z 4 4 \u03c1calcg\/cm3 1.464 1.719 \u03bc\/mm-1 4.664 6.415 F(000) 1368 1136 Crystal size\/mm3 0.13 \u00d7 0.1 \u00d7 0.09 0.2 \u00d7 0.08 \u00d7 0.08 Radiation MoK\u03b1 (\u03bb = 0.71073) MoK\u03b1 (\u03bb = 0.71073) 2\u0398 range for data collection\/\u00b0 3.818 to 63.326 3.74 to 63.008 Index ranges -10 \u2264 h \u2264 18, -27 \u2264 k \u2264 28, -18 \u2264 l \u2264 18 -13 \u2264 h \u2264 11, -21 \u2264 k \u2264 21, -16 \u2264 l \u2264 23 Reflections collected 74991 20232 Independent reflections 10320 [Rint = 0.0405, Rsigma = 0.0277] 7060 [Rint = 0.0652, Rsigma = 0.0773] Data\/restraints\/parameters 10320\/0\/328 7060\/0\/261 Goodness-of-fit on F2 1.022 1.002 Final R indexes [I>=2\u03c3 (I)] R1 = 0.0198, wR2 = 0.0385 R1 = 0.0359, wR2 = 0.0595 295  Final R indexes [all data] R1 = 0.0278, wR2 = 0.0407 R1 = 0.0651, wR2 = 0.0666 Largest diff. peak\/hole \/ e \u00c5-3 0.81\/-0.66 2.37\/-0.97 Flack Parameter C31H48N2PtS C24H32N2PtS Table B1 Crystallographic data for compounds 2.1 and 2,4 Complex 2.6     Complex 2.8  Compound 2.6 2.8 Empirical formula C28H35N3Pt C27H31N3Pt Formula weight 608.68 592.64 Temperature\/K 90 90 Crystal system monoclinic monoclinic Space group P21\/n P21\/n a\/\u00c5 12.4804(11) 11.780(2) b\/\u00c5 15.4521(14) 17.027(3) c\/\u00c5 14.1248(13) 11.769(2) \u03b1\/\u00b0 90 90 \u03b2\/\u00b0 112.659(2) 96.54(3) \u03b3\/\u00b0 90 90 Volume\/\u00c53 2513.7(4) 2345.1(7) Z 4 4 \u03c1calcg\/cm3 1.608 1.679 \u03bc\/mm-1 5.602 6.002 F(000) 1208 1168 Crystal size\/mm3 0.24 \u00d7 0.18 \u00d7 0.02 0.2 \u00d7 0.15 \u00d7 0.019 Radiation MoK\u03b1 (\u03bb = 0.71073) MoK\u03b1 (\u03bb = 0.71073) 2\u0398 range for data collection\/\u00b0 4.088 to 61.038 4.224 to 61.488 Index ranges -17 \u2264 h \u2264 17, -21 \u2264 k \u2264 22, -20 \u2264 l \u2264 20 -16 \u2264 h \u2264 16, -24 \u2264 k \u2264 24, -16 \u2264 l \u2264 16 Reflections collected 32960 81847 Independent reflections 7663 [Rint = 0.0351, Rsigma = 0.0306] 7270 [Rint = 0.0480, Rsigma = 0.0242] Data\/restraints\/parameters 7663\/0\/297 7270\/0\/286 Goodness-of-fit on F2 1.023 1.032 Final R indexes [I>=2\u03c3 (I)] R1 = 0.0210, wR2 = 0.0416 R1 = 0.0177, wR2 = 0.0342 Final R indexes [all data] R1 = 0.0307, wR2 = 0.0447 R1 = 0.0262, wR2 = 0.0364 Largest diff. peak\/hole \/ e \u00c5-3 0.87\/-0.89 0.56\/-0.70 Flack Parameter C28H35N3Pt C27H31N3Pt 296  Figure B2 ORTEP depiction of the solid-state molecular structure of complex 2.6 and 2.8 (ellipsoids are set at 50% probability; H atoms have been omitted for clarity). Selected bond lengths (\u00c5) and angles (\u00b0) 2.6: C1-Pt1 2.049(3), C2-Pt1 2.084(2), C3-Pt1 2.027(2), N1-Pt1 2.126(2), C1-Pt1-C2 88.8(1), C2-Pt1-N1 88.28(9), C3-Pt1-C1 90.11(9), N1-Pt1-C3 92.77(8). 2.8: C1-Pt1 2.079(2), C2-Pt1 2.021(2), C7-Pt1 2.045(2), N1-Pt1 2.102(2), C1-Pt1-N1 88.57(7), C2-Pt1-C7 83.49(8), C7-Pt1-C1 90.07(8), N1-Pt1-C2 97.83(7). Table B2 Crystallographic data for compounds 2.6 and 2.8   Complex 2.3      Complex 2.5  Figure B3 ORTEP depiction of the solid-state molecular structure of complex 2.3 and 2.5 (ellipsoids are set at 50% probability; H atoms have been omitted for clarity). Selected bond lengths (\u00c5) and angles (\u00b0) 2.3: Pt1-C1 2.064(2), Pt1-C2 1.972(2), Pt1-S1 2.3941(5), Pt1-I1 2.6631(5), C1-Pt1-C2 87.69(7), C2-Pt1-S1 91.69(5), S1-Pt1-I1 92.31(1), I1-Pt1-C188.44(5). 2.5: Pt1-C1 1.972(2), Pt1-C6 2.068(2), Pt1-I1 2.6350(4), Pt1-S1 2.3871(6), S1-Pt1-C1 94.66(6), C1-Pt1-C6 81.61(8), C6-Pt1-I 90.21(6), I1-Pt-1-S1 93.53(2). Compound 2.3 2.5 Empirical formula C24H33IN2PtS C23H29IN2PtS Formula weight 703.57 687.53 Temperature\/K 90 90 Crystal system monoclinic monoclinic Space group P21\/c P21\/c a\/\u00c5 10.4632(10) 9.5034(7) b\/\u00c5 14.6453(14) 15.2304(11) c\/\u00c5 16.4371(15) 16.3957(11) \u03b1\/\u00b0 90 90 \u03b2\/\u00b0 93.941(2) 102.914(2) \u03b3\/\u00b0 90 90 Volume\/\u00c53 2512.8(4) 2313.1(3) Z 4 4 \u03c1calcg\/cm3 1.86 1.974 \u03bc\/mm-1 6.908 7.502 F(000) 1352 1312 Crystal size\/mm3 0.29 \u00d7 0.29 \u00d7 0.28 0.26 \u00d7 0.22 \u00d7 0.14 297  Radiation MoK\u03b1 (\u03bb = 0.71073) MoK\u03b1 (\u03bb = 0.71073) 2\u0398 range for data collection\/\u00b0 3.728 to 63.564 3.694 to 66.324 Index ranges -15 \u2264 h \u2264 15, -21 \u2264 k \u2264 21, -24 \u2264 l \u2264 24 -14 \u2264 h \u2264 14, -19 \u2264 k \u2264 23, -25 \u2264 l \u2264 25 Reflections collected 166812 35721 Independent reflections 8517 [Rint = 0.0406, Rsigma = 0.0136] 8839 [Rint = 0.0325, Rsigma = 0.0281] Data\/restraints\/parameters 8517\/0\/271 8839\/0\/260 Goodness-of-fit on F2 1.157 1.053 Final R indexes [I>=2\u03c3 (I)] R1 = 0.0146, wR2 = 0.0305 R1 = 0.0209, wR2 = 0.0493 Final R indexes [all data] R1 = 0.0176, wR2 = 0.0316 R1 = 0.0247, wR2 = 0.0506 Largest diff. peak\/hole \/ e \u00c5-3 0.69\/-0.72 2.98\/-1.18  Table B3 Crystallographic data for compounds 2.3 and 2.4 Complex 2.18 major 0.8 (left), minor 0.2 (right)  Figure B4 Ortep depiction of the solid-state molecular structure of complex 2.18 (ellipsoids are set at 50% probability; H atoms and three acetonitrile molecules have been omitted for clarity). The complex is substitutionally disordered at C1 (0.8) and I1 (0.8), with the alternate positions of iodide (cis to NHC) and methyl (cis to phenyl) holding occupancies of (0.2). Selected bond lengths (\u00c5) and angles (\u00b0) angle and lengths the same across both isomers except for C1 and I1: C1-Pt 2.161(6), C1a-Pt 2.20(2), C2-Pt1 2.015(3), C23-Pt1 2.076(3), C7-Pt1 2.083(3), I1-Pt1 2.6849(6), I1a-Pt 2.649(1) ,N1-P1 2.164(2), C2-Pt1-N1 100.4(1), C23-Pt1-N1 79.1(1), C2-Pt1-C7 82.4(1), N1-Pt1-I1 86.19(7). Empirical formula C37H40IN5Pt Formula weight 876.73 Temperature\/K 90 Crystal system triclinic Space group P-1 a\/\u00c5 9.8998(17) b\/\u00c5 11.630(2) c\/\u00c5 15.561(3) \u03b1\/\u00b0 75.326(4) \u03b2\/\u00b0 77.955(4) \u03b3\/\u00b0 78.978(4) Volume\/\u00c53 1676.7(5) Z 2 298  \u03c1calcg\/cm3 1.737 \u03bc\/mm-1 5.139 F(000) 856 Crystal size\/mm3 0.23 \u00d7 0.22 \u00d7 0.025 Radiation MoK\u03b1 (\u03bb = 0.71073) 2\u0398 range for data collection\/\u00b0 2.744 to 61.08 Index ranges -14 \u2264 h \u2264 14, -16 \u2264 k \u2264 15, -22 \u2264 l \u2264 22 Reflections collected 38751 Independent reflections 10237 [Rint = 0.0347, Rsigma = 0.0330] Data\/restraints\/parameters 10237\/724\/443 Goodness-of-fit on F2 1.271 Final R indexes [I>=2\u03c3 (I)] R1 = 0.0259, wR2 = 0.0576 Final R indexes [all data] R1 = 0.0287, wR2 = 0.0584 Largest diff. peak\/hole \/ e \u00c5-3 1.06\/-1.64 Flack Parameter C37H40IN5Pt Table B4 Crystallographic data for the compound 2.18 B 2. Crystallographic tables for chapter 3 Diffraction experiments for 3.13, 3.28, 3.29, 3.22 and 3.23 were performed on a Bruker Smart diffractometer equipped with a Siemens Fine Focus Ceramic Tube (graphite monochromated Mo K\u03b1, \u03bb = 0.71069 \u00c5) and an APEX II CCD detector. Data was collected and refined by Dr. Benjamin Gelfand at the University of Calgary. The crystal was kept at 173 K during data collection. Diffractions spots were integrated and scaled with SAINT [1] and the space group was determined with XPREP. Using Olex2, the structure was solved with the ShelXT structure solution program using Intrinsic Phasing and refined with the ShelXL refinement package using Least Squares minimization. 3.13  Figure B5 ORTEP depiction of the solid-state molecular structure of 3.13 (ellipsoids are set at 50% probability; H atoms and minor portions of disorder been omitted for clarity).  299  Empirical formula  C25H35F6N4P  Formula weight  536.54  Temperature\/K  173.0  Crystal system  triclinic  Space group  P-1  a\/\u00c5  9.8906(8)  b\/\u00c5  12.7340(11)  c\/\u00c5  23.2227(19)  \u03b1\/\u00b0  85.4540(10)  \u03b2\/\u00b0  77.7450(10)  \u03b3\/\u00b0  71.1470(10)  Volume\/\u00c53  2704.7(4)  Z  4  \u03c1calcg\/cm3  1.318  \u03bc\/mm-1  0.164  F(000)  1128.0  Crystal size\/mm3  0.486 \u00d7 0.253 \u00d7 0.13  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  1.794 to 56.562  Index ranges  -13 \u2264 h \u2264 13, -16 \u2264 k \u2264 16, -30 \u2264 l \u2264 30  Reflections collected  63699  Independent reflections  13407 [Rint = 0.0339, Rsigma = 0.0275]  Data\/restraints\/parameters  13407\/4496\/957  Goodness-of-fit on F2  1.025  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0445, wR2 = 0.1098  Final R indexes [all data]  R1 = 0.0656, wR2 = 0.1227  Largest diff. peak\/hole \/ e \u00c5-3  0.27\/-0.30  Table B5 Crystallographic data for compounds 3.13 300  3.28  Figure B6 Figure S3.1 ORTEP depiction of the solid-state molecular structure of 3.28 (ellipsoids are set at 50% probability, H atoms, PF6 anion and 2 molecules of acetone along with minor portions of disorder have been removed for clarity). Selected bond lengths (\u00c5) and angles (\u00b0): Pt-C2 1.968(3), Pt-C1 2.044(3), Pt-N3 2.147(3), Pt1-N4 2.146(2). C2-Pt-N3 94.3(1), C2-Pt1-C1 90.9(1), N3-Pt1-N4 81.38(9), N4-Pt1-C1 93.5(1). Empirical formula C32H49F6N4O2PPt  Formula weight  861.81  Temperature\/K  173.0  Crystal system  monoclinic  Space group  P21\/c  a\/\u00c5  15.9216(8)  b\/\u00c5  13.9356(7)  c\/\u00c5  17.5129(8)  \u03b1\/\u00b0  90  \u03b2\/\u00b0  111.7850(10)  \u03b3\/\u00b0  90  Volume\/\u00c53  3608.2(3)  Z  4  \u03c1calcg\/cm3  1.586  \u03bc\/mm-1  3.998  F(000)  1728.0  Crystal size\/mm3  0.273 \u00d7 0.218 \u00d7 0.126  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  2.754 to 61.012  Index ranges  -22 \u2264 h \u2264 22, -19 \u2264 k \u2264 19, -25 \u2264 l \u2264 25  Reflections collected  79269  Independent reflections  10998 [Rint = 0.0477, Rsigma = 0.0301]  Data\/restraints\/parameters  10998\/152\/465  Goodness-of-fit on F2  0.982  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0257, wR2 = 0.0555  Final R indexes [all data]  R1 = 0.0408, wR2 = 0.0616  301  Largest diff. peak\/hole \/ e \u00c5-3  1.32\/-0.43  Table B6 Crystallographic data for compound 3.28  3.29  Figure B7 ORTEP depiction of the solid-state molecular structure of complex 3.29 (ellipsoids are set at 50% probability; two molecules of acetone and a PF6 anion have been omitted for clarity). Selected bond lengths (\u00c5) and angles (\u00b0): Pt1-C1 2.039(2), Pt1-C2 1.945(2), Pt1-N3 2.166(2), Pt1-N4 2.128(2). C1-Pt1-C2 94.7(1), C1-Pt1-N4 92.63(9), C2-Pt1-N3 89.69(9), N3-Pt1-N4 82.97(8). Empirical formula  C27.5H40F6N4O0.5PPt  Formula weight  774.69  Temperature\/K  173.0  Crystal system  monoclinic  Space group  C2\/c  a\/\u00c5  39.904(4)  b\/\u00c5  11.2425(12)  c\/\u00c5  13.8808(15)  \u03b1\/\u00b0  90  \u03b2\/\u00b0  96.8870(10)  \u03b3\/\u00b0  90  Volume\/\u00c53  6182.3(12)  Z  8  \u03c1calcg\/cm3  1.665  \u03bc\/mm-1  4.653  F(000)  3072.0  Crystal size\/mm3  0.483 \u00d7 0.199 \u00d7 0.183  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  3.766 to 61.076  Index ranges  -56 \u2264 h \u2264 56, -16 \u2264 k \u2264 16, -19 \u2264 l \u2264 19  Reflections collected  53915  302  Independent reflections  9390 [Rint = 0.0421, Rsigma = 0.0330]  Data\/restraints\/parameters  9390\/39\/388  Goodness-of-fit on F2  1.022  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0266, wR2 = 0.0497  Final R indexes [all data]  R1 = 0.0402, wR2 = 0.0528  Largest diff. peak\/hole \/ e \u00c5-3  1.06\/-0.64  Table B7 Crystallographic data for compound 3.29 3.22  Figure B8 ORTEP depiction of the solid-state molecular structure of 3.22 (ellipsoids are set at 50% probability, H atoms, PF6 anion and portions of minor disorder have been removed for clarity). Selected bond lengths (\u00c5): C1-Ag1 2.069. Selected Angles (\u00b0): C1-Ag1-C26 180.00.  Empirical formula  C50H68AgF6N8P  Formula weight  1033.96  Temperature\/K  173  Crystal system  triclinic  Space group  P-1  a\/\u00c5  9.2482(11)  b\/\u00c5  12.4031(16)  c\/\u00c5  12.4869(14)  \u03b1\/\u00b0  115.896(2)  \u03b2\/\u00b0  92.936(3)  \u03b3\/\u00b0  92.920(2)  Volume\/\u00c53  1282.5(3)  Z  1  \u03c1calcg\/cm3  1.339  \u03bc\/mm-1  0.488  F(000)  540.0  Crystal size\/mm3  0.434 \u00d7 0.369 \u00d7 0.122  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  3.638 to 57.43  303  Index ranges  -12 \u2264 h \u2264 12, -16 \u2264 k \u2264 16, -16 \u2264 l \u2264 16  Reflections collected  25035  Independent reflections  6633 [Rint = 0.0313, Rsigma = 0.0320]  Data\/restraints\/parameters  6633\/972\/409  Goodness-of-fit on F2  1.038  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0328, wR2 = 0.0694  Final R indexes [all data]  R1 = 0.0444, wR2 = 0.0751  Largest diff. peak\/hole \/ e \u00c5-3  0.44\/-0.29  Table B8 Crystallographic data for compound 3.22 3.23  Figure B9 ORTEP depiction of the solid-state molecular structure of 3.23 (ellipsoids are set at 50% probability, another molecule of 3.23 and minor portions of disorder have been omitted for clarity). Selected bond lengths (\u00c5): C1_1-Pt_1 2.082(3), S1_1-Pt_1 2.108(3), N3_1-Pt_1 2.2555(9), C8_1-Pt_1 2.059(3). Selected angles (\u00b0). C1_1-Pt_1-N3_1 86.7(1), C8_1-Pt_1-S1_1 90.53(9), S1_1-Pt_1-C1_1 91.8(1), N3_1-Pt_1-C8_1 90.9(1). Empirical formula C28H43F6N4PPtS  Formula weight  807.78  Temperature\/K  173.0  Crystal system  triclinic  Space group  P-1  a\/\u00c5  10.9381(4)  b\/\u00c5  16.0757(6)  c\/\u00c5  19.3321(7)  \u03b1\/\u00b0  72.3840(10)  \u03b2\/\u00b0  82.7250(10)  \u03b3\/\u00b0  80.3510(10)  Volume\/\u00c53  3183.6(2)  Z  4  \u03c1calcg\/cm3  1.685  304  \u03bc\/mm-1  4.583  F(000)  1608.0  Crystal size\/mm3  0.222 \u00d7 0.221 \u00d7 0.154  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  2.218 to 56.564  Index ranges  -14 \u2264 h \u2264 14, -21 \u2264 k \u2264 21, -25 \u2264 l \u2264 25  Reflections collected  109974  Independent reflections  15801 [Rint = 0.0388, Rsigma = 0.0260]  Data\/restraints\/parameters  15801\/2214\/867  Goodness-of-fit on F2  1.036  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0245, wR2 = 0.0563  Final R indexes [all data]  R1 = 0.0355, wR2 = 0.0601  Largest diff. peak\/hole \/ e \u00c5-3  0.92\/-0.91  Table B9 Crystallographic data for compounds 3.23 B 3. Crystallographic tables for chapter 4 Diffraction experiments for 4.1, 4.2, 4.4, 4.6, 4.1-CF3 and 4.1-NMe2 were performed on a Bruker Smart diffractometer equipped with a Siemens Fine Focus Ceramic Tube (graphite monochromated Mo K\u03b1, \u03bb = 0.71069 \u00c5) and an APEX II CCD detector. Data was collected and refined by Dr. Benjamin Gelfand at the University of Calgary. The crystal was kept at 173 K during data collection. Diffractions spots were integrated and scaled with SAINT and the space group was determined with XPREP. Using Olex2, the structure was solved with the ShelXT structure solution program using Intrinsic Phasing and refined with the ShelXL refinement package using Least Squares minimization.  305   4.1  Figure B10 ORTEP depiction of the solid-state molecular structure of 4.1 (ellipsoids are set at 50% probability, H atoms and another molecule of 4.1 has been omitted for clarity). Selected bond angles (\u00c5): C1-Pt1 2.040(4), C2-Pt1 2.034(4), N1-Pt1 2.129(3), N2-Pt1 2.126(3). Selected bond angles (\u00b0): C1-Pt1-C2, C1-Pt1-N1, N1-Pt1-N2, N2-Pt1-C2. Empirical formula C24H32N4Pt2  Formula weight  766.71  Temperature\/K  173.0  Crystal system  triclinic  Space group  P-1  a\/\u00c5  9.2475(13)  b\/\u00c5  9.4590(13)  c\/\u00c5  14.3112(19)  \u03b1\/\u00b0  96.231(2)  \u03b2\/\u00b0  100.781(2)  \u03b3\/\u00b0  90.251(2)  Volume\/\u00c53  1222.1(3)  Z  2  \u03c1calcg\/cm3  2.084  \u03bc\/mm-1  11.452  F(000)  720.0  Crystal size\/mm3  0.334 \u00d7 0.333 \u00d7 0.3  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  2.916 to 56.78  Index ranges  -12 \u2264 h \u2264 12, -12 \u2264 k \u2264 12, -19 \u2264 l \u2264 19  Reflections collected  24343  Independent reflections  6086 [Rint = 0.0417, Rsigma = 0.0290]  Data\/restraints\/parameters  6086\/0\/276  Goodness-of-fit on F2  1.085  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0194, wR2 = 0.0405  Final R indexes [all data]  R1 = 0.0240, wR2 = 0.0417  Largest diff. peak\/hole \/ e \u00c5-3  1.00\/-0.61  Table B10 Crystallographic data for compound 4.1 306  4.4  Figure B11 ORTEP depiction of the solid-state molecular structure of 4.4 (ellipsoids are set at 50% probability and H atoms have been omitted for clarity). Selected bond lengths (\u00c5):C1-Pt1 2.028(5), C2-Pt1 2.035(4), N1-Pt1 2.142(3), N2-Pt1 2.103(3), Pt1-Pt2 2.6998(6), C8-Pt2 2.033(3), N3-Pt2 2.107(4), C9-Pt2 1.958(4). Selected bond angles (\u00b0):C1-Pt1-C2 88.3(2), C1-Pt1-Pt2 86.6(1), C2-Pt1-N1 90.7(2), C2-Pt1-Pt2 108.4(1), N1-Pt1-N2 89.9(1), N1-Pt1-Pt2 97.66(9), N2-Pt1-C1 91.4(2), N2-Pt1-Pt2 67.78(9), C8-Pt2-C9 94.5(2), N3-Pt2-Pt1 100.52(9), C9-Pt2-Pt1 74.0(1),C8-Pt2-N3 90.9(1) . Empirical formula  C18H23N3Pt2  Formula weight  671.57  Temperature\/K  173.0  Crystal system  triclinic  Space group  P-1  a\/\u00c5  9.015(2)  b\/\u00c5  9.864(3)  c\/\u00c5  11.679(3)  \u03b1\/\u00b0  99.438(6)  \u03b2\/\u00b0  99.110(5)  \u03b3\/\u00b0  108.353(4)  Volume\/\u00c53  947.6(4)  Z  2  \u03c1calcg\/cm3  2.354  \u03bc\/mm-1  14.749  F(000)  616.0  Crystal size\/mm3  0.179 \u00d7 0.156 \u00d7 0.15  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  3.628 to 56.772  Index ranges  -12 \u2264 h \u2264 12, -13 \u2264 k \u2264 13, -15 \u2264 l \u2264 15  Reflections collected  36329  Independent reflections  4735 [Rint = 0.0348, Rsigma = 0.0206]  Data\/restraints\/parameters  4735\/0\/211  Goodness-of-fit on F2  1.048  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0187, wR2 = 0.0415  307  Final R indexes [all data]  R1 = 0.0250, wR2 = 0.0433  Largest diff. peak\/hole \/ e \u00c5-3  1.21\/-0.60  Table B11 Crystallographic data for compound 4.4 4.2  Figure B12  ORTEP depiction of the solid-state molecular structure of 4.2 (ellipsoids are set at 50% probability, H atoms, two molecules of THF and a second molecule of 4.2 have been removed for clarity). Selected bond lengths (\u00c5): Pt1-C24 2.062(4), Pt1-C30 1.971(4), Pt1-N6 2.119(3), Pt1-N7 2.107(3), Pt02-C23 2.060(4), Pt02-C25 (1.982(4)), Pt02-N5 2.122(3), Pt02-N8 2.107(3). Selected bond angles (\u00b0): C24-Pt02-C25 89.1(2), C24-Pt1-C30 88.1(2), C25-Pt02-N5 92.0(1), C30-Pt1-N6 92.2(1), N5-Pt02-N8 88.9(1), N6-Pt1-N7 89.1(1), N7-Pt1-C24 90.5(2), N8-Pt02-C23 90.1(1). Empirical formula C48H56N8OPt4 Formula weight 1541.36 Temperature\/K 173.15 Crystal system monoclinic Space group P21\/c a\/\u00c5 19.0874(8) b\/\u00c5 28.4111(13) c\/\u00c5 8.9309(4) \u03b1\/\u00b0 90 \u03b2\/\u00b0 99.979(2) \u03b3\/\u00b0 90 Volume\/\u00c53 4769.9(4) Z 4 \u03c1calcg\/cm3 2.146 \u03bc\/mm-1 11.738 F(000) 2880.0 Crystal size\/mm3 0.18 \u00d7 0.1 \u00d7 0.07 Radiation MoK\u03b1 (\u03bb = 0.71073) 2\u0398 range for data collection\/\u00b0 2.166 to 56.638 Index ranges -25 \u2264 h \u2264 25, -37 \u2264 k \u2264 36, -9 \u2264 l \u2264 11 Reflections collected 45286 308  Independent reflections 11807 [Rint = 0.0271, Rsigma = 0.0271] Data\/restraints\/parameters 11807\/355\/599 Goodness-of-fit on F2 1.048 Final R indexes [I>=2\u03c3 (I)] R1 = 0.0243, wR2 = 0.0450 Final R indexes [all data] R1 = 0.0304, wR2 = 0.0464 Largest diff. peak\/hole \/ e \u00c5-3 1.47\/-1.18 Table B12 Crystallographic data for compound 4.2 4.1-CF3  Figure B13 ORTEP depiction of the solid-state molecular structure of 4.1-CF3 (ellipsoids are set at 50% probability, H atoms and minor portions of disorder have been removed for clarity). Selected bond lengths(\u00c5): C1-Pt1 2.034(3), C2-Pt1 2.039(4), N1-Pt1 2.119(3), N2-Pt 2.118(2). Selected bond angles (\u00b0): N1-Pt1-N2 91.85(8), N2-Pt1-C2 89.9(1), C2-Pt1-C1 88.3(1), C1-Pt1-N1 89.9(1).  Empirical formula  C14H14F6N2Pt  Formula weight  519.36  Temperature\/K  173.0  Crystal system  triclinic  Space group  P-1  a\/\u00c5  7.6900(14)  b\/\u00c5  9.4046(17)  c\/\u00c5  11.945(2)  \u03b1\/\u00b0  95.280(3)  \u03b2\/\u00b0  102.121(4)  \u03b3\/\u00b0  92.921(3)  Volume\/\u00c53  838.8(3)  Z  2  \u03c1calcg\/cm3  2.056  \u03bc\/mm-1  8.421  F(000)  488.0  Crystal size\/mm3  0.197 \u00d7 0.185 \u00d7 0.175  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  3.506 to 58.176  Index ranges -10 \u2264 h \u2264 10, -12 \u2264 k \u2264 12, -16 \u2264 l \u2264 16  Reflections collected  14138  Independent reflections  4497 [Rint = 0.0255, Rsigma = 0.0288]  309  Data\/restraints\/parameters  4497\/163\/267  Goodness-of-fit on F2  1.044  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0208, wR2 = 0.0375  Final R indexes [all data]  R1 = 0.0251, wR2 = 0.0385  Largest diff. peak\/hole \/ e \u00c5-3  0.62\/-0.73  Table B13 Crystallographic data for compound 4.1-CF3 4.1-NMe2  Figure B14 ORTEP depiction of the solid-state molecular structure of 4.1-NMe2 (ellipsoids are set at 50% probability, H atoms have been removed for clarity). Selected bond lengths (\u00c5):Pt1-N1 2.127(2), Pt1-C1 2.040(5), Pt1-C2 2.033(3), Pt1-N2 2.128(3). Selected bond angles (\u00b0): N2-Pt1-N1 91.0(1), N1-Pt1-C1 90.7(1), C1-Pt1-C2 87.9(2), C2-Pt1-N2 90.6(1). Empirical formula C16H26N4Pt  Formula weight  469.50  Temperature\/K  173.0  Crystal system  monoclinic  Space group  P21\/n  a\/\u00c5  11.9493(14)  b\/\u00c5  9.6479(11)  c\/\u00c5  16.0281(18)  \u03b1\/\u00b0  90  \u03b2\/\u00b0  109.9190(10)  \u03b3\/\u00b0  90  Volume\/\u00c53  1737.3(3)  Z  4  \u03c1calcg\/cm3  1.795  \u03bc\/mm-1  8.077  F(000)  912.0  Crystal size\/mm3  0.344 \u00d7 0.261 \u00d7 0.234  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  3.712 to 56.618  Index ranges  -15 \u2264 h \u2264 15, -12 \u2264 k \u2264 12, -21 \u2264 l \u2264 21  310  Reflections collected  22375  Independent reflections  4315 [Rint = 0.0346, Rsigma = 0.0255]  Data\/restraints\/parameters  4315\/0\/196  Goodness-of-fit on F2  1.055  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0222, wR2 = 0.0397  Final R indexes [all data]  R1 = 0.0379, wR2 = 0.0439  Largest diff. peak\/hole \/ e \u00c5-3  0.98\/-0.90  Table B14 Crystallographic data for compound 4.1-NMe2  4.6  Figure B15 ORTEP depiction of the solid-state molecular structure of 4.6 (ellipsoids are set at 50% probability, H atoms, and five molecules of benzene along with minor portions of disorder have been omitted for clarity) Selected bond lengths (\u00c5): C23-Pt3 2.038(8), N5-Pt3 2.112(5), N3-Pt3 2.113(6), Pt3-Pt2 3.0634(4), C18-Pt3 1.976(5), C12-Pt2 2.037(6), C13-Pt2 1.988(7), N4-Pt2 2.120(4), N2-Pt2 2.099(5), C7-Pt1 1.962(7), Pt2-Pt1 2.7109(4), C1-Pt1 2.052(5), C7-Pt1, N1-Pt1 2.105(5). Selected bond angles (\u00b0): N5-Pt3-N3 90.8(2), N3-Pt3-C18 90.8(2), C18-Pt3-C23 89.6(2), C23-Pt3-N5 89.6(2), N5-Pt3-Pt2 113.7(1), N3-Pt3-Pt2 63.1(1), C18-Pt3-Pt2 67.1(2), C23-Pt3-Pt2 114.5(2), C13-Pt2-C12 89.5(3), C12-Pt2-N2 90.2(2), N2-Pt2-N4 89.9(2), N4-Pt2-C13 90.4(2), N1-Pt-C1 91.7(2), C1-Pt1-C7 94.8(2), C7-Pt1-Pt2 73.6(2), Pt2-Pt1-N1 99.9(1). Empirical formula  C40H43N5Pt3  Formula weight  1179.06  Temperature\/K  173.0  Crystal system  triclinic  Space group  P-1  a\/\u00c5  9.9513(11)  b\/\u00c5  14.9719(16)  c\/\u00c5  15.3443(17)  \u03b1\/\u00b0  61.3727(13)  \u03b2\/\u00b0  74.2248(14)  \u03b3\/\u00b0  81.2370(13)  Volume\/\u00c53  1930.4(4)  Z  2  \u03c1calcg\/cm3  2.028  \u03bc\/mm-1  10.877  F(000)  1104.0  Crystal size\/mm3  0.363 \u00d7 0.133 \u00d7 0.109  Radiation  MoK\u03b1 (\u03bb = 0.71073)  2\u0398 range for data collection\/\u00b0  3.1 to 54.966  Index ranges  -12 \u2264 h \u2264 11, -19 \u2264 k \u2264 19, -19 \u2264 l \u2264 19  311  Reflections collected  26484  Independent reflections  8850 [Rint = 0.0375, Rsigma = 0.0427]  Data\/restraints\/parameters  8850\/753\/536  Goodness-of-fit on F2  1.030  Final R indexes [I>=2\u03c3 (I)]  R1 = 0.0285, wR2 = 0.0638  Final R indexes [all data]  R1 = 0.0394, wR2 = 0.0683  Largest diff. peak\/hole \/ e \u00c5-3  1.93\/-1.37  Table B15 Crystallographic data for compound 4.6  312  Appendix C. Computational details C 1. Computational details for chapter 2 Density functional theory was employed using Gaussian 09, revision D.01.243 The gradient-corrected functional BP86 (incorporating Becke\u2019s exchange functional244 and the correlation functional of Perdew245) was used in all calculations, and geometry optimizations were performed with no symmetry restrictions. The double-\uf07a basis set 6-31G(d,p) was used for non-metal atoms in all calculations, and the SDD basis set and associated effective core-potentials were used for S, I and Pt. Additional d (S, I) and f (Pt) polarization functions were added as recommended by Frenking et al.246,247 This basis set has been used with success by us (a) and others (b) in studies of C-C RE from Pt(IV). The calculated barriers are comparable to those for related systems calculated at a higher level of theory (c). Analytical computation of the Hessian matrix was performed on each output geometry to ensure the presence of local minima (no imaginary frequencies) or transition states (one imaginary frequency). Single point energy calculations were performed on the optimized coordinates with the same basis set and inclusion of solvent (PCM, solvent = benzene) and dispersion corrections.248,249 Statistical mechanics calculations of entropic and thermal effects were performed using the rigid rotor and harmonic oscillator approximations at 298.15 K and 1 atm. Connectivity between transition states and intermediates was established by means of intrinsic reaction coordinate (IRC) calculations. NBO analysis was performed using the NBO 3.1 program as implemented in Gaussian 09.250 Full pathways for Csp2-I cleavage starting from 2.1 and 2.4 are shown in Figures S60 and S61, respectively. Attempts to locate Csp2-I OA transition states with PhI in the opposite orientation (i.e. to give the square pyramidal Pt(IV) product with I in the apical position) were not successful. A variety of reductive elimination (RE) pathways yielding toluene are possible from 2.12\/2.16 due to facile isomerization of the 5-coordinate intermediate.101 As such, only one pathway \u2013 Csp2-Csp3 RE of the apical Ph group and the alkyl group trans to the NHC donor - was considered. Pathways for PhI OA that involved a trans-configuration of anionic C donors were considered, and in all cases were found to be higher in energy than OA to isomers in which anionic C donors were in a cis configuration. This is illustrated in Figure S62, which shows the relative energies of Csp2-I OA transition states for different isomers of the cyclometallated and dimethyl NHC complexes. The barriers (\uf044G\u2021) to Csp2-I OA to 2.1 are significantly higher than those for 2.4 as a consequence of greater steric repulsion between the NHC mesityl substituents and the PhI moiety when the NHC is not cyclometallated (Figure S62). 313  In the Csp2-I OA step, the PhI group interacts with Pt in a face-on fashion, resulting in strong steric repulsion with the cis NHC group in the non-cyclometallated complex. The \uf044G values for the OA step are similar in both systems due to reorientation of the Ph group after the OA step, which results in a parallel arrangement of the NHC-mesityl and Pt-Ph aromatic rings. Attempts were made to identify other rotameric transition states such as 2.15_rotTS (+1.5 kcal\u00b7mol-1 relative to 2.15TS) which would have fewer repulsive interactions, but no lower energy transition states were found using several different input geometries. The difference in \uf044G\u2021 values for 2.15TS and 2.15_transalkylTS (4.6 kcal\u00b7mol-1) are smaller than \uf044\uf044G\u2021 for cyclometallated transition states 2.11TS and 2.11_transalkylTS (9.2 kcal\u00b7mol-1). This observation is attributed to the relief of steric repulsion between PhI and the NHC upon moving from 2.15TS to 2.15_transalkylTS, which partially offsets the higher energy of the trans-alkyl arrangement. IRC calculations in the reverse direction for Csp2-Csp3 reductive elimination transition states 2.17TS and 2.13TS confirmed connectivity of the transition state to the Pt(IV) intermediates 2.16 and 2.12, respectively. The IRC calculations in the forward direction were consistent with the intermediacy of \uf073-(Csp3-H) complexes 2.17tol and 2.13tol, in line with expectations based on our previous work101 and evidenced by elongation of the interacting Csp3-H bond throughout the reaction coordinate (Figure S62). IRC calculations in the forward direction (to 2.17tol\/2.13tol) failed after 25-40 steps of 0.1 (amu)1\/2Bohr for both systems and attempts to optimize the geometry of the structures late in the reaction coordinate resulted in dissociation of toluene \u2013 no minima corresponding to 2.17tol \/2.13tol were found. This observation may be attributed to a shallow potential energy surface surrounding the \uf073-toluene intermediates 2.17tol \/2.13tol, or in these systems it is possible that they do not exist as intermediates due to steric repulsion with the NHC. In Figures S60 and S61, complexes 2.17tol \/2.13tol are shown as proposed intermediates for clarity, along with upper energy bounds estimated from the electronic energies of the furthest point obtained in the IRC starting from 2.17TS and 2.13TS. 314   Figure B16 Reaction coordinate for Csp2-I oxidative addition starting from the Pt(II) dimethyl complex 2.1. 315   Figure B17 Reaction coordinate for Csp2-I oxidative addition starting from cyclometallated complex 2.4.       316   Figure B18 Transition states for Csp2-I OA showing higher energies when Pt-alkyl groups are in a mutally trans configuration. Relative energies reported relative to 2.1 for 2.15TS and 2.15_transalkylTS, relative to 2.4 for 2.11TS and 2.11_transalkylTS.       317   Figure B19 Csp2-I OA transition state geometries. 318  C 2. Computational details for chapter 4 Density functional theory (DFT) calculations were carried out using the ORCA computational package,251 Version 4.2.1. Geometry optimization and numeric frequency calculations of all the involved molecules were initially performed with hybrid generalized-gradient-approximation functional PBE0, and grid 5 integration.252 Ahlrichs def2 basis set def2-SVP was used in the initial calculations for all non-metal atoms, while the basis set def2-TZVP and its associated effective core potential was utilized for Pt atoms.253,254 Resolution of identity approximation (RIJCOSX) was applied to enhance calculation efficiency. Geometries of the reactants and products were optimized to a local minimum, and the subsequent frequency calculations performed to verify the absence of imaginary frequencies. Geometry optimizations of transition states were performed using the relaxed surface scan method (with an eigenvector-following saddle point optimization) and NEB (i.e., Nudged Elastic Band) approach.255 All structures marked as transition states have only one imaginary frequency. Single point energy calculations were employed on the optimized geometries with DLPNO-CCSD correlated method, def2-TZVP basis set and inclusion of solvent (CPCM, solvent = Toluene) in order to correct the electronic energies. CDA230 calculations were performed in Multiwfn software using the MO outputs of isolated fragments with DLPNO-CCSD\/def2-TZVP level. 319  Entry donation backdonation Donation-backdonation r* 4.11 (frag a to c) 0.107 0.008 0.099 -0.029 4.11 (frag b to c) 0.016 0.043 -0.027 -0.049 4.11 (frag d to c) 0.233 0.087 0.147 -0.060 4.11-TS (frag a to c) 0.129 -0.000 0.129 -0.015 4.11-TS (frag b to c) 0.236 0.080 0.157 0.065 4.11-TS (frag d to c) 0.263 0.049 0.214 -0.036 4.12 (frag a to c) 0.088 0.002 0.086 -0.046 4.12 (frag b to c) 0.317 0.064 0.253 0.029 4.12 (frag d to c) 0.210 0.058 0.151 -0.005 4.9\u2019 (frag a to c) 0.078 0.003 0.075 0.001 4.9\u2019 (frag b to c) -0.030 -0.002 -0.029 -0.019 4.9\u2019 (frag d to c) 0.215 0.088 0.128 -0.024 4.14-TS (frag a to c) 0.019 0.000 0.019 -0.002 4.14-TS (frag b to c) 0.152 0.086 0.066 -0.042 4.14-TS (frag d to c) 0.377 0.038 0.339 -0.180 4.15 (frag a to c) 0.156 -0.007 0.163 -0.009 4.15 (frag b to c) 0.305 0.049 0.256 -0.121 4.15 (frag d to c) 0.215 0.037 0.178 -0.209 4.18 (frag a to c) 0.083 0.014 0.068 -0.051 4.18 (frag b to c) -0.019 0.001 -0.020 -0.009 4.18 (frag d to c) 0.190 0.091 0.098 -0.024 4.18-TS (frag a to c) 0.054 0.004 0.049 -0.053 4.18-TS (frag b to c) 0.258 0.065 0.193 -0.099 4.18-TS (frag d to c) 0.309 0.050 0.259 -0.123 4.20 (frag a to c) -0.035 0.005 -0.040 -0.073 4.20 (frag b to c) 0.330 0.051 0.279 -0.043 4.20 (frag d to c) 0.284 0.040 0.244 -0.127 Table C1. Summary of charge decomposition analysis results  * \u201cr\u201d represents the overlap degree between the occupied fragment orbitals of the two investigated fragments. The positive value stands for the electron accumulation in the overlap area of the two fragments, while the negative sign implies that the electron population was depleted from the overlap region due to the significant repulsive effect.  320   Figure C1 Optimised geometries for calculated structures in chapter 4  321   Figure C2 Optimised geometries for calculated structures in chapter 4  322   Figure C3 Optimised geometries for calculated structures in chapter 4 ","@language":"en"}],"Genre":[{"@value":"Thesis\/Dissertation","@language":"en"}],"GraduationDate":[{"@value":"2022-11","@language":"en"}],"IsShownAt":[{"@value":"10.14288\/1.0418555","@language":"en"}],"Language":[{"@value":"eng","@language":"en"}],"Program":[{"@value":"Chemistry","@language":"en"}],"Provider":[{"@value":"Vancouver : University of British Columbia Library","@language":"en"}],"Publisher":[{"@value":"University of British Columbia","@language":"en"}],"Rights":[{"@value":"Attribution-NonCommercial-NoDerivatives 4.0 International","@language":"*"}],"RightsURI":[{"@value":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/","@language":"*"}],"ScholarlyLevel":[{"@value":"Graduate","@language":"en"}],"Supervisor":[{"@value":"Love, Jennifer","@language":"en"},{"@value":"Hein, Jason","@language":"en"}],"Title":[{"@value":"Synthesis and characterisation of platinum(II) methyl complexes and their reactivity towards carbon-hydrogen (C-H) and carbon-halogen bonds (C-X)","@language":"en"}],"Type":[{"@value":"Text","@language":"en"}],"URI":[{"@value":"http:\/\/hdl.handle.net\/2429\/82637","@language":"en"}],"SortDate":[{"@value":"2022-12-31 AD","@language":"en"}],"@id":"doi:10.14288\/1.0418555"}