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Structural characterization and catalytic activity of rhodium pyrazolylborate complexes in alkyne hydrothiolation Fraser, Lauren Rae 2007

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STRUCTURAL CHARACTERIZATION AND CATALYTIC ACTIVITY OF RHODIUM PYRAZOLYLBORATE COMPLEXES IN A L K Y N E HYDROTHIOLATION by LAUREN RAE FRASER B.Sc, University of British Columbia, 2004 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Chemistry) THE UNIVERSITY OF BRITISH COLUMBIA August 2007 © Lauren Rae Fraser, 2007 Abstract A series of hydrobis- and hydrotris(pyrazolyl)borate bis(triphenylphosphine) rhodium (I) complexes were synthesized and structurally characterized. These complexes are of the general form [BpRRh(PPh3)2] {BpR = H 2 BR' 2 , R' = 3,5-dimethylpyrazolyl (2), pyrazolyl (3)}, and [TpRRh(PPh3)2] {TpR = HBR' 3 , R' = 3,5-dimethylpyrazolyl (1), pyrazolyl (4), 3-methylpyrazolyl (5), 3-phenylpyrazolyl (6), or 3-phenyl-5-methylpyrazolyl (7)}. Wilkinson's catalyst, [ClRh(PPli3)3], and the corresponding potassium salt of the ligands were mixed together in THF or toluene to produce known complexes 1-4 and new complexes 5-7. Both solid state and solution phase characterization were carried out for these complexes. The X-ray crystal structures were obtained for complexes 2, 4 and 5-7. All showed approximate square planar geometry with coordination of two pyrazolyl rings. IR spectroscopy (KBr pellet) was performed on complexes 1, 2 and 4-7 and the B-H stretching frequencies were in the range of K2-coordination. ] H and 3 1P{ 1H} NMR spectroscopy was performed on all seven complexes and variable temperature NMR spectroscopy for complexes 1 and 4-7 to examine the solution phase structures of these complexes. Complexes 1-7 were then used in alkyne hydrothiolation reactions with alkyl thiols as catalysts and their activities were examined. It was found that tris(pyrazolyl)borate complexes were superior to bis(pyrazolyl)borate complexes. As well, tris(pyrazolyl)borate rhodium complexes with substitution at the 3- and 5-positions on the pyrazolyl rings gave the best selectivity and yields, favoring the branched alkyl vinyl sulfides. Thus, complexes 1 and 7 have shown to be effective catalysts in alkyne hydrothiolation when using alkyl thiols to give regioselectively the branched isomer. A n general method to produce branched alkyl vinyl sulfides has been discovered and will be presented in the body of this thesis. 111 Table of Contents Abstract ii Table of Contents iv List of Tables vii List of Figures x List of Schemes xi List of Symbols and Abbreviations xiii Acknowledgements xvi Chapter 1 - Introduction 1 1.1 Background 1 1.2 Hydrothiolation Reactions 3 1.2.1 Radical Hydrothiolation 3 1.2.2 Nucleophilic Hydrothiolation 4 1.2.3 Transition Metal-Catalyzed Hydrothiolation 4 1.2.3-1 Intramolecular Hydrothiolation 5 1.2.3- 2 Intermolecular Hydrothiolation 5 a) £-Linear and Z-Linear Products 5 b) Isomerization and Bis(arylthio)alkene Products 8 c) Branched Product 10 1.3 Polypyrazolylborates 16 1.3.1 Denticity of Pyrazolylborate Ligands 19 1.3.1-1 K 2 and K 3 Binding Modes 19 1.3.1-2 K° to K 3 Coordination: PPBs as Counterions or with Agostic Interactions 20 1.3.2 Characterization Methods 22 1.3.3 1,2-Borotropic Shift 26 1.3.4 Applications of PPBs 27 1.3.4- 1 Stoichiometric Bond Activation Reactions 27 1.3.4-2 Catalytic Reactions 30 1.4 Conclusions 35 iv Chapter 2 - Synthesis and Structural Characterization of Pyrazolylborate Complexes 37 2.1 Introduction 37 2.2 Results and Discussion 39 2.2.1 Synthesis of Potassium Pyrazolylborate Sal 39 KBp* 39 K T p M e 40 2.2.2 Synthesis and Characterization of Rhodium Pyrazolylborate Complexes 41 Tp*Rh(PPh3)2, 1 42 Bp*Rh(PPh3)2, 2 44 BpRh(PPh3)2, 3 46 TpRh(PPh3)2, 4 47 TpMeRh(PPh3)2, 5 50 TpphRh(PPh3)2, 6 53 TpP h'M eRh(PPh3)2, 7 56 2.2.3 Summary of Spectroscopic Data for Complexes 1-7 63 2.3 Conclusions 65 2.4 Experimental Procedures 66 2.4.1 General Methods 66 2.4.2 Materials and Methods 66 2.4.3 Synthesis of Potassium Pyrazolylborate Salts 67 2.4.4 Synthesis of Rhodium Pyrazolylborate Complexes 68 2.4.5 X-ray Crystal Structures of Complexes 2, 4 and 5*-7 79 Chapter 3 — Alkyne Hydrothiolation Activity of Rhodium Pyrazolylborate Complexes 81 3.1 Introduction 81 3.2 Results and Discussion 83 3.2.1 Procedure and Optimization of Hydrothiolation Reactions 83 3.2.2 Substrate Scope of Hydrothiolation Reactions 86 3.2.3 Catalytic Activity of Complexes 1-7 in Alkyne Hydrothiolation Reactions 87 3.2.3-1 Tp*Rh(PPh3)2,1 87 3.2.3-2 Bis(pyrazolyl)borate Complexes 91 a) Bp*Rh(PPh3)2, 2 91 b) BpRh(PPh3)2, 3 93 3.2.3-3 Tris(pyrazolyl)borate Complexes 95 a) TpRh(PPh3)2, 4 95 b) TpM eRh(PPh3)2, 5 98 c) TpphRh(PPh3)2, 6 100 d) Tp p h 'M eRh(PPh 3) 2, 7 102 3.2.3-4 Complexes 1-7 Comparative Studies 104 3.2.4 Phenyl acetylene Dimer and Other Unidentified Byproducts 106 3.3 Conclusions 108 3.4 Experimental Procedures 109 3.4.1 General Methods 109 3.4.2 Reagents and Solvents 109 3.4.3 Chromatography 110 3.4.4 Physical and Spectroscopic Measurements 110 3.4.5 Synthesis and Characterization of Hydrothiolation Products 111 Chapter 4 — Summary, Conclusions and Future Work 141 4.1 Summary 141 4.2 Future Work 143 Bibliography 145 Appendices 153 Appendix I: X-ray Crystallographic Data for Bp*Rh(PPh3)2 (2) 153 Appendix II: X-ray Crystallographic Data for TpRh(PPh3)2 (4) 159 Appendix III: X-ray Crystallographic Data for TpMe*Rh(PPh3)2 (5*) 166 Appendix IV: X-ray Crystallographic Data for TpphRh(PPh3)2 (6) 174 Appendix V: X-ray Crystallographic Data for Tp p h 'M eRh(PPh 3) 2 (7) 182 vi List of Tables Table 1.1. Abbreviation system for PPBs 18 Table 2.1. Synthesis of rhodium pyrazolyl borate complexes 1-7 42 Table 2.2. Selected bond distances and angles of complex 2 46 Table 2.3. Selected bond distances and angles of complex 4 49 Table 2.4. Selected bond distances and angles of complex 5* 53 Table 2.5. Selected bond distances and angles of complex 6 56 31 I Table 2.6. Low temperature P{ H} NMR spectroscopic data for complex 7 59 Table 2.7. High temperature 3 1P{'H} NMR spectroscopic data for complex 7 61 Table 2.8. Selected bond distances and angles of complex 7 63 Table 2.9. *H, 3IP{'H} NMR and IR spectroscopic data for rhodium pyrazolylborate complexes 64 Table 3.1. Solvent studies for complexes 1-3 and 6 86 Table 3.2. Substrate scope of alkyne hydrothiolation catalyzed by complex 1 90 Table 3.3. Substrate scope of alkyne hydrothiolation catalyzed by complex 2 93 Table 3.4. Substrate scope of alkyne hydrothiolation catalyzed by complex 3 94 Table 3.5. Substrate scope of alkyne hydrothiolation catalyzed by complex 4 97 Table 3.6. Substrate scope of alkyne hydrothiolation catalyzed by complex 5 99 Table 3.7. Substrate scope of alkyne hydrothiolation catalyzed by complex 6 101 Table 3.8. Substrate scope of alkyne hydrothiolation catalyzed by complex 7 103 Table 3.9. Hydrothiolation of benzylthiol with phenylacetylene catalyzed by complexes 1-7 105 vii Table 3.10. Hydrothiolation of 2,2,2-trifluoroethanethiol with phenyl acetylene catalyzed by complexes 1-7 106 Table 3.11. Hydrothiolation of benzylthiol with phenyl acetylene catalyzed by complexes 1-7 113 Table 3.12. Hydrothiolation of 2,2,2-trifluoroethanethiol with phenylacetylene catalyzed by complexes 1-7 115 Table 3.13. Hydrothiolation of cyclopentylthiol with phenylacetylene catalyzed by complexes 1, 5 and 6 119 Table 3.14. Hydrothiolation of phenoxyethanethiol with 4-ethynylanisole catalyzed by complexes 1 and 4-7 120 Table 3.15. Hydrothiolation of cyclopentylthiol with 4-ethynylanisole catalyzed by complexes 1 and 4-7 121 Table 3.16. Hydrothiolation of benzenethiol with phenylacetylene catalyzed by complexes 1 and 4 125 Table 3.17. Hydrothiolation of benylthiol with 1-octyne catalyzed by complexes 1 and 5-7 126 Table 3.18. Hydrothiolation of butyl 3-mercaptopropionate with 4-ethynylanisole catalyzed by complexes 1 and 5-7 127 Table 3.19. Hydrothiolation of benzylthiol with ethylpropiolate catalyzed by complexes 1 and 4 129 Table 3.20. Hydrothiolation of cyclopentylthiol with 1-ethynylcyclohexene catalyzed by complexes 1 and 4-7 133 V l l l Table 3.21. Hydrothiolation of benzylthiol with 1-phenyl-1-propyne catalyzed by complexes 1 and 5-7 137 Table 3.22. Hydrothiolation of benzylthiol with tert-butylacetylene catalyzed by complexes 2 and 3 138 Table 3.23. Hydrothiolation of benzylthiol with 1-ethynylcyclohexene catalyzed by complexes 2 and 3 139 I X List of Figures Figure 1.1. Boat conformation and agostic interactions in a PPB complex 17 Figure 1.2. Isomeric forms of tris(pyrazolyl)borate rhodium complexes 19 Figure 1.3. \^NJi binding mode 22 Figure 1.4. Tp*Rh(PPri3)2 complex 32 Figure 2.1. Rhodium pyrazolylborate complexes 38 Figure 2.2. ORTEP diagram of complex 2 45 Figure 2.3. ORTEP diagram of complex 4 49 Figure 2.4. ORTEP diagram of complex 5* 52 Figure 2.5. ORTEP diagram of complex 6 55 Figure 2.6. Low temperature 3 1P{'H} NMR spectra for complex 7 observed in CD2CI2 at 162 MHz 58 Figure 2.7. High temperature 3 IP{'H} NMR spectra for complex 7 observed in ^ -toluene at 162 MHz ..60 Figure 2.8. ORTEP diagram of complex 7 62 Figure 3.1. Thiols and alkynes 87 Figure 3.2. Postulated byproduct for hydrothiolation reactions 108 List of Schemes Scheme 1.1. Alkyne hydrothiolation 1 Scheme 1.2. Vinyl sulfide utility 2 Scheme 1.3. Radical addition of a thiol to an acetylene 4 Scheme 1.4. First example of transition metal-catalyzed hydrothiolation 5 Scheme 1.5. Proposed mechanism for cycloisomerization 5 Scheme 1.6. Possible pathway for ClRh(PPh3)3-catalyzed hydrothiolation 6 Scheme 1.7. Possible pathway for Pd(OAc)2-catalyzed aw '^-hydrothiolation of 1 -alkynylphosphines 8 Scheme 1.8. Possible pathway for PdCl2(PhCN)2-catalyzed hydrothiolation 9 Scheme 1.9. Formation of a bis(phenylthio)alkene 10 Scheme 1.10. Possible pathway for Pd(OAc)2-catalyzed hydrothiolation 10 Scheme 1.11. Hydrothiolation of conjugated enynes and oxidation to sulfoxides 11 Scheme 1.12. Possible pathway for CpNi(IMes)Cl-catalyzed hydrothiolation 13 Scheme 1.13. Possible pathway for [Ni(SPh)2]n-catalyzed hydrothiolation 15 Scheme 1.14. Preparation of Pd nanoparticles 15 Scheme 1.15. K 3 to K 1 binding modes 21 Scheme 1.16. 1,2-Borotropic shift 27 Scheme 1.17. C-H bond activation 28 Scheme 1.18. C-H and C-S bond activation 29 Scheme 1.19. Possible pathway for C-H activation reaction 29 Scheme 1.20. Polymerization of phenylacetylene 30 Scheme 1.21. Aromatic C-H borylation using pinacolborane 31 xi Scheme 1.22. Possible pathway for Tp*Rh(PPh3)2-catalyzed hydrothiolation 33 Scheme 1.23. Alkyne hydrophosphinylation 33 Scheme 1.24. Possible pathway for Tp*Rh(SPh)2(MeCN)-catalyzed hydrothiolation.... 35 Scheme 2.1. Synthesis of KBp* 40 Scheme 2.2. Synthesis of K T p M e 41 Scheme 2.3. 1,2-Borotropic shift 51 Scheme 3.1. Alkyne hydrothiolation 81 Scheme 3.2. Michael addition reactions 82 Scheme 3.3. Orthometalation of Tp*Rh(PPh3)2 84 Scheme 3.4. Possible pathway for Tp*Rh(PPh3)2-catalyzed hydrothiolation 91 xii List of Symbols and Abbreviations A angstroms (10"10 meters) app d apparent doublet bim bis(l-methylimidazol-2-yl)methane bpm bis(pyrazolyl-l-yl)methane u. mu, micro br broad calcd calculated CO carbonyl cat. catalyst cm centimeters J coupling constant Cy cyclohexane COD cyclooctadiene Cp cyclopentadienyl ° degrees °C degrees Celcius D deuterium DCE 1,2-dichloroethane Bp dihydrobis(pyrazolyl)borate DMSO dimethylsulfoxide PyP 1 -(2-diphenylphosphino)ethylpyrazolyl d doublet dd doublet of doublets dq duroquinone EI electron impact E entgegen equiv. equivalents Et ethyl v frequency 5 gamma GC gas chromatography GCMS gas chromatography-mass spectroscopy g gram Hz hertz HRMS high resolution mass spectroscopy h hours Tp hydrotris(pyrazolyl)borate IR infrared X l l l i iso z'-Pr isopropyl K kappa K kelvin kcal kilocalorie L liter LRMS low resolution mass spectroscopy m/z mass/charge MALDI matrix-assisted laser desorption/ionization MHz mega hertz Me methyl DCM dichloromethane u,L microliter mg milligram mL milliliter mmol millimole min minutes M molar (mol L"1) mol mole m multiplet IMes 7v",A^-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene nbd norbornadiene n normal NMR nuclear magnetic resonance ORTEP Oakridge Thermal Ellipsoid Plot ppm parts per million Ph phenyl P Pi pip piperidine PPB polypyrazolylborate pz pyrazolyl q quartet rt room temperature SEM scanning electron microscopy s~ singlet t tertiary t triplet THF tetrahydrofuran tempo 2,2,6,6-tetramethylpiperidine-7V-oxyl PMe3 trimethylphosphine xiv PPh3 triphenylphosphine t triplet UV ultra violet VT variable temperature Z zusammen xv Acknowledgements There are so many people that I would like to thank for all of their support throughout my graduate education and all of my endeavors. Firstly, I would like to thank my supervisor Dr. Jennifer A. Love for all of her encouragement, motivation, patience and advice that allowed this research to be a success. Not only am I grateful to have such a kind and caring person as a supervisor but her enthusiasm and knowledge was definitely inspiring. I also want to thank her for our many discussions about our love for dogs and their daily comic activities that always keeps life entertaining! I would not be where I am today if it was not for the people who I have spent the last couple of years getting to know, my group members. I want to thank Paul Bichler, Jeffery Bird, Heather Buckley, Changsheng Cao, Alex Dauth, Anthony Sabarre, Shiva Shoai, Alex Sun, Sara van Rooy, Tongen Wang and Jun Yang for all of their help and support throughout the last couple of years. I want to give special thanks to Heather Buckley, Alex Dauth and Shiva Shoai for all their hours spent proof reading my thesis. I especially want to thank Shiva Shoai for keeping me sane, all the laughs, helping me with my scientific frustrations and becoming a great friend in the process. Thanks to Howie Jong and Tamara Kunz for all the great talks, always chemistry related of course. Thanks also to Howie for all his help with ORTEP. Special thanks go to the NMR staff (Nick Burlinson, Maria Ezhova and Zorana Danilovic) for all of their help using the machines. Thanks to the mass spectroscopy staff, the mechanical workshop staff (especially Ken Bach), the glass blower (Brian Ditchburn), and the stores staff. I would not have any of the X-ray crystal structures that I will present in this thesis if it was not for Brian Patrick and I am very grateful for all of his help. Many people outside of the chemistry realm have also been extremely important throughout my life. Thanks to Nicole Mukai for being so supportive and always making me laugh, to Christine Fritz for keeping me sane and being so encouraging and to Roxanne Perry for keeping me motivated and positive. Also, thanks to Meredith Turner for her support and humor all the way from Korea. To Jenny Chu for being a positive role xvi model and opening my eyes to new ideas. You are all great friends and I'm very lucky to have such supportive people in my life. Thanks to my grandma and grandpa, Vee and Richard Kellerman, for all the love and laughs and to my other grandma, Betty Murakami, for being a great roommate and to both, thanks for spoiling me like grandparents always do. Thank you to my parents, Bud and Rita Fraser, for all of their support, financially and emotionally. I would not be where I am today if it was not for them and I am thankful everyday to have such wonderful parents. They have been there for me always and I do not have words to say how thankful I am. Thanks to my sister, Erin Fraser, for spoiling me in pretty much every aspect of my life. Also, for always looking out for me and guiding me in the right direction. You are one of a kind who I truly look up to and I could not ask for more. I want to acknowledge my significant other, Monti Cahley. Thank you for all of your support and positive motivation. You have been there every step of the way, encouraging me and I am so grateful to have such a kind hearted and genuine person in my life. Last, but not least, I would like to thank my dog, Dulce, for helping me type out my thesis, because a 50 pound dog on my lap made it very easy to type on the computer and I am more than happy to credit any spelling errors to him. And a special thanks to Albert Einstein for his motivating quote that I kept up at my desk to remind me why we do what we do... xvn Chapter 1 - Introduction 1.1 Background Sulfur is ubiquitous in nature, bioactive molecules and synthetic materials, some of which include penicillins, cephalosporin and Singulair. As well, sulfur compounds can be used as synthetic precursors or as reagents for methodology and thus it is important to have efficient methods to produce sulfur containing molecules.1 Transition metal catalyzed reactions are efficient methods of forming C-X (X = heteroatom) bonds. However, sulfur compounds have been known to poison metal catalysts due to their strong coordinating properties, which can prevent catalytic reactions from occurring.2 It is for this reason that reactions of thiols have not been as extensively studied as amines, alcohols and phosphines in transition metal catalyzed reactions. However, some examples of catalytic reactions using thiols have still been investigated. One example is alkyne hydrothiolation in which a thiol reacts across an acetylene 7i-bond forming vinyl sulfide products (see Scheme 1.1). = — - r + r i ^ s r + r 1 ^ R 1 " ^ K SR branched E-linear Z-linear Scheme 1.1. Alkyne hydrothiolation Vinyl sulfides are important as they can be used as synthetic intermediates in total synthesis,"3 as well as precursors to many functionalized molecules (see Scheme 1.2).3 1 Scheme 1.2. Vinyl sulfide utility One example is the oxidation of these vinyl sulfides to sulfoxides. The sulfoxide moiety is present in many pharmaceutical drugs4 and sulfoxides are also potential ligands for a variety of transition metals.le'5 Chiral variants have the potential for use in catalytic asymmetric transformations.le'4 A variety of methods including radical,6 nucleophilic7 and metal catalyzed8 hydrothiolation have been developed for C-S bond formation. However, these methods are generally used for aryl thiols with radical reactions giving a mixture of linear isomers and nucleophilic reactions giving the Z-isomer. Moreover, at the outset of this thesis project, alkyl thiols were reported as being unreactive in metal catalyzed hydrothiolation with Pd- and Rh-based catalysts.8f'g Thus, the limited substrate scope, selectivity and reaction conditions demand improvement. The alkyne hydrothiolation reaction catalyzed by transition metal catalysts can hypothetically be carried out without any waste products in comparison with substitution reactions giving the same vinyl sulfide products. This 100% atom economy is favorable as it satisfies the requirements of green chemistry by minimizing waste and maximizing efficiency.9 2 1.2 Hydrothiolation Reactions The main products obtained from alkyne hydrothiolation reactions are the branched (Markovnikov) and E- and Z-linear (anti-Markovnikov) isomers. The E- and Z-linear products can be obtained from radical,6 nucleophlic7 and metal catalyzed conditions.8b'h'° The branched product can be obtained from nucleophilic addition of sulfur to Michael-type acceptors (vinylpyridinium cations)7d and metal catalyzed reactions.8d~g''~n'p However, the majority of examples report the use of aryl thiols. In comparison, alkyl thiols have not been as widely explored. A selective method for the formation of Z-linear vinyl sulfides was reported in 2005 ; 7 e however, general methods for the stereo- and regiocontrolled synthesis of branched and TJ-linear alkyl vinyl sulfides remain elusive. The above methods will be discussed in further detail throughout the remainder of this chapter. 1.2.1 Radical Hydrothiolation Radical hydrothiolation has been investigated and found to give predominantly the linear isomers. The ratio of the E- and Z-linear isomers seems to depend on the ratio of thiol to alkyne.6a'b These free radical additions progress via a chain reaction mechanism and can occur in the presence of UV irradiation or chemical initiators.613 One such reaction involves 1 -dodecyne and benzene thiol catalyzed by Et3B to give a mixture of E-and Z-linear products (see Scheme 1.3).6d This reaction works well for both aromatic and aliphatic alkynes with aromatic thiols but methanol must be used as an additive to increase the yield when aliphatic thiols are employed.6d 3 Et 3B n - C 1 0 H 2 1 SPh n - C 1 0 H 2 i SPh PhSH + n - C 1 0 H 2 1 ^ ^ • i = f ^ >=( H H H Scheme 1.3. Radical addition of a thiol to an acetylene 1.2.2 Nucleophilic Hydrothiolation To obtain the Z-linear hydrothiolation product, nucleophilic hydrothiolation can be used. Base mediated reactions with ethanol produced the Z-linear products in moderate to good yields (65-87%) for aryl and aliphatic alkynes and aryl and alkyl thiols.73 Kondoh and coworkers tested cesium carbonate in base mediated hydrothiolation with aryl alkynes and alkyl thiols. They reported high selectivities favoring in the Z-linear isomer in good yields.76 A radical inhibitor, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), was used to prevent the radical reaction from occurring. When aryl thiols were employed they were found to give poor yields. In the absence of base, a radical reaction occurs which is completely inhibited by the radical inhibitor.76 1.2.3 Transition Metal-Catalyzed Hydrothiolation The first example of transition metal-catalyzed hydrothiolation was reported in 1976 by Newton and coworkers using a molybdenum catalyst. They studied the addition of benzene thiol to dimethyl acetylenedicarboxylate and obtained a 25% yield of a 19:1 mixture of the E and Z products (see Scheme 1.4).8a 4 SPh Mo07[S?C(1-pip)lo I SPh M e 0 2 C - ^ C 0 2 M e > M e 0 2 C ^ + J L . C 0 2 M e CHCI3,16h lQ2Me M e 0 2 C ^ PhSH E-linear Z-linear Scheme 1.4. First example of transition metal-catalyzed hydrothiolation 1.2.3-1 Intramolecular Hydrothiolation In 2000, Gabriele and coworkers showed the only example of Pd-catalyzed cycloisomerization of (Z)-2-en-4-yne-l-thiols to give thiophenes.80 Pdl2 was used as the catalyst, along with two equivalents of KI. The proposed mechanism involves activation of the alkyne by Pd(II), intramolecular nucleophilic attack by the thiol, followed by protonolysis and finally aromatization (see Scheme 1.5). Scheme 1.5. Proposed mechanism for cycloisomerization 1.2.3-2 Intermolecular Hydrothiolation a) E-linear and Z-linear Products In 1999, Ogawa and coworkers discovered that Wilkinson's catalyst, ClRh(PPh3)3, gave a mixture of the branched and .E-linear isomers, favoring the latter, when 1-octyne was reacted with benzene thiol. This was further explored using a variety of aliphatic and aromatic alkynes with benzene thiol in ethanol; after 20 hours the reactions gave predominantly the ii-linear isomers in good to excellent yields (62-97%).8g They also 5 reported that under the same conditions using alkyl thiols, namely cyclohexanethiol, the reaction did not proceed and only the starting materials were recovered. Our research group has recently discovered that although Wilkinson's catalyst was reported as ineffective at catalyzing hydrothiolation reactions with alkyl thiols,81'8 it does in fact catalyze this reaction producing predominantly the is-linear isomer with good regioselectivity.80 Ogawa and coworkers postulated that the reaction proceeds via migratory insertion into the Rh-H bond on the basis of mechanistic studies (see Scheme 1.6).8g'° (Nb Proposed mechanisms will be presented as they appear in the literature and have not been subject to further interpretation) RhCILn ^--PhSH Scheme 1.6. Possible pathway for ClRh(PPh3)3-catalyzed hydrothiolation Burling and coworkers reported in 2003 that bidentate N,N- and P,N-ligands on rhodium(I) and iridium(I) make active catalysts for hydrothiolation of alkynes giving predominantly the linear isomers.811 They synthesized and structurally characterized a 6 wide range of complexes: [M(bim)(CO)2]BPh4, [M(bpm)(CO)2]BPh4, [M(PyP)(COD)]BPh4, [M(PyP)(CO)2]BF4 and [M(PyP)(CO)Cl], where [bim = bis(l-methylimidazol-2-yl)methane; bpm = bis(pyrazolyl-l-yl)methane; PyP = l-(2-diphenylphosphino)ethylpyrazolyl; M = Ir or Rh). It was found that the metal complexes with mixed P,N ligand systems were better catalysts for hydrothiolation than the corresponding complexes with N,N ligand systems. It was also reported that iridium complexes were more effective than the corresponding rhodium complexes; as well, cationic complexes were better then their neutral analogues. Phenylacetylene, propargyl alcohol and 1-pentyne were reacted with benzene thiol. The Z-linear isomer predominates with all catalysts for phenylacetylene, the /i-linear isomer predominates with propargyl alcohol and a 1:1 mixture of linear isomers is found for 1-pentyne. These reactions were carried out at temperatures ranging from 25-55 °C and alkyl thiols were not tested in the substrate scope. Recently, an article on awri-hydrothiolation of 1-alkynylphosphines using Pd(OAc)2 with both alkyl and aryl thiols has been reported.86 These reactions proceed in ethanol at room temperature with high stereo- and regioselectivity giving the (Z)-l-phosphino-2-thio-l-alkene after 1 hour. Kondoh and coworkers postulated mechanism involves the reaction between palladium and the alkyne giving the corresponding palladium(l-alkynylphosphine) complex. The thiol can then attack the triple bond (activated by its coordination to palladium) to give an intermediate that can be protonated, resulting in the phosphine sulfide product and the original palladium species (see Scheme 1.7). 7 R 1 H Scheme 1.7. Possible pathway for Pd(OAc)2-catalyzed anri-hydrothiolation of 1 -alkynylphosphines b) Isomerization and Bis(arylthio)alkene Products In 1999 Ogawa and coworkers examined the catalytic activity of a variety of palladium complexes in hydrothiolation reactions. When PdCl2(PhCN)2 was used as a catalyst with terminal alkynes with propargylic hydrogens, the isomerized internal vinyl sulfide product was formed predominantly in a 1:1 diastereomeric mixture.86 The catalytic cycle proposed by Ogawa and coworkers is shown in Scheme 1.8. This cycle involves ligand exchange with PhSH to form the active catalyst [Pd(SPh)ClLn]. This catalyst adds to the alkyne giving the vinylic palladium intermediate which is then protonated using PhSH, followed by double bond isomerization to give a cationic intermediate. The allylpalladium intermediate forms and finally the isomerized product is 8 released leading back to the active catalyst. This reaction requires heating to 80 °C for 20 hours and only benzene thiol was examined. PdCI2(PhCN)2 Scheme 1.8. Possible pathway for PdCl2(PhCN)2-catalyzed hydrothiolation When Ogawa and coworkers employed Pd(PPh3)4 as a catalyst for the reaction of 1-octyne with benzene thiol they observed 10-15% of an unexpected product, the bis(phenylthio)alkene, as well as the branched, E- and Z-linear products and a small amount of the isomerized product (see Scheme 1.9).8g No explanation was provided for the unexpected product or how to avoid its formation. 9 V _ _ • P h S H P d ( P P h 3 ) 4 • • R " V • p' — = 8 0 ° C , 20 h S P h S P h S P h S P h R = n - C 5 H 11 1 7 % 2 % 1 6 % (10:1, £ :Z ) Scheme 1.9. Formation of a bis(phenylthio)alkene S P h 1 0 - 1 5 % c) Branched Product In 1992 Ogawa and coworkers compared a variety of transition metal catalysts for the reaction of 1-octyne with benzene thiol.8' They found that Pd(OAc)2 gave predominantly the branched isomer in reasonable yields (55-85%) for a variety of terminal aliphatic alkynes with aryl thiols. However, these reactions required heating at 67 °C for 12-16 hours. They also reported a postulated reaction mechanism involving the following steps: ligand exchange, coordination of the alkyne, migratory insertion followed by trapping of the vinyl product and regeneration of the catalyst (see Scheme 1.10). Pd(OAc)2 2AcOH 2PhSH R H SPh PhSH R Pd(SPh)2Ln . X R Pd(SPh)Ln SPh R ^ = Pd(SPh)2Ln Scheme 1.10. Possible pathway for Pd(OAc)2-catalyzed hydrothiolation 10 In 1994, Backvall and coworkers found that Pd(OAc)2 catalyzes the addition of benzene thiol to conjugated enynes.8b This reaction formed the branched diene in moderate yields (41-75%) and gave complete selectivity of addition to the alkyne over the alkene. A range of terminal enynes were examined; all required elevated temperatures of 50 °C and 14-18 hour reaction times. The use of alkyl thiols was not reported. The corresponding sulfoxide derivatives were prepared in 60-67% yields using oxone in a methanol-water solution at 0 °C for 10 minutes to 3 hours, longer reaction times led to the formation of the corresponding sulfone products (see Scheme 1.11). cat. Pd(OAc)2 _ D. Q n p . p n S h SPh Oxone SOPh MeOH/H20 FT 0°C 41-75% 60-67% Scheme 1.11. Hydrothiolation of conjugated enynes and oxidation to sulfoxides In 2005, Beletskaya and coworkers began investigating Ni complexes as catalysts for alkyne hydrothiolation in attempts to improve regioselectivity of the branched product.8' Nickel was chosen as it is relatively inexpensive and had not been extensively studied for these types of reactions. They used N i C l 2 and a 2:1 thiohalkyne ratio to examine benzene thiol with a range of alkynes (alkyl thiols were not reported). The reactions gave good to excellent yields (60-85%) with 7:1 to 18:1 selectivity favoring the branched:linear isomers. It was found that the presence of triethylamine facilitated the formation of the branched product. Activated alkynes such as phenylacetylene and 11 methyl propiolate gave poor yields and low selectivity of the branched product. These reactions were done at elevated temperatures (80-100 °C) for 2.5-6 hours. Beletskaya and coworkers also examined the effects of phosphine and phosphite ligands on catalytic activity. They found that phosphite ligands increased the formation of the bis(phenylthio)alkene side-product (the same product observed by Ogawa and coworkers in 19998g) and that triphenylphosphine addition hindered the production of the branched product. In order to prevent the formation of the isomerized internal vinyl sulfide and Z-bis(arylfhio)alkene products, Beletskaya and coworkers developed another Ni catalyst which had N-heterocyclic carbene ligands.8k They found that the CpNi(IMes)Cl [Cp = cyclopentadienyl; IMes = A^,A^-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene] was a good catalyst for alkyne hydrothiolation using aryl thiols. A range of alkynes and aryl thiols were examined and found to give 61-87% yields with excellent selectivity favoring the branched isomer. The isomerization product and the bis(arylthio)alkene product were not formed during these reactions. Optimized reaction conditions required elevated temperatures (80 °C) for 5 hours. Their proposed mechanistic cycle (see Scheme 1.12) involves the chloride initially being replaced by a thiolate ion, this intermediate was isolated, characterized and proposed to be the active catalyst in the cycle. Next, the alkyne inserts into the Ni-S bond forming another intermediate which is trapped with an aryl thiol to give the branched product, regenerating the active catalyst. 12 =< SAr R ArSH Ni IMes/ X C| [Et 3 NH] + Cr ArSH + Et3N Scheme 1.12. Possible pathway for CpNi(IMes)Cl-catalyzed hydrothiolation Then in 2006, Beletskaya and coworkers reported the catalytic ability of Ni(acac)2 ot under solvent-free conditions. In comparison to Pd(OAc)2, the reaction between 1-heptyne and benzene thiol went to 99% conversion in high selectivity favoring the branched product in only 30 minutes. They optimized the conditions to minimize the formation of side products and found that reaction temperature, catalyst loading and ratio of thiol to alkyne were all factors. Temperatures between 25-40 °C, 2 mol% catalyst and a 2:1 thiol:alkyne ratio were found to give the highest selectivity of the branched isomer and lowest isomerization product yields. The active catalyst was found to be an insoluble polymer, [Ni(SPh)2]n, which was studied using light and scanning electron microscopy (SEM) and found to be built of nanosized structural units. Using a series of 13 stoichiometric reactions they proposed a catalytic cycle that involves replacement of the acac ligands with PhS ligands, alkyne insertion into the Ni-S bond and protonolysis by PhSH to yield the branched isomer and regenerate the active catalyst (see Scheme 1.13). Aryl thiols were investigated in hydrothiolation reactions and found to give good yields (50-87%) in relatively short reaction times (8 min. - 3.5 h). This was an important advance as it uses solvent free conditions, satisfying some requirements of green chemistry as there is less waste. However, the purification process to separate the products still required the use of solvents but the overall amount of solvent used is presumably less than a reaction where solvent is present. In a later paper in 2006, Beletskaya and coworkers reported that a 1:1 ratio of thiol:alkyne, with dropwise addition of the alkyne, gave an, on average 18% higher yield of the branched product in comparison to a 2:1 ratio of thiol:alkyne.8j When the benzene thiol is in excess it is postulated to trap the intermediate leading to the formation of the branched product. Thus using the dropwise addition method ensures an excess of thiol and although this method is more tedious it decreases the amount of thiol required. 14 Ni(acac)2 ^ _ PhSH acacH — Scheme 1.13. Possible pathway for [Ni(SPh)2]n-catalyzed hydrothiolation Earlier this year Beletskaya and coworkers reported that palladium nanoparticles were capable of catalyzing hydrothiolation reactions with both aryl and alkyl thiols.8d Pd(OAc)2 was dissolved in the alkyne and this solution was then reacted with the thiol to give the Pd nanoparticles with organic ligands (see Scheme 1.14). Pd(OAc)2 + R'-RSH solution of Pd(OAc)2 -in alkyne -HOAc Pd: ,SR S^R [Pd(SR)2]n Scheme 1.14. Preparation of Pd nanoparticles The reaction of aryl thiols with a variety of functionalized terminal alkynes gave excellent yields (>95%) with high selectivities. With alkyl thiols the yields were slightly lower but high selectivities were still obtained. Using a series of stoichiometric reactions 15 with the Pd nanoparticle catalysts, Beletskaya and coworkers postulated the reaction followed the same mechanistic pathway shown in Scheme 1.13. The cycle involves ligand exchange from Pd(OAc)2 to [Pd(SR)2]n, followed by alkyne coordination, alkyne insertion into the Pd-S bond and finally protonolysis by RSH to give the branched product and regeneration of the catalyst. This paper was an important contribution as it was the second reported selective addition of alkyl thiols to alkynes; the first report will be discussed later in this chapter. The transition metal catalysts that have been shown to give predominantly the branched product include: Pd(OAc)2,8 b' f'g NiCl 2 , 8 i Ni(acac)2,81 CpNi(IMes)Cl,8k and [Pd(SR)2]n.8d All of these catalysts were shown to be effective when using aryl thiols but alkyl thiols were only explored using [Pd(SR)2]n. 1.3 Polypyrazolylborates Polypyrazolylborate (PPB) ligands have been reported in the literature for over 40 years with the first communication published in 1966 by Trofimenko.10 They are a well defined ligand system that have caught the interest of many researchers because they are versatile, relatively easy to synthesize and can influence stereochemical outcomes.11 PPBs are made up of a tetra-substituted boron anion with two or more pyrazolyl substituents. Tris- and tetrapyrazolylborates are also commonly referred to as scorpionates as their binding motif mimics that of a scorpion capturing its prey. Two claws are represented by the pyrazolyl rings and the overreaching tail is another substituent on the boron atom. PPB complexes are usually at least bidentate forming a six membered ring comprised of two bridging pyrazolyl groups, the boron atom and the 16 metal center. This B(u-pz)2M ring is found predominately in the boat configuration which gives the third substituent on the boron the potential to bind to the metal centre, forming a tridentate species (Figure 1.1)." R1 N — — N o M R R R Figure 1.1. Boat conformation and agostic interactions in a PPB complex There are two major groups of PPBs: homoscorpionates (R'TpR) [Tp = tris(pyrazolyl)borate] and heteroscorpionates (R'R"BpR) [Bp = bis(pyrazolyl)borate], where R7 R" = H, alkyl, aryl or pyrazolyl groups and R can be any substituent at the 3-, 4- and/or 5-positions of the pyrazolyl ring. Homoscorpionates are the more commonly 2 3 used PPBs. These PPBs have the potential to bind either bidentate (K ) or tridentate (K ); when bound in a K 2 manner the uncoordinated and coordinated pyrazolyl groups can exchange rapidly, which can be observed via NMR spectroscopy." These ligands have very lengthy names and thus an abbreviation system has been developed. Curtis proposed for homoscorpionates the use of Tp in place of [HB(pz)3]~ and the use of Tp* in place of [HB(3,5-dimethylpyrazol-l-yl)3]\12 In accordance with this nomenclature heteroscorpionates [H2B(pz)2]" are named Bp. The substituents on the pyrazolyl ring are denoted by superscripts. The 3-substituent comes first, followed by a 17 5-substituent. The 4-substituent is denoted with the number 4 preceding the substituent. Finally non-hydrogen groups on the boron are written before the abbreviation; see Table 1.1 for some examples. Table 1.1. Abbreviation system for PPBs Compound Name Abbreviation [HB(3-phenyl-5-methylpyrazol-l-yl)3]~ T P [HB(3-methylpyrazol-l-yl)3]~ Tp M e [HB(3-isopropyl-4-bromopyrazol-l-yl)3]~ rppiPr,4Br [Et2B(pyrazolyl-l -yl)2]~ Et2Bp The PPB ligands are often compared to cyclopentadienyl (Cp) ligands. Tp and Cp ligands have many similarities, such as similar metal complexes, having a -1 charge, donating six electrons and having the potential to occupy three coordination sites. However, there are also many differences associated with these common ligand sets. For example, they have different point groups, Tp has the potential for more substitution variations, Tp alkali metal salts are air stable where Cp salts are not and Tp can form neutral analogues with carbon. The huge versatility of PPBs makes them attractive compounds to study. Substitution on the pyrazolyl rings allows one to tune the electronics and sterics which can potentially alter the metal-ligand interaction and thus change the coordination environment. 18 1.3.1 Denticity of Pyrazolylborate Ligands 1.3.1-1 K 2 and K 3 Binding Modes It has been well established in the literature that the denticity of poly(pyrazolyl)borate ligands can differ from K ° , in which the PPB acts as a counterion, to K 3 , depending on the number of pyrazolyl rings attached to the boron, substituents on these rings and the participation of side chains in agostic interactions.13 This flexible coordination geometry contributes to the unique properties of the pyrazolylborate motif and can influence reactivity. Rhodium tris(pyrazolyl)borates typically exist in an equilibrium between four isomers, A-D (Figure 1.2).8p A B C D Figure 1.2. Isomeric fonns of tris(pyrazolyl)borate rhodium complexes Isomers A and B are both 16-electron square planar species, where C and D are both 18-electron species with trigonal bipyramidal and square pyramidal geometries, respectively. The equilibrium between these isomeric forms depends upon the substitution on the pyrazolyl rings (see Scheme 1-15, type A for numbering of the pyrazolyl ring substituents) as well as bulkiness of the ancillary ligands (L). The trends in isomer preference are: bulky substituents in the 3-position of the pyrazolyl and bulky ancillary ligands favor forms A and B, whereas smaller substituents on the pyrazolyl and less 19 bulky ancillary ligands favor the C and D isomers. Isomer A is favored over B when there are bulky substituents in the 3-position. Isomer B is favored over A when there are smaller substituents in the 3-position and substituents in the 5-position enhance this preference.14 1.3.1-2 K° to K 3 Coordination: PPBs as Counterions or with Agostic Interactions Tris(pyrazolyl)borate ligands often act as spectator ligands, but can also be "non-2 3 innocent" because of changes in denticity. K and K tris(pyrazolyl)borate complexes are well established in the literature, although K° and K 1 complexes are not as well known. For example, in 2000 Paneque and coworkers reported the synthesis of a K 1 complex. Treatment of K3-Tp*Rh(C2H4)(PMe3) with 5-6 equivalents of PMe 3 at 20 °C for <1 hour produced a new complex K'-Tp*Rh(PMe3)3 (see Scheme 1.15).15 The crystal structure of the K'-Tp*Rh(PMe3)3 complex showed no agostic interactions as the Rh - H(B) distance was 2.59(4) A (which is too long to be considered a bonding interaction). The K 2 complex was not detected in this reaction but can be synthesized by dropwise addition of 1 equivalent of PMe 3 to the K 3 complex. They also found that the Tp* ligand completely dissociated upon heating to 120 °C for 6 hours and hypothesized that it formed [Rh(PMe3)4]Tp* (effectively, K°-Tp*). Unfortunately, this species decomposed upon workup and therefore full characterization could not be obtained. However, they did manage to show that the bis-hydrido complex (K3-Tp)Rh(H)2(PMe3) forms ( K 2 -Tp)Rh(H)2(PMe3)2 complex upon heating at 50 °C for 2 hours. Additional heating at this temperature for 8 hours gives [Rh(H)2(PMe3)4]Tp. These assignments were confirmed by NMR spectroscopy and X-ray analysis. The molecular structure shows that the closest 20 Rh-N distance was 4.627 A , which is much larger than the van der Waals radius.15 This contribution was important as it is the first time the denticity changes of the Tp* and Tp ligands from K 3 to K° were observed. Until this point the only K 1 complexes known were Ni complexes with bulky hydrotris(3-fcr/-butylpyrazolyl)borate ligands and K° complexes were unprecedented.16 H. B. N P M e 3 P M e 3 N H i . / P M e 3 PMe 3 PMe Nk N y — H Msk ^ P M e 3 — Rh M e 3 P ^ ^ P M e 3 I = Tp* Scheme 1.15. K 3 to K 1 binding modes In 2000, Herberhold and coworkers synthesized Tp*Rh{P(C7H7)3}which had an interesting K2N,H binding mode.17 One pyrazolyl ring is attached to the metal centre and there is also an agostic interaction with the B-H hydrogen and the metal centre. The Rh-H(B) distance was 1.789(7) A (two independent molecules were found per unit cell differing only in Rh-H(B) distance, the second being 1.899(7) A) which is close to a typical Rh-H bond distance of 1.55 A . Through X-ray crystallography, 'H, n B , l 3 C , 3 1 P and l 0 3 Rh NMR spectroscopy the geometry of the Rh-H-B bridged complex with two uncoordinated pyrazolyl rings was established, demonstrating K2N,H binding (Figure 1.3). 21 C 7 H 7 2 Figure 1.3. K N,H binding mode Other binding modes have been mentioned throughout the literature, including: K^N.N'.H seen in Tp*Ru(CH3)(COD),18 Bp ( C F 3 ) 2Ru(H)(PPh3)2 and Bp ( C F 3 ) 2Ru(H)(COD) and a K2N,H in Bp ( C F 3 ) 2RuH(H 2)(PCy 3) 2 which was proposed to be due to the different cone angles of the phosphines.19 However, these binding modes have not been observed in any rhodium pyrazolylborate complexes. 1.3.2 Characterization Methods The interconversion and fluxional processes between isomers A-D makes the solution phase assignment of TpR denticity very difficult.20 Solvent effects must also be taken into consideration as it has been noted that the equilibrium between forms of pyrazolylborate rhodium complexes can be shifted by changing the polarity of the solvent. Tp'Pr' 4 B rRh(CO) 2 and TpM eRh(CO)2 were found to be in an equilibrium between A and B/C where the B/C forms were favored in solvents having a higher dipole moment.13 Also, TpphRh(COD) exists in forms A and B and as the solvent becomes more polar the equilibrium shifts towards form B. 2 1 However, other pyrazolylborate rhodium 22 complexes such as Tp C F 3 'M eRh(CO) 2 and Tp'PrRh(COD), have been examined and no solvent effects were found.14'203 A number of techniques have been used to determine denticity, including infrared (IR) spectroscopy, variable temperature and multinuclear NMR spectroscopy. In 2001, Connelly and coworkers reported what was believed to be the first rhodium hydrotris(pyrazolyl)borate complex, Tp*Rh(PPli3)2, where the unbound pyrazolyl ring is frozen on the NMR timescale at -80 °C. They observed that the three pyrazolyl rings and phosphorous atoms became inequivalent as the temperature was decreased. This 22 phenomenon was attributed to the fixed orientation of the unbound pyrazolyl ring. Other Tp R ML 2 complexes have shown only a single set of pyrazolyl resonances at both room temperature and low temperature. This has been documented in the literature and 23 24 some examples include Tp*Rh(C2H4)2 and Tp*Rh[CN-(neopentyl)]2, possibly indicating that these complexes are present in only one isomeric form with fast exchange of the pyrazolyl rings or that the interconversion between isomers is too fast for the NMR time scale. The exchange rates of the pyrazolyl rings were examined in 1982 by Cocivera and coworkers working with [B(pz)4]RhL [L = duroquinone (dq), 1,5-cyclooctadiene (COD) and norbornadiene (nbd)]. They postulated that the rate of exchange is dependent upon the strength of the rhodium diene interaction. Therefore with more electron-donating dienes, the exchange between uncoordinated and coordinated pyrazolyl groups increases, indicating the Rh-N bond strength decreases. Other examples demonstrate that equilibration between K 2 and K 3 can be seen using variable temperature NMR spectroscopy. For example, TpM e n t hRh(CO) 2, gave a 1:1:1 ratio for the pyrazolyl 23 resonances in the 'H NMR spectrum with an additional singlet at low temperature.26 They attribute the 1:1:1 peaks to form A and the forth peak as an equilibrium between forms B and C or B and D accounting for the singlet due to fast exchange making the pyrazolyl rings appear equivalent on the NMR time scale. It seems that each complex behaves differently in solution and therefore careful analysis is required to determine what isomers and/or fluxional processes are occurring in each case. Akita and coworkers have shown that IR stretching frequencies, particularly the 2 3 v(B-H) values, seem to be diagnostic of K and K binding modes. The solution and solid state structures of K 3 complexes generally show higher frequencies in the IR spectrum.20a This was shown for (K3-Tp l P l)ML,,-type (M = Mn, Fe, Co, Ni, Cu, Rh) complexes where the v(B-H) bands are between 2527-2554 cm"1 and the (K2-Tp i P r)ML„-type (M = Ru, Rh, Pd) complexes had v(B-H) bands between 2471-2486 cm"'.20a However (K 3-TpR)ML„-type (M = Zn, Ru, Cu, Ni, Co, Fe, Rh, Ni, In) complexes have shown v(B-H) bands between 2476-2552 cm"1 which show overlap with (K 2-TpR)ML, rtype complexes. This overlap has been attributed to the substituents on the pyrazolyl ring; an increase in the electron donating ability of these substituents caused a shift toward higher wavenumbers in the IR spectrum.203 In general B-H stretching frequencies < 2480 cm"1 indicate K 2 binding while B-H stretching frequencies > 2480 indicate K 3 binding.203 1 0 3 Rh NMR spectroscopy has been employed to differentiate between forms A to D as there are expected to be large chemical shift differences between 16 and 18 electron species. Venanzi and coworkers used this technique and found that K 2 complexes typically had a lower chemical shift (5 947-1374) versus K 3 complexes (8 1475-1777).13 However, no solid state 1 0 3 Rh NMR measurements have been carried out to determine the 24 limiting value of chemical shift of a K species, thus other methods must also be used to characterize the forms present in solution. If the complex of interest has olefinic carbons, l 3 C NMR spectroscopic data can be 2 3 used to provide evidence towards K and K species. This is based on the K-backbonding ability, as the 18 electron K j species should have higher 7i-backbonding ability in comparison to the 16 electron K species. Thus, the olefinic carbons should be shifted 3 13 upfield for the K species. To confirm this hypothesis, the C solid-state NMR spectrum was taken of a known K 3 species. The X-ray structure of TpM eRh(NBD) shows trigonal bipyramidal geometry and it gave upfield chemical shifts in agreement with the solution state spectra.13 1 5 N NMR spectroscopy is also used to determine the denticity of the pyrazolylborate ligands. The uncoordinated versus coordinated nitrogen atoms of the pyrazolyl rings give significantly different chemical shifts. Nitrogen atoms on uncoordinated pyrazolyl rings give an approximate chemical shift of 5 -75. In comparison, nitrogen atoms on bound pyrazolyl rings give a chemical shift around 5 -138. If there is fast exchange on the NMR time scale these values give an averaged approximate 8 -117. Therefore, if the chemical 3 27 shift is more negative this indicates an equilibrium favoring the K -form. 11 2 Using B NMR spectroscopy, it was found that K complexes show resonances between 5 -5.90 and -6.99 versus K 3 complexes with resonances between 5 -8.44 and -9.76.2 0 0 These resonances appear to be independent of both solvent and charge on the metal for group 9 and 10 metals.20c Thus, there appears to be a strong correlation between the chemical shift of the boron atom and the denticity of the tris(pyrazolyl)borate ligand. 25 X-ray crystallography has been used to determine the solid state structures of rhodium pyrazolylborate complexes. 8 n ' 1 3- 1 5 ' 1 7 J 9 ' 2 0 a c ' 2 1 ' 2 2 ' 2 4 ' 2 5- 2 7 ' 2 8 However, X-ray structures may be dependent upon the solvent used for crystallization, the isolation method and crystal packing effects of whether these complexes adopt K 2 or K3-forms in the solid state.14 For example, Cocivera and coworkers described in 1982 that 2 3 2 [B(pz)4]Rh(COD) favored K - K equilibrium in solution phase but crystallized as the K -1.3.3 1,2-Borotropic Shift Depending on the position and extent of substitution of the pyrazolyl ring, rearrangements of the ligand via a 1,2-borotropic shift can occur. The occurrence of such rearrangements is attributed to a reduction in van der Waals repulsion and can be induced thermally. I 3 ' 2 8 a ' 3 0 This isomerization has been observed for a broad range of Tp R M complexes. Rearrangements in octahedral metal complexes with the tris(pyrazolyl)borate 3 31 32 30 31b ligand bound K have been well documented for transition metals: Co, Ti, Mo, Ni and Fe 3 1 b. However, square planar and tetrahedral complexes with the same rearrangement are less common; some examples are with Rh, 1 3 ' 3 3 Ir,28a Zn, 3 3 Cd 3 3 and A l 3 4 complexes (see Scheme 1.16). The substituents at the 3-position of the pyrazolyl ring that were used in combination with the above metals include methyl, isopropyl, menthyl, mesityl, neopentyl, or 3,3-dimethylbenzyl groups. A particular example of the 1,2-borotropic rearrangement occurs in the reaction between [Ir2(u-Cl)2(COD)2] with Na[TpMe]. This reaction produced the expected [TpMeIr(COD)] complex in forms A and B but also gave the rearranged product, [{HB(3-Mepz)2(5-Mepz)}Ir(COD)], where one 26 of the methyl groups is now at the 5-position of the pyrazolyl ring. Upon heating to 70 °C for 45 minutes another rearranged product, [{HB(3-Mepz)(5-Mepz)2}Ir(COD)], is observed which does not change upon further heating.283 The 1,2-borotropic shift typically occurs for pyrazolylborates with 3- or 3,4-substitution.l3'3la Scheme 1.16. 1,2-Borotropic shift 1.3.4 Applications of PPBs PPB metal complexes have been used in many different applications including catalytic and stoichiometric reactivity. Rhodium pyrazolylborate complexes have been studied extensively for the stoichiometric activation of H-X bonds (X = H, C, S, etc.).281'35 Although catalytic reactions with these complexes have not been widely investigated some examples do exist.356 These are discussed in greater detail below. 1.3.4-1 Stoichiometric Bond Activation Reactions Bond activation has been studied using pyrazolylborate complexes with some examples described below. The first example of C-H bond activation using a PPB complex was in 1987 with Tp*Rh(CO)2 which photochemically activated both aromatic and saturated hydrocarbons at room temperature (see Scheme 1.17).35a 27 hv, -CO R-H R = C 6H 5, cyclohexyl, CH 3 Scheme 1.17. C-H bond activation Hydrodesulfurization reactions are important as it is a process that removes sulfur from natural gas and refined petroleum products. This is done in order to reduce sulfur dioxide emissions that are the result of fuel combustion. Thiophenes are a group of aromatic sulfur containing substrates that are common in petroleum products and have been investigated in order to gain information about the hydrodesulfurization mechanism.36 It is known that thiophenes are activated (C-H and/or C-S activation) by many metals37 and by changing the ligands different reactivity has been observed.35d One such case was reported in 1996 when the thermodynamic stability of the products of C-H and C-S activation of thiophene by Tp*Rh(C2H4)(PR3) was investigated.35d Under thermal conditions, the C-H activation product was found to be preferred in contrast to the Cp*RhL (L = PMe 3 3 8) complexes which gave predominantly the C-S activation product. However, under photochemical conditions this preference was reversed (see Scheme 1.18).35d 28 A: 15% 85% hv: 75% 25% Scheme 1.18. C-H and C-S bond activation In 1997, Bergman and coworkers investigated the reactivity of K 3-Tp*Rh(CO)2 in an alkane solvent. They used time-resolved ultra fast infrared studies to postulate intermediate structures and the energy barriers between them. The proposed mechanism involves the loss of a CO ligand by irradiation followed by fast solvation with an alkane (RH) solvent. This complex is then converted to the lower energy K2-Tp*Rh(CO)(RH) complex with a 4.2 kcal/mol barrier. K2-Tp*Rh(CO)(RH) then undergoes C-H activation with an 8.3 kcal/mol barrier and finally the third pyrazolyl ring reattaches to the rhodium to form a lower energy complex (see Scheme 1.19).39 4.2 kcal/mol Scheme 1.19. Possible pathway for C-H activation reaction 29 1.3.4-2 Catalytic Reactions Rhodium tris(pyrazolyl)borate complexes of the form Tp Rh(COD) (R=H, Me, Et, Ph, z'-Pr) and BpRh(COD) have been used to catalyze the polymerization of phenylacetylene (see Scheme 1.20).40 It was found that the more sterically demanding R group at the 3- and 5-positions of the pyrazolyl rings led to higher catalytic activity, suggesting that a K 2 isomer is essential for catalytic activity based on the trends of pyrazolylborate complexes when varying the substituents.403 This was further supported by the findings that the complex bearing the Bp* ligand gave higher catalytic activity towards phenylacetylene polymerization than the complex bearing the Tp* ligand.403 Ph HPh H catalyst Ph — H CH2CI2 Ph' H Ph' H Scheme 1.20. Polymerization of phenylacetylene The hydrogenation of quinoline has been examined using a range of catalyst precursors including [ClRh(COD)]2. Addition of NaTp leads, presumably, to TpRh(COD). After 2 hours, this complex gave 100% conversion for quinoline hydrogenation.41 Tp*Rh(COD) was also tested and found that the initial reaction rate was faster with better yields then that with Tp 4 1 Catalytic hydrosilylation activity of Tp P h 'M eRh(CO)2 was examined by Ganicz and coworkers in 2004.42 They examined the reaction between 1-octene and triethoxysilane and found that the tris(pyrazyolyl)borate rhodium catalyst was highly active. Trzeciak and coworkers have shown that rhodium bis(pyrazolyl)borate complexes [RhBp(CO)P] 30 [P=P(NC4H4)3, PPh3, PCy3, P(C6H4OMe-4)3] have catalytic activity for the hydroformylation of 1 -hexene, producing approximately 80% of aldehydes and 20% of 2-hexene.43 Murata and coworkers have recently demonstrated the aromatic C-H borylation reaction catalyzed by hydrotris(pyrazolyl)borate complexes of rhodium and iridium 4 4 Most reactions were carried out with a metal complex prepared in situ. For example [ClRh(COD)]2 was combined with KTp, KBp or KTp* and added to a mixture of pinacolborane and benzene to give the corresponding phenylpinacolborane (see Scheme 1.21). f ~ \ c a i a i y s t . PinBH + <( 7 • PinB-\==/ 100-120°C Scheme 1.21. Aromatic C-H borylation using pinacolborane Methods for the formation of branched aryl vinyl sulfides have been reported, however general methods for the formation of branched alkyl vinyl sulfides are just surfacing. We have recently reported the first general method for metal-catalyzed alkyne hydrothiolation using alkyl thiols.8m'p Tp*Rh(PPh3)2 (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate, Figure 1.4)22,45 is used as the catalyst, and generates the branched isomer in good to excellent yields. 31 U ^ B ^ Rh H e ^ N U K 1 ^ N» ' N P P r n ^ J l Figure 1.4. Tp*Rh(PPh3)2 complex Preliminary mechanistic investigations have been carried out on Tp*Rh(PPh3)2 by a coworker (Bal Kang). It was found, using labeling studies with deuterated phenyl acetylene, that the branched and .E-linear products are both obtained with syn addition.46 This indicates that the reaction likely proceeds via S-H bond activation followed by alkyne coordination, migratory insertion into the Rh-S bond and reductive elimination giving the syn-branched product predominantly (see Scheme 1.22). The syn-Ti-linear isomer can be obtained from the same mechanism if one imagines the R' group on the alkyne facing towards the tris(pyrazolyl)borate group. This is less likely due to steric interactions and hence the Ti-linear isomer is the minor product. 32 Scheme 1.22. Possible pathway for Tp*Rh(PPh3)2-catalyzed hydrothiolation Our group has also shown that Tp*Rh(PPh3)2 catalyzes alkyne hydrophosphinylation (see Scheme 1.23). In hydrothiolation, this tris(pyrazolyl)borate catalyst formed the complimentary isomer to Wilkinson's catalyst (vide infra). Therefore, it was expected to produce the branched isomer for hydrophosphinylation. Although it was found that Tp*Rh(PPh3)2 does catalyze alkyne hydrophosphinylation, higher yields were obtained with Wilkinson's catalyst. Interestingly, both Tp*Rh(PPh3)2 and Wilkinson's catalyst gave the /i-linear product.47 R 2 P ( 0 ) H * R = — R X ' R ! + ^ P ( 0 ' R ! + O , 0 , R 2 branched £-linear Z-linear Scheme 1.23. Alkyne hydrophosphinylation 33 Misumi and coworkers have recently reported the hydrothiolation activity of [Tp*Rh(SPh)2(MeCN)] which gave predominantly the branched product.8" The minor product for the reaction between 4-ethynyl anisole and benzene thiol was the Z-linear isomer when using Tp*Rh(SPh)2(MeCN) as a catalyst and the is-linear isomer when using Tp*Rh(PPh3)2. This can be attributed to the different mechanisms between the two catalyst systems. It was proposed by Misumi and coworkers that the Z-linear isomer is formed independently via a nucleophilic or radical mechanism. The formation of this isomer appeared to be dependent only on the concentration of the alkyne, whereas the formation of the branched isomer was dependent on the concentration of the thiol and the catalyst. The proposed catalytic cycle for the Tp*Rh(SPh)2(MeCN) is outlined in Scheme 1.24. This cycle involves the dissociation of MeCN to give an open coordination site on the active catalyst. Next, the alkyne adds regioselectively to give a four membered ring. The X-ray structure when R = CH 2Ph has been obtained; however, two species are seen in the 'H nuclear magnetic resonance (NMR) spectrum which are attributed to the phenyl group on the sulfur atom within the ring facing opposite directions. The four membered ring is then protonated by PhSH to give the branched product and coordination of the remaining thiolate ion regenerates the active catalyst. 34 SPh SPh K 3-Tp*Rh' NCMe H = R H >=< H R Scheme 1.24. Possible pathway for Tp*Rh(SPh)2(MeCN)-catalyzed hydrothiolation 1.4 Conclusions Pyrazolylborate complexes have been used in many reactions, both stoichiometric and catalytic in nature. We hypothesized that rhodium pyrazolylborate complexes would be sufficiently reactive to allow catalytic reactions with alkyl thiols, which had not been successful substrates for catalytic hydrothiolation at the outset of this thesis project. The large number of existing pyrazoles and their capability to tolerate a wide range of steric and electronic modifications allowed the construction of a variety of metal pyrazolylborate complexes. The scope of this thesis involves the synthesis of a series of pyrazolylborate rhodium complexes where the number of pyrazolyl rings as well as the substituents on the pyrazolyl rings have been changed. These complexes were used in a series of alkyne hydrothiolation reactions to probe their catalytic activity. Our goal was to improve upon the present synthetic methods for the formation of branched alkyl vinyl 35 sulfides and to determine what components of the ligand are needed for high reactivity and selectivity in alkyne hydrothiolation reactions. "If you find some chemistry that looks beautiful and you think it is important, you should pursue your vision—even if the circumstances are not the best.. .all in all, this is a vast and promising area, the riches of which are yet to be fully exploited by the scorpionate community." °Q Swiatslaw Trofimenko 36 Chapter 2 - Synthesis and Structural Characterization of Pyrazolylborate Complexes 2.1 Introduction As described in Chapter 1, pyrazolylborates have been studied for over 40 years with over 2000 documented articles attributed to them. The number of known pyrazolylborates has flourished over the years as they are attractive ligands due to their versatility and their ease of synthesis." Rhodium pyrazolylborate complexes have been used as catalysts for a number of reactions, including polymerization of phenylacetylene,40 homogeneous hydrogenation of quinoline,41 dimerization of terminal alkynes,35e alkyne hydrophosphinylation,47 aromatic C-H borylation,44 hydrosilylation,42 hydroarylation,48 hydroformylation43 and alkyne hydrothiolation.8171'" In this study, a series of rhodium pyrazolylborate complexes were prepared and structurally characterized in order to probe their catalytic activity in alkyne hydrothiolation. The complexes selected for study are shown in Figure 2.1: {[H2B(pz)2] ~ = Bp; [H2B(3,5-Me2)2] " = Bp M e 2 = Bp*; [HB(pz)3] ~ = Tp; [HB(3,5-Me2pz)3]- = Tp M e 2 = Tp*; [HB(3-Mepz)3]" = TpM e; [HB(3-Phpz)3]" = Tp P h; [HB(3-Ph-5-Mepz)3]" = Tp p h ' M e }. 37 u - ^ C Rri A N ' ^PPh, 1 [Tp*Rh(PPh3)2] <f if 1 / ^ 2 [Bp*Rh(PPh3)2] V N ' , .PPhq 3 [BpRh(PPh3)2] <XNpph3 • 5 [TpMeRh(PPh3)2] <f 1 . s P P h 3 U ^ B ^ Rh 4 [TpRh(PPh3)2] Ph Ph <f if ^PPh3 u - ^ B \ Rh Ph 6 [TpPhRh(PPh3)2] 7 [TpP h 'M eRh(PPh 3) 2] Figure 2.1. Pvhodium pyrazolylborate complexes Complexes 1-7 were selected based on the number of pyrazolyl rings as well as the substitution patterns on each pyrazolyl ring. The study of bis(pyrazolyl)borate complexes will test whether or not K3-coordination is required for reactivity and selectivity. All of the complexes will be used to investigate the effect of pyrazolyl substitution. Various techniques, described in chapter 1, have been reported in the literature for the 38 characterization of rhodium pyrazolylborate complexes. The techniques that were employed in this study include variable temperature 'H and 3 1P{'H} NMR spectroscopy, X-ray crystallography and IR spectroscopy. Phosphine-containing rhodium tris(pyrazolyl)borate complexes, TpxRh(PR3)2, are not as well precedented in the literature as carbonyl, TpxRh(CO)2, and olefin-containing, TpxRh(R)2 [R = C 2 H 2 , COD, nbd,dq, etc.], complexes l 3 ' 1 4 , 2 0 a ' 2 1 ' 2 6 ' 2 7 ' 2 9 although a few 15 17 22 28b h phosphine-containing complexes have been structurally characterized. ' ' ' TpRRhLL' [TpR = substituted pyrazolylborate; L, L ' = ancillary ligands; Rh(I)] complexes typically exist in an equilibrium between up to four isomers (A-D), as described in Chapter 1. The interconversion between these species plays a crucial role in C-H activation reactions35e'49 and therefore is postulated to play a role in catalytic bond activation reactions. 2.2 Results and Discussion 2.2.1 Synthesis of Potassium Pyrazolylborate Salts The starting materials for the synthesis of the rhodium pyrazolylborate complexes are potassium pyrazolylborate salts and Wilkinson's catalyst, ClRh(PPh3)3. The potassium pyrazolylborate salts KTp*, KBp, KTp, KTp p h and K T p p h ' M e are commercially available. KBp* and K T p M e were synthesized using modified literature methods.50 50a Potassium dihydrobis(3,5-dimethylpyrazol-l-yl)borate [KBp*] (8) KBp* (8) was used as the starting material to produce the corresponding rhodium pyrazolylborate complex [Bp*Rh(PPh3)2] (2). Compound 8 was prepared by melting 4.0 39 equivalents of 3,5-dimethylpyrazole at 120 °C and then adding 1.0 equivalents of potassium borohydride (see Scheme 2.1). This mixture was then heated (at temperatures not exceeding 140 °C) for 20 hours, after which time the slurry had become a solid white mass. Toluene was added and the white solid slightly dissolved. The resulting slurry was filtered and washed with hot toluene. Finally the solid was dried under vacuum to give a white solid. Because the ! H NMR spectrum showed extra peaks, compound 8 was dissolved in acetone and filtered to remove any potential impurities The volatiles were then removed under vacuum and the white solid was sublimed to remove excess 3,5-dimethylpyrazole. After attempted purification, KBp* was obtained with an unidentified byproduct; this mixture was used to make complex 2. KBH4 1.0 equiv. 120-140 °C 20 h, neat 4.0 equiv. i e Scheme 2.1. Synthesis of KBp" Potassium hydrobis(3-methylpyrazol-l-yl)borate [KTp c] (9) K T p M e (9) was used as the starting material for the preparation of the rhodium pyrazolylborate complex [TpMeRh(PPh3)2] (5). Compound 9 was prepared by melting 1.0 equivalents of K B H 4 with 3.3 equivalents of 3-methylpyrazole (see Scheme 2.2). This reaction mixture was heated at 190 °C for 9 hours after which time the reaction was allowed to cool to room temperature. The solution solidified and was then filtered and 40 washed with benzene and petroleum ether. The solid was dried under vacuum. The H NMR spectrum confirmed the presence of compound 9 and 3-methylpyrazole. The solid mixture was sublimed to remove any excess 3-methylpyrazole; however, this was unsuccessful and the white solid mixture, a 13:1 ratio of compound 9 to 3-methylpyrazolyl, was used without further purification for the preparation of complex 5. KBH 4 1.0 equiv. // HN—N 3.3 equiv. 190 °C © 9 h, neat l© H / B X N - N Scheme 2.2. Synthesis of KTp Me 2.2.2 Synthesis and Characterization of Rhodium Pyrazolylborate Complexes Wilkinson's catalyst, ClRh(PPh3)3, was mixed with the corresponding potassium 22 pyrazolylborate salt, K X (X = pyrazolylborate ligand), to produce known complexes 1, 2 28b 3 2 8 b a n d 4 2 8 c a n d n e w c o m p i e x e s 5^ g a n c j 7 (Table 2.1). These reactions were all carried out at room temperature in THF (except toluene was used for the synthesis of complex 7) and gave good-to-excellent yields (58-92%) after workup. 41 Table 2.1. Synthesis of rhodium pyrazolylborate complexes 1-7 KX, THF CIRh(PPh3)3 • XRh(PPh3)2 rt Entry X Complex Time Yield (%)a Literature 1 Tp* Tp*Rh(PPh3)2(1) 1 h 92% 48%b, 66% c 2 Bp* Bp*Rh(PPh3)2 (2) 24 h 87% 80% d 3 Bp BpRh(PPh3)2 (3) 24 h 86% 80%d 4 Tp TpRh(PPh3)2 (4) 24 h 86% 66%e 5 T pMe TpM eRh(PPh 3) 2 (5) 4h 59% -6 Tp P h Tp P hRh(PPh 3) 2 (6) 24 h 83% -7 jpPh.Me Tp P h ' M eRh(PPh 3) 2 (7) 24 h 58% f -a Isolated yields. b See ref 22. c See ref 28i. d See ref 28b.e See ref 28c. 1 Toluene used as solvent in place of THF. Tp*Rh(PPh3)2,1 Complex 1 was prepared by combining 1 equivalent of both ClRh(PPh3)3 and KTp* in THF and stirring for 1 hour at room temperature. We have observed that longer reaction times cause decomposition of the product.28j The volatiles were removed under vacuum, followed by addition of toluene and layering with hexanes. This solution was left at -35 °C for 7 days in which time orange crystals formed. After washing with hexanes and drying under vacuum, complex 1 was obtained in 92% yield; this complex was used without further purification. Our spectral data for complex 1 is consistent with literature reports at room temperature.22,28' At room temperature two sets of signals in a 2:1 ratio were observed for the pyrazolyl rings in the 'H NMR spectrum indicating that 31 1 there are two equivalent and one inequivalent pyrazolyl rings. The P{ H} NMR spectrum shows a doublet indicating two equivalent phosphines at room temperature (§ 42 44.04 JRh-p = 177 Hz), see Table 2.9. The equivalency of the bound pyrazolyl rings and phosphines are due to the free rotation of the unbound pyrazolyl ring. At -85 °C two sets of signals are still observed for the 'H NMR spectrum with a 2:1 ratio of the pyrazolyl 22 rings; however, Connelly reports that all pyrazolyl rings were inequivalent at -80 °C. In the 3 1 P { ' H } NMR spectrum at -85 °C the doublet that was observed at room temperature split into two broad doublets (5 44.76, JRh.P = 164 Hz; 5 41.89, JRh.P> = 180 Hz). In contrast, Connelly reports two doublets of doublets.22 This difference may be due to slow rotation of the unbound pyrazolyl ring with the rotation rapid enough to give a 2:1 ratio of pyrazolyl rings on the 'H NMR time scale in our study. This contrasts with the suggestion by Connelly that there is restricted rotation of the free pyrazolyl at low temperature, which would result in the inequivalence of the bound pyrazolyl rings and the phosphines. Also consistent with our data, Carlton and coworkers reported a doublet in the 3 IP{'H} NMR spectrum at room temperature that becomes broadened at -60 °C, which they attributed to the interconversion between the K 2 and K 3 forms. They found that the addition of phosphine at low temperature did not significantly change the 3 1 P{'H} NMR spectrum and thus phosphine dissociation is unlikely to cause the broadening seen at lower temperatures.28' Therefore it is difficult to attribute the spectrum to the interconversions occurring either between forms A and B or between the K 2 and K 3 forms due to fast exchange on the NMR time scale. In addition, at room temperature the IR 1 2 shows a single stretching frequency at 2447 cm" which is in the range for K -coordination. 43 Bp*Rh(PPh3)2, 2 Complex 2 was prepared by mixing 1 equivalent ClRh(PPh3)3 with 1.5 equivalents of KBp* in THF at room temperature for 24 hours. After this time the volatiles were removed, and a minimal amount of toluene was added, which was layered with hexanes. This layered mixture was allowed to sit at -35 °C for 7 days after which time orange crystals formed. The crystals were washed with hexanes and dried under vacuum and gave an 87% yield; the crystals were used for alkyne hydrothiolation. The *H and j lP{ 1H} NMR spectra were mostly consistent with literature reports except in the aromatic region of the 'H NMR spectrum. For the two triphenylphosphine ligands, Baena and coworkers reported three multiplets at 8 7.77 (12H), 6.87 (12H), 6.85 (6H) when carried out in CeD6. Our spectra show two multiplets 8 7.74-7.73 (6H) and 7.10-6.85 (24 H) in CD2C12 and therefore the discrepancies between our spectra and Baena's spectra could be due to the different solvent (Table 2.9).28b The *H NMR spectrum indicated the equivalence of the two pyrazolyl rings and 3 1P{'H} NMR spectrum indicated equivalence of the two phosphorous atoms which is consistent with the solid state structure. The IR spectrum also showed two stretching frequencies assigned to the two boron hydrogen stretches at 2449 and 2378 cm" , both of which were in the range for K -coordination. The molecular structure of 2 (Figure 2.2) determined by X-ray crystallography shows that the geometry about the central rhodium atom is approximately square planar which is typical of a d 8 electronic configuration. The sum of the angles about the rhodium atom is equal to 361.13°, consistent with square planar geometry. K2-Coordination of the Bp* ligand is observed with coordination through one nitrogen of each pyrazolyl ring. Two bridging pyrazolyl rings, the boron atom and the rhodium metal centre make up a six 44 membered ring in the boat conformation. The Rhl-Nl and RM-N4 bond distances of 2.132(2) A and 2.092(2) A , respectively, fall within the range of other reported rhodium pyrazolylborate complexes (2.081-2.140 A) (Table 2.2). 2 2 2 8 i The Rhl-Pl and Rhl-P2 bond distances of 2.2202(7) A and 2.2468(7) A , respectively, also fall within the range reported in the literature (2.210-2.280 A ) . 2 8 e j The angle between the two phosphorous atoms [95.43(3)°] is slightly larger than that between the nitrogen atoms [79.84(8)°], which is attributed to steric interactions between the large triphenylphosphine groups maximizing the distance between each other; this is consistent with literature reports.22'28b'' Crystallographic data for complex 2 is given in Appendix I. Figure 2.2. ORTEP diagram of complex 2. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogens, and phenyl groups of PPti3 are excluded for clarity. Selected bond lengths (A) and angles (°) are given in Table 2-2. 45 Table 2.2. Selected bond distances and angles of complex 2 Atoms Bond Distances (A) or Angles (°) Rhl-Nl 2.132(2) RM-N4 2.092(2) Rhl-Pl 2.2202(7) Rhl-P2 2.2468(7) N1-RM-N4 79.84(8) Pl-Rhl-P2 95.43(3) NI-Rhl-Pl 164.16(6) Nl-Rhl-P2 92.91(6) N4-Rhl-Pl 92.93(6) N4-Rhl-P2 170.88(6) BpRh(PPh3)2, 3 Complex 3 was prepared by the reaction of 1 equivalent of ClRh(PPh3)3 with 1.1 equivalents of KBp in THF at room temperature. After 24 hours the volatiles were removed, a minimal amount of toluene was added and layered with hexanes. This layered mixture was left at room temperature for 15 days after which time orange crystals formed. After washing with hexanes and drying under vacuum an 86% yield was 31 1 obtained of complex 3. The P{ H} NMR spectrum of these crystals was consistent with literature reports showing a doublet at § 52.63 (Jr^-p = 176 Hz), see Table 2.9.28b The coupling constant is typical of rhodium-phosphorous coupling. The crystals were used without further purification in alkyne hydrothiolation reactions. 46 TpRh(PPh3)2, 4 Complex 4 was prepared by mixing 1 equivalent of ClRh(PPli3)3 with 1.5 equivalents of KTp in THF. After 24 hours at room temperature the volatiles were removed and a minimal amount of toluene was added, which was then layered with hexanes. This layered mixture was left for 12 days at -35 °C after which time orange crystals of complex 4 formed in an 86 % yield. The crystals were washed with hexanes, dried under vacuum and were used without further purification in alkyne hydrothiolation. The ! H NMR data is consistent with that reported'by Connelly and coworkers. However, both our spectra and Connelly's spectra differ from the previously reported spectra by Hill and coworkers. In our *H NMR spectrum at room temperature, two equivalent and one inequivalent pyrazolyl ring are observed. As the temperature is lowered the peaks begin to sharpen and split; however, no assignment of the -85 °C spectra has been possible. The 3 I P{'H} NMR spectrum at room temperature is consistent with both literature reports, see Table 2.9.2 2'2 8 c The room temperature 3 I P{'H} NMR spectrum reported by Connelly and coworkers indicated a broad doublet at 5 50.9 ( JRh -p = 165 Hz); at -40 °C this doublet splits into two doublets of equal intensity 8 51.0 ( J R h - p = 174 Hz) and 8 49.3 (J R h- P = 176 Hz). At -80 °C, the doublet at 8 49.3 became broadened, whereas the other doublet remained unchanged. Based on this data Connelly, and coworkers assigned the doublet at 8 51.0 to form A and the doublet at 8 49.3 to form B. Our room temperature 3 1P{'H} NMR spectrum shows a doublet at 8 53.11 (Jri,-p = 173 Hz). At -45 °C this doublet splits into two doublets of unequal intensity [8 53.60 ( JRh -p = 177 Hz) and 8 52.00 (J R h- P = 177 Hz)]. At -85 °C our spectrum shows the doublet at 8 53.39 ( j R h - p = 173 Hz) remains unchanged. The doublet at 8 51.63 ( jRh -p = 173 Hz) 47 decreases in intensity and broadens, and a new broad doublet at 5 49.16 ( JRh -p = 172 Hz) appears. Based on comparison to Connelly's assignments the doublet at 5 53.39 is assigned as form A and the broad doublets at 8 51.63 and 8 49.16 are both assigned as form B with restricted rotation around the pyrazolyl ring. As well, a single stretching frequency at 2392 cm" is seen in the room temperature IR, which is consistent with K -coordination. The molecular structure of complex 4 (Figure 2.3) shows square planar geometry with respect to the rhodium centre, as the sum of the angles around the rhodium atom equals 361.48°. The six membered ring with boron, rhodium and two bridging pyrazolyl rings is in a boat conformation. The Tp ligand is bound K 2 with the third uncoordinated pyrazolyl ring facing away from the rhodium in form A configuration. The Rhl-Nl and Rhl-N4 are 2.1575(13) and 2.1111(13) A , respectively. The Rhl-Nl bond length is in the range for square planar pyrazolylborate rhodium bis(triphenylphosphine) complexes however the Rhl-N4 bond length slightly exceeds the reported length. The Rhl-Pl [2.2299(4) A] and Rhl-P2 [2.2558(4) A] bond lengths are both within literature values (Table 2.3). The angle between the two phosphorous atoms [93.605(15)°] is slightly larger then that between the nitrogen atoms [83.37(5)°], again due to the large triphenylphosphine groups maximizing the distance between themselves. Crystallographic data for complex 3 is given in Appendix II. 4S C44 Figure 2.3. ORTEP diagram of complex 4. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPI13 are excluded for clarity. Selected bond lengths (A) and angles (°) are given in Table 2-3. Table 2.3. Selected bond distances and angles of complex 4 Atoms Bond Distances (A) or Angles (°) Rhl-Nl 2.1575(13) Rhl-N4 2.1111(13) Rhl-Pl 2.2299(4) Rhl-P2 2.2558(4) N1-RM-N4 83.37(5) P1-RM-P2 93.605(15) Nl-Rhl-Pl 169.58(4) N1-RM-P2 92.98(4) N4-RM-P1 91.52(3) N4-RM-P2 169.18(4) 49 Tp M c Rh(PPh 3 ) 2 , 5 Complex 5 was prepared by combining 1 equivalent of ClRh(PPh3)3 with 1.6 equivalents of KTp M e in THF and stirred at room temperature for 4 hours. The volatiles were removed under vacuum, followed by addition of toluene and layering with hexanes. After 12 days at -35 °C the resulting orange crystals were washed with hexanes and dried under vacuum to give a 59% yield which was used without further purification. The room temperature 'H NMR spectrum shows two products in a 7:1 ratio. Both species have two equivalent pyrazolyl rings and one inequivalent pyrazolyl ring. The major product is presumably formed by a 1,2-borotropic shift where one of the methyl groups is now in the 5-position to form 5*: [HB(3-Mepz)2(5-Mepz)] ~ = TpM e*, and the minor product is proposed to be complex 5 (see Scheme 2.3). From the *H NMR spectrum for the major product, there are two possible scenarios: in one case, both 3-methylpyrazolyl rings are coordinated and the 5-methylpyrazolyl ring is unbound, whereas in the other case, one 3-methylpyrazolyl ring and the 5-methylpyrazolyl ring are bound and the remaining 3-methylpyrazolyl ring is unbound. The phosphines would be equivalent in the first case and the P{ H} NMR spectrum would be expected to show a single resonance, appearing as a doublet due to rhodium-phosphorus coupling. The phosphines would be inequivalent in the second case and the 3 IP{'H} NMR spectrum would be expected to show two doublets of doublets, each with rhodium-phosphorus and phosphorus-phosphorus coupling. The room temperature 3 1P{ 1H} NMR spectrum shows two doublets of doublets providing evidence that the second case is more probable. The solid state structure is consistent with this analysis. At -85 °C no assignment of the 'H NMR spectrum has been possible and the 3 IP{'H} NMR spectrum gives the same two 50 doublets of doublets for each product. The IR spectrum shows a single stretching B-H -1 2 frequency at 2429 cm" , indicating K -coordination. t l <, N L 1.2-Borotropic M O , ^ V N V shift \ V ^ R ^ \ / 5 Scheme 2.3. 1,2-Borotropic shift X-ray analysis of crystals obtained from the attempted preparation of complex 5 revealed the formation of [HB(3-Mepz)2(5-Mepz)]Rh(PPh3)2 (5*). The driving force for the formation of the 1,2-borotropic shift product can be attributed to reduction of van der Waals repulsions. The molecular structure of 5* (Figure 2.4) shows an approximate square planar geometry around rhodium with the sum of the angles equal to 363.10 A . The six membered ring with boron, rhodium and two bridging pyrazolyl rings is in a boat conformation. The pyrazolylborate ligand is bound K 2 with the third uncoordinated pyrazolyl ring overtop of the rhodium in form B. The X-ray structure indicates one 3-methylpyrazolyl is bound and the 5-methylpyrazolyl is bound while the additional 3-methylpyrazolyl is unbound. The Rhl-Nl [2.110(2) A] and Rhl-N4 [2.084(2) A] bond lengths are within the range for Rh-N bonds reported in the literature. As well, the Rhl-Pl [2.2404(7) A] and RM-P2 [2.2585(7) A] are also within the literature range for Rh-P bonds of complexes of this type (Table 2.4). The angle between the phosphines is larger than that between the nitrogens; this is attributed to the repulsion between the large 51 triphenylphosphine groups. Crystallographic data for complex 5* is given in Appendix III. C40 C19 C13 Figure 2.4. ORTEP diagram of complex 5*. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPI13 are excluded for clarity. Selected bond lengths (A) and angles (°) are given in Table 2-4. 52 Table 2.4. Selected bond distances and angles of complex 5 Atoms Bond Distances (A) or Angles (°) Rhl-Nl 2.110(2) RM-N4 2.084(2) Rhl-Pl 2.2404(7) Rhl-P2 2.2585(7) Nl-Rhl-N4 82.46(8) Pl-Rhl-P2 94.66(3) Nl-Rhl-Pl 164.93(6) Nl-Rhl-P2 94.27(6) N4-Rhl-Pl 91.69(6) N4-RM-P2 165.68(6) Tp™Rh(PPh3)2, 6 Complex 6 was prepared by mixing 1 equivalent of ClRh(PPh3)3 with 1.5 equivalents of KTp P h in THF for 24 hours at room temperature. The volatiles were removed under vacuum, followed by addition of toluene and layering with hexanes. This was then left in the freezer at -35 °C and after 7 days orange crystals formed. After washing with hexanes and drying under vacuum an 83% yield was obtained. The ! H NMR spectra at both room temperature and at -85 °C show a 2:1 ratio of pyrazolyl rings and the 3 1P{'H} NMR spectrum shows a doublet both at room temperature (5 46.89, d, J R h . P = 178 Hz) and at -85 °C (5 46.69, d, J R h - P = 176 Hz), see Table 2.9. This data is consistent with K2-coordination with free rotation of the free pyrazolyl ring, even at lower temperatures. There is no evidence for the 1,2-borotropic shift product as seen with complex 5. The IR spectrum shows a single stretching B-H frequency at 2426 cm"1, 53 2 indicating K -coordination. The solid state molecular structure also supports this data (Figure 2.5). The molecular structure shows approximate square planar geometry around the rhodium centre with the sum of the angles around rhodium equal to 359.67°. There is also ^-coordination of the tris(pyrazoyl)borate ligand with the uncoordinated pyrazolyl ring facing away from the rhodium in form A. The six membered chelate ring with boron and rhodium is in the boat conformation. The Rhl-Nl [2.1240(18) A] and the Rhl-N4 [2.1000(18) A] bond lengths fall within the ranee of known values and so do the Rhl-Pl [2.2429(6) A] and Rhl-P2 [2.2618(6) A] bond lengths (Table 2.5). The angle between the phosphine atoms is larger then that between the nitrogen atoms; this is attributed to the repulsion between the large triphenylphosphine groups. Crystallographic data for complex 6 is given in Appendix IV. 54 Figure 2.5. ORTEP diagram of complex 6. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPti3 are excluded for clarity. Selected bond lengths (A) and angles (°) are given in Table 2-5. 55 Table 2.5. Selected bond distances and angles of complex 6 Atoms Bond Distances (A) or Angles (°) Rhl-Nl 2.1240(18) Rhl-N4 2.1000(18) Rhl-Pl 2.2429(6) Rhl-P2 2.2618(6) Nl-Rhl'-N4 78.99(7) P1-RM-P2 96.31(2) Nl-Rhl-Pl 167.28(5) Nl-Rhl-P2 92.53(5) N4-Rhl-Pl 91.82(5) N4-Rhl-P2 171.38(5) TpP h M eRh(PPh 3)2, 7 Complex 7 was prepared by mixing 1 equivalent of ClRh(PPh3)3 with 1.5 equivalents of K T p p h ' M e in toluene for 24 hours at room temperature. The volatiles were removed under vacuum, followed by addition of toluene and layering with hexanes. This was then left in the freezer at -35 °C for 7 days after which time small orange crystals formed of complex 7. These were washed with hexanes and dried under vacuum to give 58% yield. At room temperature the 'H NMR spectrum show two equivalent and one inequivalent pyrazolyl ring (2:1 ratio) which indicates K2-coordination and as the temperature is decreased to -85 °C all three pyazoles become inequivalent, which suggests restricted rotation of the unbound pyrazolyl ring. The 3 1P{'H} NMR spectrum at room temperature shows a doublet at 5 48.12 ( j R h - p = 182 Hz) and a multiplet at 8 43.44-39.33, in a 1:5 ratio in deuterated methylene chloride (CD2C12). As the temperature is 56 decreased, the doublet (5 48.12) begins to disappear, and is completely unobservable at -85 °C. At this temperature, the multiplet becomes resolved into two doublets of doublets (5 42.60 . /R h .p = 178 Hz, JP.?> = 50 Hz; 5 39.42 J R h-P> = 172 Hz, JP.P> = 51 Hz), see Table 2.9. The low temperature 3 1P{'H} NMR spectra and corresponding chemical shift values are shown in Figure 2.6 and Table' 2.6. Two possible scenarios exist to explain these results: 1) two species are present at room temperature and at lower temperatures one predominates or 2) both species may be present at both room temperature and lower temperatures and one species peaks may be broadened due to restricted rotation at lower temperatures. When the NMR spectrum was taken in ^ -toluene the spectrum was similar but more convoluted. The ratio of isomers in the (^-toluene 3 IP{'H} spectrum at room temperature was 1:7, which was different then that in CD2CI2. 57 298 K 273 K 253 K 233 K 213 K 188 K Chemical Shiitftpm} »ure 2.6. Low temperature 3 1P{'H} NMR spectra for complex 7 observed CD 2 Cl 2 atl62 MHz 58 31 1 Table 2.6. Low temperature P{ H} NMR spectroscopic data for complex 7 Temperature 'P{'H} NMR Chemical Shifts 298 K 273 K 253 K MIN 5 48.12 (d, J R h . P = 182 Hz); MAJ 5 43.44-39.33 (m) MIN 8 48.15 (d, J R h _ P = 180 Hz); MAJ 8 44.00-42.34 (m) MIN 8 48.19 (d, J R h . P = 180 Hz); MAJ 8 43.14 (dd, JRh_P= 180, JP.P> = 51 Hz), 8 39.56 (dd, y R h . P . = 174 Hz, JP.P> = 51 Hz) MIN 8 48.23 (d, JR h_P= 180 Hz); MAJ 8 42.99 (dd, J R h . P= 180, JP.P> = 50 Hz), 8 39.51 (dd, J R h . P - = 172 Hz, JP.P- - 50 Hz) MIN 8 48.28 (d, JRU.P = 182 Hz); MAJ 8 43.83 (dd, J R h . P = 180, JP.P- = 50 Hz), 8 39.47 (dd, JRh.P> = 174 Hz, JP.r = 50 Hz) MAJ 8 42.60 (dd, J R h . P= 180, JP.P> = 52 Hz), 8 39.42 (dd, JRh_P> = 174 Hz, JP_P> = 52 Hz) 233 K 213 K 188 K When the high temperature 3 1P{'H}NMR spectra were obtained in Js-toluene it was found that the doublet at room temperature remains unchanged and the multiplet coalesces into a doublet, see Figure 2.7 and Table 2.7 for the high temperature 3 IP{ 1H} NMR spectra and corresponding chemical shift values. At temperatures reaching 100 °C this complex forms a new doublet, presumably a rhodium hydrido species based on the appearance of a hydride peak in the *H NMR spectra. Upon cooling back to room temperature three new signals, apparently doublets are observed which have not been characterized. The data for the major product supports equivalent phosphines at elevated temperatures, indicating free rotation of the unbound pyrazolyl ring and restricted rotation at lower temperatures as the phosphines become inequivalent. Thus the two species could be forms A and B. Alternatively, the initial product could have partially isomerized by a 1,2-borotropic shift; however, other data are needed to determine the identities of the products. The IR spectrum shows a single stretching B-H frequency at _ i 2 2463 cm" , indicating K -coordination. 59 298 K before h 6 a t i n g l / l 318K i V 338 K 358 K L A 373 K I 298 K after heating 62 SO 58 54 53 50 48 46 Chemica l Sh in {00m) 31r> (h 44 40 38 Figure 2.7. High temperature P{ H} NMR spectra for complex 7 observed in ^5-toluene at 162 MHz 60 31 1 Table 2.7. High temperature P{ H} NMR spectroscopic data for complex 7 Temperature J IP{'H} NMR Chemical Shifts 298 K before MIN 5 49.29-47.99 (m); MAJ 5 45.85-40.09 (m) heating 318 K MIN 5 48.60 (d, J R h _ P = 185 Hz); MAJ 5 43.44-41.44 (m) 338 K MIN 5 48.49 (d, J R h . P= 180 Hz); MAJ 5 42.37 (d, J R h . P= 178) 358 K NEW 5 58.06 (app d, J= 149 Hz); MIN 5 48.40 (d, J R h . P = 181 Hz); MAJ 5 42.40 (d, J R h . P = 180); 5 -1.46 (s) 373 K NEW 5 57.96 (app d,J= 151 Hz); MIN 5 48.33 (d, J R h _ P = 180 Hz); MAJ 5 42.40 (d, J R h . P= 178); 8-1.13 (s) 298 K NEW 5 58.48 (app d, J= 149 Hz); NEW 5 44.78 (app d, J = 205 Hz); after NEW 5 40.81 (app d,J= 120 Hz); MIN 8 48.55 (d, J R h - P = 183 Hz); heating MAJ 5 45.84-39.40 (m); 5 -2.70 (s) The molecular structure of complex 7 (Figure 2.8) shows an approximate square planar geometry with the sum of the angles around rhodium equal to 360.26°. The tris(pyrazolyl)borate ligand is bound K 2 with the unbound pyrazolyl above the rhodium atom in form B. The six membered chelate ring with boron and rhodium has a boat conformation. The Rhl-Nl [2.100(2) A ] , Rhl-N4 [2.140(2) A ] , Rhl-Pl [2.2683(7) A ] and Rhl-P2 [2.2572(7) A] bond lengths are all within those previously reported (Table 2.8). The angle between the phosphines is larger then that between the nitrogen atoms; as with complexes 2, 4, 5 and 6, this is attributed to the repulsion between the large triphenylphosphine ligands. Crystallographic data for complex 7 is given in Appendix V. 61 Figure 2.8. ORTEP diagram of complex 7. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPli3 are excluded for clarity. Selected bond lengths (A) and angles (°) are given in Table 2-6. 62 Table 2.8. Selected bond distances and angles of complex 7 Atoms Bond Distances (A) or Angles (°) Rhl-Nl 2.100(2) RM-N4 2.140(2) Rhl-Pl 2.2683(7) Rhl-P2 2.2572(7) Nl-Rhl-N4 77.49(8) Pl-Rhl-P2 94.15(3) Nl-Rhl-Pl 173.25(6) Nl-Rhl-P2 92.42(6) N4-Rhl-Pl 96.18(6) N4-Rhl-P2 167.66(6) 2.2.3 Summary of Spectroscopic Data for Complexes 1-7 *H, 3 I P { ' H } NMR and IR spectroscopic data for complexes 1-7 are summarized in Table 2.9. NMR spectroscopic data are given for room temperature and -85 °C in CD2CI2. The IR spectra were taken at room temperature using KBr pellet. The IR spectra for complexes 1-7 have stretching frequencies within the normal range for in-coordination. Also, the coupling constants are typical of rhodium-phosphorous and phosphorous-phosphorous coupling. 63 Table 2.9. ' H , 3 I P { ' H } N M R and IR spectroscopic data for rhodium pyrazolylborate complexes a Complex ' H N M R J 1P{'H} NMR IR/cm"' v(BH) b Tp*Rh(PPh 3) 2,1 25 °C 7.6-6.9 (m, 30H, PPh 3), 5.81 (s, 1H, pz H), 5.27 (s, 2H, pz H), 2.35 (s, 3H, CH 3), 2.27 (s, 6H, CH 3), 2.26 (s, 3H, CH 3), 1.79 (s, 6H, CH 3) 43.78 (d, J R h . P = 175 Hz) 2447 -85 °C 7.7-6.7 (m, 30H, PPh3), 5.80 (s, 1H, pz H), 5.24 (br s, 2H, pz H), 4.35 (br s, 1H, BH), 2.51 (br s, 3H, CH 3), 2.28 (s, 6H, CH 3), 2.22 (br s, 6H, CH 3), 1.39 (br s, 3H, CH 3) 44.17 ((1,7^= 186 Hz), 41.22 ( c L J r ^ 185 Hz) Bp*Rh(PPh 3) 2, 2 25 °C 7.74-7.73 (m, 6H, PPh3), 7.10-6.85 (m, 24H, PPh3), 5.1 (s, 2H, pz H), 2.35 (s, 6H, CH 3), 1.83 (s, 6H, CH 3) 47.22 (d,J^P= 178 Hz) 2449, 2378 BpRh(PPh 3) 2, 3 25 °C 7.61-7.50 (m, 12H, PPh 3), 7.37 (s, 2H, pz H), 7.22-7.15 (m, 6H, PPh 3), 7.10-7.00 (m, 12H, PPh3), 6.31 (s, 2H, pz H), 5.53 (s, 2H, pz H) 53.91 (d,J R h. P= 177 Hz) -TpRh(PPh3)2, 4 25 °C 8.06 (s, 2H, pz H), 7.7-7.0 (m, 30H, PPh 3), 6.90 (s, 2H, pz H), 6.44 (s, 1H, pz H), 6.14 (s, 2H, pz H), 5.97 (s, 1H, pz H), 5.80 (s, 1H, BH) 53.11 (d, J R h . P = 173 Hz) 2392 -85 °C NDC 53.39 (d,J R h . P = 173 Hz), 51.63 (d,J R M> = 172 Hz), 49.16 (d, y R h. P=172 Hz) Tp M e*Rh(PPh 3) 2, 5C 25 °C Major: 7.63 (br s, 2H, pz H), 7.5-6.9 (m, 30H, PPh3), 6.49 (s, 1H, pz H), 5.90 (s, 2H, pz H), 5.37 (s, 1H, pz H), 2.30 (s, 3H, CH 3), 2.15 (s, 6H, CH 3) Minor: 8.07 (s, 2H, pz H), 7.5-6.9 (m, 30H, PPh3), 6.03 (s, 1H, pz H), 5.83 (s, 2H, pz H), 5.14 (s, 1H, pz H), 2.20 (s, 6H, CH 3), 1.43 (s, 3H, CH 3) 50.82 (dd, J R h.p= 182 Hz, Jp.P. = 54 Hz), 48.19 (dd,J R h. P.= 172 Hz, Jp.P. = 54 Hz) 54.21 (dd, J R h . P = 185 Hz, ./p.p. = 52 Hz), 50.70 (dd,JR h. P.= 172 Hz, Jp.P. = 52 Hz) 2429 -85 °C Major: NDd 49.93 (dd,y R h. P= 178 Hz, ./p.p. = 53 Hz), 47.66 (dd,J R h. P.= 175 Hz,Jp.P. = 53 Hz) 64 Table 2.9. 'H, ^Pl 'H} NMR and IR spectroscopic data...continued Minor: ND d 53.80 (dd,7R h. P= 182 Hz, Jp.p. = 54 Hz), 50.81 (dd, J R h. P.= 170 Hz, ./p.p. = 52 Hz) Tp P hRh(PPh 3) 2, 6 25 °C -85 °C 8.26 (s, 1H, pz H), 7.97 (m, pz C 6H 5), 7.43 (s, 2H, pz H), 7.4-6.9 (m, 45H, PPh 3 + pz C 6H 5), 6.83 (s, 1H, pz H), 5.75 (s, 2H, pz H) 8.25 (s, 1H, pz H), 7.91 (m, pz C 6H 5), 7.37 (s, 2H, pz H), 7.4-6.9 (m, 45H, PPh 3 + pz C 6H 5), 6.81 (s, 1H, pz H), 5.73 (s, 2H, pz H) 46.89 (d,JR1,.P= 178 Hz) 46.69 (d,JKh.P= 176 Hz) 2426 Tp p h M c Rh(PPh 3 ) 2 , 7 25 °C -85 °C 8.27 (d, J= 8.8 Hz, 4H, pz C 6H 5), 7.77 (d, ./ = 7.3 Hz, 2H, pz C 6H 5), 7.6-6.8 (m, 45H, PPh 3 + pz C 6H 5), 6.40 (s, 1H, pz H), 6.36 (s, 2H, pz H), 5.81 (s, 1H, BH), 2.51 (s, 6H, CH 3), 2.14 (s, 3H, CH 3) 8.24 (d, J= 7.3 Hz, 2H, pz C 6H 5), 7.76 (d,J = 7.3 Hz, 2H, pz C 6H 5), 7.6-6.8 (m, 45H, PPh 3 + pz C 6H 5), 6.38 (s, 1H, pz H), 6.03 (s, 1H, pz H), 5.74 (s, 1H, BH), 5.58 (s, 1H, pz H), 2.47 (s, 3H, CH 3), 2.46 (s, 3H, CH 3), 2.04 (s, 3H, CH 3) 48.12 (d,J R b . P = 182 Hz), 43.44-39.33 (m) 42.60 (dd,y R h. P= 178 Hz, Jp.p. = 50 Hz), 39.42 (dd,JR h. P.= 172 Hz, ./p.p. = 51 Hz) 2463 a Chemical shift (<5) in ppm, J values in Hz. Spectra taken in CD2CI2. b KB r pellet. cMajor:Minor = 7:1. d N D = not determined - spectra very convoluted and difficult to characterize. 2.3 Conclusions Three new rhodium pyrazolylborate complexes (5*-7) and four known complexes (1-4) have been synthesized using modified literature procedures. The syntheses of known complexes 1-4 were carried out with better yields then previously reported.123'*''133'16 All complexes were characterized by *H, 3 1 P { ' H } NMR and IR spectroscopy. Complexes 2, 4 and 5*-7 have also been characterized by X-ray crystallography. Al l the X-ray structures show approximate square planar geometry. The 65 ease of synthesis and opportunity to examine rhodium pyrazolylborate complexes with different substituents and differing numbers of pyrazolyl rings has made these complexes interesting to study. Chapter 3 examines the alkyne hydrothiolation activity of these complexes and whether electronics and/or denticity affects their catalytic activity. 2.4 Experimental Procedures 2.4.1 General Methods Manipulation of inorganic compounds was performed in a nitrogen-filled MBraun glovebox (O2 < 2 ppm). NMR spectra were recorded on Bruker Avance 300 or Bruker Avance 400 spectrometers. *H and 3 1P{'H} NMR spectra are reported in parts per million and were referenced to residual solvent. Coupling constant values were extracted assuming first-order coupling. The multiplicities are abbreviated as follows: s = singlet, d = doublet, app d = apparent doublet, q = quartet, m = multiplet, dd = doublet of doublets. 3 IP{'H} NMR spectra were referenced to an external 85% H3PO4 standard. All spectra were obtained at 25 °C, unless otherwise stated. GC spectra were recorded on a Varian CP-3800 or an HP 5890 Series II gas chromatograph. Mass spectra were recorded on a Kratos MS-50 mass spectrometer. MALDI specta were recorded on a Bruker biflex IV mass spectrometer. 2.4.2 Materials and Methods Pentane, hexanes, 1,2-dichloroethane (DCE), THF and toluene were dried by passage through solvent purification columns.51 CD2CI2 and ^ -toluene were purchased in 66 1 g ampules and used without further purification. Wilkinson's catalyst [ClRh(PPli3)3], KBp, KTp and KTp* were purchased from Strem Chemicals. KTp p h and K T p P h ' M e were purchased from Acros. 3-Methylpyrazole was purchased from Lancaster. 3,5-dimethypyrazole was purchased from Aldrich. KBH4 was purchased from Aldrich. Al l commercial reagents were used without further purification. 2.4.3 Synthesis of Potassium Pyrazolylborate Salts Synthesis of KBp*. In a fumehood, 3,5-dimethylpyrazole (14.26 g, 148 mmol) was added to a 100 mL Schlenk flask, equipped with a Teflon-coated magnetic stir bar. The flask was fitted with a glass stopper and was heated to 120 °C to melt the pyrazole (mp = 106-109 °C). K B H 4 (2.02 g, 37 mmol) was crushed with a pestle and mortar and added to the flask by spatula in small portions. The flask was then put under a flow of nitrogen and the resulting mixture was heated to 140 °C. After 20 hours, the mixture had turned into a solid white mass. Toluene (20 mL) was added and the resulting slurry was filtered through a Buchner funnel and was washed with 2 x 20 mL of warm (60 °C) toluene. The remaining white solid was dried under vacuum and then 2 mL of benzene was added. This solution was frozen and the solvent removed in vacuo to yield a fluffy white powder. To remove excess KBH 4 , the white powder was dissolved in acetone and filtered. The remaining solid was dried under vacuum. Excess 3,5-dimethylpyrazole was then removed by sublimation. The 'lT NMR spectrum showed compound 8 along with some unidentified byproduct, which was not able to be removed. *H NMR (CD3CN, 300 MHz) at 25 °C: [Major] 5.53 (s, 2H, pz H), 2.21 (s, CH 3), 2.08 (s, 6H, CH 3); [Minor] 5.60 (s, 0.70H), 2.21 (s), 2.08 (s, 2.1H). 67 Synthesis of KTp c . In a fumehood, K B H 4 (1.0 g, 19 mmol), that had been crashed with a pestle and mortar, was added to a 50 mL double neck round bottom equipped with a Teflon-coated magnetic stir bar. 3-Methylpyrazole (4.9 mL, 61 mmol) was added in one portion via syringe. The flask was then put under a flow of nitrogen and the resulting mixture was heated to 190 °C. After 9 hours, the clear solution was cooled to room temperature and became a solid white mass. Benzene (10 mL) was added and the resulting slurry was filtered through a Buchner funnel and was washed with 4 x 20 mL of benzene, followed by 20 mL petroleum ether. The remaining white solid was dried under vacuum. The 'H NMR spectrum showed the presence of 3-methylpyazole. To remove the excess pyrazolyl sublimation was attempted; however this was unsuccessful and the white solid mixture was used without further purification. The ratio of compound 9 to 3-methylpyrazole was 13:1. ! H NMR (CD 3CN, 300 MHz) at 25 °C: [Major] 7.40 (s, 3H, pz H), 5.81 (s, 3H, pz H), 2.19 (s, 9H, CH3); [Minor] 7.26 (s, 0.24H, pz H), 6.01 (s, 0.24H, pz H), 2.24 (s, CH 3). The ! H NMR data was consistent with literature data except the literature reported the pyrazole hydrogens as two doublets (J = 1.9 Hz, J = 1.7 Hz). It is possible the doublets were unresolved in our spectrum.50b 2.4.4 Synthesis of Rhodium Pyrazolylborate Complexes Synthesis of [Tp*Rh(PPh3)2] (1). In the glove box, ClRh(PPh3)2 (202 mg, 0.22 mmol) was weighed into a 20 mL vial equipped with a Teflon-coated magnetic stir bar. KTp* (74 mg, 0.22 mmol) and THF (4 mL) were then added sequentially. The vial was covered with a plastic cap and the solution was stirred at room temperature. The solution changed color from maroon to orange within ten minutes. After stirring for 1 hour, the volatiles 68 were removed under reduced pressure. The residue was dissolved in toluene (2 mL) and was layered with hexanes (8 mL). The solution was cooled to -35 °C; after 7 days orange crystals formed. The solution was decanted and the crystals were washed with hexanes (4 x 5 mL). The product was dried under reduced pressure to give 187 mg (92%) of an orange crystalline solid. Room temperature "H and 3 1P{'H} NMR data, as well as IR data, were consistent with literature reports.22'28' Low temperature NMR spectra indicate equivalence of two pyrazoles, whereas Connelly reports the inequivalence of all three pyrazoles (see Results and Discussion section). Synthesis of [Bp*Rh(PPh3)2] (2). In the glove box, ClRh(PPh3)2 (103 mg, 0.11 mmol) was weighed into a 20 mL vial equipped with a Teflon-coated magnetic stir bar. KBp* (39 mg, 0.16 mmol) and THF (2 mL) were then added sequentially. The vial was covered with a plastic cap and the solution was stirred at room temperature. The solution changed color from maroon to orange within ten minutes. After stirring for 24 hours, the volatiles were removed under reduced pressure. The residue was dissolved in toluene (2 mL) and was layered with hexanes (8 mL). The solution was cooled to -35 °C; after 7 days orange crystals formed. The solution was decanted and the crystals were washed with hexanes (4x5 mL). The product was dried under reduced pressure to give 80 mg (87%) of an orange crystalline solid. 'H and "''P{IH} NMR data, as well as IR data, were consistent with literature values.28b Synthesis of [BpRh(PPh3)2] (3). In the glove box, ClRh(PPh3)2 (204 mg, 0.22 mmol) was weighed into a 20 mL vial equipped with a Teflon-coated magnetic stir bar. KBp (44 mg, 0.24 mmol) and THF (6 mL) were then added sequentially. The vial was covered with a plastic cap and the solution was stirred at room temperature. The solution changed 69 color from maroon to orange within ten minutes. After stirring for 24 hours, the volatiles were removed under reduced pressure. The residue was dissolved in toluene (4 mL) and was layered with hexanes (4 mL). The solution was left in the glovebox and after 15 days orange crystals formed. The solution was decanted and the crystals were washed with hexanes ( 4 x 5 mL).. The product was dried under reduced pressure to give 147 mg (86%) of an orange crystalline solid. 'H and 3 1P{'H} NMR data were consistent with literature values.28b Synthesis of [TpRh(PPh3)2] (4). In the glove box, ClRh(PPh3)2 (200 mg, 0.22 mmol) was weighed into a 20 mL vial equipped with a Teflon-coated magnetic stir bar. KTp (80 mg, 0.32 mmol) and THF (3 mL) were then added sequentially. The vial was covered with a plastic cap and the solution was stirred at room temperature. The solution changed color from maroon to orange within ten minutes. After stirring for 24 hours, the volatiles were removed under reduced pressure. The residue was dissolved in toluene (2 mL) and was layered with hexanes (8 mL). The solution was cooled to -35 °C; after 12 days orange crystals formed. The solution was decanted and the crystals were washed with hexanes (4x5 mL). The product was dried under reduced pressure to give 155 mg (86%) 1 3 1 1 of an orange crystalline solid. H and P{ H} NMR data, as well as IR data, are tabulated in Table 2.9. 3 IP{'H} NMR data, as well as IR data, were consistent with literature values.22'280 Although the *H NMR data was consistent with Connelly's data, our data and Connelly's data were both inconsistent with Hill's data (see Results and Discussion section). 70 Synthesis of [TpMeRh(PPh3)2] (5 and 5*). In the glove box, ClRh(PPh3)2 (101 mg, 0.11 mmol) was weighed into a 20 mL vial equipped with a Teflon-coated magnetic stir bar. KTp M e (52 mg, 0.18mmol) and THF (2 mL) were then added sequentially. The vial was covered with a plastic cap and mixture was stirred at room temperature. The solution changed color from maroon to orange within ten minutes. After stirring for 4 hours, the volatiles were removed under reduced pressure. The residue was dissolved in toluene (2 mL) and was layered with hexanes (8 mL). The solution was cooled to -35 °C; after 12 days orange crystals formed. The solution was decanted and the crystals were washed with hexanes (4x5 mL). The product was dried under reduced pressure to give 56 mg (59%) of an orange crystalline solid. 'H NMR (CD2C12, 400 MHz) at 25 °C: [Major] 7.63 (br s, 2H, pz H), 7.5-6.9 (m, 30H, PPh3), 6.49 (s, 1H, pz H), 5.90 (s, 2H, pz H), 5.37 (s, 1H, pz H), 2.30 (s, 3H, CH 3), 2.15 (s, 6H, CH 3); [Minor] 8.07 (s, 2H, pz H), 7.5-6.9 (m, 30H, PPh3), 6.03 (s, 1H, pz H), 5.83 (s, 2H, pz H), 5.14 (s, 1H, pz H), 2.20 (s, 6H, CH 3), 1.43 (s, 3H, CH 3); 3 1P{'H} NMR (CD2C12, 162 MHz) at 25 °C: [Major] 50.82 (dd, J R h _ P = 182 Hz, yP.P> = 54 Hz), 48.19 (dd, JRh-P> = 172 Hz, JP.r = 54 Hz); [Minor] 54.21 (dd, J R h . P = 185 Hz, Jp.P. = 52 Hz), 50.70 (dd, < W = 172 Hz, JP.r = 52 Hz); at -85 °C: [Major] 49.93 (dd, J R H _ P = 178 Hz, J P . P - - 53 Hz), 47.66 (dd, J ^ f = 175 Hz, JP.P< = 53 Hz); [Minor] 53.80 (dd, J^.p = 182 Hz, JP.P> = 54 Hz), 50.81 (dd, J R h_ P . = 170 Hz, JP.P< = 52 Hz). IR (KBr Pellet) at 25 °C: 2429 [v(B-H)] cm"1. LRMS (EI) m/z calcd for C4 8H46BN6P2Rh: 882.24; found: 262 (PPh3, Ci 8 H 1 5 P), 620 [TpMeRh(PPh3), C 3 0H 3 ,BN 6PRh]. HRMS (EI) m/z calcd for TpMeRh(PPh3), C 3 0 H 3 ,BN 6 PRh: 620.1500; found: 620.1496. MALDI m/z calcd for C48H 4 6 BN 6 P 2 Rh: 882; found: 620, 882. 71 a ' o ^ 5 7 ' . 0 6 ' . 5 5 . 0 '"' 5.5'"' 5.0 "' 4.5 'A'Q"""'"""^3.0 2 . 5 2 . 0 \ ' . 5 i ! o u ! s " ' ' " D Chemical Shift (ppm) 'H NMR (CD2C12, 400 MHz) spectrum of complexes 5 and 5* at 298 K 72 298 K 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Chemical Shirt (ppm) 3 I t . fl P{'H} NMR (CD2C12, 162 MHz) spectrum of complexes 5 and 5* at 298 K 31r»rl 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Chemical Shift (ppm) P{'H} NMR (CD2CI2, 162 MHz) spectrum of complexes 5 and 5* at 188 K 73 Synthesis of [Tp™Rh(PPh3)2] (6). In the glove box, ClRh(PPh3)2 (100 mg, 0.11 mmol) was weighed into a 20 mL vial equipped with a Teflon-coated magnetic stir bar. KTp p h (84 mg, 0.17 mmol) and THF (2 mL) were then added sequentially. The vial was covered with a plastic cap and the solution was stirred at room temperature. The solution changed color from maroon to orange within ten minutes. After stirring for 24 hours, the volatiles were removed under reduced pressure. The residue was dissolved in toluene (2 mL) and was layered with hexanes (8 mL). The solution was cooled to -35 °C; after 7 days orange crystals formed. The solution was decanted and the crystals were washed with hexanes (4 x 5 mL). The product was dried under reduced pressure to give 96 mg (83%) of an orange crystalline solid. ] H NMR (CD2C12, 400 MHz) at 25 °C: 8.26 (s, 1H, pz H), 7.97 (m, pz C 6H 5), 7.43 (s, 2H, pz H), 7.4-6.9 (m, 45H, PPh3 + pz C 6H 5), 6.83 (s, 1H, pz H), 5.75 (s, 2H, pz H); at -85 °C: 8.25 (s, 1H, pz H), 7.91 (m, pz C 6H 5), 7.37 (s, 2H, pz H), 7.4-6.9 (m, 45H, PPh3 + pz C 6H 5), 6.81 (s, 1H, pz H), 5.73 (s, 2H, pz H). 3 IP{'H} NMR (CD2C12, 162 MHz) at 25 °C: 46.89 (d, J R h . P = 178 Hz); at -85 °C: 46.69 (d, J R h . P = 176 Hz). IR (KBr Pellet) at 25 °C: 2426 [v(B-H)] cm"1. LRMS (EI) m/z calcd for C 6 3 H 5 2 BN 6 P 2 Rh: 1068.29; found: 262 (PPh3, C 1 8H, 5P), 806 [TpPhRh(PPh3), C45H3 7BN6PRh]. HRMS (EI) m/z calcd for TpPhRh(PPh3), C 45H 3 7BN 6PRh: 806.1965; found: 806.1951. MALDI m/z calcd for C 6 3 H 5 2 BN 6 P 2 Rh: 1068; found: 1068. 74 238 K J L I kJ JL 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Chemical Shift (ppm) "H NMR (CD2C12, 400 MHz) spectrum of complex 6 at 298 K 298 K 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Chemical Sfiifl(ppm) 31r. fl P{'H} NMR (CD2C12, 162 MHz) spectrum of complex 6 at 298 K 75 Synthesis of [Tpp"'MeRh(PPh3)2] (7). In the glove box, ClRh(PPh3)2 (101 mg, 0.11 mmol) was weighed into a 20 mL vial equipped with a Teflon-coated magnetic stir bar. K T p P h , M e ( g 7 m & 0 1 ? m m o l ^ a n d t o l u e n e (2 mL) were then added sequentially. The vial was covered with a plastic cap and the solution was stirred at room temperature. The solution changed color from maroon to orange within ten minutes. After stirring for 24 hours, the volatiles were removed under reduced pressure. The residue was dissolved in toluene (2 mL) and was layered with hexanes (8 mL). The solution was cooled to -35 °C; after 7 days orange crystals formed. The solution was decanted and the crystals were washed with hexanes (4x5 mL).. The product was dried under reduced pressure to give 70 mg (58%) of an orange crystalline solid. 'H NMR (CD2C12, 400 MHz) at 25 °C: 8.27 (d, J= 8.8 Hz, 4H, pz C 6H 5), 7.77 (d, J= 7.3 Hz, 2H, pz C 6H 5), 7.6-6.8 (m, 45H, PPh3 + pz C 6H 5), 6.40 (s, 1H, pz H), 6.36 (s, 2H, pz H), 5.81 (s, 1H, BH), 2.51 (s, 6H, CH 3), 2.14 (s, 3H, CH 3); at -85 °C: 8.24 (d, J= 7.3 Hz, 2H, pz C 6H 5), 7.76 (d, J= 7.3 Hz, 2H, pz C 6H 5), 7.6-6.8 (m, 45H, PPh3 + pz C 6H 5), 6.38 (s, 1H, pz H), 6.03 (s, 1H, pz H), 5.74 (s, 1H, BH), 5.58 (s, 1H, pz H), 2.47 (s, 3H, CH 3), 2.46 (s, 3H, CH3), 2.04 (s, 3H, CH 3). 3 1P{'H} NMR (CD2C12, 162 MHz) at 25 °C: 48.12 (d, JKh.P = 182 Hz), 43.44-39.33 (m); at -85 °C: 42.60 (dd, J R h . P = 178 Hz, JP.P- = 50 Hz), 39.42 (dd, JRh.P- = 172 Hz, JP.P> = 51 Hz). IR (KBr Pellet) at 25 °C: 2463 [v(B-H)] cm"1. LRMS (EI) m/z calcd for C 6 6H58BN 6 P 2 Rh: 1110.33; found: 262 (PPh3, CigHisP), 848 [TpPh'MeRh(PPh3), C48H43BN6PRh]. HRMS (EI) m/z calcd for Tpp h'M eRh(PPh3), C 4 8 H 4 3 BN 6 PRh: 848.2435; found: 848.2429. MALDI m/z calcd for C66H58BN6P2Rh: 1110; found: 848.6. Elemental Analysis: calcd for C 6 6 H 5 8 BN 6 P 2 Rh: C, 71.36; H, 5.26; N, 7.57. Found: C, 71.52; H, 5.42; N , 7.37. 76 298 K 8.5 8.0 7.5 7 0 6 5 6 0 5.5 5 0 4.5 (.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Chemical Shift (ppm) "H NMR (CD2C12, 400 MHz) spectrum of complex 7 at 298 K 188 K I I " I I I I I I | j j , , i-RT-rrn-r.-|- [ | , 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 v 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Chemical Shift (ppm) 'H NMR (CD2C12, 400 MHz) spectrum of complex 7 at 188 K 77 298 K 80 75 70 65 60 55 50 45 40 35 30 ' 25 20 15 tO 5 0 Chemical Shin (ppm) 3 lP{'H} NMR (CD2C12, 162 MHz) spectrum of complex 7 at 298 K 80 75 70 65 60 55 50 45 4 0 3 5 3 0 25 20 15 10 5 0 Chemical Shift (ppm) "Pl'H} NMR (CD2C12, 162 MHz) spectrum of complex 7 at 188 K 78 2.4.5 X-ray Crystal Structures of Complexes 2, 4 and 5*-7. Crystal intensity collection and refinement details are summarized in Appendices I-V. All measurements for complexes 2, 5, 6 and 7 were made on a Bruker X8 APEX II diffractometer and all measurements for complex 4 were made on a Bruker X8 APEX diffractometer, both with graphite monochromated Mo-Ka radiation. Data were collected in a series of § and co scans and subsequently processed with the Bruker SAINT 5 2 software package. Data were corrected for absorption effects using the multi-scan technique (SADABS). 5 3 The data were corrected for Lorentz and polarization effects. The structures were solved using direct methods54 and refined using SHELXTL. 5 5 All non-hydrogen atoms were refined anisotropically, while all hydrogen atoms were placed in calculated positions and not refined, except for B-H hydrogens which were located in difference maps and refined isotropically. For complex 2 the material crystallizes with both toluene and hexane in the lattice. In this case there is a 50:50 mixture of toluene and hexane occupying the same space in the asymmetric unit. Mild restraints were employed to maintain reasonable geometries for both solvent molecules. For complex 4 the material crystallizes with toluene in the lattice. For complex 6 the material crystallizes with one disordered molecule of solvent, C5H12, in the asymmetric unit. This solvent molecule was modeled in two orientations with isotropic thermal parameters. For complex 7 the material crystallizes with disordered hexanes in the lattice. This disordered solvent molecule could not be modeled reasonably, therefore the PLATON/SQUEEZE 5 6 program was used to correct the data for any unresolved residual electron density in the lattice. The formula and any subsequent values calculated from it reflect the presence of one 79 molecule of hexane in the asymmetric unit. Full details for characterization of 2, 4 and 5*-7 are presented in Appendices I-V. 80 Chapter 3 - Alkyne Hydrothiolation Activity of Rhodium Pyrazolylborate Complexes 3.1 Introduction Alkyne hydrothiolation, as previously discussed, is the reaction of a thiol across an alkyne p bond. The possible products of this reaction include the branched, E- and Z-linear vinyl sulfides. However, reports of the internal vinyl sulfides via isomerization as well as bis(arylthio)alkene products have also been reported (see Scheme 3.1).8g'k ,1 D i / \ ^ - . SR SR " Ri RSH + R x »• R R' ^ ^SR + R 1 - ^ branched E-linear Z-linear R1 + R1 ' y "SR SR SR isomerized bis(arylthio)alkene Scheme 3.1. Alkyne hydrothiolation The use of aryl thiols in radical,6 b d nucleophilic7 and metal catalyzed8b'f"''k'm~° hydrothiolation is very prevalent throughout the literature. However, the use of alkyl thiols is much more limited. Radical methods have been reported using alkyl thiols to give the E- and Z-linear vinyl sulfides.66 Nucleophilic methods have also been reported giving the Z-linear vinyl sulfides.7b Michael addition reactions with aryl and alkyl thiols to give the branched vinyl sulfide product have also been reported (see Scheme 3.2).7d 81 However, because this requires isomerization to the allene or internal alkyne the substrate scope is limited. R R R = NMe 2 , Ph o r C H 3 R' = P h C H 2 o r Ph Scheme 3.2. Michael addition reactions Alkyl thiols have been reported as ineffective when used in metal catalyzed hydrothiolation reactions.8t'g Since alkylthiols have a stronger S-H bond and are less acidic then arylthiols their reactivity in catalytic reactions involving S-H bond breaking is likely lower than arylthiols. We postulated that the highly electron rich pyrazolylborate complexes should be reactive enough to catalyze hydrothiolation reactions with alkylthiols. In 2005, we reported that Tp*Rh(PPh3)2 (1) was an effective catalyst for hydrothiolation for both alkyl and arylthiols, favoring the branched product.8'11 Recently, our group also discovered that Wilkinson's catalyst, although reportedly ineffective with 82 alkylthiols,1 does in fact catalyze the hydrothiolation between alkylthiols and alkynes, favoring the Zs-linear product.80 To probe what affects the catalytic activity and regioselectivity seen for complex 1 we decided to explore a range of rhodium pyrazolylborate complexes. This chapter describes studies of the ability of complexes 1-7 to catalyze hydrothiolation reactions using both alkyl and arylthiols. The electronic effects and denticity of each complex will be examined to determine if correlations exist between structure and catalytic ability and regioselectivity. 3.2 Results and Discussion 3.2.1 Procedure and Optimization of Hydrothiolation Reactions All hydrothiolation reactions were carried out in a nitrogen-filled Vacuum Atmospheres glovebox (O2 < 2 ppm). Each complex (1-7) and 1,3,5-trimethoxybenzene (internal standard) were weighed out and dissolved in the appropriate amount of solvent. Next, 1.1 equivalents of the thiol followed by 1.0 equivalent of the alkyne were added via micropipette. The plastic cap was secured on the vial and it was brought out of the glovebox, covered in foil and stirred at room temperature, unless otherwise stated. Reactions were monitored by removing an aliquot via syringe, concentrating the sample and then taking the 'HNMR spectrum. The yields are based on the olefinic peaks of the product in the *H NMR spectrum versus the 1,3,5-trimethoxybenzene peaks. Optimization studies have previously been carried out by our group using Tp*Rh(PPh3)2. The best solvent system was found to be a 1:1 mixture of 1,2-dichloroethane (DCE) and toluene. It has been found that Tp*Rh(PPh3)2 decomposes in THF and DCE if left for prolonged times, producing a complex via orthometalation of r 83 one of the phosphine ligands (see Scheme 3.3). J The resulting complex was inactive in alkyne hydrothiolation reactions. No decomposition was found to occur when using a 1:1 ratio of DCE:toluene or when short reaction times were employed. As we were interested in expanding the substrate scope for hydrothiolation reactions, NMR scale reactions were more appropriate for our study to minimize the amount of reagents required. Although we had previously found that a 1:1 ratio of DCE:toluene was an ideal solvent, we wanted to be able to use NMR spectroscopy to determine the reaction yields. Therefore, we originally carried out NMR scale reactions in a 1:1 deuterated chloroform (CDCI3)^-toluene combination. This combination was found to give lower yields as well as poorer or even reverse regioselectivities as compared to the 1:1 DCE:toluene combination (Table 3.1). To more closely mimic the preparative scale reaction conditions, a 1:1 mixture of CD2Cl2:<i<s-toluene was used. This combination was found to give better selectivities than using a 1:1 mixture of CDCly.ds-toluene, however, the regioselectivities were not as high as with the 1:1 mixture of DCE:toluene (entry 4). Therefore, reactions were carried out using 1:1 DCE:toluene and monitored with 'H NMR spectroscopy by taking aliquots from the original reaction mixture. When using only DCE as a solvent the reactions seemed to produce good p PPh 2 Scheme 3.3. Orthometalation of Tp*Rh(PPh3)2 84 selectivities; however, orthometalation could become a problem and therefore this solvent system was avoided. Table 3.1 gives some examples of different solvent combinations used in hydrothiolation reactions. Entry 1 shows that complex 1 has lower regioselectivity (2:1 vs. 16:1) favoring the branched product and a 13% lower yield when using 1:1 CDCl3:<i,r toluene than with a 1:1 ratio of DCE:toluene. Complex 2 (entry 2) gave a reverse in regioselectivity and a much poorer yield when using 1:1 CDC^^s-toluene as compared to the 1:1 DCE:toluene combination. Complex 3 (entry 3) showed the same trends as both complex 1 and complex 2 with lower yields and selectivities in the 1:1 CDCly.ds-toluene solvent system. Lastly, complex 6 (entry 4) showed similar trends with lower yields and selectivities for the 1:1 CDC^^s-toluene combination over a 1:1 ratio of DCE:toluene. However, when a 1:1 ratio of CD2CI2: ^-toluene was employed, a comparable yield to the 1:1 DCE:toluene combination was observed with slightly lower selectivity (6:1 vs. 11:1) favoring the branched product (entry 4). For reactions <100% yield, starting material accounted for the remainder of the material. As well, longer reaction times did not seem to significantly increase the yields; this is possibly due to 31 1 catalyst decomposition, which can be seen in the J ,P{'H} NMR spectrum. 85 Table 3.1. Solvent studies for complexes 1-3 and 6 X R h ( P P h 3 ) 2 S ^ P h Phi SH + P h ^ 10 17 Ph 25a + p h ^ - S ^ / P h + 25b P h ' 25c Entry a Complex Solvent Time Ratio 25a : 25b : 25c Yield b 1 T p * R h ( P P h 3 ) 2 , 1 DCE:To l 2 h 16: 1 : 0 93% CDCI 3 :d 8 -To l 24 h 2 : 1 : 0 80% 2 B p * R h ( P P h 3 ) 2 , 2 DCE:To l 2 h 5 : 1 : 0 55% CDCI 3 :d 8 -To l 3 h 1 : 2 : 0 18% 3 B p R h ( P P h 3 ) 2 , 3 DCE:To l 4 h 1.5 : 1 : 0 67% CDCI 3 :d 8 -To l 24 h 2 : 5 : 1 33% 4 T p p h R h ( P P h 3 ) 2 , 6 DCE:To l 2 h 1 1 : 1 : 0 87% CDCI 3 :d 8 -To l 3 h 2.5 : 1 : 0 25% C D 2 C I 2 : d 8 - T o l 1 h 6 : 1 : 0 90% a Reactions conducted with 3 mol % catalyst, 1.1 equiv. thiol, 1.0 equiv. alkyne. Yields based on 'H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. 3.2.2 Substrate Scope of Hydrothiolation Reactions A variety of thiols and alkynes were chosen to test the substrate scope of the reaction with the different complexes. These include alkyl and arylthiols, aliphatic, aryl and internal alkynes with a variety of functionalities (see Figure 3.1). The background reactions for the alkyne and thiol combinations (without metal complex) were carried out and found to either give no reaction at all or a reaction that was significantly slower than the catalyzed reaction. 86 THIOLS Al iphat ic Th io ls P h C H 2 S H C F 3 C H 2 S H 10 P h O ' 11 O 13 rt-BuO' v " S H 14 Arylthiol P h - S H 16 , S H 12 S H 15 ALKYNES Aryl A lkynes P h — = M e O — — = 17 18 Al iphat ic A l k y n e s n - C 6 H 1 3 ^ ^ t-Bu—= M e 3 S i — = 19 20 0 EtO' 21 22 23 Internal A lkyne Ph = C H 3 24 Figure 3.1. Thiols and alkynes 3.2.3 Catalytic Activity of Complexes 1-7 in Alkyne Hydrothiolation Reactions 3.2.3-1 Tp*Rh(PPh3)2,1 The first complex that was tested for catalytic activity in alkyne hydrothiolation reactions was complex 1. This is a highly electron rich tris(pyrazolyl)borate complex with the potential to bind in a K 3 configuration during the catalytic cycle. Complex 1 has methyl substituents in both the 3- and 5-positions of the pyrazolyl rings. In preliminary studies this complex was found to give good-to-excellent yields (63-93%) using a series of aliphatic and arylthiols with aliphatic, aryl and internal alkynes.8m Thus, we sought to expand the substrate scope and study its reactivity further. Complex 1 was found to give good to excellent yields (56% to >95%), Table 3.2; the branched isomer was formed 87 preferentially in reactions between aliphatic thiols and aryl and aliphatic alkynes (entries 1-7 and 9). All reactions were carried out using 3 mol% of catalyst, a 1.1:1 ratio of thiol to alkyne and covered with aluminum foil for precautions relating to radical-promoted hydrothiolation reactions. Using 3 mol% of complex 1, benzylthiol (10) was reacted with phenylacetylene (17) (entry 1). The reaction was monitored by 'H NMR spectroscopy where the appearance of new peaks in the diagnostic region for olefinic protons indicated formation of the products. Two singlets for the branched isomer (25a) at 5 5.51 and 8 5.27 were observed, as well as two doublets for the TJ-linear isomer (25b) at 8 6.77 ( J h - h 1 = 15.6 Hz) and 8 6.58 ( J h ' - h = 15.5 Hz). After 2 hours at room temperature a 16:1 ratio of the branched:/^ -linear products (25a:25b) was observed in a 93% yield along with an additional - 5 % of an unidentified byproduct. 2,2,2-trifluoroethane thiol (11) reacted with phenylacetylene to give a 3:1 ratio of the branched to £-linear isomers in a 65% yield (entry 2). In the previous reaction an additional ~ 5 % of the /J-linear phenylacetylene dimer and an additional - 5 % of an unidentified byproduct were also observed. The reaction between benzylthiol and ethylpropiolate (22) did not give the branched isomer but instead gave a mixture of E- and Z-linear isomers (entry 9). If left for prolonged reaction times, the alkyl vinyl sulfide 31a isomerized to the internal vinyl sulfide as has previously been reported (entry 7 ) . 8 M The reaction between benzylthiol and 1-phenyl-1-propyne (24) gave a mixture of isomers in a 1:3.5 ratio and a 70% yield (entry 11). Complex 1 was found to be an excellent catalyst for hydrothiolation reactions and therefore the factors that affect its catalytic ability and regioselectivity were further investigated. This was done first by examining complexes that had no access to K -88 coordination to test denticity effects. The complexes chosen for study were Bp*Rh(PPh3)2 (2) and BpRh(PPh3)2 (3), which both lack access to the K 3 form. 89 Table 3.2. Substrate scope of alkyne hydrothiolation catalyzed by complex 1 3 mol % Tp*Rh(PPh 3 ) 2 R\ R1 „, RSH + R 1^EE \ = + K ^ = s + R ! _ , S R D C E : P h C H 3 (1:1), rt RS SR 10-16 17-24 Entry Thiol Alkyne Time Ratio Yie ld ; 1.1 equiv. 1.0 equiv. P h C H 2 S H P h — = 2 h 25a : 25b 93% 10 17 (16:1) 11 17 0 o/ b C F 3 C H 2 S H P h - ^ 2 h 26a : 26b 65% b c (3:1) SH P h ^ ^ 2 h 27a 78% 15 17 P n 0 - / \ - ' S H U e O - f ^ — = 2 h 28a >95% 13 18 SH M e O - < ^ ^ > — = 2 h 29a 6 1 % b 15 18 PhSH P h — = 2 h 30a: 30b 8 4 % d e ( 6 : 1 ) P h C H 2 S H / ? - C 6 H 1 3 — = 2 h 31a >95% 10 19 o/_ b M e 3 S i — = 2 h 32a 74% B u O ' ^ " S H 14 21 O P h C H 2 S H Jl 24 h 33b : 33c 5 9 % f EtO ^ (2.5:1) 10 22 10 0 ^ s h — = 3 h 3 4 a 5 6 % b 15 23 11 P h C H 2 S H Ph = C H 3 4 h 35a : 35b 70% 10 24 <1:3"5> a Yields based on 'H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. b An additional -5-10% of an unidentified byproduct was observed.c An additional ~5% of the ^-linear phenylacetylene dimer was observed. d This experiment was performed by C. Cao, see ref 8m. e Isolated yield. * Percent conversion with respect to remaining thiol. 90 3.2.3-2 Bis(pyrazolyl)borate Complexes Preliminary mechanistic investigations using deuterated phenyl acetylene have been carried out by a coworker (Bal Kang). We postulate that the mechanism likely involves a Rh(I)/Rh(III) cycle, implying that K3-coordination is involved (see Scheme 3.4). To test this hypothesis, we chose to study bis(pyrazolyl)borate complexes 2 and 3, which cannot adopt K3-coordination. Scheme 3.4. Possible pathway for Tp*Rh(PPli3)2-catalyzed hydrothiolation a) Bp*Rh(PPh3)2, 2 Complex 2 has the same substitution patterns on the pyrazolyl rings as complex 1, with methyl groups in both the 3- and 5-positions. However, complex 2 has one less pyrazolyl ring attached to the boron atom and thus cannot adopt K -coordination geometry. The results of the hydrothiolation reactions for complex 2 are shown in Table 91 3.3. The reaction between benzylthiol and phenylacetylene gave lower selectivity [5:1 branched (25a):£'-linear (25b)] and lower yield (55%) as compared to complex 1 (entry 1). The reaction between 2,2,2-trifluoroethanethiol and phenylacetylene gave no selectivity with only a 32% conversion and an additional ~5% of the ii-linear phenylacetylene dimer was also observed (entry 2). Benzylthiol reacted with tert-butylacetylene (20) and gave solely the branched product with a poor conversion of only 28% (entry 3). Entries 4 and 5 show the reaction between benzylthiol and 1-ethynylcyclohexene (23) in different solvents. This reaction gave moderate selectivity of the branched (37a) to Ti-linear (37b) isomers (7.5:1) when carried out in only DCE but when using a CDC^cis-toluene (1:1) solvent combination, we saw reversal in regioselectivity to a 1:6.5 ratio of 37a:37b. Like complex 1, complex 2 favored the branched isomer. However, the yields were considerably lower than with complex 1. 92 Table 3.3. Substrate scope of alkyne hydrothiolation catalyzed by complex 2 RSH R 1 ^ 3 mol % Bp*Rh(PPh 3 ) 2 ^ + R l ^ S R D C E : P h C H 3 (1:1), rt RS SR 10-11 17-23 a b c Entry Thiol Alkyne Time Ratio Yield a / Conversion b 1.1 equiv. 1.0 equiv. 1 P h C H 2 S H Ph^== . 2 h 25a : 25b 55% a 10 17 (5:1) 2 C F 3 C H 2 S H P h — = 2 h 26a : 26b 32% b ' c 11 17 (1:1) 3 P h C H 2 S H f - B u — = 4 h • 36a 28% M 10 20 4 P h C H 2 S H 24 h 37a : 37b 53% M N / (7.5:1) 10 23 5 P h C H 2 S H 24 h 37a : 37b 69% b ' e (1:6.5) 10 23 a Yields based on *H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. b Percent conversion with respect to remaining thiol. c An additional ~5% of the Ti-linear phenylacetylene dimer was observed. d Solvent = DCE. e Solvent = CDC13: d8-toluene (1:1). b) BpRh(PPh3)2, 3 Complex 3 was synthesized using a modified literature procedure.8"1 This complex presumably adopts K2-coordination as indicated in the X-ray structure reported by Carmona and coworkers.28b Using complex 3, the reaction between benzylthiol and phenylacetylene gave only a 24% yield after 24 hours at room temperature with a 6:5:1 ratio of branched:£-linear:Z-linear products (Table 3.4, entry 1). The 'H NMR data for 25a, 25b and 25c matches previously reported data.2'8'11'57 Next, phenylacetylene was 93 added to 2,2,2-trifluoroethanethiol but no reaction took place (entry 2). The reaction between propane thiol (12) and phenylacetylene gave only a 6% combined yield of branched, is-linear and Z-linear isomers after 48 hours (entry 3). Benzylthiol was reacted with ter/-butylacetylene and 1-ethynlcyclohexene resulting in conversions of 35% and 54%, respectively (entries 4 and 5). The regioselectivity of these reactions slightly favored the /^-linear isomers (36b and 37b) over the branched isomers with 1:2 and 1:3 .selectivities, respectively. The 'H NMR spectra for 36a, 36b, 37a and 37b are all in agreement with literature reports.8"1'0'58 Table 3.4. Substrate scope of alkyne hydrothiolation catalyzed by complex 3 RSH R 1 ^ 3 mol % BpRh(PPh 3 ) 2 R l R 1 x + R ^ S R D C E : P h C H 3 (1:1), rt R S ^ "SR 10-12 17-23 a b c Entry Thiol Alkyne Time Ratio Yield 31 Conversion b 1.1 equiv. 1.0 equiv. 1 P h C H 2 S H P h ^ ^ 24 h 25a : 25b : 25c 24% a 10 17 (6:5:1) 2 CF3CH2SH P h ^ ^ 24 h No rxn 11 17 3 P h ^ ^ 48 h 38a : 38b 6% a 12 17 (1:1) 4 P h C H 2 S H 24 h 36a : 36b 35% b 10 20 (1:2) 5 P h C H 2 S H 48 h 37a : 37b 54% b \ / (1:3) 10 23 a Yields based on H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. b Percent conversion with respect to remaining thiol. 94 In these five examples, complex 3 gave low selectivity and moderate to low yields/conversions (8-54%). As compared to complexes 1 and 2, which favored the branched isomer, complex 3 slightly favored the is-linear isomer. Therefore, because complexes 2 and 3 gave poor yields and selectivities they are not good choices as catalysts for hydrothiolation reactions. 3.2.3-3 Tris(pyrazolyl)borate Complexes Having established that denticity plays an important role in both reactivity and selectivity, we turned our attention to the effect of pyrazolyl substitution on reactivity and selectivity. A series of tris(pyrazolyl)borate complexes with varying substitution patterns on the pyrazolyl rings were synthesized and their hydrothiolation activity examined. These complexes included TpRh(PPh3)2 (4), TpMeRh(PPh3)2 (5), TpphRh(PPh3)2 (6) and Tp p h 'M cRh(PPh 3) 2 (7), which will all be further discussed in detail. a) TpRh(PPh 3) 2, 4 Complex 4, which lacks substitution on the pyrazolyl rings, was found to give poor to moderate yields/conversions (<5% to 67%) or resulted in no reaction at all when tested in hydrothiolation reactions (Table 3.5). The reaction between benzylthiol and phenylacetylene proceeded to only 7% conversion and produced solely the Z-linear isomer (25c) (entry 1). The reaction between 2,2,2-trifluoroethane thiol and phenylacetylene gave selectivity favoring the is-linear isomer over the Z-linear isomer in a 3:1 ratio with only a 14% combined yield (entry 4). When phenoxyethane thiol (13) was mixed with 4-ethynylanisole (18) and benzene thiol (16) was mixed with 95 phenylacetylene both showed no selectivity between the E- and Z-linear isomers with 14% and 60% yields, respectively (entries 5 and 7). Benzylthiol reacted with ethylpropiolate (22) to give a 1:2.5 ratio of the E- to Z-linear isomers in a 67% yield (entry 9). In most cases, complex 4 gave a mixture of linear isomers or just the Z-linear product. To ensure that the formation of the linear isomers was not due to a background radical reaction, galvinoxyl was used as a radical scavenger in several reactions (entries 3 and 8). The results were then compared to reactions without these radical scavenging reagents. The production of the linear isomers was not suppressed in the presence of galvinoxyl; hence, we postulate that the formation of the linear products observed for complex 4 were not due to a non-metal catalyzed radical reaction. 96 Table 3.5. Substrate scope of alkyne hydrothiolation catalyzed by complex 4 RSH + R 1 — ^ 10-16 17-23 3 mol % TpRh(PPh 3 ) 2 R 1 x D C E : P h C H 3 (1:1), rt *" R S ' SR + R l .SR Entry Thiol 1.1 equiv. Alkyne 1.0 equiv. Time Ratio Yield P h C H 2 S H 10 P h C H 2 S H 10 P h C H 2 S H 10 Ph-17 Ph-17 Ph-24 h 2 h 3 h 25c 25c 0/ b 17 25a : 25c (1:1) 7% 3 0/ b,c o/ b,c,d C F 3 C H 2 S H 11 Ph-P h O ' 13 15 P h - S H 16 P h - S H 16 P h C H 2 S H 10 17 . S H M e 0 ^ ~ ^ _ = SH MeO 18 18 Ph-17 Ph-17 0 EtO 48 h 24 h 24 h 24 h 24 h 24 h 26b : 26c (3:1) 28a : 28c (1:1) 22 30b : 30c (1.5:1) 30b : 30c (1:3) 33b: 33c (1:2.5) 14% 14% no rxn 6 0 % 51 % d 6 7 % 10 SH 15 23 24 h no rxn a Yields based on H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. b Percent conversion with respect to remaining thiol. c Solvent = DCE. d With an additional 3 mol% galvinoxyl. 97 Complex 4 gave opposite regioselectivity, favoring the linear isomers, as compared to complex 1, which favored the branched product. Thus it seems that substitution is necessary on the pyrazolyl rings for regioselectivity favoring the branched product and for higher yields. b) Tp M e Rh(PPh 3 ) 2 , 5 To examine if one methyl substituent on the pyrazolyl rings would be sufficient for catalytic activity of tris(pyrazolyl)borate complexes in hydrothiolation reactions, we synthesized complex 5: This complex has a methyl group in the 3-position of each pyrazolyl ring and no substitution at the 5-position. During the attempted synthesis of 5, a mixture of two isomers was obtained. This mixture included complex 5 and complex 5*, in which one methyl group is located in the 5-, rather than the 3-position of the pyrazolyl ring. Complex 5* was presumably formed by a 1,2-borotropic shift as discussed in section 2.2.2 of Chapter 2. Hydrothiolation reactions were performed with the isomeric mixture. In the hydrothiolation reactions that were tested, complex 5 favored the branched product, but with poor to moderate yields (<5% to 62%) (Table 3.6). In the reaction between benzylthiol and phenylacetylene there was good selectivity, as only the branched product was formed (entry 1). However, the yield of this reaction was only 15%. There was no selectivity in the reaction between 2,2,2-trifluoroethanethiol and phenylacetylene, which gave a 1:1:1 ratio of all three isomers 26a:26b:26c (entry 2). No reaction was observed between benzylthiol and the internal alkyne 1-phenyl-1-propyne (entry 9). 98 Table 3.6. Substrate scope of alkyne hydrothiolation catalyzed by complex 5 RSH + R i - = 3 mol % T p M e R n ( P P n 3 ) 2 _ Ri + R i + R D C E : P h C H 3 (1:1), rt RS SR 10-15 17-24 a b c Entry Thiol Alkyne Time Ratio Y i e l d a 1.1 equiv. 1.0 equiv. 1 P h C H 2 S H P h ^ ^ 2 h 25a 15% 10 17 2 C F 3 C H 2 S H P h ^ ^ 2 h 26a: 26b: 26c 7% 11 17 ( 1 : 1 : 1> SH P h ^ ^ 2 h 27a 1 6 % b 15 17 p h 0 / \ / S H M e O - < ^ ) — = 2 h 28a 49% 13 18 SH M e 0 ^ f ~ V ^ 2 h 29a 6 2 % b 15 18 P h C H 2 S H n - C 6 H 1 3 ^ ^ 2 h 31a <5% 10 19 0 = 3 B u O ' ^ " S H 14 21 [ > S H O 15 23 M e 3 S i — = 2 h 32a <5% 2 h 34a 48% 9 P h C H 2 S H Ph — C H 3 1 h - no rxn 10 24 3 Yields based on 'H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. b An additional -5-15% of an unidentified byproduct was observed. As complex 5 was used as a mixture of isomers (5 and 5*) we are not certain whether the low reactivity and selectivity is due to the product mixture or due to the lack 99 of substitution on the pyrazolyl rings. Therefore, because this complex is difficult to prepare as solely complex 5 and the mixture gives poor yields and selectivities it is not a good choice as a catalyst for hydrothiolation reactions. c) Tp P h Rh(PPh 3 ) 2 , 6 Next we decided to place a larger substituent at the 3-position. We prepared complex 6 where instead of a methyl group in the 3-position there is a phenyl group. This complex showed no indication of a 1,2-borotropic shift product in the 'H, 3 I P {'H} NMR or by X-ray analysis. Complex 6 gave a range of yields from 11% to >95% and favored the formation of the branched product in most cases (Table 3.7, entries 1-8). The reaction between benzylthiol and phenylacetylene gave an 87% yield with an 11:1 ratio of the branched to is-linear isomers (entry 1). 2,2,2-Trifluoroethane thiol reacted with phenylacetylene to give a 4:1 ratio of the branched to is-linear isomers in a 64% yield (entry 2). The reactions carried out in entries 3-8 all gave the branched product with 18% to >95% yields. Benzylthiol reacted with 1-phenyl-1-propyne to give only an 11% yield and no selectivity was observed between isomers (entry 9). This low yield was not surprising as reactions with an internal alkyne generally gave relatively low yields with most of the complexes studied thus far. 100 Table 3.7. Substrate scope of alkyne hydrothiolation catalyzed by complex 6 RSH 10-15 + R 1 17-24 3 mol % T p F n R h ( P P h 3 ) 2 R 1 N D C E : P h C H 3 (1:1), rt RS' SR + R! ,SR Entry Thiol 1.1 equiv. Alkyne 1.0 equiv. Time Ratio Yield 1 P h C H 2 S H 10 C F 3 C H 2 S H 11 Ph-17 Ph-17 2 h 2 h 25a : 25b (11:1) 26a : 26b (4:1) 87% 0/ b 64% 0/ b,c 15 P h O ' SH . S H 13 15 Ph-MeO 17 SH MeO 18 18 5 h 2 h 2 h 27a 28a 29a 0/ b,d 54% >95% 73% 0/. b P h C H 2 S H 10 o BuO v "SH 14 19 M e 3 S i -21 2 h 2 h 31a 32a 71% 18% 0/. b SH 15 P h C H 2 S H 10 23 Ph — C H 3 24 3 h 1 h 34a 35a : 35b (1:1) 60% 11% a Yields based on 'fi NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. b An additional -5-20% of an unidentified byproduct was observed. c An additional -5% of the /^-linear phenylacetylene dimer was observed. d Solvent = CD2CI2 : d$-toluene (1:1). The overall yields obtained with complex 6 were higher than those obtained with complex 5 but generally lower then those obtained for complex 1. It seems if there is only 101 one substituent on each pyrazolyl ring, in the 3-position, a larger substituent is preferred. The larger phenyl group present in complex 6 causes it to favor adoption of form A over form B and this may affect its catalytic activity. However, further mechanistic investigations are required to fully understand the factors that affect the catalytic activity of these complexes. d) TpPhMeRh(PPh3)2, 7 Thus far, there appears be a correlation between the substituents in the 3- and 5-position or large substituents in the 3-position and catalytic activity, as well as the potential to bind in a K 3 configuration. We therefore decided to examine another rhodium tris(pyrazolyl)borate complex that had a large substituent in the 3-position and another substituent in the 5-position to see if this complex would be superior to complex 1. We prepared complex 7 with phenyl groups at the 3-position and methyl groups at the 5-position of the pyrazolyl rings. The catalytic activity of complex 7 in hydrothiolation reactions was comparable to complex 1, giving similar yields and selectivities. The results are shown in Table 3.8. The reaction between benzylthiol and phenylacetylene gave a 6:1 ratio favoring the branched over the £"-linear isomer in a 78% yield (entry 1). 2,2,2-trifluoroethane thiol reacted with phenylacetylene to give a 3:1 ratio of branched to ^-linear in an 84% yield (entry 2). Entries 3-7 showed reactions between aliphatic thiols and aryl and aliphatic alkynes, which all gave predominantly the branched product in good to excellent yields (40->95%). The reaction between benzylthiol and 1-phenyl-1-propyne resulted in no selectivity between isomers and only 24% yield (entry 8). These results suggest that complexes with substituents in both the 3- and 5-positions of the 102 pyrazolyl rings and the ability to bind K outperform those complexes that do not have these factors. Table 3.8. Substrate scope of alkyne hydrothiolation catalyzed by complex 7 RSH + R i ^ 3 m ° l % T p P h ' M e R h ( P P h ^ R1>= + R U + R 1 _ S R DCE:PhCH 3 (1 :1) , rt RS SR ^ 10-15 17-24 a b c Entry Thiol Alkyne Time Ratio Y i e l d 3 1.1 equiv. 1.0 equiv. 1 P h C H 2 S H P h — = 2 h 25a : 25b 78% b 10 17 <6:1> 2 C F 3 C H 2 S H P h ^ E E 2 h 26a : 26b 84% b c 11 17 (3:1) P h O / x ^ ' S H M e O - < ^ j ) — = 2 h 28a >95% 13 18 SH MeO-/T~%—= 2 h 29a 75% b 15 18 5 P h C H 2 S H n - C 6 H 1 3 ^ ^ 2 h 31a >95% 10 19 O 6 j i _ M e 3 S i ^ ^ 2 h 3 2 a 40% b BuO SH 14 21 SH <^  y—= 3 h 34a 80% b 15 23 P h C H 2 S H Ph = C H 3 1 h 35a: 35b 24% 10 24 <1:1> a Yields based on ] H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. b An additional -5-20% of an unidentified byproduct was observed. 0 An additional -5% of the .E-linear phenylacetylene dimer was observed. 103 3.2.3-4 Complexes 1-7 Comparative Studies For a more direct comparison between complexes 1-7 the results for the reaction between 10 and 17 are summarized in Table 3.9. The results of this reaction are representative of the trends observed for complexes 1-7. It seems that for catalytic activity, substitution in the 3-position and the 5-position of the pyrazolyl rings are important. If there is solely substitution in the 3-position, a large substituent appears to be necessary. In addition, the ability to achieve K3-coordination also appears to be important as higher yields were obtained with the tris(pyrazolyl)borate complexes 1, 6 and 7. It is interesting to note that complex 4 has minimal catalytic activity and favors the Z-linear isomer, possibly suggesting the reaction in its presence proceeds through a different mechanism. 104 Table 3.9. Hydrothiolation of benzylthiol with phenylacetylene catalyzed by complexes 1-7 P h ^ S H + _ XRh(PPh 3 ) 2 P h — D C E : P h C H 3 (1:1) * S"~"Ph PIA + p h ^ S ^ P h + P n " S ^ P h 10 17 r t 25a 25b 25c Entry 3 Complex Time Ratio Yield b 1 Tp*Rh(PPh 3 ) 2 2 h 25a : 25b (16:1) 93% 0 2 Bp*Rh(PPh 3 ) 2 2 h 25a : 25b (5:1) 55% 3 BpRh(PPh 3 ) 2 24 h 25a : 25b :25c (6:5:1) 24% 4 TpRh(PPh 3 ) 2 24 h 25c 7% d 5 T p M e R h ( P P h 3 ) 2 2 h 25a 15% 6 T p p h R h ( P P h 3 ) 2 2 h 25a : 25b (11:1) 87% c 7 T p p h ' M e R h ( P P h 3 ) 2 2 h 25a : 25b (6:1) 78% c a Reactions conducted with 3 mol % catalyst, 1.1 equiv. thiol, 1.0 equiv. alkyne. b Yields based on 'H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard.c An additional -5-10% of an unidentified byproduct was observed. d Percent conversion with respect to benzylthiol. The results for the reaction between 11 and 17 (Table 3.10) are consistent with the trends seen for the reaction between 10 and 17 (Table 3.9). Complexes 1, 6 and 7 again gave the highest yields (64-84%) with the highest selectivity favoring the branched over the .E-linear isomer. Furthermore, tris(pyrazolyl)borate complexes are superior to the bis(pyrazolyl)borate complexes. The reaction using 2,2,2-trifluoroethanethiol gave slightly lower selectivities and yields as compared to that using benzylthiol but the general trends remain constant. 105 Table 3.10. Hydrothiolation of 2,2,2-trifluoroethanethiol with phenylacetylene catalyzed by complexes 1-7 F 3 C ^ S H + XRh(PPh 3 ) 2 D C E : P h C H 3 (1:1) " S ^ C F 3 - P t A + P n / ^ S ^ - C F 3 + P h S ^ C F 3 11 17 r t 26a 26b 26c Entry 3 Complex Time Ratio Yield b 1 Tp*Rh(PPh 3 ) 2 2 h 26a : 26b (3:1) 65% c ' d 2 Bp*Rh(PPh 3 ) 2 2 h 26a : 26b (1:1) 32 % c 3 BpRh(PPh 3 ) 2 24 h - No rxn 4 TpRh(PPh 3 ) 2 48 h 26b : 26c (3:1) 14% 5 T p M e R h ( P P h 3 ) 2 2 h 26a : 26b : 26c (1:1:1) 7% 6 T p p h R h ( P P h 3 ) 2 2 h 26a : 26b (4:1) 64% c ' d 7 T p p h ' M e R h ( P P h 3 ) 2 2 h 26a : 26b (3:1) 84% c ' d a Reactions conducted with 3 mol % catalyst, 1.1 equiv. thiol, 1.0 equiv. alkyne. b Yields based on ! H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard.0 An additional -5% of the is-linear phenylacetylene dimer was observed. d An additional -5% of an unidentified byproduct was observed. 3.2.4 Phenylacetlyene Dimerization and Other Unidentified Byproducts Beletskaya and coworkers found when using their nickel catalysts that oligo- and Q 1 polymerization reactions with the alkyne substrates occurred readily. Therefore they carried out a series of optimization studies in order to minimize the polymerization reactions. When using a 1:1 ratio of thiokalkyne they found about 10-12% of the alkyne formed oligomers. When the ratio of thiol to alkyne was 0.5:1 they reported an ever higher production of the oligomer products. However, when using an excess of thiol in a 106 2:1 ratio of thiol:alkyne there was no detectable production of the oligomers by 'H NMR spectroscopy. Therefore they concluded that it is important for the thiol to be in excess to avoid oligo- and polymerization products. In our studies we have found that the is-linear phenylacetylene dimer formed in the reaction between 2,2,2-trifluoroethanethiol and phenylacetylene when using a ratio of 1.1:1 thiokalkyne. However, this thiol is extremely volatile (bp = 34-35 °C) and thus some of this reagent may have evaporated before the reaction flask was sealed. This would result in a lack of excess thiol and could possibly lead to the formation of the dimer. Therefore, future studies with 2,2,2-trifluoroethane thiol should be carried out using an increased ratio of thiol to alkyne to determine if the ratio affects the yield of oligomerization products. The unidentified byproducts that were observed in the hydrothiolation reactions in 5-20% yields have not been characterized. Attempts to separate the byproducts from the desired products were unsuccessful and thus far the identities of the byproducts are unknown. However, we speculate the byproduct may be the product of hydrothiolation of dimerized phenylacetylene, see Figure 3.2. This would account for the gas chromatography/mass spectroscopy data where only masses corresponding to the hydrothiolation products were observed. The postulated byproduct would have the same fragmentation pattern as the hydrothiolation products and thus it is possible for the same peaks to be observed. As well, generally three singlets in a 1:1:1 ratio are observed in the ' H NMR spectrum. These occur in the diagnostic olefinic region which is also in agreement with this structure. It must also be noted that the byproduct(s) seen in the reaction been butyl 3-mercaptopropionate and trimethylsilylacetylene do not seem to 107 match this interpretation with respect to the 'H NMR data. Further investigations need to be carried out to fully characterize the unknown byproduct(s). R1 SR Figure 3.2. Postulated byproduct for hydrothiolation reactions 3.3 Conclusions From the hydrothiolation reaction results obtained for complexes 1-7 it is clear that tris(pyrazolyl)borate complexes are superior to bis(pyrazolyl)borate complexes. Presumably the ability to adopt K3-coordination is an important factor in the catalytic cycle (see Scheme 1.22 in Chapter 1). Complexes with substitution on the pyrazolyl rings gave better yields and selectivity, favoring the branched product, than complexes lacking substitution. In addition, substitution at the 3- and 5-positions of the pyrazolyl rings enhances the catalytic ability of those complexes in comparison to substitution at only the 3-position of the pyrazolyl rings. The size of the substituent at the 3-position also seems to have a large effect on the yield. Replacement of the methyl group in complex 5 with a phenyl group in complex 6 greatly increased the yields of the hydrothiolation reactions. However, since complex 5 was used as a mixture of isomers (5 and 5*) we cannot be certain whether the poor catalytic activity is due to the product mixture or to the lack of substitution on the pyrazolyl rings. We have established that tris(pyrazolyl)borate complexes are better than bispyraozlylborate complexes and that substitution on the 108 pyrazolyl rings is needed for catalytic activity, however the reasons for this are still unclear. Mechanistic investigations for alkyne hydrothiolation reactions catalyzed by rhodium pyrazolylborate complexes need to be carried out to fully comprehend the effect that denticity and pyrazolyl substitution have on the catalytic activity of these complexes. 3.4 Experimental Procedures 3.4.1 General Methods The manipulation of air and moisture sensitive organometallic compounds was carried out using standard Schlenk techniques under a positive pressure of dry nitrogen or in a nitrogen-filled Vacuum Atmospheres glovebox (0 2 < 2 ppm). Reactions were run at room temperature (20-28 °C) and stirred with a Teflon-coated magnetic stir bar, unless otherwise stated. Reaction mixtures were concentrated using rotary evaporation methods combined with pumping on the vacuum line for nonvolatile compounds. A base bath composed of potassium hydroxide, isopropanol and water was used to clean glassware, followed by rinsing with deionized water and then acetone. 3.4.2 Reagents and Solvents All organic reagents were obtained from commercial sources and used as received, unless otherwise stated. Hexanes and toluene were dried by passage through solvent purification columns.51 DCE was distilled and degassed prior to use. Deuterated chloroform was purified by vacuum transfer from P2O5 and was degassed prior to use. 109 C D 2 G 2 and ds-toluene were used from 1 g ampules and 1,3,5-trimethoxybenzene was sublimed prior to use. 3.4.3 Chromatography Flash chromatography was used to separate products as described by Still and coworkers.59 The solvent was eluted using either nitrogen or air pressure at an approximate rate of two inches per minute. 3.4.4 Physical and Spectroscopic Measurements Bruker Avance 300 ('H at 300MHz and 1 3 C at 75MHz) or Bruker Avance 400 ('H at 400MHz and 1 3 C at 100MHz) magnetic resonance spectrometers were used to collect NMR spectra. Values for *H and 1 3 C spectra are reported as chemical shifts as parts per million (ppm) and were referenced to a residual solvent. Coupling constants (J) are reported in Hertz (Hz) and were extracted assuming first-order coupling. Spin multiplicities are abbreviated as follows: s = singlet, d = doublet, t = triplet, q = quartet, qn = quintet, sx = sextet, m = multiplet. Unless otherwise indicated, all spectra were obtained at 25 °C. 1,3,5-Trimethoxybenzene was used as an internal standard to determine NMR yields. GCMS data was recorded on a Varian CP-3800 or an HP 5890 Series II gas chromatograph. Mass spectra were recorded on a Kratos MS-50 mass spectrometer. 110 3.4.5 Synthesis and Characterization of Hydrothiolation Products All of the following hydrothiolation reactions were conducted in a Vacuum Atmospheres glovebox. 20 mL or 5 mL vials were equipped with Teflon-coated magnetic stir bars. After addition of all reagents, the vials were sealed with plastic screw caps, taken out of the glovebox and covered in aluminum foil. Reactions were stirred at room temperature. All stock solutions were made with a 1:1 DCE:toluene mixture, unless otherwise stated. The reaction mixtures were concentrated under vacuum. The residue was dissolved in ~ 1 mL of CDC13 and the resulting solution was analyzed by *H NMR spectroscopy. The yields were determined using 1,3,5-trimethoxybenzene as an internal standard or the conversion was calculated based on remaining thiol. The reaction mixture was then transferred to a 20 mL vial and petroleum ether (boiling range 35-60°C) was added to precipitate the rhodium complex. The solution was filtered through silica gel and the resulting solution was concentrated under vacuum. Flash chromatography (SiC>2, solvent combination for eluant) provided the product. For each reaction, a representative experimental procedure is given. Results with each complex are tabulated after the experimental procedure, followed by characterization data or literature references. I l l Reaction of Benzylthiol (10) and Phenylaceytlene (17) + SH + 1,3,5-trimethoxybenzene DCE:PhCH3, rt 3 mol% XRh(PPh3)2 ^ / S 25b 10 17 + 25c Tp*Rh(PPh3)2 (17 mg, 0.018 mmol) was weighed out using a spatula into a 20 mL vial. 1,3,5-Trimethoxybenzene, (30 mg, 0.18 mmol, 408 uL of a 0.44 M stock solution in a 1:1 DCE:toluene mixture) was added via micropipette. To this solution, benzylthiol (70 uL, 0.60 mmol) and phenylacetylene (59 uL, 0.54 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. 'H NMR analysis indicated the formation of the branched (25a) and /^-linear (25b) isomers in a 16:1 ratio in 93% combined yield. An additional 6% yield of an unidentified product was also observed. 112 Table 3.11. Hydrothiolation of benzylthiol with phenylacetylene catalyzed by complexes 1-7 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 2 h 25a : 25b (16:1) 93% a 2 Bp*Rh(PPh 3 ) 2 2 h 25a : 25b (5:1) 55% 3 BpRh(PPh 3 ) 2 24 h 25a : 25b :25c (6:5:1) 24% 4 TpRh(PPh 3 ) 2 24 h 25c 7% b 5 T p M e R h ( P P h 3 ) 2 2 h 25a 15% 6 T p p h R h ( P P h 3 ) 2 2 h 25a : 25b (11:1) 87% a 7 T p p h ' M e R h ( P P h 3 ) 2 2 h 25a : 25b (6:1) 78% a a An additional -5-10% of an unidentified byproduct was observed. b Percent conversion with respect to benzylthiol. Branched (25a): Characterization matches previously reported data, ii-linear (25b): Characterization matches previously reported data.57 Z-linear (25c): Characterization matches previously reported data. 113 Reaction of 2,2,2-Trifluoroethanethiol (11) and Phenylacetylene (17) 26c Tp*Rh(PPh3)2 (17 mg, 0.018 mmol) was weighed out using a spatula into a 20 mL vial. 1,3,5-Trimethoxybenzene, (30 mg, 0.18 mmol, 408 uL of a 0.44 M stock solution in a 1:1 DCE:toluene mixture) was added via micropipette. To this solution, 2,2,2-trifluoroethanethiol (53 uL, 0.60 mmol) and phenylacetylene (59 uL, 0.54 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. ! H NMR analysis indicated the formation of the branched (26a) and ii-linear (26b) isomers in a 3:1 ratio in 65% combined yield. An additional 7% yield of an unidentified product as well as 8% of the ^-linear phenylacetylene dimer was also observed. 114 Table 3.12. Hydrothiolation of 2,2,2-trifluoroethanethiol with phenylacetylene catalyzed by complexes 1-7 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 2 h 26a : 26b (3:1) 65% a ' b 2 Bp*Rh(PPh 3 ) 2 2 h 26a : 26b (1:1) 32 % a 3 BpRh(PPh 3 ) 2 24 h - No rxn 4 TpRh(PPh 3 ) 2 48 h 26b : 26c (3:1) 14% 5 T p M e R h ( P P h 3 ) 2 2 h 26a : 26b : 26c (1:1:1) 7% 6 . T p p h R h ( P P h 3 ) 2 2 h 26a : 26b (4:1) 64% a ' b 7 T p p h ' M e R h ( P P h 3 ) 2 2 h 26a : 26b (3:1) 84% a ' b a An additional -5% of the TJ-linear phenylacetylene dimer was observed. b An additional -5% of an unidentified byproduct was observed. Branched (26a): light yellow oil; 15% ethyl acetate/petroleum ether used as eluant for flash chromatography. *H NMR (CDC13, 300 MHz): 5 7.55 - 7.52 (m, 2H), 7.41 - 7.37 (m, 3H), 5.61 (s, 1H), 5.55 (s, 1H), 3.11 (q, 2H, J = 9.6 Hz). I 3C{'H} NMR (CDCI3, 100 MHz): 5 142.2, 137.8, 128.9, 128.6, 127.7, 117.3, 34.6. HRMS (EI) m/z calcd for C 1 0 H 9 S F 3 : 218.0377; found: 218.0373. ii-linear (26b): Characterization matches previously reported data.80 115 Z-linear (26c): light yellow oil; 10% ethyl acetate/petroleum ether used as eluant for flash chromatography. 'H NMR (CDCI3, 400 MHz): 8 7.46 - 7.29 (m, 5H), 6.53 (d, 1H, J = 10.7 Hz), 6.19 (d, 1H, / = 10.7 Hz), 3.33 (q, 2H, J = 10.7 Hz). 1 3C{'H} NMR (CDCI3, 100 MHz): 5 136.4, 136.2, 132.1, 128.9, 128.6, 128.2, 127.6, 37.7. HRMS (EI) m/z calcd for CioH9SF3: 218.0377; found: 218.0384. 116 1 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 J.O 35 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shin (ppm) 'H NMR (CDCI3, 300 MHz) spectrum of compound 26a at 298 K 144 136 128 120 112 104 96 80 72 64 56 48 40 32 24 16 Chemical Shift (ppm) C{'H} NMR (CDCI3, 100 MHz) spectrum of compound 26a at 298 K 117 Compound 26c observed in situ as mixture with 26b U u 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Chemical Shirt (ppm) 'H NMR (CDC1 3 , 400 MHz) spectrum of compound 26c at 298 K 136 128 120 112 104 96 72 64 56 48 40 32 24 16 8 0 Chemical Shift (ppm) 13^ f l C{'H} NMR (CDCI3, 100 MHz) spectrum of compound 26c at 298 K 118 Reaction of Cyclopentylthiol (15) and Phenylacetylene (17) S o SH + 3 mol% XRh(PPh3)2 15 17 1,3,5-trimethoxybenzene DCE:PhCH3, rt 27a Tp*Rh(PPh3)2 (12 mg, 0.013 mmol) was weighed out using a spatula into a 20 mL vial. 1,3,5-Trimethoxybenzene, (24 mg, 0.14 mmol, 360 uL of a 0.40 M stock solution in a 1:1 DCErtoluene mixture) was added via micropipette. To this solution, cyclopentylthiol (51 uL, 0.48 mmol) and phenylacetylene (47 uL, 0.43 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. *H NMR analysis indicated the formation of the branched (27a) isomer in 78% yield. Table 3.13. Hydrothiolation of cyclopentylthiol with phenylacetylene catalyzed by complexes 1, 5 and 6 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 2 h 27a 78% 2 T p M e R h ( P P h 3 ) 2 2 h 27a 16% 3 T p p h R h ( P P h 3 ) 2 2 h 27a 5 4 % a ' b a An additional 9% yield of an unidentified byproduct was observed. b Solvent = CD2Cl2:tirtoluene(l:l). Branched (27a): Characterization matches previously reported data.8"1 119 Reaction of Phenoxvethane Thiol (13) and 4-Ethvnvlanisole (18) - S H + M e O - ^ y — = — v .OPh 3 mol% XRh(PPh3)2 S P h D \ / t I V i e u — V 7 = " r n w \ — / 1,3,5-trimethoxybenzene 13 18 DCE:PhCH3, rt MeO" ^ 28a Tp Rh(PPh3)2 (0.005 mmol, 44 uL of a 0.12M stock solution in a 1:1 DCE:toluene mixture) was added to a 5 mL vial via micropipette. 1,3,5-Trimethoxybenzene, (8 mg, 0.05 mmol, 81 uL of a 0.62 M stock solution in a 1:1 DCE:toluene mixture) was added via micropipette. To this solution, phenoxyethane thiol (23 uL, 0.165 mmol) and 4-ethynylanisole (20 uL, 0.15 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. 'H NMR analysis indicated the formation of the branched (28a) isomer in >95% yield. Table 3.14. Hydrothiolation of phenoxyethanethiol with 4-ethynylanisole catalyzed by complexes 1 and 4-7 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 2 h 28a >95% 2 TpRh(PPh 3 ) 2 24 h 28a : 28c (1:1) 14% 3 T p M e R h ( P P h 3 ) 2 2 h 28a 49% 4 T p P h R h ( P P h 3 ) 2 2 h 28a >95% 5 T p P h ' M e R h ( P P h 3 ) 2 2 h 28a >95% Branched (28a): Characterization matches previously reported data. 120 Reaction of Cyclopentylthiol (15) and 4-EthynylanisoIe (18) S o SH + MeO 1,3,5-trimethoxybenzene DCE:PhCH3, rt 3 mol% XRh(PPh3)2 15 18 MeO 29a Tp Rh(PPh3)2 (9 mg, 0.01 mmol) was weighed out using a spatula into a 5 mL vial. 1,3,5-Trimethoxybenzene, (17 mg, 0.10 mmol) was added using a spatula and 250 uL 1:1 DCE:toluene was added via micropipette. To this solution, cyclopentylthiol (36 uL, 0.34 mmol) and 4-ethynylanisole (40 uL, 0.31 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDCI3. ] H NMR analysis indicated the formation of the branched (29a) isomer in 61% yield. An additional 10% yield of an unidentified product was also observed. Table 3.15. Hydrothiolation of cyclopentylthiol with 4-ethynylanisole catalyzed by complexes 1 and 4-7 Entry Complex Time Ratio Yield 3 1 Tp*Rh(PPh 3 ) 2 2 h 29a 61% 2 TpRh(PPh 3 ) 2 24 h - no rxn 3 T p M e R h ( P P h 3 ) 2 2 h 29a 62% 4 T p p h R h ( P P h 3 ) 2 2 h 29a 73% 5 T p p h ' M e R h ( P P h 3 ) 2 2 h 29a 75% a An additional 5-20%> yield of an unidentified byproduct was observed. 121 Branched (29a): orange oil; 10% ethyl acetate/petroleum ether used as eluant for flash chromatography. ! H NMR (CDCI3, 300 MHz): 5 7.59 (d, 2H, J = 9.0 Hz), 6.95 (d, 2H, J = 9.0 Hz), 5.50 (s, 1H), 5.26 (s, 1H), 3.87 (s, 3H), 3.45-3.42 (m, 1H), 2.16-2.02 (m, 2H), 1.80-1.59 (m, 6H). I 3C{'H} NMR (CDCI3, 75 MHz):5 159.9, 145.4, 132.7, 129.2, 128.5, 125.5, 113.8, 110.6,55.4,44.2,33.3,25.2. HRMS (EI) m/z calcd for Ci 4 Hi 8 OS: 234.1078; found: 234.1074. 122 123 Reaction of Benzenethiol (16) and Phenylacetylene (17) TpRh(PPh3)2 (8 mg, 0.01 mmol) was weighed out using a spatula into a 5 mL vial. 1,3,5-Trimethoxybenzene, (17 mg, 0.10 mmol) was added using a spatula and 250 uL 1:1 DCE:toluene was added via micropipette. To this solution, benzenethiol (35 uL, 0.34 mmol) and phenylacetylene (34 uL, 0.31 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. 'H NMR analysis indicated the formation of the E'-linear (30b) and Z-linear (30c) isomers in a 1.5:1 ratio in 60% combined yield. 124 Table 3.16. Hydrothiolation of benzenethiol with phenylacetylene catalyzed by complexes 1 and 4 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 2 h 30a 84% a ' b 2 TpRh(PPh 3 ) 2 24 h 30b: 30c 60% (1.5:1) a This experiment was performed by C. Cao, see ref 8m. b Isolated yield. Branched (30a): Characterization from previously reported data. m /^-linear (30b): Characterization matches previously reported data. Z-linear (30c): Characterization matches previously reported data.8 125 Reaction of Benzylthiol (10) and 1-Octyne (19) SH + r?-C 6 H 1 3 1,3,5-trimethoxybenzene DCE:PhCH3 3 mol% XRh(PPh3)2 n-CgH-o' A s 10 19 31a Tp*Rh(PPh3)2 (17 mg, 0.018 mmol) was weighed out using a spatula into a 20 mL vial. 1,3,5-Trimethoxybenzene, (30 mg, 0.18 mmol, 408 uL of a 0.44 M stock solution in a 1:1 DCE:toluene mixture) was added via micropipette. To this solution, benzylthiol (70 uL, 0.59 mmol) and 1-octyne (80 uL, 0.54 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. 'H NMR analysis indicated the formation of the branched (31a) isomer in >95% yield. Table 3.17. Hydrothiolation of benylthiol with 1-octyne catalyzed by complexes 1 and 5-7 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 2 h 31a >95% 2 T p M e R h ( P P h 3 ) 2 2 h 31a <5% 3 T p p h R h ( P P h 3 ) 2 2 h 31a 71% 4 T p p h ' M e R h ( P P h 3 ) 2 2 h 31a >95% Branched (31a): Characterization matches previously reported data. 126 Reaction of Butyl 3-Mercaptopropionate (14) and Trimethylsilylacetylene (21) 0 o 3 mol% XRh(PPh3)2 S OBu BuO SH + TMS— 1,3,5-trimethoxybenzene DCE:PhCH3, rt TMS 14 21 32a Tp Rh(PPh3)2 (9 mg, 0.01 mmol) was weighed out using a spatula into a 5 mL vial. 1,3,5-Trimethoxybenzene, (17 mg, 0.10 mmol) was added using a spatula and 250 uL 1:1 DCE:toluene was added via micropipette. To this solution, butyl 3-mercaptopropionate (55 uL, 0.34 mmol) and trimethylsilylacetylene (44 uL, 0.31 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDCI3. 'H NMR analysis indicated the formation of the branched (32a) isomer in 74% yield. An additional 10% yield of an unidentified product was also observed. Table 3.18. Hydrothiolation of butyl 3-mercaptopropionate with 4-ethynylanisole catalyzed by complexes 1 and 5-7 Entry Complex Time Ratio Yield a 1 Tp*Rh(PPh 3 ) 2 2 h 32a 74% 2 T p M e R h ( P P h 3 ) 2 2 h 32a <5% 3 T p p h R h ( P P h 3 ) 2 2 h 32a 18% 4 T p p h ' M e R h ( P P h 3 ) 2 2 h 32a 40% a An additional 5-20% yield of an unidentified byproduct was observed. 127 Branched (32a): clear, colorless oil. 'H NMR (CDCI3, 400 MHz): 5 5.49 (s, 1H), 5.40 (s, 1H), 4.13 (t, 2H, J= 6.6 Hz), 3.04 (t, 2H, J= 13 Hz), 2.66 (t, 2H, J= 7.3 Hz), 1.64 (qn, 2H, J= 6.6 Hz), 1.40 (sx, 2H, J= 7.3 Hz), 0.96 (t, 3H,J= 7.3 Hz), 0.19 (s, 9H). HRMS (EI) m/z calcd for Ci 2H24S0 2Si: 260.1266; found: 260.1265. 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Chemical Shift (ppm) 'H NMR (CDCI3, 400 MHz) spectrum of compound 32a at 298 K Spectrum also contains the unidentified byproduct 128 Reaction of Benzylthiol (10) and Ethylpropiolate (22) 33c Tp*Rh(PPh3)2 (39 mg, 0.03 mmol) was weighed out using a spatula into a 5 mL vial. Next, 840 uL of a 1:1 DCE:toluene mixture was added via micropipette. To this solution, benzylthiol (136 uL, 1.15 mmol) and ethylpropiolate (106 uL, 1.05 mmol) were added sequentially via micropipette. After stirring for 48 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. ! H NMR analysis indicated the formation of the ^-linear (33b) and Z-linear (33c) isomers in a 2.5:1 ratio in 59% combined conversion relative to the benzylthiol starting material. Table 3.19. Hydrothiolation of benzylthiol with ethylpropiolate catalyzed by complexes 1 and 4 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 24 h 33b: 33c 5 9 % a (2.5:1) 2 TpRh(PPh 3 ) 2 24 h 33b: 33c 67% (1:2.5) Percent conversion with respect to remaining thiol. 129 Zs-linear (33b): clear oil; 10% ethyl acetate/petroleum ether used as eluant for flash chromatography. *H NMR (CDCI3, 300 MHz): 5 7.65 (d, 1H, J= 15.0 Hz), 7.29-7.11 (m, 5H), 5.76 (d, 1H, J= 15.0 Hz), 4.11 (q, 2H, J = 7.0 Hz), 3.94 (s, 2H), 1.22(t,2H, J=7.0Hz). 1 3C{'H} NMR (CDC13, 75 MHz):6 165.3, 146.1, 135.7, 129.3, 128.7, 127.9, 114.6,60.4,36.7, 14.5. HRMS (EI) m/z calcd for C, 2Hi40 2S: 222.3068; found: 222.0715. Z-linear (33c): clear oil; 10% ethyl acetate/petroleum ether used as eluant for flash chromatography. 'H NMR (CDC13, 300 MHz): 5 7.27 - 7.11 (m, 5H), 6.97 (d, 1H, J = 10.2 Hz), 5.76 (d, 1H, J= 10.2 Hz), 3.65 (q, 2H, J= 7.7 Hz), 3.87 (s, 2H), 1.69 (t, 2H, J = 1.1 Hz). 1 3C{'H} NMR (CDCI3, 75 MHz): 5 148.6, 138.8, 137.3, 129.1, 128.5, 127.6, 113.8,62.1,39.6, 14.4. HRMS (EI) m/z calcd for C 1 2 H, 4 0 2 S: 222.3068; found: 222.0715. 130 Chemical Shift (ppm) 'H NMR (CDCI3, 300 MHz) spectrum of compound 33b at 298 K 168 160 152 144 136 128 120 112 104 96 80 72 64 56 Chemical Shift (ppm) 1 3C{'H} NMR (CDC13, 75 MHz) spectrum of compound 33b at 298 K 131 Compound 33c observed in situ as mixture with 33b 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Chemical Shift (ppm) 'H NMR (CDCI3, 300 MHz) spectrum of compound 33c at 298 K 52 144 "' ' "l36 1 2 8 1 2 0 112* "'"/I!04 96 " " ' " ' 8BI '""' 60 72 64 56 48 4 0 3 2 2 4 1 6 8 0 Chemical Shift (ppm) 1 3C{'H} NMR (CDCI3, 75 MHz) spectrum of compound 33c at 298 K 132 Reaction of Cyclopentylthiol (15) and 1-Ethynylcyclohexene (23) | )—SH + 3 mol% XRh(PPh3)2 1,3,5-trimethoxybenzene s 15 23 DCE:PhCH3, rt L J ^ 34a Tp Rh(PPh3)2 (10 mg, 0.01 mmol) was weighed out using a spatula into a 5 mL vial. 1,3,5-Trimethoxybenzene, (17 mg, 0.10 mmol) was added using a spatula and 250 uL 1:1 DCE:toluene was added via micropipette. To this solution, cyclopentylthiol (37 uL, 0.34 mmol) and 1-ethynylcyclohexene (36 uL, 0.31 mmol) were added sequentially via micropipette. After stirring for 3 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. 'H NMR analysis indicated the formation of the branched (34a) isomer in 56% yield. An additional 5% yield of an unidentified product was also observed. Table 3.20. Hydrothiolation of cyclopentylthiol with 1 -ethynylcyclohexene catalyzed by complexes 1 and 4-7 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 3 h 34a 56% a 2 TpRh(PPh 3 ) 2 24 h - no rxn 3 T p M e R h ( P P h 3 ) 2 2 h 34a 48% 4 T p p h R h ( P P h 3 ) 2 3 h 34a 60% 5 T p P h ' M e R h ( P P h 3 ) 2 3 h 34a 80% a a An additional -5-10% yield of an unidentified byproduct was observed. 133 Branched (34a): light yellow oil; 5% ethyl acetate/petroleum ether used as eluant for flash chromatography. 'H NMR (CDC1 3 , 300 MHz): 5 6.31-6.20 (m, 1H), 5.29 (s, 1H), 4.99 (s, 1H), 3.35-3.40 (m, 1H), 2.25-2.23 (m, 2H), 2.16-2.15 (m, 2H), 2.02-1.99 (m, 2H), 1.76-1.66 (m, 10H). 1 3C{'H} NMR (CDCI3, 75 MHz): 5 162.5, 128.1, 109.1, 93.9, 56.3, 51.4, 44.6, 34.1', 26.0, 25.7, 23.9. HRMS (EI) m/z calcd for C1 3H2oS: 208.1286; found: 208.1279. 134 s ! o 7 ! 5 7 . 0 6 . 5 ' " ' e ' o 5 . 5 ' " ' " ' 5 . 0 4 . 5 4 . 0 3 . 5 3 * 0 2 . 5 z ' o ' ' ' " " ' l ! s 1 0 0 . 5 0 Chemical Shifl (ppm) 'H NMR (CDCI3, 300 MHz) spectrum of compound 34a at 298 K 135 Reaction of Benzylthiol (10) and 1-Phenyl-l-Propyne (24) 3 mol% XRh(PPh3)2 SH CH 3 35a + 10 24 1,3,5-trimethoxybenzene DCE:PhCH3, rt + S CH3 35b Tp*Rh(PPh3)2 (0.005 mmol, 44 iaL of a 0.12M stock solution in a 1:1 DCE:toluene mixture) was added to a 5 mL vial. 1,3,5-Trimethoxybenzene, (8 mg, 0.05 mmol, 81 uL of a 0.62 M stock solution in a 1:1 DCE:toluene mixture) was added via micropipette. To this solution, benzene thiol (19 uL, 0.165 mmol) and 1 -phenyl- 1-propyne (19 uL, 0.15 mmol) were added sequentially via micropipette. After stirring for 2 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. 'lT NMR analysis indicated the formation of the branched (35a) and iT-linear (35b) isomers in a 1:3.5 ratio in 70% combined yield. 136 Table 3.21. Hydrothiolation of benzylthiol with 1-phenyl-1-propyne catalyzed by complexes 1 and 5-7 Entry Complex Time Ratio Yield 1 Tp*Rh(PPh 3 ) 2 4 h 35a : 35b (1:3.5) 70% 2 T p M e R h ( P P h 3 ) 2 1 h - no rxn 3 T p P h R h ( P P h 3 ) 2 1 h 35a : 35b (1:1) 11% 4 T p p h ' M e R h ( P P h 3 ) 2 1 h 35a : 35b (1:1) 24% 35a: Characterization matches previously reported data.' 35b: Characterization matches previously reported data. 137 Reaction of Benzylthiol (10) and fert-Butylacetvlene (20) \ - 3 mol% XRh(PPh3)2 36a Kj > ^ + / - DCE:PhCH3, rt n 10 20 36b BpPvh(PPh3)2 (12 mg, 0.016 mmol) was weighed out using a spatula into a 20 mL vial. Next, 3.0 mL of a 1:1 DCE:toluene mixture was added via micropipette. To this solution, benzylthiol (65 uL, 0.55 mmol) and tert-butylacetylene (62 uL, 0.50 mmol) were added sequentially via micropipette. After stirring for 24 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. 'H NMR analysis indicated the formation of the branched (36a) and /^-linear (36b) isomers in a 1:2 ratio in 35% combined conversion relative to the benzylthiol starting material. Table 3.22. Hydrothiolation of benzylthiol with tert-butylacetylene catalyzed by complexes 2 and 3 Entry Complex Time Ratio Yield a 1 BpRh(PPh 3 ) 2 24 h 36a : 36b 35% (1:2) 2 Bp*Rh(PPh 3 ) 2 4 h 36a 28% b a Percent yield with respect to remaining thiol. b Solvent = DCE. Branched (36a): Characterization matches previously reported data. CO is-linear (36b): Characterization matches previously reported data. 138 Reaction of Benvlthiol (10) and 1-Ethynylcyclohexene (23) 3 mol% XRh(PPh3)2 10 23 DCE:PhCH3, rt BpRh(PPh3)2 (7 mg, 0.009 mmol) was weighed out using a spatula into a 20 mL vial. Next, 1.5 mL of a 1:1 DCE:toluene mixture was added via micropipette. To this solution, benzylthiol (33 uL, 0.28 mmol) and 1 -ethynylcyclohexene (29 uL, 0.25 mmol) were added sequentially via micropipette. After stirring for 48 hours at room temperature, the reaction was concentrated and the residue dissolved in CDC13. *H NMR analysis indicated the formation of the branched (37a) and is-linear (37b) isomers in a 1:3 ratio in 54% combined conversion relative to the benzylthiol starting material. Table 3.23. Hydrothiolation of benzylthiol with 1-ethynylcyclohexene catalyzed by complexes 2 and 3 Entry Complex Time Ratio Y i e l d a 1 BpRh(PPh 3 ) 2 48 h 37a : 37b 54% (1:3) 2 Bp*Rh(PPh 3 ) 2 24 h 37a : 37b (7.5:1) 53% b a Percent conversion with respect to remaining thiol. b Solvent = DCE. Branched (37a): Characterization matches previously reported data. 8m is-linear (37b): Characterization matches previously reported data. 8o 139 Reaction of Propane Thiol (12) and Phenylacetylene (17) BpRh(PPh3)2 (0.03 mmol, 600 uL of a 0.05M stock solution in a 1:1 DCE:toluene mixture) was added to a 5 mL vial. 1,3,5-Trimethoxybenzene, (56 mg, 0.33 mmol, 200 uL of a 1.6 M stock solution in a 1:1 DCE:toluene mixture) was added via micropipette. To this solution, propane thiol (100 uL, 1.1 mmol) and phenylacetylene (110 uL, 1.1 mmol) were added sequentially via micropipette. After stirring for 48 hours at room temperature, the reaction was concentrated and the residue dissolved in CDCI3. 'H NMR analysis indicated the formation of the branched (38a) and is-linear (38b) isomers in a 1:1 ratio in 6% combined yield. Branched (38a): Characterization matches previously reported data.8"1 ^-linear (38b): 'H NMR (CDCI3, 300 MHz): 8 7.39-7.21 (m), 6.78 (d, 1H, J= 15.5 Hz), 6.53 (d, 1H, J= 15.5 Hz), 2.80 (t, 2H, J = 7.3 Hz), 1.80-1.61 (m), 0.83 (t, 3H, J = 7.3 Hz). 140 Chapter 4 - Summary, Conclusions and Future Work 4.1 Summary This thesis covers two areas: the solution and solid state structures of rhodium pyrazolylborate complexes and their utility in catalytic alkyne hydrothiolation. Pyrazolylborate complexes were chosen as they are easily manipulated and have versatility with respect to substitution on and the number of pyrazolyl rings attached to the boron. As well, their highly electron-rich nature made them good candidates for the use in hydrothiolation reactions with alkyl thiols. A series of bis- and tris(pyrazolyl)borate complexes (1-7) were synthesized and structurally characterized. These include bis(pyrazolyl)borate complexes Bp*Rh(PPh3)2 (2) and BpRh(PPh3)2 (3) and tris(pyrazolyl)borate complexes Tp*Rh(PPh3)2 (1), TpRh(PPh3)2 (4), TpM eRh(PPh3)2 (5), TpphRh(PPh3)2 (6) and TpP h'M eRh(PPh 3) 2 (7). These were all synthesized by modified literature methods with higher yields than have previously been reported. The crystals used to obtain X-ray structures of known complexes 2 and 4 and new complexes 5-7 were obtained by layering a saturated solution of each complex in toluene with hexanes and leaving the resulting biphasic solution at -35 °C for approximately one week. Tris(pyrazolyl)borate complexes have been cited in the literature as adopting certain structural geometries based on the solvent system as well as the substitution around the pyrazolyl rings. 1 3 ' 1 4 ' 2 g a The solid state structures of the complexes appear to be in agreement with the previously reported literature data. Complexes 1, 5 and 7, which have 141 substituents in the 5-position, are all in form B, where the third uncoordinated pyrazolyl ring is located overtop of the rhodium atom. Complexes 4 and 6, which lack substitution in the 5-positon, favor form A, where the third uncoordinated pyrazolyl ring is rotated away from the rhodium centre. Al l seven complexes were tested in a series of hydrothiolation reactions. Common reactivity trends were found with respect to substitution and number of pyrazolyl rings on the boron. The methyl substituted bis(pyrazolyl)borate complex 2 gave better regioselecitvity than complex 3, which lacked substitution on the pyrazolyl rings. The majority of tris(pyrazolyl)borate complexes (1, 6 and 7) were superior with respect to yield and regioselectivity in comparison to the bis(pyrazolyl)borate complexes (2 and 3). Tris(pyrazolyl)borate complexes with substitution on all pyrazolyl rings at both the 3-and 5-positions (1 and 7) were superior with respect to yield and regioselectivity to those with substitution only at the 3-position (5 and 6). Tris(pyrazolyl)borate complex 4, which lacked substitution on the pyrazolyl rings, favored the Z-linear isomer and therefore possibly goes through a different mechanism. Consequently, the ability to adopt a K 3 -coordinated intermediate during the postulated catalytic cycle and substitution at both the 3- and 5-positions of the pyrazolyl rings seems to be important for the regioselectivity and yields of hydrothiolation reactions. It is also interesting to note that all seven complexes catalyzed alkyne hydrothiolation reactions using alkyl thiols. 142 4.2 Future Work In this thesis, work concerning the synthesis, structure and hydrothiolation activity of rhodium pyrazolylborate complexes has been presented. Additional studies are expected to reveal greater insight into the catalytic activity. Mechanistic investigations are currently being studied within our group. This will presumably provide evidence as to whether tris(pyrazolyl)borate complexes go through the postulated K3-coordinated intermediate and explain how the substitution on the pyrazolyl rings affects the rate, yield and selectivity of the reaction. Additionally, the identity of the byproduct should be determined. Using the mechanistic information along with the byproduct identity, perhaps conditions can be found that minimize the formation of this compound. Furthermore, the scope of the hydrothiolation reaction can be expanded to include more examples of aryl thiols and as well as a variety of functionalized substrates. The rhodium pyrazolylborate complexes have been shown to decompose after prolonged reaction times as shown in the 3 1P{'H}NMR spectra. Complex 7, in particular, produced a thermal decomposition product that was presumably irreversible because it remained upon cooling back to room temperature. This product showed a rhodium hydride peak in the 'H NMR spectrum. Therefore, the identity of the decomposition products should be investigated and compared to the known orthometallation product.28j Electron withdrawing (ie. nitro, cyano, halo etc.) or electron donating (hydroxy, methoxy) substituents can be added to the 3-, 4- or 5-positions on the pyrazolyl rings. The catalytic activity of complexes containing pyrazolyl rings with these electron withdrawing or electron donating substituents can then be studied. Furthermore, other ligand systems such as monoanionic tridentate phosphine ligands or 143 tris(pyrazolyl)methane ligands can be synthesized. These ligands can be used to form rhodium complexes and their catalytic activity tested in hydrothiolation reactions. Although hydrothiolation reactions are a starting point to test the ability of rhodium pyrazolylborate complexes as effective catalysts other reactions can also be examined. For example, activation of H-X bonds (X = heteroatom) can be investigated. Our group has demonstrated the use of Tp*Pvh(PPh3)2 in P-H bond activation reactions and are currently studying O-H bond activation reactions. Using alkyne hydrothiolation reactions we have the potential to produce vinyl sulfide products that are not commercially available or readily synthesized by other means. This is an important advance as vinyl sulfides are precursors to many functionalized molecules and can be used as synthetic intermediates as described in Chapter 1. There are a variety of directions available for continuing studies in this area of research. From mechanistic investigations to substrate scope, ligand design and H-X bond activation reactions. 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Tetrahedron Lett. 2006, 47, 1217-1220. (58) Benati, L.; Capella, L.; Montevecchi, P. C.; Spagnolo, P. J. Org. Chem. 1994, 59, 2818-2823. (59) Still, W. C ; Kahn, M. ; Mitra, A. J. Org. Chem. 1978, 43, 2923-2925. 152 Appendix I: X-ray Crystallographic Data for Bp*Rh(PPh3)2 (2) Configuration represented in Chapter 2 Configuration including all atoms Figure 1. ORTEP diagrams of complex 2. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogens, and phenyl groups of PPh3 (in configuration represented in Chapter 2) are excluded for clarity. 153 A. Crystal Data Empirical Formula Formula Weight Crystal Color, Habit Crystal Dimensions Crystal System Lattice Type Lattice Parameters Space Group Z value Dcalc FOOO u(MoKa) B. Intensity Measurements Diffractometer Radiation Data Images Detector Position 26max No. of Reflections Measured Corrections C. Structure Solution and Refinement Structure Solution Refinement Function Minimized Least Squares Weights Anomalous Dispersion No. Observations (I>0.00a(I)) No. Variables Reflection/Parameter Ratio Residuals (refined on F 2 , all data): R l ; wR2 C 5 2 . 5 H 5 7 B N 4 P 2 R h 919.68 orange, prism 0.25 X 0.25 X 0.40 mm monoclinic primitive a = 11.168(1) A a = 90.0° b= 17.004(2) A p = 98.470(6)° c = 24.853(2) A y= 90.0° V = 4667.9(8) A 3 P2xlc (#14) 4 1.309 g/cm3 1920.00 4.74 cm"1 Bruker X8 APEX II MoKa (X = 0.71073 A ) graphite monochromated 1322 exposures @ 10.0 seconds 36.00 mm 56.4° Total: 50326 Unique: 11268 (R m t = 0.052) Absorption (Tmin = 0.802, Tmax = 0.888); Lorentz-polarization Direct Methods (SIR97) Full-matrix least-squares on F 2 I w (Fo 2 - F c 2 ) 2 w=l/(a2(Fo2)+(0.0403P) 2+ 3.468P) All non-hydrogen atoms 11268 573 19.66 0.061; 0.098 154 Goodness of Fit Indicator 1.02 No. Observations (I>2.00a(I)) 8528 Residuals (refined on F): R l ; wR2 0.039; 0.087 Max Shift/Error in Final Cycle 0.00 Maximum peak in Final Diff. Map 0.47 e"/A^ Minimum peak in Final Diff. Map -0.44 e'/A^ Table 1. Atomic Coordinates (x 104) and Equivalent Isotropic Displacement Parameters (A x 103) Atom X Y Z Ueq C1 -1026(2) 1740(2) 2262(1) 22(1) C7 801(2) 965(1) 2956(1) 20(1) C13 960(2) 2642(2) 2732(1) 22(1) C19 2169(2) 2394(2) 4100(1) 23(1) C25 621(2) 2186(2) 4883(1) 22(1) C31 542(2) 3628(1) 4235(1) 22(1) C37 -2211(3) 3109(2) 4792(1) 31(1) C38 -2354(2) 2244(2) 4718(1) 24(1) C39 -2866(2) 1713(2) 5044(1) 29(1) C40 . -2860(2) 996(2) 4789(1) 27(1) C41 -3306(3) 213(2) 4952(1) 38(1) C42 -3374(3) 2809(2) 2614(1) 36(1) C43 -3543(2) 2013(2) 2846(1) 26(1) C44 -4529(3) 1510(2) 2753(1) 34(1) C45 -4236(2) 861(2) 3073(1) 30(1) C46 -4974(3) 151(2) 3159(1) 49(1) B1 -2368(3) 532(2) 3832(1) 26(1) N1 -2028(2) 1869(1) 4291(1) 20(1) N2 -2365(2) 1091(1) 4332(1) 23(1) N3 -3110(2) 971(1) 3349(1) 24(1) N4 -2684(2) 1684(1) 3204(1) 21(1) P1 -63(1) 1891(1) 2923(1) 18(1) P2 573(1) 2551(1) 4183(1) 18(1) Rh1 -1027(1) 2053(1) 3635(1) 17(1) H1B -2810(20) -18(15) 3915(10) 20(7) H2B -1420(20) 409(16) 3723(10) 27(7) 155 Table 2. Bond Lengths (A) Atoms Length Atoms C1-P1 1.842(2) C43-C44 C7-P1 1.842(2) C44-C45 C13-P1 1.822(3) C45-N3 C19-P2 1.844(3) C45-C46 C25-P2 1.840(3) B1-N3 C31-P2 1.837(3) B1-N2 C37-C38 1.487(4) B1-H1B C38-N1 1.333(3) B1-H2B C38-C39 1.392(4) N1-N2 C39-C40 1.374(4) N1-RM C40-N2 1.342(3) N3-N4 C40-C41 1.498(4) N4-Rh1 C42-C43 1.494(4) P1-Rh1 C43-N4 1.332(3) P2-RM Table 3. Bond Angl es O Atoms Angle N1-C38-C39 109.7(2) N1-C38-C37 122.3(2) C39-C38-C37 128,0(2) C40-C39-C38 106.0(2) N2-C40-C39 108.3(2) N2-C40-C41 122.0(3) C39-C40-C41 129.7(3) N4-C43-C44 109.2(2) N4-C43-C42 121.3(2) C44-C43-C42 129.5(3) C45-C44-C43 106.4(2) N3-C45-C44 107.9(2) N3-C45-C46 122.0(3) C44-C45-C46 130.0(3) N3-B1-N2 105.2(2) N3-B1-H1B 110.8(13) N2-B1-H1B 108.5(13) N3-B1-H2B 108.2(13) N2-B1-H2B 113.7(13) H1B-B1-H2B 110.3(19) C38-N1-N2 106.8(2) C38-N1-Rh1 140.67(18) N2-N1-Rh1 112.11(15) C40-N2-N1 109.1(2) C40-N2-B1 130.3(2) Atoms N1-N2-B1 C45-N3-N4 C45-N3-B1 N4-N3-B1 C43-N4-N3 C43-N4-Rh1 N3-N4-Rh1 C13-P1-C7 C13-P1-C1 C7-P1-C1 C13-P1-Rh1 C7-P1-Rh1 C1-P1-RM C31-P2-C25 C31-P2-C19 C25-P2-C19 C31-P2-RM C25-P2-RM C19-P2-RM N4-RM-N1 N4-RM-P1 N1-RM-P1 N4-RM-P2 N1-RM-P2 P1-Rh1-P2 Length 1.387(4) 1.373(4) 1.353(3) 1.495(4) 1.547(4) 1.564(4) 1.09(3) 1.16(3) 1.384(3) 2.132(2) 1.369(3) 2.092(2) 2.2202(7) 2.2468(7) Angle 119.4(2) 108.8(2) 132.7(2) 117.6(2) 107.6(2) 135.31(18) 116.56(15) 105.46(12) 99.93(11) 98.90(11) 121.05(8) 112.49(8) 116.06(8) 105.53(11) 100.43(12) 99.36(12) 113.37(8) 110.88(8) 124.97(8) 79.84(8) 92.93(6) 164.16(6) 170.88(6) 92.91(6) 95.43(3) 156 Table 4. Anisotropic Displacement Parameters (A x 103) Atom U 1 1 U 2 2 u 3 3 u 2 3 u 1 3 U 1 2 C1 21(1) 27(1) 17(1) -4(1) 4(1) 3(1) C7 17(1) 20(1) 22(1) -2(1) 2(1) -1(1) C13 25(1) 24(1) 18(1) 2(1) 2(1) -2(1) C19 18(1) 29(1) 21(1) -5(1) 0(1) -3(1) C25 19(1) 28(1) 20(1) 1(1) 3(1) 1(1) C31 26(1) 21(1) 21(1) 0(1) 5(1) -2(1) C37 34(2) 32(2) 28(1) -6(1) 10(1) 2(1) C38 18(1) 32(1) 21(1) -4(1) 3(1) -1(1) C39 25(1) 43(2) 20(1) 1(1) 6(1) -3(1) C40 21(1) 37(2) 24(1) 8(1) 5(1) -4(1) C41 39(2) 40(2) 38(2) 13(1) 13(1) -7(1) C42 32(2) 38(2) 37(2) 8(1) 2(1) 8(1) C43 21(1) 35(1) 22(1) -2(1) 5(1) 3(1) C44 20(1) 51(2) 28(1) -2(1) -1(1) 1(1) C45 21(1) 40(2) 31(1) -10(1) 6(1) -8(1) C46 33(2) 55(2) 58(2) -8(2) 5(2) -21(2) B1 26(2) 21(1) 32(2) 1(1) 6(1) -2(1) N1 19(1) 23(1) 20(1) 0(1) 4(1) -3(1) N2 24(1) 24(1) 23(1) 2(1) 5(1) -3(1) N3 22(1) 25(1) 25(1) -4(1) 5(1) -6(1) N4 20(1) 24(1) 19(1) -1(1) 2(1) -3(1) P1 19(1) 19(1) 17(1) 1(1) 3(1) 0(1) P2 19(1) 19(1) 18(1) 0(1) 2(1) -1(1) Rh1 17(1) 17(1) 16(1) 0(1) 3(1) -1(1) Table 5. Torsional Angles (°) Atoms Angle Atoms Angle N1-C38-C39-C40 -1.2(3) C2-C1-P1-C7 60.0(2) C37-C38-C39-C40 176.2(3) C6-C1-P1-Rh1 118.7(2) C38-C39-C40-N2 0.2(3) C2-C1-P1-Rh1 -60.5(2) C38-C39-C40-C41 -179.5(3) C36-C31-P2-C25 -119.4(2) N4-C43-C44-C45 0.5(3) C32-C31-P2-C25 62.2(3) C42-C43-C44-C45 -178.9(3) C36-C31-P2-C19 137.7(2) C43-C44-C45-N3 -0.2(3) C32-C31-P2-C19 -40.7(2) C43-C44-C45-C46 176.6(3) C36-C31-P2-Rh1 2.1(2) C39-C38-N1 -N2 1.8(3) C32-C31-P2-Rh1 -176.3(2) C37-C38-N1-N2 -175.8(2) C30-C25-P2-C31 -16.4(3) C39-C38-N1 -Rh1 -169.9(2) C26-C25-P2-C31 165.8(2) C37-C38-N1 -Rh1 12.5(4) C30-C25-P2-C19 87.3(2) C39-C40-N2-N1 0.9(3) C26-C25-P2-C19 -90.5(2) C41-C40-N2-N1 -179.4(2) C30-C25-P2-RM -139.5(2) 157 Table 5. Torsional Angles (°)...continued C39-C40-N2-B1 -165.8(3) C41-C40-N2-B1 13.9(4) C38-N1-N2-C40 -1.7(3) Rh1-N1-N2-C40 172.64(16) C38-N1-N2-B1 166.7(2) RM-N1-N2-B1 -19.0(3) N3-B1-N2-C40 114.4(3) N3-B1-N2-N1 -51.2(3) C44-C45-N3-N4 -0.2(3) C46-C45-N3-N4 -177.3(3) C44-C45-N3-B1 168.4(3) C46-C45-N3-B1 -8.8(5) N2-B1-N3-C45 -106.5(3) N2-B1-N3-N4 61.3(3) C44-C43-N4-N3 -0.6(3) C42-C43-N4-N3 178.8(2) C44-C43-N4-Rh1 -171.93(19) C42-C43-N4-Rh1 7.5(4) C45-N3-N4-C43 0.5(3) B1-N3-N4-C43 -170.0(2) C45-N3-N4-Rh1 173.70(16) B1-N3-N4-Rh1 3.2(3) C14-C13-P1-C7 10.8(3) C18-C13-P1-C7 -173.28(19) C14-C13-P1-C1 -91.4(2) C18-C13-P1-C1 84.5(2) C14-C13-P1-Rh1 139.9(2) C18-C13-P1-Rh1 -44.3(2) C12-C7-P1-C13 120.3(2) C8-C7-P1-C13 -64.8(2) C12-C7-P1-C1 -136.7(2) C8-C7-P1-C1 38.1(2) C12-C7-P1-Rh1 -13.6(2) C8-C7-P1-Rh1 161.24(19) C6-C1-P1-C13 -13.2(3) C2-C1-P1-C13 167.5(2) C6-C1-P1-C7 -120.8(2) C26-C25-P2-Rh1 42.7(2) C24-C19-P2-C31 147.2(2) C20-C19-P2-C31 -33.4(2) C24-C19-P2-C25 39.4(2) C20-C19-P2-C25 -141.2(2) C24-C19-P2-Rh1 -84.4(2) C20-C19-P2-Rh1 95.0(2) C43-N4-Rh1-N1 114.9(3) N3-N4-Rh1-N1 -55.89(17) C43-N4-Rh1-P1 -79.3(2) N3-N4-Rh1-P1 109.91(16) C43-N4-Rh1-P2 77.1(5) N3-N4-RM-P2 -93.6(4) C38-N1-Rh1-N4 -125.5(3) N2-N1-Rh1-N4 63.08(16) C38-N1-Rh1-P1 170.69(19) N2-N1-Rh1-P1 -0.7(3) C38-N1-Rh1-P2 48.9(3) N2-N1-Rh1-P2 -122.49(15) C13-P1-Rh1-N4 133.82(11) C7-P1-Rh1-N4 -100.30(10) C1-P1-Rh1-N4 12.58(11) C13-P1-Rh1-N1 -164.0(2) C7-P1-Rh1-N1 -38.1(2) C1-P1-Rh1-N1 74.8(2) C13-P1-Rh1-P2 -42.53(10) C7-P1-Rh1-P2 83.35(9) C1-P1-Rh1-P2 -163.77(9) C31-P2-Rh1-N4 -56.4(4) C25-P2-Rh1-N4 62.1(4) C19-P2-Rh1-N4 -179(19) C31-P2-Rh1-N1 -93.46(10) C25-P2-Rh1-N1 25.03(10) C19-P2-Rh1-N1 143.67(12) C31-P2-Rh1-P1 100.02(9) C25-P2-Rh1-P1 -141.49(9) C19-P2-Rh1-P1 -22.85(11) 158 Appendix II: X-ray Crystallographic Data for TpRh(PPh3)2 (4) Configuration including all atoms Figure 1. ORTEP diagrams of complex 4. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPh3 (in configuration represented in Chapter 2) are excluded for clarity. 159 A. Crystal Data Empirical Formula Formula Weight Crystal Color, Habit Crystal Dimensions Crystal System Lattice Type Lattice Parameters Space Group Z value Dcalc FOOO l^(MoKa) B. Intensity Measurements Diffractometer Radiation Data Images Detector Position 29max No. of Reflections Measured Corrections C. Structure Solution and Refinement Structure Solution Refinement Function Minimized Least Squares Weights Anomalous Dispersion No. Observations (I>0.00a(I)) No. Variables Reflection/Parameter Ratio C 5 2H 4 8BN 6P 2RhFeP 932.62 red, irregular 0.20X0.20X0.10 mm triclinic primitive a = 12.2490(9) A a = 112.004(3) 0 b= 13.637(1) A (3 = 98.051(3)° c= 14.971(1) A 7 = 90.387(3)° V = 2291.0(3) A 3 P -1 (#2) 2 1.352 g/cm3 964.00 4.86 cm"1 Bruker X8 APEX MoKa(X = 0.71073 A ) graphite monochromated 3504 exposures @ 5.0 seconds 38.01 mm 55.8° Total: 77370 Unique: 10812 ( R i n t = 0.042) Absorption (Tmjn = 0.858, Tmax = 0.953); Lorentz-polarization Direct Methods (SIR97) Full-matrix least-squares on F 2 S w (Fo 2 - F c 2 ) 2 w=l/(a2(Fo2)+(0.0287P) 2+0.3727P) All non-hydrogen atoms 10812 603 17.93 160 Residuals (refined on F 2 , all data): R l ; wR2 0.036; 0.064 Goodness of Fit Indicator 1.11 No. Observations (I>2.00a(I)) 9032 Residuals (refined on F): R l ; wR2 0.027; 0.063 Max Shift/Error in Final Cycle 0.00 Maximum peak in Final Diff. Map 0.37 e7A 3 Minimum peak in Final Diff. Map -0.35 e~/A3 Table 1. Atomic Coordinates (x 104) and Equivalent Isotropic Displacement Parameters (A x 103) Atom X Y Z Ueq C1 1746(1) 1039(1) 3272(1) 19( r C7 2385(1) 3099(1) 3637(1) 20(1 C13 2279(1) 1426(1) 1632(1) 20(1 C 19 1584(1) 3717(1) 1421(1) 21(1 C25 -2(1) 4976(1) 2488(1) 22(1 C31 -693(1) 3350(1) 599(1) 21(1 C37 -2709(1) 2902(1) 1611(1) 29(1 C38 -3739(1) 2984(2) 1915(1) 33(1 C39 -3580(1) 2757(1) 2747(1) 28(1 C40 -666(1) -62(1) 2110(1) 25(1 C41 -1297(2) -648(1) 2461(1) 31(1 C42 -1840(1) 98(1) 3128(1) 29(1 C43 -4142(2) 1787(2) 4931(2) 42(1 C44 -3522(2) 2570(2) 5734(2) 44(1 C45 -2609(2) 2798(2) 5391(1) 34(1 B1 -1913(2) 2192(2) 3727(1) 22(1 N1 -1959(1) 2646(1) 2216(1) 22(1 N2 -2513(1) 2556(1) 2922(1) 21(1 N3 -1535(1) 1065(1) 3169(1) 22(1 N4 -806(1) 979(1) 2535(1) 20(1 N5 -2700(1) 2174(1) 4427(1) 27(1 N6 -3663(1) 1534(1) 4132(1) 36(1 P1 1521(1) 1999(1) 2668(1) 17(1 P2 210(1) 3583(1) 1766(1) 18(1 Rh1 -236(1) 2316(1) 2303(1) 17(1 H1 -1176(12) 2756(12) 4143(11) 12(4 161 Table 2. Bond Lengths (A) Atoms Length Atoms C1-P1 1.8521(15) C43-C44 C7-P1 1.8422(16) C44-C45 C13-P1 1.8397(16) C45-N5 C19-P2 1.8553(16) B1-N5 C25-P2 1.8414(16) B1-N3 C31-P2 1,8474(16) B1-N2 C37-N1 1.340(2) B1-H1 C37-C38 1.392(2) N1-N2 C38-C39 1.381(2) N1-Rh1 C39-N2 1.347(2) N3-N4 C40-N4 1.343(2) N4-RM C40-C41 1.390(2) N5-N6 C41-C42 1.381(3) P1-Rh1 C42-N3 1.346(2) P2-RM C43-N6 1.335(2) Table 3. Bond Atoms N1-C37-C38 C39-C38-C37 N2-C39-C38 N4-C40-C41 C42-C41-C40 N3-C42-C41 N6-C43-C44 C45-C44-C43 N5-C45-C44 N5-B1-N3 N5-B1-N2 N3-B1-N2 N5-B1-H1 N3-B1-H1 N2-B1-H1 C37-N1-N2 C37-N1-Rh1 N2-N1-RM C39-N2-N1 C39-N2-B1 N1-N2-B1 C42-N3-N4 C42-N3-B1 N4-N3-B1 C40-N4-N3 les (°) Angle 110.89(15) 104.87(15) 108.56(15) 110.92(15) 104.62(15) 108.63(16) 112.14(19) 104.74(18) 108.09(19) 111.70(14) 110.16(13) 105.52(13) 109.6(8) •110.5(8) 109.3(8) 105.97(13) 136.79(11) 117.20(9) 109.72(13) 129.64(14) 120.52(12) 109.90(13) 132.53(14) 117.41(13) 105.92(13) Atoms C40-N4-RM N3-N4-RM C45-N5-N6 C45-N5-B1 N6-N5-B1 C43-N6-N5 C13-P1-C7 C13-P1-C1 C7-P1-C1 C13-P1-RM C7-P1-RM C1-P1-RH1 C25-P2-C31 C25-P2-C19 C31-P2-C19 C25-P2-RM C31-P2-RM C19-P2-RM N4-RM-N1 N4-RM-P1 N1-Rh1-P1 N4-RM-P2 N1-RM-P2 P1-RM-P2 Length 1.391(3) 1.374(3) 1.361(2) 1.526(2) 1.558(2) 1.564(2) 1.126(15) 1.3741(18) 2.1575(13) 1.3661(18) 2.1111(13) 1.378(2) 2.2299(4) 2.2558(4) Angle 132.63(11) 121.24(9) 110.12(15) 126.85(16) 122.94(14) 104.91(16) 109.05(7) 101.25(7) 95.69(7) 116.17(5) 116.23(5) 115.72(5) 102.16(7) 100.96(7) 100.48(7) 119.22(6) 108.34(5) 122.50(5) 83.37(5) 91.52(3) 169.58(4) 169.18(4) 92.98(4). 93.605(15) 162 Table 4. Anisotropic Displacement Parameters (A x 103) Atom U 1 1 U 2 2 u 3 3 u 2 3 u 1 3 U 1 2 C1 20(1) 16(1) 19(1) 8(1) -1(1) 1(1) C7 23(1) 19(1) 22(1) 12(1) 3(1) 1(1) C13 23(1) 20(1) 23(1) 13(1) 7(1) 8(1) C19 22(1) 20(1) 27(1) 15(1) 8(1) 6(1) C25 23(1) 21(1) 24(1) 11(1) 4(1) 6(1) C31 21(1) 25(1) 22(1) 14(1) 6(1) 2(1) C37 22(1) 38(1) 36(1) 25(1) 4(1) 5(1) C38 19(1) 46(1) 45(1) 30(1) 3(1) 7(1) C39 19(1) 31(1) 36(1) 15(1) 9(1) 5(1) C40 27(1) 22(1) 28(1) 10(1) 5(1) 5(1) C41 37(1) 20(1) 39(1) 14(1) 6(1) 2(1) C42 29(1) 29(1) 37(1) 21(1) 7(1) -1(1) C43 37(1) 54(1) 58(1) 40(1) 26(1) 21(1) C44 60(1) 47(1) 42(1) 30(1) 32(1) 33(1) C45 49(1) 30(1) 29(1) 16(1) 12(1) 18(1) B1 23(1) 23(1) 23(1) 11(1) 4(1) 3(1) N1 20(1) 25(1) 26(1) 14(1) 5(1) 4(1) N2 18(1) 22(1) 24(1) 11(1) 5(1) 3(1) N3 21(1) 22(1) 26(1) 13(1) 5(1) 3(1) N4 19(1) 20(1) 24(1) 10(1) 5(1) 4(1) N5 28(1) 31(1) 28(1) 16(1) 9(1) 7(1) N6 28(1) 46(1) 43(1) 27(1) 12(1) 4(1) P1 17(1) 17(1) 20(1) 9(1) 3(1) 3(1) P2 19(1) 19(1) 21(1) 11(1) 5(1) 4(1) Rh1 15(1) 18(1) 21(1) 11(1) 3(1) 3(1) 163 Table 5. Torsional Angles (°) Atoms Angle N1-C37-C38-C39 -0.2(2) C37-C38-C39-N2 0.2(2) N4-C40-C41-C42 0.23(19) C40-C41-C42-N3 -0.45(19) N6-C43-C44-C45 -0.1(2) C43-C44-C45-N5 0.2(2) C38-C37-N1-N2 0.2(2) C38-C37-N1-Rh1 177.75(13) C38-C39-N2-N1 -0.05(19) C38-C39-N2-B1 -175.80(16) C37-N1-N2-C39 -0.10(18) Rh1-N1-N2-C39 -178.21(11) C37-N1-N2-B1 176.10(14) RM-N1-N2-B1 -2.00(18) N5-B1-N2-C39 -5.5(2) N3-B1-N2-C39 115.21(18) N5-B1-N2-N1 179.14(13) N3-B1-N2-N1 -60.15(18) C41-C42-N3-N4 0.52(18) C41-C42-N3-B1 175.71(16) N5-B1-N3-C42 6.6(2) N2-B1-N3-C42 -113.13(18) N5-B1-N3-N4 -178.52(12) N2-B1-N3-N4 61.78(17) C41-C40-N4-N3 0.07(18) C41-C40-N4-Rh1 -174.50(11) C42-N3-N4-C40 -0.36(17) B1-N3-N4-C40 -176.37(13) C42-N3-N4-RM 174.97(10) B1-N3-N4-Rh1 -1.04(17) C44-C45-N5-N6 -0.20(19) C44-C45-N5-B1 176.43(15) N3-B1-N5-C45 128.26(16) N2-B1-N5-C45 -114.82(17) N3-B1-N5-N6 -55.50(19) Atoms Angle C6-C1-P1-C7 -97.13(14) C2-C1-P1-C7 78.10(13) C6-C1-P1-Rh1 140.12(12) C2-C1-P1-Rh1 -44.65(13) C26-C25-P2-C31 107.90(14) C30-C25-P2-C31 -68.45(14) C26-C25-P2-C19 -148.73(13) C30-C25-P2-C19 34.92(14) C26-C25-P2-Rh1 -11.39(15) C30-C25-P2-Rh1 172.26(11) C36-C31-P2-C25 -170.89(13) C32-C31-P2-C25 5.42(16) C36-C31-P2-C19 85.36(14) C32-C31-P2-C19 -98.33(15) C36-C31-P2-Rh1 -44.20(14) C32-C31-P2-Rh1 132.10(13) C24-C19-P2-C25 -135.95(13) C20-C19-P2-C25 44.53(14) C24-C19-P2-C31 -31.24(14) C20-C19-P2-C31 149.24(13) C24-C19-P2-Rh1 88.58(13) C20-C19-P2-Rh1 -90.94(13) C40-N4-Rh1-N1 128.30(14) N3-N4-Rh1-N1 -45.59(11) C40-N4-Rh1-P1 -60.81(14) N3-N4-Rh1-P1 125.30(10) C40-N4-Rh1-P2 57.5(3) N3-N4-Rh1-P2 -116.38(18) C37-N1-Rh1-N4 -131.17(17) N2-N1-Rh1-N4 46.16(11) C37-N1-Rh1-P1 167.77(15) N2-N1-Rh1-P1 -14.9(3) C37-N1-RM-P2 38.61(17) N2-N1-Rh1-P2 -144.06(10) C13-P1-Rh1-N4 104.30(7) 164 Table 5. Torsional Angles (°)...continued N2-B1-N5-N6 61.42(19) C44-C43-N6-N5 0.0(2) C45-N5-N6-C43 0.14(18) B1-N5-N6-C43 -176.66(15) C14-C13-P1-C7 7.27(16) C18-C13-P1-C7 -175.87(11) C14-C13-P1-C1 -92.85(15) C18-C13-P1-C1 84.01(12) C14-C13-P1-Rh1 140.94(13) C18-C13-P1-Rh1 -42.20(13) C12-C7-P1-C13 -51.03(15) C8-C7-P1-C13 138.76(12) C12-C7-P1-C1 52.96(15) C8-C7-P1-C1 -117.25(13) C12-C7-P1-Rh1 175.33(12) C6-C1-P1-C13 13.62(15) C2-C1-P1-C13 -171.15(12) C7-P1-Rh1-N4 -125.35(7) C1-P1-Rh1-N4 -14.25(7) C13-P1-Rh1-N1 164.7(2) C7-P1-Rh1-N1 -64.9(2) C1-P1-Rh1-N1 46.2(2) C13-P1-Rh1-P2 -66.18(6) C7-P1-Rh1-P2 64.17(6) C1-P1-Rh1-P2 175.28(6) C25-P2-Rh1-N4 132.11(19) C31-P2-Rh1-N4 16.0(2) C19-P2-Rh1-N4 -100.0(2) C25-P2-RM-N1 62.17(7) C31-P2-Rh1-N1 -53.90(7) C19-P2-Rh1-N1 -169.91(7) C25-P2-Rh1-P1 -109.75(6) C31-P2-Rh1-P1 134.17(5) C19-P2-Rh1-P1 18.17(6) 165 Appendix III: X-ray Crystallographic Data for TpMe*Rh(PPh3)2 (5*) C16 Configuration including all atoms Figure 1. ORTEP diagrams of complex 5*. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPh3 (in configuration represented in Chapter 2) are excluded for clarity. 166 A. Crystal Data Empirical Formula Formula Weight Crystal Color, Habit Crystal Dimensions Crystal System Lattice Type Lattice Parameters Space Group Z value Dcalc FOOO (i(MoKa) B. Intensity Measurements Diffractometer Radiation Data Images Detector Position 26max No. of Reflections Measured Corrections C. Structure Solution and Refinement Structure Solution Refinement Function Minimized Least Squares Weights Anomalous Dispersion No. Observations (I>0!00CT(I)) No. Variables Reflection/Parameter Ratio C 4 8H 4 6 BN 6 P 2 Rh 882.57 orange, prism 0.10X0.15X0.15mm triclinic primitive a= 11.2313(7) A a = 83.741(3)° b= 12.5804(7) A p = 73.336(3)° c= 16.992(1) A y = 65.135(2)° V = 2086.6(2) A 3 P-\ (#2) 2 1.405 g/cm3 912.00 5.29 cm"1 Bruker X8 APEX II MoKa (K = 0.71073 A) graphite monochromated 1814 exposures @ 10.0 seconds 36.00 mm 50.2° Total: 32934 Unique: 7377 ( R i n t = 0.042) Absorption (T m m = 0.883, T m a x = 0.945); Lorentz-polarization Direct Methods (SIR97) Full-matrix least-squares on F 2 £ w (Fo 2 - F c 2 ) 2 w=l/(o2(Fo2)+(0.0228P) 2 + 2.0617P) All non-hydrogen atoms 7377 530 13.92 167 Residuals (refined on F 2 , all data): RI; wR2 0.040; 0.072 Goodness of Fit Indicator 1.07 No. Observations (I>2.00CT(I)) 6335 Residuals (refined on F): RI; wR2 0.037; 0.086 Max Shift/Error in Final Cycle 0.00 Maximum peak in Final Diff. Map 0.38 e~/A3 Minimum peak in Final Diff. Map -0.31 e~/A3 Table 1. Atomic Coordinates (x 104) and Equivalent Isotropic Displacement Parameters (A x 103) Atom X Y Z Ueq C1 7416(3) 2969(2) 1947(2) 20(1] C7 5658(3) 2947(2) 3527(2) 21(1 C13 4936(3) 4986(2) 2451(2) 22(1 C19 2262(3) 4007(^) 3794(2) 23(1 C25 1520(3) 4297(2) 2261(2) 23(1 C31 1699(3) 2260(2) 3267(2) 23(1 C37 3215(3) 987(2) 1506(2) 23(1 C38 3492(3) -46(2) 1129(2) 26(1 C39 4872(3) -680(2) 996(2) 22(1 C40 5731(3) -1874(2) 610(2) 31(1 C41 8320(3) 496(2) 189(2) 22(1 C42 8128(3) 1573(2) -150(2) 23(1 C43 6901(3) 2352(2) 344(2) 20(1 C44 6134(3) 3629(2) 224(2) 27(1 C45 6111(3) -817(2) 2834(2) 26(1 C46 6752(3) -1209(2) 3452(2) 31(1 C47 8037(3) -1201(2) 3119(2) 31(1 C48 9184(4) -1540(3) 3509(2) 47(1 B1 6872(3) -377(3) 1281(2) 22(1 N1 4343(2) 1010(2) 1601(1) 20(1 N2 5383(2) -48(2) 1280(1) 20(1 N3 7278(2) 612(2) 860(1) 19(1 N4 6403(2) 1771(2) 964(1) 17(1 N5 6973(2) -589(2) 2174(1) 22(1 N6 8190(2) -839(2) 2340(2) 27(1 P1 5589(1) 3378(1) 2462(1) 18(1 P2 2619(1) 3201(1) 2847(1) 19(1 Rh1 4721(1) 2352(1) 1983(1) 16(1 H1 7520(20) -1190(20) 908(15) 17(7 168 Table 2. Bond Lengths (A) Atoms Length C1-P1 1.849(3 C7-P1 1.847(3 C13-P1 1.838(3 C19-P2 1.850(3 C25-P2 1.841(3 C31-P2 1.844(3 C37-N1 1.335(3 C37-C38 1.386(4 C38-C39 1.374(4 C39-N2 1.349(3 C39-C40 1.500(4 C41-N3 1.349(3 C41-C42 1.368(4 C42-C43 1.394(4 C43-N4 1.340(3 C43-C44 1.494(4 Atoms Length C45-N5 1.349(3) C45-C46 1.374(4) C46-C47 1.396(4) C47-N6 1.338(4) C47-C48 1.499(4) P1-RM 2.2404(7) P2-RM 2.2585(7) RM-N4 2.084(2) Rh1-N1 2.110(2) B1-N3 1.538(4) B1-N5 1.539(4) B1-N2 1.544(4) B1-H1 1.11(2) N1-N2 1.386(3) N3-N4 1.369(3) N5-N6 1.373(3) 169 Table 3. Bond Angles (°) Atoms Angle N1-C37-C38 111.5(2) C39-C38-C37 105.1(2) N2-C39-C38 108.4(2) N2-C39-C40 123.2(2) C38-C39-C40 128.4(3) N3-C41-C42 109.1(2) C41-C42-C43 105.3(2) N4-C43-C42 109.6(2) N4-C43-C44 121.5(2) C42-C43-C44 128.7(2) N5-C45-C46 108.3(3) C45-C46-C47 104.9(3) N6-C47-C46 111.1(3) N6-C47-C48 119.8(3) C46-C47-C48 129.1(3) C13-P1-C7 106.00(12) C13-P1-C1 100.94(12) C7-P1-C1 100.67(12) C13-P1-Rh1 124.13(9) C7-P1-RM 109.76(9) C1-P1-RM 112.62(8) C25-P2-C31 103.12(12) C25-P2-C19 103.44(12) C31-P2-C19 99.58(12) C25-P2-RM 107.65(9) C31-P2-Rh1 117.27(9) C19-P2-Rh1 123.35(9) N4-Rh1-N1 82.46(8) Atoms Angle N4-Rh1-P1 91.69(6) N1-RM-P1 164.93(6) N4-RM-P2 165.68(6) N1-Rh1-P2 94.27(6) P1-RM-P2 94.66(3) N3-B1-N5 113.8(2) N3-B1-N2 107.9(2) N5-B1-N2 108.5(2) N3-B1-H1 108.4(13) N5-B1-H1 110.2(13) N2-B1-H1 107.8(13) C37-N1-N2 105.3(2) C37-N1-RM 131.98(18) N2-N1-RM 122.20(16) C39-N2-N1 109.6(2) C39-N2-B1 128.6(2) N1-N2-B1 121.8(2) C41-N3-N4 108.7(2) C41-N3-B1 126.0(2) N4-N3-B1 122.8(2) C43-N4-N3 107.2(2) C43-N4-RM 131.59(17) N3-N4-RM 121.12(16) C45-N5-N6 110.2(2) C45-N5-B1 128.6(2) N6-N5-B1 119.6(2) C47-N6-N5 105.4(2) 170 Table 4. Anisotropic Displacement Parameters (A x 103) Atom U 1 1 U 2 2 u 3 3 u 2 3 u 1 3 U 1 2 C1 21(1) 26(2) 18(1) -4(1) -5(1) -12(1) C7 18(1) 23(1) 19(1) -3(1) -1(1) -7(1) C13 26(1) 15(1) 22(2) -2(1) 1(1) -10(1) C19 15(1) 26(2) 21(2) -4(1) 2(1) -7(1) C25 20(1) 20(1) .28(2) 1(1) -5(1) -8(1) C31 23(1) 24(1) 19(2) -2(1) 0(1) -10(1) C37 18(1) 29(2) 24(2) 1(1) -8(1) -10(1) C38 26(2) 34(2) 26(2) -1(1) -9(1) -18(1) C39 30(2) 25(2) 17(1) 2(1) -6(1) -18(1) C40 36(2) 27(2) 33(2) -8(1) -4(1) -18(1) C41 16(1) 29(2) 20(2) -7(1) -3(1) -8(1) C42 19(1) 32(2) 20(2) -3(1) 0(1) -13(1) C43 23(1) 27(2) 15(1) 0(1) -7(1) -13(1) C44 30(2) 25(2) 25(2) 4(1) -7(1) -11(1) C45 27(2) 19(1) 33(2) 1(1) -6(1) -11(1) C46 44(2) 20(2) 29(2) 5(1) -12(1) -13(1) C47 42(2) 19(2) 36(2) 4(1) -20(1) -10(1) C48 55(2) 43(2) 53(2) 11(2) -36(2) -18(2) B1 19(2) 19(2) 27(2) -2(1) -6(1) -7(1) N1 20(1) 17(1) 21(1) -3(1) -4(1) -6(1) N2 19(1) 18(1) 22(1) -3(1) -4(1) -8(1) N3 15(1) 17(1) 23(1) -3(1) -6(1) -5(1) N4 15(1) 18(1) 20(1) -3(1) -4(1) -7(1) N5 23(1) 18(1) 30(1) 2(1) -10(1) -9(1) N6 26(1) 23(1) 36(2) 4(1) -15(1) -9(1) P1 19(1) 16(1) 19(1) -1(1) -3(1) -8(1) P2 16(1) 19(1) 20(1) 0(1) -2(1) -5(1) Rh1 14(1) 15(1) 18(1) -2(1) -3(1) -5(1) 171 Table 5. Torsional Angles (°) Atoms Angle Atoms Angle N1-C37-C38-C39 0.4(3) C25-P2-Rh1-N1 -90.04(11) C37-C38-C39-N2 -0.1(3) C31-P2-Rh1-N1 25.57(12) C37-C38-C39-C40 179.6(3) C19-P2-RM-N1 149.86(12) N3-C41-C42-C43 -0.9(3) C25-P2-RM-P1 102.11(9) C41-C42-C43-N4 1.8(3) C31-P2-RM-P1 -142.28(10) C41-C42-C43-C44 -174.5(3) C19-P2-RM-P1 -17.99(11) N5-C45-C46-C47 -0.1(3) C38-C37-N1-N2 -0.5(3) C45-C46-C47-N6 -0.7(3) C38-C37-N1-Rh1 171.44(19) C45-C46-C47-C48 180.0(3) N4-RM-N1-C37 -133.5(2) C14-C13-P1-C7 -130.5(2) P1-RM-N1-C37 158.70(19) C18-C13-P1-C7 51.5(3) P2-RM-N1-C37 32.5(2) C14-C13-P1-C1 124.9(2) N4-Rh1-N1-N2 37.31(18) C18-C13-P1-C1 -53.0(3) P1-RM-N1-N2 -30.5(4) C14-C13-P1-Rh1 -2.3(3) P2-RM-N1-N2 -156.71(18) C18-C13-P1-Rh1 179.78(19) C38-C39-N2-N1 -0.2(3) C8-C7-P1-C13 169.0(2) C40-C39-N2-N1 -179.9(2) C12-C7-P1-C13 -12.5(3) C38-C39-N2-B1 179.4(3) C8-C7-P1-C1 -86.2(2) C40-C39-N2-B1 -0.3(4) C12-C7-P1-C1 92.2(3) C37-N1-N2-C39 0.4(3) C8-C7-P1-Rh1 32.7(2) RM-N1-N2-C39 -172.51(17) C12-C7-P1-Rh1 -148.8(2) C37-N1-N2-B1 -179.3(2) C2-C1-P1-C13 -17.1(3) Rh1-N1-N2-B1 7.8(3) C6-C1-P1-C13 168.6(2) N3-B1-N2-C39 126.1(3) C2-C1-P1-C7 -125.8(2) N5-B1-N2-C39 -110.2(3) C6-C1-P1-C7 59.9(2) N3-B1-N2-N1 -54.3(3) C2-C1-P1-Rh1 117.3(2) N5-B1-N2-N1 69.4(3) C6-C1-P1-Rh1 -57.0(2) C42-C41-N3-N4 -0.3(3) C26-C25-P2-C31 -110.8(2) C42-C41-N3-B1 161.9(2) C30-C25-P2-C31 70.5(3) N5-B1-N3-C41 118.0(3) C26-C25-P2-C19 145.8(2) N2-B1-N3-C41 -121.5(3) C30-C25-P2-C19 -32.9(3) N5-B1-N3-N4 -82.2(3) C26-C25-P2-Rh1 13.8(2) N2-B1-N3-N4 38.3(3) C30-C25-P2-RH1 -164.9(2) C42-C43-N4-N3 -1.9(3) C36-C31-P2-C25 169.0(2) C44-C43-N4-N3 174.7(2) C32-C31-P2-C25 -12.0(3) C42-C43-N4-RM 174.45(18) C36-C31-P2-C19 -84.7(2) C44-C43-N4-RM -8.9(4) C32-C31-P2-C19 94.3(2) C41-N3-N4-C43 1.4(3) C36-C31-P2-Rh1 50.9(2) B1-N3-N4-C43 -161.5(2) C32-C31-P2-Rh1 -130.1(2) C41-N3-N4-RM -175.48(16) C24-C19-P2-C25 -33.1(3) B1-N3-N4-RM 21.7(3) C20-C19-P2-C25 151.0(2) N1-Rh1-N4-C43 131.7(2) C24-C19-P2-C31 -139.2(2) P1-Rh1-N4-C43 -62.2(2) 172 Table 5. Torsional Angles (°)...continued C20-C19-P2-C31 44.9(2) P2-Rh1-N4-C43 54.1(4) C24-C19-P2-RM 88.9(2) N1-RM-N4-N3 -52.29(17) C20-C19-P2-Rh1 -87.0(2) P1-Rh1-N4-N3 113.77(17) C13-P1-Rh1-N4 107.70(12) P2-Rh1-N4-N3 -129.9(2) C7-P1-Rh1-N4 -125.62(10) C46-C45-N5-N6 0.8(3) C1-P1-Rh1-N4 -14.36(11) C46-C45-N5-B1 166.2(2) C13-P1-Rh1-N1 174.4(2) N3-B1-N5-C45 139.1(3) C7-P1-Rh1-N1 -58.9(3) N2-B1-N5-C45 19.0(4) C1-P1-Rh1-N1 52.4(3) N3-B1-N5-N6 -56.6(3) C13-P1-Rh1-P2 -59.44(11) N2-B1-N5-N6 -176.8(2) C7-P1-Rh1-P2 67.23(9) C46-C47-N6-N5 1.1(3) C1-P1-Rh1-P2 178.50(9) C48-C47-N6-N5 -179.5(3) C25-P2-Rh1-N4 -13.9(3) C45-N5-N6-C47 -1.2(3) C31-P2-Rh1-N4 101.7(3) B1-N5-N6-C47 -168.1(2) C19-P2-Rh1-N4 -134.0(3) 173 Appendix IV: X-ray Crystallographic Data for TpPhRh(PPh3)2 (6) Configuration including all atoms Figure 1. ORTEP diagrams of complex 6. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPI13 are excluded for clarity. 174 A. Crystal Data Empirical Formula Formula Weight Crystal Color, Habit Crystal Dimensions Crystal System Lattice Type Lattice Parameters Space Group Z value Dcalc FOOO (i(MoKa) B. Intensity Measurements Diffractometer Radiation Data Images Detector Position 26max No. of Reflections Measured Corrections C. Structure Solution and Refinement C 6 8 H64BN 6 P 2 Rh 1140.91 orange, irregular 0.035X0.10X0.20 mm monoclinic primitive a = 17.4909(9) A a = 90.0 ° b= 18.524(1) A p = 107.914(5)° c= 18.517(1) A y = 90.0° V = 5708.7(5) A 3 P2\ln (#14) 4 1.327 g/cm3 2376.00 4.03 cm"1 Bruker X8 APEX II MoKa (X = 0.71073 A) graphite monochromated 1220 exposures @ 9.0 seconds 36.00 mm 56.0° Total: 60965 Unique: 13758(Rint = 0.044) Absorption (Tmjn = 0.839, Tm a x= 0.986); Lorentz-polarization Structure Solution Refinement Function Minimized Least Squares Weights Anomalous Dispersion No. Observations (I>0.00a(I)) No. Variables Reflection/Parameter Ratio Residuals (refined on F 2 , all data): RI; wR2 Direct Methods (SIR97) Full-matrix least-squares on F 2 I w (Fo2 - F c 2 ) 2 w=l/(a2(Fo2)+(0.0396P) 2+ 4.037P) All non-hydrogen atoms 13758 701 19.63 0.053; 0.093 175 Goodness of Fit Indicator 1.02 No. Observations (I>2.00o(I)) 10811 Residuals (refined on F): R l ; wR2 0.037; 0.085 Max Shift/Error in Final Cycle 0.00 Maximum peak in Final Diff. Map 0.82 e ' /A 3 Minimum peak in Final Diff. Map -0.55 e~/A3 Table 1. Atomic Coordinates (x 104) and Equivalent Isotropic Displacement Parameters (A x 103) Atom X Y Z Ueq C1 5586(1) 1262(1) 8085(1) 19(1) C7 5152(1) 1713(1) 6555(1) 21(1) C13 4903(1) 2618(1) 7774(1) 18(1) C19 3205(1) 2880(1) 6092(1) 25(1) C25 1827(1) 2087(1) 6053(1) 22(1) C31 2903(1) 1559(1) 5260(1) 22(1) C37 1751(1) 558(1) 6903(1) 23(1) C38 1152(1) 624(1) 7251(2) 30(1) C39 1498(1) 1000(1) 7907(2) 27(1) C40 4334(1) 15(1) 8402(1) 22(1) C41 4295(2) -181(2) 9120(1) 31(1] C42 3838(2) 335(2) 9311(1) 30(1) C43 2350(1) 1412(1) 10283(1) 25(1 , C44 2750(2) 2077(2) 10396(2) 32 ( r C45 2999(2) 2164(1) 9771(2) 30(1 C46 1765(1) 95(1) 6265(1) 24(1 C47 1169(2) 108(1) 5567(2) 32(1 C48 1188(2) -382(2) 5009(2) 42(1 C49 1792(2) -877(2) 5133(2) 43(1 C50 2389(2) -901(2) 5823(2) 36(1 C51 2374(1) -417(1) 6387(2) 29(1 C52 4720(1) -386(1) 7929(1) 24(1 C53 4475(2) -315(1) 7146(1) 27(1 C54 4830(2) -720(2) 6709(2) 39(1 C55 5427(2) -1206(2) 7043(2) 47(1 C56 5674(2) -1282(2) 7822(2) 46(1 C57 5329(2) -877(2) 8260(2) 35(1 C58 1932(1) 1051(1) 10760(1) 25(1 C59 2060(2) 1262(2) 11511(1) 32(1 C60 1649(2) 937(2) 11949(2) 38(1 C61 11-13(2) 391(2) 11659(2) 41(1 C62 986(2) 167(2) 10917(2) 39(1 176 Table 1. Atomic Coordinates. .continued C63 1392(2) 500(2) 10474(2) 32(1) B1 2988(2) 1441(2) 8602(2) 24(1) N2 2259(1) 1157(1) 7948(1) 23(1) N1 2413(1) 898(1) 7318(1) 20(1) N5 2761(1) 1588(1) 9316(1) 25(1) N6 2357(1) 1115(1) 9629(1) 26(1) N3 3621(1) 826(1) 8750(1) 21(1) N4 3927(1) 632(1) 8185(1) 19(1) P1 4757(1) 1708(1) 7365(1) 17(1) P2 2894(1) 1941(1) 6170(1) 19(1) Rh1 3519(1) 1272(1) 7206(1) 16(1) H1B 3264(14) 1922(13) 8464(13) 19(6) Table 2. Bond Lengths (A) Atoms Length Atoms Length C1-P1 1.838(2) C49-C50 1.379(4) C7-P1 1.833(2) C50-C51 1.382(4) C13-P1 1.833(2) C52-C53 1.387(3) C19-P2 1.843(2) C52-C57 1.390(3) C25-P2 1.831(2) C53-C54 1.382(3) C31-P2 1.832(2) C54-C55 1.374(4) C37-N1 1.335(3) C55-C56 1.379(5) C37-C38 1.394(3) C56-C57 1.374(4) C37-C46 1.466(3) C58-C63 1.381(4) C38-C39 1.370(4) C58-C59 1.395(3) C39-N2 1.343(3) C59-C60 1.376(4) C40-N4 1.341(3) C60-C61 1.372(4) C40-C41 1.400(3) C61-C62 1.385(4) C40-C52 1.462(3) C62-C63 1.385(4) C41-C42 1.362(4) B1-N5 1.518(3) C42-N3 1.345(3) B1-N3 1.553(3) C43-N6 1.332(3) B1-N2 1.555(3) C43-C44 1.400(4) B1-H1B 1.08(2) C43-C58 1.470(3) N2-N1 1.363(3) C44-C45 1.366(4) N1-Rh1 2.1240(18) C45-N5 1.344(3) N5-N6 1.362(3) C46-C47 1.388(3) N3-N4 1.361(2) C46-C51 1.392(3) N4-Rh1 2.1000(18) C47-C48 1.383(4) P1-Rh1 2.2429(6) C48-C49 1.365(4) P2-RM 2.2618(6) 177 Table 3. Bond Angles (°) Atoms Angle N1-C37-C38 109.6(2) N1-C37-C46 120.9(2) C38-C37-C46 128.7(2) C39-C38-C37 105.4(2) N2-C39-C38 108.7(2) N4-C40-C41 109.2(2) N4-C40-C52 123.6(2) C41-C40-C52 127.1(2) C42-C41-C40 105.6(2) N3-C42-C41 108.8(2) N6-C43-C44 110.9(2) N6-C43-C58 120.2(2) C44-C43-C58 128.9(2) C45-C44-C43 104.6(2) N5-C45-C44 108.5(2) C47-C46-C51 118.7(2) C47-C46-C37 123.1(2) C51-C46-C37 118.0(2) C48-C47-C46 120.0(3) C49-C48-C47 120.7(3) C48-C49-C50 120.2(3) C49-C50-C51 119.6(3) C50-C51-C46 120.7(2) C53-C52-C57 118.2(2) C53-C52-C40 121.7(2) C57-C52-C40 120.0(2) C54-C53-C52 120.6(2) C55-C54-C53 120.6(3) C54-C55-C56 119.2(3) C57-C56-C55 120.6(3) C56-C57-C52 120.8(3) C63-C58-C59 118.0(2) C63-C58-C43 120.9(2) C59-C58-C43 121.1(2) C60-C59-C58 120.9(3) C61-C60-C59 120.6(3) C60-C61-C62 119.4(3) C61-C62-C63 119.9(3) C58-C63-C62 121.1(3) N5-B1-N3 110.0(2) Atoms Angle N5-B1-N2 111.6(2) N3-B1-N2 104.97(19) N5-B1-H1B 108.3(13) N3-B1-H1B 107.4(12) N2-B1-H1B 114.4(13) C39-N2-N1 109.26(19) C39-N2-B1 132.7(2) N1-N2-B1 117.08(18) C37-N1-N2 107.05(18) C37-N1-Rh1 138.84(16) N2-N1-Rh1 113.28(14) C45-N5-N6 110.3(2) C45-N5-B1 125.0(2) N6-N5-B1 124.4(2) C43-N6-N5 105.7(2) C42-N3-N4 109.35(19) C42-N3-B1 130.3(2) N4-N3-B1 119.14(18) C40-N4-N3 107.03(18) C40-N4-RM 138.44(16) N3-N4-Rh1 113.85(14) C13-P1-C7 107.10(10) C13-P1-C1 97.75(10) C7-P1-C1 100.58(10) C13-P1-Rh1 113.06(7) C7-P1-Rh1 119.04(7) C1-P1-RM 116.60(7) C25-P2-C31 104.17(11) C25-P2-C19 99.55(11) C31-P2-C19 101.89(11) C25-P2-RM 113.04(8) C31-P2-Rh1 115.42(8) C19-P2-RM 120.40(7) N4-RM-N1 78.98(7) N4-RM-P1 91.82(5) N1-RM-P1 167.28(5) N4-Rh1-P2 171.38(5) N1-Rh1-P2 92.54(5) P1-Rh1-P2 96.32(2) 178 Table 4. Anisotropic Displacement Parameters (A x 103) Atom U 1 1 U 2 2 u 3 3 u 2 3 u 1 3 U 1 2 C1 18(1) 18(1) 21(1) 3(1) 6(1) -2.(1) C7 22(1) 24(1) 19(1) -1(1) 9(1) -1(1) C13 22(1) 17(1) 15(1) 0(1) 6(1) -1(1) C19 29(1) 22(1) 19(1) 5(1) -2(1) -4(1) C25 23(1) 19(1) 23(1) 4(1) 6(1) 1(1) C31 21(1) 28(1) 18(1) -2(1) 6(1) -6(1) C37 21(1) 21(1) 26(1) 4(1) 7(1) -1(1) C38 21(1) 31(1) 39(2) 1(1) 12(1) -4(1) C39 23(1) 28(1) 35(1) 2(1) 16(1) 1(1) C40 21(1) 22(1) 24(1) 5(1) 7(1) 0(1) C41 36(1) 32(2) 26(1) 12(1) 11(1) 8(1) C42 35(1) 38(2) 20(1) 9(1) 12(1) 3(1) C43 27(1) 27(1) 23(1) 0(1) 11(1) 7(1) C44 39(1) 32(2) 28(1) -10(1) 15(1) -2(1) C45 36(1) 24(1) 35(1) -4(1) 16(1) -2(1) C46 26(1) 20(1) 28(1) 2(1) 10(1) -7(1) C47 35(1) 24(1) 34(1) 4(1) 4(1) -2(1) C48 55(2) 32(2) 30(2) -2(1) 1(1) -7(1) C49 71(2) 23(2) 35(2) -6(1) 19(2) -7(1) C50 41(2) 25(1) 45(2) -2(1) 17(1) -2(1) C51 27(1) 26(1) 33(1) 1(1) 8(1) -4(1) C52 21(1) 19(1) 33(1) 2(1) 11(1) -1(1) C53 31(1) 22(1) 32(1) -1(1) 14(1) -1(1) C54 52(2) 32(2) 41(2) -6(1) 27(1) -1(1) C55 51(2) 32(2) 72(2) -6(2) 40(2) 5(1) C56 35(2) 35(2) 72(2) 6(2) 24(2) 13(1) C57 28(1) 32(2) 45(2) 8(1) 11(1) 4(1) C58 29(1) 26(1) 24(1) 4(1) 13(1) 11(1) C59 35(1) 37(2) 24(1) -1(1) 11(1) 12(1) C60 42(2) 51(2) 25(1) 7(1) 18(1) 19(1) C61 41(2) 51(2) 38(2) 19(1) 23(1) 13(1) C62 37(2) 41(2) 43(2) 7(1) 17(1) 1(1) B1 28(1) 24(2) 23(1) 0(1) 11(1) -1(1) N2 24(1) 24(1) 23(1) 2(1) 11(1) 1(1) N1 21(1) 21(1) 19(1) 1(1) 8(1) -1(1) N5 32(1) 22(1) 24(1) -1(1) 14(1) 0(1) N6 35(1) 24(1) 25(1) -1(1) 16(1) -1(1) N3 24(1) 24(1) 17(1) 1(1) 9(1) 0(1) N4 20(1) 21(1) 17(1) 1(1) 7(1) 0(1) P1 18(1) 17(1) 16(1) -1(1) 6(1) 0(1) P2 20(1) 19(1) 16(1) 1(1) 4(1) -2(1) Rh1 17(1) 16(1) 15(1) 1(1) 6(1) -1(1) 179 Table 5. Torsional Angles (°) Atoms Angle N1-C37-C38-C39 -2.1(3) C46-C37-C38-C39 167.4(2) C37-C38-C39-N2 0.6(3) N4-C40-C41-C42 1.2(3) C52-C40-C41-C42 -176.5(2) C40-C41-C42-N3 -1.1(3) N6-C43-C44-C45 0.0(3) C58-C43-C44-C45 -177.7(2) C43-C44-C45-N5 0.1(3) N1-C37-C46-C47 -136.0(2) C38-C37-C46-C47 55.6(4) N1-C37-C46-C51 49.0(3) C38-C37-C46-C51 -119.5(3) C51-C46-C47-C48 0.0(4) C37-C46-C47-C48 -175.0(2) C46-C47-C48-C49 -0.5(4) C47-C48-C49-C50 0.7(5) C48-C49-C50-C51 -0.3(4) C49-C50-C51-C46 -0.3(4) C47-C46-C51-C50 0.4(4) C37-C46-C51-C50 175.7(2) N4-C40-C52-C53 -23.1(4) C41-C40-C52-C53 154.3(3) N4-C40-C52-C57 159.5(2) C41-C40-C52-C57 -23.1(4) C57-C52-C53-C54 -0.2(4) C40-C52-C53-C54 -177.6(2) C52-C53-C54-C55 0.7(4) C53-C54-C55-C56 -0.6(4) C54-C55-C56-C57 0.1(5) C55-C56-C57-C52 0.4(4) C53-C52-C57-C56 -0.4(4) C40-C52-C57-C56 177.1(2) N6-C43-C58-C63 -15.1(3) C44-C43-C58-C63 162.4(3) N6-C43-C58-C59 165.9(2) C44-C43-C58-C59 -16.6(4) C63-C58-C59-C60 -1.0(4) C43-C58-C59-C60 178.1(2) C58-C59-C60-C61 0.9(4) C59-C60-C61-C62 0.0(4) C60-C61-C62-C63 -0.7(4) Atoms Angle C41-C40-N4-N3 -0.8(3) C52-C40-N4-N3 176.9(2) C41-C40-N4-Rh1 -170.32(18) C52-C40-N4-Rh1 7.5(4) C42-N3-N4-C40 0.2(2) B1-N3-N4-C40 -168.6(2) C42-N3-N4-Rh1 172.55(16) B1-N3-N4-Rh1 3.8(2) C14-C13-P1-C7 126.22(18) C18-C13-P1-C7 -60.8(2) C14-C13-P1-C1 -130.14(18) C18-C13-P1-C1 42.8(2) C14-C13-P1-Rh1 -6.8(2) C18-C13-P1-Rh1 166.13(17) C8-C7-P1-C13 -164.83(18) C12-C7-P1-C13 15.2(2) C8-C7-P1-C1 93.6(2) C12-C7-P1-C1 -86.4(2) C8-C7-P1-Rh1 -35.1(2) C12-C7-P1-Rh1 144.91(19) C6-C1-P1-C13 -129.3(2) C2-C1-P1-C13 48.1(2) C6-C1-P1-C7 -20.2(2) C2-C1-P1-C7 157.17(19) C6-C1-P1-Rh1 110.06(19) C2-C1-P1-Rh1 -72.61(19) C26-C25-P2-C31 -9.0(2) C30-C25-P2-C31 175.45(19) C26-C25-P2-C19 95.9(2) C30-C25-P2-C19 -79.6(2) C26-C25-P2-RM -135.10(19) C30-C25-P2-RM 49.4(2) C32-C31-P2-C25 -101.60(19) C36-C31-P2-C25 80.3(2) C32-C31-P2-C19 155.22(19) C36-C31-P2-C19 -22.9(2) C32-C31-P2-RM 22.9(2) C36-C31-P2-Rh1 -155.19(18) C20-C19-P2-C25 29.8(2) C24-C19-P2-C25 -156.00(19) C20-C19-P2-C31 136.6(2) C24-C19-P2-C31 -49.2(2) 180 Table 5. Torsional Angles (°)...continued C59-C58-C63-C62 0.2(4) C20-C19-P2-Rh1 -94.2(2) C43-C58-C63-C62 -178.8(2) C24-C19-P2-Rh1 80.0(2) C61-C62-C63-C58 0.6(4) C40-N4-Rh1-N1 112.6(2) C38-C39-N2-N1 1.0(3) N3-N4-Rh1-N1 -56.39(14) C38-C39-N2-B1 -167.2(2) C40-N4-Rh1-P1 -76.3(2) N5-B1-N2-C39 -2.5(4) N3-N4-RM-P1 114.76(14) N3-B1-N2-C39 116.7(3) C40-N4-Rh1-P2 123.1(3) N5-B1-N2-N1 -169.96(19) N3-N4-Rh1-P2 -45.9(4) N3-B1-N2-N1 -50.8(3) C37-N1-Rh1-N4 -125.8(2) C38-C37-N1-N2 2.7(3) N2-N1-Rh1-N4 66.39(15) C46-C37-N1-N2 -167.8(2) C37-N1-Rh1-P1 -170.11(18) C38-C37-N1-Rh1 -165.57(19) N2-N1-Rh1-P1 22.1(4) C46-C37-N1-Rh1 24.0(4) C37-N1-Rh1-P2 55.7(2) C39-N2-N1-C37 -2.3(3) N2-N1-Rh1-P2 -112.04(14) B1-N2-N1-C37 168.0(2) C13-P1-Rh1-N4 -101.43(9) C39-N2-N1-Rh1 169.30(16) C7-P1-Rh1-N4 131.56(10) B1-N2-N1-Rh1 -20.4(2) C1-P1-Rh1-N4 10.71(10) C44-C45-N5-N6 -0.1(3) C13-P1-Rh1-N1 -58.2(3) C44-C45-N5-B1 -173.7(2) C7-P1-Rh1-N1 174.8(3) N3-B1-N5-C45 105.7(3) C1-P1-Rh1-N1 54.0(3) N2-B1-N5-C45 -138.2(2) C13-P1-Rh1-P2 75.70(8) N3-B1-N5-N6 -67.0(3) C7-P1-Rh1-P2 -51.31(9) N2-B1-N5-N6 49.1(3) C1-P1-Rh1-P2 -172.16(9) C44-C43-N6-N5 -0.1(3) C25-P2-Rh1-N4 5.9(4) C58-C43-N6-N5 177.8(2) C31-P2-Rh1-N4 -113.9(4) C45-N5-N6-C43 0.1(3) C19-P2-Rh1-N4 123.2(4) B1-N5-N6-C43 173.7(2) C25-P2-Rh1-N1 16.28(10) C41-C42-N3-N4 0.6(3) C31-P2-Rh1-N1 -103.51(10) C41-C42-N3-B1 167.7(2) C19-P2-Rh1-N1 133.57(11) N5-B1-N3-C42 16.5(4) C25-P2-Rh1-P1 -154.57(9) N2-B1-N3-C42 -103.7(3) C31-P2-Rh1-P1 85.64(8) N5-B1-N3-N4 -177.46(18) C19-P2-Rh1-P1 -37.28(10) N2-B1-N3-N4 62.3(2) 181 Appendix V: X-ray Crystallographic Data for Tp P h M eRh(PPh 3) 2 (7) Configuration represented in Chapter 2 C56 C48 £ 6 6 C63 Configuration including all atoms Figure 1. ORTEP diagrams of complex 7. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms, except for the B-H hydrogen, and phenyl groups of PPh3 are excluded for clarity. 182 A. Crystal Data Empirical Formula Formula Weight Crystal Color, Habit Crystal Dimensions Crystal System Lattice Type Lattice Parameters Space Group Z value Dcalc FOOO (i(MoKa) B. Intensity Measurements Diffractometer Radiation Data Images Detector Position 26max No. of Reflections Measured Corrections C. Structure Solution and Refinement Structure Solution Refinement Function Minimized Least Squares Weights Anomalous Dispersion No. Observations (I>0.00CT(I)) No. Variables Reflection/Parameter Ratio C72H72BN6P2Rh 1197.02 red, irregular 0.05X0.12 X0.25 mm monoclinic primitive a = 14.9000(5) A a = 90.0 0 b= 14.8303(5) A (3 = 92.260(2) c = 29.460(1) A y= 90.0° V = 6504.8(4) A 3 P2xln (#14) 4 1.222 g/cm3 2504.00 3.57 cm"1 Bruker X8 APEX II MoKa (A. = 0.71073 A ) graphite monochromated 1138 exposures @ 30.0 seconds 36.00 mm 50.1° Total: 49830 Unique: 11499 (R m t = 0.052) Absorption (Tmi„ = 0.842, Tmax= 0.982); Lorentz-polarization Direct Methods (SIR97) Full-matrix least-squares on F 2 E w (Fo 2 - F c 2 ) 2 W=1/(G 2(FO 2)+(0.0474P) 2 + 0.0000P) All non-hydrogen atoms 11499 692 16.62 183 Residuals (refined on F 2 , all data): RI; wR2 0.058; 0.090 Goodness of Fit Indicator 0.99 No. Observations (I>2.00o(I)) 8482 Residuals (refined on F): RI; wR2 0.037; 0.084 Max Shift/Error in Final Cycle 0.00 Maximum peak in Final Diff. Map 0.46 e"/A 3 Minimum peak in Final Diff. Map -0.31 e"/A 3 Table 1. Atomic Coordinates (x 104) and Equivalent Isotropic Displacement Parameters (A x 103) Atom X Y Z Ueq C1 5415(2) 2035(2) 2536(1) 26(1 C7 3900(2) 3147(2) 2327(1) 24(1 C13 3998(2) 2042(2) 3134(1) 24(1 C19 3892(2) 3620(2) 4054(1) 22(1 C25 3031(2) 4541(2) 3278(1) 22(1 C31 4272(2) 5407(2) 3905(1) 22(1 C37 5408(2) 6513(2) 3063(1) 30(1 C38 5225(2) 7428(2) 3129(1) 39(1 C39 4668(2) 7886(2) 2825(1) 52(1 C40 4270(2) 7456(2) 2455(1) 52(1 C41 4450(2) 6560(2) 2385(1) 46(1 C42 5011(2) 6091(2) 2685(1) 35(1 C43 6040(2) 6041(2) 3377(1) 27(1 C44 6746(2) 6427(2) 3634(1) 32(1 C45 7218(2) 5740(2) 3828(1) 33(1 C46 8066(2) 5809(2) 4121(1) 44(1 C47 6577(2) 3863(2) 2052(1) 31(1 C48 6304(2) 4740(2) 1958(1) 37(1 C49 5982(2) 4982(2) 1532(1) 49(1 C50 5919(3) 4343(3) 1192(1) 62(1 C51 6187(3) 3466(3) 1280(1) 61(1 C52 6522(2) 3227(2) 1705(1) 43(1 C53 7006(2) 3635(2) 2497(1) 29(1 C54 7857(2) 3275(2) 2575(1) 37(1 C55 8012(2) 3288(2) 3035(1) 35(1 C56 8819(2) 2975(3) 3312(1) 55(1 C57 6372(2) 941(2) 4191(1) 33(1 C58 6590(2) 465(2) 3807(1) 40(1 C59 6447(2) -449(2) 3771(1) 50(1 C60 6075(2) -915(2) 4120(1) 51(1 C61 5852(2) -463(2) 4506(1) 53(1 C62 6005(2) 458(2) 4547(1) 46(1 184 Table 1. Atomic Coordinates. .continued C63 6532(2) 1916(2) 4234(1) 32(1) C64 6577(2) 2442(2) 4632(1) 37(1) C65 6753(2) 3306(2) 4488(1) 34(1) C66 6938(2) 4126(2) 4771(1) 43(1) B1 7236(2) 3994(2) 3722(1) 30(1) N1 6067(1) 5140(1) 3432(1) 23(1) N2 6808(1) 4949(2) 3709(1) 26(1) N3 7283(1) 3642(2) 3230(1) 28(1) N4 6636(1) 3840(1) 2895(1) 25(1) N5 6785(2) 3290(2) 4029(1) 29(1) N6 6659(2) 2426(2) 3868(1) 30(1) P1 4671(1) 2844(1) 2806(1) 22(1) P2 4133(1) 4363(1) 3575(1) 20(1) Rh1 5336(1) 4041(1) 3161(1) 20(1) H1 7923(18) 4055(17) 3870(8) 34(8) Table 2. Bond Lengths (A) Atoms Length Atoms Length C1-P1 1.837(3) C54-C55 1.366(4) C7-P1 1.839(3) C55-N3 1.354(3) C13-P1 1.852(3) C55-C56 1.500(4) C19-P2 1.839(3) C57-C58 1.383(4) C25-P2 1.849(3) C57-C62 1.397(4) C31-P2 1.837(3) C57-C63 1.471(4) C37-C42 1.388(4) C58-C59 1.376(4) C37-C38 1.399(4) C59-C60 1.375(4) C37-C43 1.471(4) C60-C61 1.372(5) C38-C39 1.377(4) C61-C62 1.389(4) C39-C40 1.375(5) C63-N6 1.337(3) C40-C41 1.373(5) C63-C64 1.405(4) C41-C42 1.381(4) C64-C65 1.378(4) C43-N1 1.346(3) C65-N5 1.355(3) C43-C44 1.396(4) C65-C66 1.494(4) C44-C45 1.352(4) B1-N3 1.545(4) C45-N2 1.362(3) B1-N5 1.551(4) C45-C46 1.504(4) B1-N2 1.554(4) C47-C48 1.387(4) B1-H1 1.10(3) C47-C52 1.391(4) N1-N2 1.377(3) C47-C53 1.475(4) N1-Rh1 2.100(2) C48-C49 1.374(4) N3-N4 1.383(3) C49-C50 1.379(5) N4-Rh1 2.140(2) C50-C51 1.382(5) N5-N6 1.377(3) C51-C52 1.377(4) PT-Rh1 2.2683(7) C53-N4 1.350(3) P2-Rh1 2.2572(7) 185 Table 3. Bond Angles (°) Atoms Angle C42-C37-C38 118.0(3) C42-C37-C43 122.1(3) C38-C37-C43 119.8(3) C39-C38-C37 120.2(3) C40-C39-C38 121.1(3) C41-C40-C39 119.2(3) C40-C41-C42 120.4(3) C41-C42-C37 121.0(3) N1-C43-C44 108.9(2) N1-C43-C37 124.3(2) C44-C43-C37 126.6(3) C45-C44-C43 106.8(3) C44-C45-N2 108.6(2) C44-C45-C46 127.0(3) N2-C45-C46 124.3(3) C48-C47-C52 118.7(3) C48-C47-C53 120.4(3) C52-C47-C53 120.6(3) C49-C48-C47 121.1(3) C48-C49-C50 119.7(3) C49-C50-C51 120.0(31 C52-C51-C50 120.3(3 C51-C52-C47 120.2(3 N4-C53-C54 110.1(2 N4-C53-C47 122.9(2 C54-C53-C47 126.6(3 C55-C54-C53 106.1(3 N3-C55-C54 108.5(3 N3-C55-C56 121.9(3 C58-C57-C62 117.6(3 C58-C57-C63 122.0(3 C62-C57-C63 120.4(3 C59-C58-C57 121.7(3 C60-C59-C58 120.2(3 C61-C60-C59 119.5(3 C60-C61-C62 120.5(3 C61-C62-C57 120.5(3 N6-C63-C64 110.8(3 N6-C63-C57 120.9(3 C64-C63-C57 128.3(3 C65-C64-C63 105.3(3 N5-C65-C64 107.7(3 Atoms Angle N5-C65-C66 123.9(3) C64-C65-C66 128.3(3) N3-B1-N5 110.9(2) N3-B1-N2 108.6(2) N5-B1-N2 116.2(2) N3-B1-H1 108.9(14) N5-B1-H1 104.0(14) N2-B1-H1 108.0(14) C43-N1-N2 107.1(2) C43-N1-Rh1 135.38(17) N2-N1-Rh1 117.27(16) C45-N2-N1 108.5(2) C45-N2-B1 126.8(2) N1-N2-B1 121.3(2) C55-N3-N4 109.2(2) C55-N3-B1 126.5(2) N4-N3-B1 122.7(2) C53-N4-N3 106.0(2) C53-N4-RM 139.10(19) N3-N4-RM 112.63(15) C65-N5-N6 110.5(2) C65-N5-B1 127.1(2) N6-N5-B1 118.8(2) C63-N6-N5 105.7(2) C1-P1-C7 101.33(12) C1-P1-C13 98.93(12) C7-P1-C13 102.87(12) C1-P1-RM 116.79(9) C7-P1-RM 114.23(9) C13-P1-RM 119.87(8) C31-P2-C19 96.84(11) C31-P2-C25 102.10(12) C19-P2-C25 104.62(12) C31-P2-RM 112.89(8) C19-P2-RM 118.12(9) C25-P2-RM 118.98(8) N1-RM-N4 77.49(8) N1-RM-P2 92.42(6) N4-Rh1-P2 167.66(6) N1-RM-P1 173.25(6) N4-Rh1-P1 96.18(6) P2-RM-P1 94.15(3) 186 Table 4. Anisotropic Displacement Parameters (A x 103) Atom U 1 1 U 2 2 u 3 3 u 2 3 u 1 3 U 1 2 C1 32(2) 18(2) 28(1) 1(1) 11(1) 1(1) C7 30(2) 19(2) 24(1) -4(1) 1(1) 1(1) C13 30(2) 19(2) 22(1) -5(1) 4(1) -7(1) C19 24(1) 20(2) 23(1) -3(1) -1(1) -6(1) C25 23(1) 18(2) 25(1) -8(1) 1(1) 3(1) C31 25(1) 20(2) 22(1) -3(1) 8(1) -3(1) C37 25(2) 23(2) 45(2) 3(1) 14(1) -5(1) C38 44(2) 20(2) 55(2) 2(2) 17(2) 1(2) C39 50(2) 22(2) 86(3) 15(2) 27(2) 10(2) C40 38(2) 44(2) 75(3) 31(2) 8(2) 6(2) C41 39(2) 42(2) 57(2) 22(2) -2(2) -4(2) C42 32(2) 25(2) 47(2) 8(1) 6(1) -4(1) C43 28(2) 20(2) 34(2) -4(1) 10(1) -3(1) C44 32(2) 25(2) 40(2) -8(1) 9(1) -9(1) C45 28(2) 36(2) 34(2) -7(1) 5(1) -13(1) C46 37(2) 50(2) 46(2) -9(2) 1(1) -18(2) C47 29(2) 33(2) 33(2) -1(1) 13(1) -7(1) C48 32(2) 36(2) 44(2) 2(2) 5(1) -7(2) C49 49(2) 49(2) 49(2) 16(2) 3(2) -6(2) C50 67(3) 82(3) 35(2) 13(2) -2(2) -7(2) C51 73(3) 74(3) 37(2) -10(2) 8(2) -11(2) C52 51(2) 40(2) 40(2) -5(2) 15(2) -5(2) C53 29(2) 22(2) 37(2) -1(1) 11(1) -4(1) C54 36(2) 35(2) 43(2) 1(1) 19(1) 3(2) C55 28(2) 31(2) 48(2) 6(1) 9(1) 5(1) C56 35(2) 71(3) 61(2) 6(2) 10(2) 22(2) C57 36(2) 30(2) 33(2) 8(1) 2(1) 7(2) C58 50(2) 33(2) 37(2) 9(1) 9(2) 5(2) C59 71(3) 34(2) 44(2) 0(2) 13(2) 6(2) C60 72(3) 27(2) 56(2) 8(2) 7(2) 3(2) C61 70(3) 39(2) 51(2) 19(2) 19(2) 4(2) C62 62(2) 38(2) 40(2) 8(2) 12(2) 10(2) C63 32(2) 31(2) 32(2) 5(1) 3(1) 11(1) C64 43(2) 38(2) 29(2) 3(1) 3(1) 7(2) C65 36(2) 34(2) 30(2) -1(1) -1(1) 8(1) C66 50(2) 43(2) 35(2) -2(2) -1(1) -4(2) B1 24(2) 31(2) 36(2) 2(2) -1(1) -2(2) N1 18(1) 23(1) 29(1) -1(1) 2(1) -1(1) N2 20(1) 28(1) 31(1) -3(1) 2(1) -4(1) N3 21(1) 28(1) 35(1) 3(1) 6(1) 4(1) N4 23(1) 21(1) 31(1) -1(1) 8(1) -1(1) N5 29(1) 29(1) 30(1) 1(1) -1(1) 2(1) 187 Table 4. Anisotropic Displacement Parameters (A x 103)...continued N6 32(1) 28(1) 31(1) 3(1) 2(1) 4(1) P1 23(1) 17(1) 25(1) -2(1) 4(1) -1(1) P2 20(1) 18(1) 23(1) -2(1) 1(1) 0(1) Rh1 19(1) 16(1) 25(1) -2(1) 3(1) -1(1) Table 5. Torsional Angles (°) Atoms Angle Atoms Angle C42-C37-C38-C39 -0.1(4) B1-N3-N4-Rh1 -29.7(3) C43-C37-C38-C39 176.8(3) C64-C65-N5-N6 -1.7(3) C37-C38-C39-C40 1.0(5) C66-C65-N5-N6 174.9(3) C38-C39-C40-C41 -1.5(5) C64-C65-N5-B1 -159.8(3) C39-C40-C41-C42 1.2(5) C66-C65-N5-B1 16.9(4) C40-C41-C42-C37 -0.4(5) N3-B1-N5-C65 169.1(2) C38-C37-C42-C41 -0.2(4) N2-B1-N5-C65 -66.2(4) C43-C37-C42-C41 -177.0(3) N3-B1-N5-N6 12.7(3) C42-C37-C43-N1 -23.9(4) N2-B1-N5-N6 137.3(2) C38-C37-C43-N1 159.3(3) C64-C63-N6-N5 -0.2(3) C42-C37-C43-C44 150.6(3) C57-C63-N6-N5 179.9(2) C38-C37-C43-C44 -26.3(4) C65-N5-N6-C63 1.2(3) N1-C43-C44-C45 2.7(3) B1-N5-N6-C63 161.3(2) C37-C43-C44-C45 -172.5(3) C2-C1-P1-C7 165.4(2) C43-C44-C45-N2 -2.0(3) C6-C1-P1-C7 -19.7(3) C43-C44-C45-C46 177.1(3) C2-C1-P1-C13 -89.5(2) C52-C47-C48-C49 0.2(4) C6-C1-P1-C13 85.4(2) C53-C47-C48-C49 173.8(3) C2-C1-P1-Rh1 40.6(2) C47-C48-C49-C50 0.7(5) C6-C1-P1-Rh1 -144.5(2) C48-C49-C50-C51 -0.6(6) C12-C7-P1-C1 85.8(2) C49-C50-C51-C52 -0.4(6) C8-C7-P1-C1 -90.9(2) C50-C51-C52-C47 1.3(5) C12-C7-P1-C13 -16.2(3) C48-C47-C52-C51 -1.2(5) C8-C7-P1-C13 167.1(2) C53-C47-C52-C51 -174.7(3) C12-C7-P1-Rh1 -147.7(2) C48-C47-C53-N4 52.7(4) C8-C7-P1-Rh1 35.6(2) C52-C47-C53-N4 -133.8(3) C14-C13-P1-C1 33.1(2) C48-C47-C53-C54 -120.4(3) C18-C13-P1-C1 -151.6(2) C52-C47-C53-C54 53.0(4) C14-C13-P1-C7 137.0(2) N4-C53-C54-C55 -1.7(3) C18-C13-P1-C7 -47.7(2) C47-C53-C54-C55 172.2(3) C14-C13-P1-Rh1 -95.0(2) C53-C54-C55-N3 0.0(3) C18-C13-P1-Rh1 80.4(2) C53-C54-C55-C56 179.4(3) C32-C31-P2-C19 -127.2(2) C62-C57-C58-C59 0.6(5) C36-C31-P2-C19 54.5(2) C63-C57-C58-C59 179.4(3) C32-C31-P2-C25 -20.6(3) C57-C58-C59-C60 0.2(5) C36-C31-P2-C25 161.1(2) C58-C59-C60-C61 -0.3(5) C32-C31-P2-RM 108.3(2) 188 Table 5. Torsional Angles (°)...continued C59-C60-C61-C62 -0.5(6) C36-C31-P2-Rh1 -70.0(2) C60-C61-C62-C57 1.4(5) C20-C19-P2-C31 -127.6(2) C58-C57-C62-C61 -1.4(5) C24-C19-P2-C31 50.0(2) C63-C57-C62-C61 179.8(3) C20-C19-P2-C25 128.0(2) C58-C57-C63-N6 18.6(4) C24-C19-P2-C25 -54.4(2) C62-C57-C63-N6 -162.7(3) C20-C19-P2-Rh1 -7.0(2) C58-C57-C63-C64 -161.3(3) C24-C19-P2-Rh1 170.58(18) C62-C57-C63-C64 17.4(5) C30-C25-P2-C31 91.2(2) N6-C63-C64-C65 -0.8(3) C26-C25-P2-C31 -88.8(3) C57-C63-C64-C65 179.1(3) C30-C25-P2-C19 -168.3(2) C63-C64-C65-N5 1.5(3) C26-C25-P2-C19 11.7(3) C63-C64-C65-C66 -174.9(3) C30-C25-P2-RM -33.8(2) C44-C43-N1-N2 -2.3(3) C26-C25-P2-Rh1 146.2(2) C37-C43-N1-N2 173.0(2) C43-N1-RM-N4 113.3(3) C44-C43-N1-Rh1 -176.47(19) N2-N1-RM-N4 -60.41(17) C37-C43-N1-Rh1 -1.2(4) C43-N1-Rh1-P2 -73.9(2) C44-C45-N2-N1 0.6(3) N2-N1-RM-P2 112.42(16) C46-C45-N2-N1 -178.5(3) C43-N1-RM-P1 92.7(6) C44-C45-N2-B1 159.9(3) N2-N1-RM-P1 -81.0(5) C46-C45-N2-B1 -19.2(4) C53-N4-RM-N1 -134.1(3) C43-N1-N2-C45 1.1(3) N3-N4-Rh1-N1 66.49(16) Rh1-N1-N2-C45 176.49(17) C53-N4-Rh1-P2 -169.8(2) C43-N1-N2-B1 -159.6(2) N3-N4-Rh1-P2 30.8(4) Rh1-N1-N2-B1 15.8(3) C53-N4-Rh1-P1 43.5(3) N3-B1-N2-C45 -113.6(3) N3-N4-Rh1-P1 -115.90(16) N5-B1-N2-C45 120.6(3) C31-P2-Rh1-N1 4.18(11) N3-B1-N2-N1 43.3(3) C19-P2-Rh1-N1 -107.68(10) N5-B1-N2-N1 -82.5(3) C25-P2-Rh1-N1 123.78(11) C54-C55-N3-N4 1.6(3) C31-P2-Rh1-N4 38.9(3) C56-C55-N3-N4 -177.9(3) C19-P2-Rh1-N4 -72.9(3) C54-C55-N3-B1 -164.5(3) C25-P2-Rh1-N4 158.6(3) C56-C55-N3-B1 16.0(5) C31-P2-Rh1-P1 -174.25(9) N5-B1-N3-C55 -101.3(3) C19-P2-Rh1-P1 73.90(9) N2-B1-N3-C55 129.9(3) C25-P2-RM-P1 -54.64(10) N5-B1-N3-N4 94.3(3) C1-P1-Rh1-N1 31.8(5) N2-B1-N3-N4 -34.5(3) C7-P1-Rh1-N1 -86.2(5) C54-C53-N4-N3 2.6(3) C13-P1-Rh1-N1 151.2(5) C47-C53-N4-N3 -171.5(2) C1-P1-Rh1-N4 11.54(11) C54-C53-N4-Rh1 -157.6(2) C7-P1-RM-N4 -106.41(11) C47-C53-N4-Rh1 28.2(4) C13-P1-Rh1-N4 130.91(12) C55-N3-N4-C53 -2.6(3) C1-P1-Rh1-P2 -161.71(10) B1-N3-N4-C53 164.2(2) C7-P1-RH1-P2 80.35(10) C55-N3-N4-RM 163.53(18) C13-P1-Rh1-P2 -42.33(11) 189 

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