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O₂-oxidations catalyzed by trans-dioxoporphyrinatoruthenium(VI) species Cheng, Stephen Yau Sang 1996

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02-Oxidations Catalyzed by rra«s-Dioxoporphyrinatomtherrium(Vt) Species  by  Stephen Yau Sang Cheng B.Sc, University of British Columbia, 1992  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Chemistry)  We accept this thesis as conforming to the required standard.  THE UNIVERSITY OF BRITISH COLUMBIA July 1996 © Stephen Y. S. Cheng, 1996.  In  presenting  degree freely  at  this  the  thesis  in  partial  fulfilment  University  of  British  Columbia, I agree  available for  copying  of  department publication  this or of  reference  thesis by  this  for  his thesis  and study. scholarly  or  her  for  Department  of  Ctf£j*fi  Tfi-«/  The University of British Columbia Vancouver, Canada Date  S^Y^t V  {  DE-6  (2/88)  the  requirements that the  I further agree that  purposes  may  representatives.  financial  permission.  of  gain  It  shall not  be  allowed  advanced  Library shall make  by  understood be  an  permission for  granted  is  for  the that  without  it  extensive  head of  my  copying  or  my  written  Abstract Some /raw5-Ru (porp)(0) complexes [porp = TMP (1), TDCPP (2), TDCPP-C1 VI  2  8  (3)] were synthesized and used to oxidize, both stoichiometrically and (in the presence of air/02) catalytically, a variety of organic compounds in benzene under relatively mild conditions.  Ru(porp) (The Z labels apply to all the pyrrole positions; the ^ X / Y labels apply to all the phenyl groups)  X = Y = Me; Z = H T M P X = C1; Y = Z = H TDCPP X = Z = C1; Y = H TDCPP-C1  8  The kinetic data (measured by stopped-flow) for the stoichiometric oxidation of EAr substrates (E = P, As, Sb) by (1) to give initially Ru (TMP)(0)(OEAr ) suggest that IV  3  3  the O-atom transfer mechanism, governed by a ki second-order rate constant, involves electrophilic attack of a Ru=0 moiety on the lone-pair of electrons on the E-atom. For a k  x  series of P(p-X-C H4) substrates, the ki values do not give a linear Hammett plot Oogj^ 6  3  vs. a); however, the plot of AH* versus o is linear, and shows that a more electronreleasing para substituent gives a more favourable, lower value AH*. The AS* values correlate linearly with the molecular masses of the phosphines, with bulkier substrates giving rise to more favourable, less negative AS* values, an indication that the O-atom  transfers are strongly vibrationally coupled. In subsequent stages of the mechanism, the OEAr ligand dissociatesfromthe Ru(IV) intermediate to form Ru (TMP)(0), which IY  3  then disproportionates to (1) and Ru (TMP), and excess EAr reacts with the latter to n  3  form Ru (TMP)(EAr ) species. Under 1 atm air or O2, the oxidation of EAr substrates n  3  3  becomes catalytic; approximately 1 turnover h" is obtained for the oxidation of PPh at 1  3  ambient conditions. The oxidative dehydrogenation of'PrOH by (1) follows the indicated stoichiometry: (1) + 3 TrOH -> Ru (TMP)(0'Pr) + acetone + 2 H 0 TV  2  2  The Ru(IV) product was characterized crystallographically. Species (1) can also oxidize other primary or secondary alcohols (e.g. benzyl alcohol, 1-PrOH, l,3-dichloro-2propanol, 1-phenylethanol, etc.) to the corresponding aldehydes or ketones. The activation parameters for the stoichiometric oxidation o f PrOH and benzyl alcohol are: AH* = 45 ± 7 and 65 ± 11 kJmol" , and AS = -167 ± 10 and -70 ± 20 Jmol^K" , 1  1  respectively. A small kinetic isotope effect of k /k -1.9 observed for the stoichiometric H  D  oxidation of "PrOH at 18 °C is attributed to cleavage of the alcohol a-C-H bond in the rate-determining step. Exposure of Ru (TMP)(0'Pr) to moist air in benzene solution regenerates (1), rv  2  and thus the catalytic 0 -oxidation o f PrOH becomes viable. Complexes (1), (2) and (3) 2  are all active catalysts for the aerobic, selective oxidation of alcohols to aldehydes or ketones at room temperature or 50 °C under 1 atm air. The activities of the catalysts followed the order (1) > ( 3 ) » (2) for the oxidation of benzyl alcohol to benzaldehyde: in a 2-phase benzene/3.0 M aq. KOH system, (1) gave 2000 turnovers in 13 d at 50°C,  iii  and (3) gave 1200 turnovers in 15 d. While (1) was not very efficient in oxidizing 1phenylethanol to acetophenone, giving only a few turnovers before being deactivated, (3) produced 140 turnovers in 60 h under the same 2-phase conditions. Complex (3) does not effectively catalyze the oxidation of alkenes and alkanes in benzene under 1 atm O2 at 50 °C; however, at 35 - 90 °C under 1 atm O2, (3) (at low concentrations of ~10" M, but not at 10" M) does catalyze the oxidation of neat 5  3  cyclohexene, c/s-cyclooctene and methylcyclohexane via free-radical pathways. Hydroperoxides are present in the reaction solutions, and the addition of the radical inhibitor BHT (2,6-ditertbutyl-4-methylphenol) stops the oxidations. Approximately 60000 turnovers were realized in 26 h (and after 55 h, 120000 turnovers, 80% total conversion) for the oxidation of cyclooctene, and the reaction was > 80% selective for epoxide formation; cyclohexene yielded only ~ 3 % epoxide, the main products being cyclohexene-2-ol and cyclohexene-2-one. The oxidation of methylcyclohexane yielded mainly 1 -methylcyclohexanol and 2-, 3- and 4-methylcyclohexanones, with smaller amounts of the corresponding 2-, 3- and 4-methylcyclohexanols. The reaction of HO Ac' acids ( C F 3 C O O H and CHCl COOH) with (1) yields 2  paramagnetic Ru (TMP)(OAc')2 species. For the bis(CF COO) complex, a u,ff value of IV  3  e  2.5 p is consistent with a Ru(IV) S = 1 spin state, and the linear dependence of the H 1  B  chemical shifts of the TMP ligand with inverse temperature shows that a single spin state exists from -60 to +25 °C . The reaction of phenol with (1) studied in preliminary work earlier in this laboratory was shown to give the following products: a paramagnetic, S = 1 Ru(IV)-TMP  iv  species, 0.5 equivalents ofp-benzoquinone and 1.3 equivalents of H 0. The Ru(IV) 2  product was proposed to be Ru (TMP)(/?-OC6H40H) ; however, the data from the rv  2  present thesis work favour the formulation as Ru (TMP)(OC6H ) , while /?-hydroquinone IV  5  2  is formed via O-atom insertion at the para position of the phenol. Species (1) oxidizes the /7-hydroquinone formed to give ^-benzoquinone (and presumably H 0); the oxidation of 2  /j-hydroquinone itself is demonstrated in separate experiments (without phenol) to be catalytic, and under 1 atm 0 at -20 °C, ~ 200 turnovers are obtained after 22 h. The 0 2  oxidation of N, N-dimethylaniline to />-hydroxy-iV,iV-dimethylaniline by (1) in wet benzene is also catalytic, but less than 10 total turnovers are achieved at 50 °C under 1 atm air.  2  Table of Contents  Page  Abstract  ii  Table of Contents  vi  List of Figures  xii  List of Tables  xix  List of Abbreviations  xxi  Acknowledgements Chapter 1  xxiv Ruthenium Complexes as Oxidants for Organic Compounds  1  Introduction  2  Using 0 as a Terminal Oxidant: Nature's Cytochrome P-450  2  1.1.1 Metalloporphyrins as P-450 Models  7  1.2  Ruthenium(VIII) Complexes  9  1.3  Ruthenium(VII) Complexes  11  1.4  Ruthenium(VI) Complexes  12  1.4.1 Ruthenium(VI) Porphyrin Complexes  12  1.4.2 Ruthenium(VI) Non-Porphyrin Complexes  18  1.5  Ruthenium( V) Complexes  21  1.6  Ruthenium(IV) Complexes  22  1.7  Ruthenium(in) Complexes  26  1.8  Ruthenium(II) Complexes  27  1.9  Aims and Scope of this Thesis  29  1 1.1  2  vi  References for Chapter 1 Chapter 2  32  Experimental Methods  37  Materials  38  2.1.1 Gases  38  2.1.2 Solvents and Reagents  38  Instrumentation and General Experimental Procedures  40  2.2.1 UV-Visible Spectroscopy  40  2.2.2 Stopped-flow Kinetic Studies  41  2.2.3 Infrared Spectrophotometer  43  2.2.4 FT-NMR Instruments  43  2.2.5 Gas Chromatography Experiments  44  2.2.6 Elemental Analyses, X-ray Crystallography and Mass Spectral Analyses  46  2.3  Techniques  46  2.4  Synthesis and Characterization of Starting Compounds  46  2.1  2.2  References for Chapter 2 Chapter 3  3.1  3.2  55  Mechanism of Aerobic Oxidation of EAr3 (E = P, As, Sb)  56  Introduction  57  3.1.1 Aims of Phosphine Oxidation in Current Work  58  Sample Preparation and Data Analysis  59  3.2.1 Sample Preparation  59  3.2.1 Data Analysis  61  vii  3.3  3.4  Overview of the Mechanism of Tertiaryarylphosphine Oxidation  63  3.3.1 O-atom Transfer  68  3.3.2 Disproportionate of Ru^CTMPXO)  81  Ru (TMP)(L) Species and Catalytic Aerobic Oxidation of Phosphines  95  3.4.1 Ru (TMP)(L) Species  95  3.4.2 Catalytic Aerobic Oxidation of Phosphines  99  n  n  3.5  Conclusions  109  References for Chapter 3 Chapter 4 4.1  4.2  4.3  110  Catalytic Aerobic Oxidation of Alcohols and Alkanes  112  Introduction  113  4.1.1 Scope of Alcohol Oxidations in Current Work  114  Sample Preparation and Data Analysis  114  4.2.1 Sample Preparation  114  4.2.2 Data Acquisition and Analysis  117  Stoichiometric Oxidation of Alcohols by Oxoruthenium Species  120  4.3.1 Bis(alkoxo)porphyrinatoruthenium(IV) Species  120  4.3.2 Mechanism of Alcohol Oxidation by Ru (TMP)(0)  129  4.3.3 Aerobic Oxidations of Alcohols to Aldehydes and Ketones  141  Aerobic Oxidation of Tertiary Alkanes Catalyzed by Ru (porp)(0) Species  151  VI  2  4.4  VI  2  viii  4.5  Conclusions  154  References for Chapter 4 Chapter 5  155  Reactivities of Ru(TDCPP-Clg) Species  157  Introduction  158  5.1.1 Ru-Perhalogenated Porphyrins: Aims and Scope  159  Sample Preparation and Data Analysis  160  5.2.1 Sample Preparation in Catalysis Studies  160  5.2.2 Preparation of/ra«5-Ru (TDCPP-Cl8)(0)2  163  5.2.3 Data Acquisition and Analysis  166  5.3  Catalytic Aerobic Oxidation of Alcohols  167  5.4  Oxidation of Alkenes  171  5.5  Oxidation of Alkanes  177  5.6  Conclusions  185  5.1  5.2  VI  References for Chapter 5 Chapter 6  187  Preliminary Work: Reactions of Ru^(TMP)(0) with HX acids and Oxidation of Phenol and N,NDimethylaniline  189  6.1  Introduction  190  6.2  Experimental: Sample Preparation and Data Analysis  191  6.3  Ru (TMP)(X) Species  197  6.4  Oxidation of Phenol by Ru^(TMP)(0)  2  IV  2  2  210  6.4.1 Oxidation of Phenol  210  6.4.2 Kinetic Studies  220  ix  6.5  Oxidation of A^JV-Dimethylaniline by Ru (TMP)(0)  6.6  Conclusions  vl  2  233  References for Chapter 6 Chapter 7  225  235  Conclusion and Recommendations for Future Work  236  7.1  General Conclusions  237  7.2  Recommendations for Future Work  239  Appendix A  Kinetic Data for the Oxidation of EAr  241  Appendix B  Mathematical Derivation for the Equation Reflecting the Observed lst-Order Absorbance-Time Changes in the Oxidation of PPh by Ru (TMP)(0)  257  Appendix C  Oxidation of Alcohols and Alkanes: Kinetic and Catalysis Data  259  Appendix D  Supplementary Data for the Crystallographic Structures of Ru (TMP)(OR) Complexes  276  D.l Ru^TMPXO'Pr^  276  D.2 Ru^CTMPXOCHCC^Cl),),  284  Appendix E  Catalytic Oxidation of Alcohols, Alkenes and Alkanes by Ru(TDCPP-Clg) Species: Catalysis Data  293  E. 1  Oxidation of Benzyl Alcohol at 50 °C Under 1 atm air.  293  E.2  Oxidation of Alkenes under 1 Atm 0  294  E.3  Oxidation of Alkanes  295  E.4  GCMS Data for the Cyclohexene Oxidation  296  E.5  GCMS Data for the Cyclooctene Oxidation  300  E.6  GCMS Data for the Methylclohexane Oxidation  304  Kinetic Data for the Oxidation of Phenol by Ru (TMP)(0)  310  3  VI  3  2  IV  2  Appendix F  VI  2  2  Appendix G  Oxidation of N, N-Dimethylaniline by Ru (TMP)(0) : GCMS Data vl  2  xi  313  List of Figures Figure  Page  1.1  Molecular orbital (MO) diagram for O2 in its ground state  4  1.2  Illustration of Fe-Protoporphyrin-IX in Cytochrome P-450  5  1.3  Mechanism of Cytochrome P-450 oxidation  6  1.4  Structures of dianions of somefreebase porphyrins  8  1.5  Various 0 -oxidations catalyzed by Ru (TMP)(0)  1.6  Schematic representation of a chiral Ru (por*)(0) species  15  1.7  Illustration of several macrocyclic tetraaza and dioxadiaza ligands  19  1.8  Schematic representations of two Ru-oxo polypyridyl complexes  23  1.9  Catalytic cycle of a triple component ruthenium(II)/quinone/cobalt system for the aerobic oxidation of alcohols  30  2.1  Diagram of the sample handling unit of the Applied Photophysic stopped-flow spectrophotometer  42  3.1  Mechanism of oxidation of P(p-X-C H4)3, AsPh and SbPh by Ru (TMP)(0)  65  Room temperature UV-visible/time traces for the oxidation of PPh by Ru (TMP)(0) in benzene in the presence of 0=PPh  67  13  VI  2  2  VI  2  6  3  3  VI  2  3.2  VI  3  3.3  2  3  Plot of kobs versus [PPh ] for the initial O-atom transfer to PPh from Ru (TMP)(0)  71  Eyring Plots for the determination of AHi* and ASi* of the initial O-atom transfer reaction  72  3  3  VI  2  3.4  Hammett plot for logr values for the ki step at 20 °C -  3.6  Modified Hammett plot, AHi* versusCT,for the initial O-atom transfer reaction for P(p-X-C6H4) systems  77  Plot of molecular mass of P(/?-X-C6H4) and related substrates  78  3  3.7  3  versus AS2*  3.8  Plot of [PPh ] versus k o b s (slower 2nd reaction) at various concentrations of 0=PPh in benzne at 20 °C  82  „, „ 1 [0=PPh ] Plot of versus rpp j  84  3  3  39a  3  , „ , . , 20 °C (slower 2nd reaction) n  a t  n  3.9b  n  n  „, , 1 [OPPh l „ „ Plot of i — versus 7^7—per}—TTTTVT for the kinetic data of kobs [P(p-OMe-C H4) J the Soret shift from 430 to 412 nm (slower 2nd reaction)  85  „ 1 Plot of \ — versus  85  3  6  3.9c  t  kobs  [OPPh J \ , U  3  „ „, for the kinetic data of the  3  r T ) /  n  N n  [P(p-Me-C H4) ] 6  3  Soret shift from 430 to 412 nm (slower 2nd reaction) 39d  1 Plot of ; — versus kobs  r n  ,  [OPPh ] ; 3  c  r  i  N  1  [Pt>-F-C H4) ] 6  for the kinetic data of the  86  3  Soret shift from 430 to 412 nm (slower 2nd reaction) 3.9e  „, „ 1 [OPPbJ Plot of ; — versus , , u L  [P{/?-Cl-C H4) ] m  kobs  r  r  n  6  , „, for the kinetic data of the  86  3  Soret shift from 430 to 412 nm (slower 2nd reaction) 3.9f  „ 1 Plot of 1— versus kobs  [OPPh ] „, ™ 1^ \ i for the kinetic data of the 3  87  T T  [P(p-CF -C H4) ]  r r i /  6  3  3  Soret shift from 430 to 412 nm (slower 2nd reaction) 3.10  Plot of k o b s versus [PPh ] for the kinetic data of the Soret shift from 430 to 412 nm at 20.5 °C (slower 2nd reaction)  88  3 11  [PPh l Plots of ^ — versus [PPh ] for slower 2nd reaction  89  3  3  3  Kobs  3.12  Eyring plots derived from the temperature dependence data for the slower 2nd reaction for the PPh system  90  Room temperature ^ - N M R (200 MHz) spectra of Ru (TMP)(PPh ) in benzene-c/  97  3  3.13  n  3  6  xiii  3.14  Variable-temperature R and "P^HJ-NMR (300 MHz) > spectra of Ru (TMP)(PPh ) in toluene-o?  98  l  n  3  3.15  3.16a  8  H-NMR (300 MHz) spectrum of Ru (TMP)(AsPh ) in benzene-fife exposed to air for ~ 2 min at 25 °C  !  102  n  3  Catalytic oxidation of PPh in the presence of Ru (TMP)(0) under 1 atm air or 0 in benzene-afe at 24 °C  105  VI  3  2  2  3.16b  Catalytic oxidation of ^(p-F-CoVUh presence of Ru (TMP)(0) under 1 atm air or 0 in benzene-fife at 24 °C  106  Catalytic oxidation of P(p-OMe-C6H4) in the presence of Ru (TMP)(0) under 1 atm 0 in benzene-fife at 24 °C  107  Catalytic oxidation of P(p-Cl-C H4) in the presence of Ru (TMP)(0) under 1 atm 0 in benzene-fife at 24 °C  108  The kinetics of the stoichiometric oxidation of 'PrOH by Ru (TMP)(0) in benzene-fife under 1 atm Ar at 18.2 °C followed by H-NMR spectroscopy (300 MHz)  118  Room temperature 'H-NMR (300 MHz) spectra of Ru (TMP)(0'Pr) in benzene-fife with and without the presence excess TrOH  122  4.3  ORTEP diagram of Ru (TMP)(0 Pr)  124  4.4  ORTEP diagram of Ru (TMP)(OCH(CH Cl) )  4.5  Pseudo-1 st-order rate constant, kobs, as a function of excess "PrOH concentration in benzene-ofe under 1 atm Ar at 18.2 °C  131  4.6  Pseudo-1 st-order rate constant, k^s, as a function of [benzyl alcohol] at various temperatures in benzene-fife under 1 atm Ar  132  4.7  Eyring plots for the stoichiometric oxidation of 'PrOH by Ru (TMP)(0) under 1 atm Ar in benzene-fife  139  Eyring plots for the stoichiometric oxidation of benzyl alcohol by Ru (TMP)(0) under 1 atm Ar in benzene-fife  140  Mechanism of alkene epoxidation catalyzed by Ru (TMP)(0)  145  m  t n e  vl  2  3.16c  2  3  VI  2  3.16d  2  6  3  VI  2  4.1  2  VI  2  J  4.2  IV  2  IV  /  2  125  IV  2  2  2  VI  2  4.8  VI  2  4.9  VI  xiv  2  4.10  Plot of daily turnovers versus [benzyl alcohol] for the aerobic oxidation of benzyl alcohol catalyzed by Ru (TMP)(0) at 50 °C in benzene  149  Plot of total turnovers versus time for the aerobic oxidation of benzyl alcohol catalyzed by Ru (TMP)(0) at 50 °C  150  Plots of total turnovers versus time for the aerobic oxidations of Ph CH and adamantane catalyzed by Ru (porp)(0) species at 24 °C in benzene  153  Experimental setup for the oxidations of neat cyclohexene, cyclooctene and methylcyclohexane under 1 atm 0  162  5.2  Mass spectrum (EI) of Ru (TDCPP-Cl )(Cl)  165  5.3  Progress of the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by Ru (TDCPP-Clg)(0) in benzene at 50 °C  168  Progress of the aerobic oxidation of R, S-1 -phenylethanol to acetophenone catalyzed by Ru (TDCPP-Clg)(0) in benzene at 50 °C  169  5.5  Diagram illustrating a radical-chain mechanism proposed for the autoxidation of alkenes  174  5.6  Progress of the 0 -oxidation of neat cyclooctene under 1 atm 0 at 93 °C catalyzed by Ru (TDCPP-Cl )(0)  176  5.7  Diagram showing a radical-chain mechanism for the 0 oxidation of alkanes via peroxide decomposition catalyzed by Fe-porphyrin species  178  5.8  Aerobic oxidation of Ph CH to Ph COH catalyzed by Ru (TDCPP-Cl )(0) in benzene at 24 °C  185  6.1  Mass spectrum of Ru (TMP)(CF COO) (FAB ionization in a 3-nitrobenzylalcohol matrix)  194  6.2  UV-visible spectra recorded on monitoring the reaction of Ru (TMP)(0) with phenol in benzene under 1 atm 0 to form Ru (TMP)(OC H )  195  VI  2  4.11  VI  2  4.12  VI  3  5.1  2  2  IV  8  2  VI  2  5.4  YI  2  2  VI  2  8  2  2  3  3  VI  8  2  IV  3  2  IV  2  2  IY  6  5  2  XV  f  6.3  Mass spectra of solid residue isolated from the reaction of Ru (TMP)(0)2 with iV.iV-dimethylaniline in benzene-^ under 1 atm air  196  UV-visible spectra of Ru (TMP)(0) in benzene at 25 °C acquired after the addition of CF COOH and CHCl COOH  198  H-NMR (300 MHz) spectrum of Ru (TMP)(CF COO) in toluene-ds at -57.1 °C under air  201  H-NMR (300 MHz) spectrum of Ru (TMP)(CHCl COO) in toluene-dg at 17.3 °C in vacuo  202  VI  6.4  VI  2  3  6.5  !  6.6  X  6.7  2  IV  3  2  IV  2  2  Inverse temperature plot, 'H-chemical shifts (300 MHz) versus T\ for Ru (TMP)(CF COO) in toluene-ofe  204  Inverse temperature plot, 'H-chemical shifts (300 MHz) versus T\ for Ru (TMP)(CHCl COO) in toluene-^  205  6.9  Infrared spectra of free CF COOH and Ru (TMP)(CF COO) obtained as Nujol mulls in KBr plates  207  6.10  Infrared spectra of free CHCl COOH and Ru (TMP)(CHCl COO) obtained as Nujol mulls in KBr plates  208  6.11  Mass spectrum (EI ionization) of Ru (TMP)(OC H )  212  6.12  ^ - N M R spectrum (400 MHz, C D ) for the metathesis reaction of Ru (TMP)('OPr) with /?-hydroquinone under Ar  213  'H-NMR spectrum (200 MHz) acquired after 2 min for the reaction between Ru (TMP)(0) and /?-hydroquinone (1:2) in benzene-di, under 1 atm air  216  Illustration showing the proposed phenol oxidation mechanism based on the reversible interconversion of Ru (TMP)(0) to Ru (TMP)(OH) and phenol metathesis reactions  218  IV  3  6.8  2  IV  2  2  IV  3  3  2  2  IV  2  2  rv  6  6  5  2  6  IV  2  6.13  VI  2  6.14  IV  IV  2  6.15  Plots of kobs versus [phenol] (0.1 -1 M) for the oxidation of phenol by Ru (TMP)(0) in benzene under 1 atm air at various temperatures VI  2  xvi  221  6.16  Plot of kobs versus [phenol] (0.01 - 0.1 M) for the oxidation of phenol by Ru (TMP)(0) in benzene at 20 °C under 1 atm air  221  YI  2  6.17  Log(kobs)  versus log[phenol] plot for the oxidation of phenol at various temperatures  223  6.18  Arrhenius plot, ln(A) versus T , for the parameter A for the reaction between Ru (TMP)(0)2 and phenol  224  Illustration of the proposed scheme for the oxidation of N,Ndimethylaniline catalyzed by Ru (TMP)(0)2 under 1 atm air  226  'H-NMR (200 MHz) spectra for the reaction "Ru (TMP)(0) + 4 /V.N-dimethylaniline" in benzene-fife at 25 °C under 1 atm air  228  ^ - N M R (200 MHz) spectra monitoring the reaction "Ru (TMP)(0) + 10 iV^-dimethylaniline" in benzene-fife at 25 °C under 1 atm Ar  229  Absorbance-time traces monitored at 422 nm by stopped-flow spectrophotometry for the reaction of Ru (TMP)(0) with PPh  241  1  VI  6.19  VI  6.20  VI  2  6.21  VI  2  A. 1  VI  2  3  A.2  Semilog and Guggenheim plots for [PPh ] = 4.05 x 10' M trace in Figure A. 1  241  A. 3  Absorbance-time traces monitored at 430 nm by stopped-flow spectrophotometry for the loss of the intermediate Ru (TMP)(0)(0=PPh )  242  Semilog and Guggenheim plots for [PPh ] = 3.83 x 10" M, [0=PPh ] - 3.93 X 10" M trace in Figure A.3  242  Absorbance-time traces monitored at 412 nm by stopped-flow spectrophotometry for the appearance of the product Ru (TMP)(PPh )  243  Semilog and Guggenheim plots for [PPh ] = 3.83 x 10" M, [0=PPh ] = 3.93 X 10" M trace in Figure A.5  243  ORTEP plot of Ru (TMP)(0'Pr) (sideway view) along the porphyrin plane  276  3  3  VI  3  A.4  3  3  3  3  A. 5  n  3  A. 6  3  3  3  3  D. 1  tv  2  xvii  D.1.2  Stereoview of Ru (TMP)(0'Pr)  276  D.2.1  PLUTO plot showing the partial structure of Ru (TMP)(OCH(CH Cl) )  284  D. 2.2  Stereoview of Ru (TMP)(OCH(CH Cl) )  285  E. 4.1  GC trace for the run in Table E.2.2 for the oxidation of neat cyclohexene  296  E.4.2  Low resolution mass spectra (EI) for the various products from the cyclohexene oxidation  297  E.5.1  GC trace for the run in Table E.2.1 for the oxidation of neat c/s-cyclooctene  300  E. 5.2  Low resolution mass spectra (EI) for the various products from the cyclooctene oxidation  3 01  E.5.3  Known fragmentation patterns for cyclooctene oxide and cz's-7-oxabicyclo [4,3,0] -nonane  303  E.6.1  GC trace for the run in Table E.3.1 for the oxidation of neat methylcyclohexane  304  E.6.2  Low resolution mass spectra (EI) for the various products from the methylcyclohexane oxidation  305  IV  2  IY  2  2  2  IV  2  2  2  G. 1  GC trace of the benzene solution of Ru (TMP)(0) with added N,iV-dimethylaniline used for GCMS analysis  313  G.2  Mass spectrum of analyte at 2:23 in the GC trace in Figure G. 1  314  G.3  Mass spectrum of analyte at 4:15 in the GC trace in Figure G. 1  314  VI  2  xviii  List of Tables  Page  2.1  Optimum conditions of GC runs used throughout this thesis work for the separation of mixtures of compounds  45  3.1  Second-order rate constants, k i , for the initial O-atom transfer from Ru (TMP)(0) to various phosphines, AsPh and SbPh substrates in benzene  70  Activation parameters, AHi* and ASi*, for the initial O-atom transferfromRu (TMP)(0) to P(/>-X-C H4) , AsPh and SbPh substrates.  73  3.3  Values of j , dissociation of OPPh Ru^TMPXOXOPPh;,)  89  3.4  k. Values of, , ^ i/ obtainedfromthe kinetic data for the  VI  2  3.2  3  3  VI  2  6  3  3  3  2  from  3  93  2  K K4JS. 2  2  3  spectral change of the Soret maximumfrom430 to 412 nm 3.5 3.6  !  H and P{'H}-NMR data for various Ru (TMP)(L) species 31  100  n  Total turnovers for various phosphines catalytically oxidized in benzene-fife at 24 °C under 1 atm 0 in the presence of Ru (TMP)(0)  104  4.1  ^ - N M R data for /rfirra-Ru (TMP)(OR) species  127  4.2  Selected pseudo-1 st-order rate constants, kobs, for the stoichiometric oxidation of'PrOH to acetone by Ru (TMP)(0) in benzene-fife  134  2nd-order rate constants, k , for the stoichiometric oxidations of 'PrOH and benzyl alcohol in benzene-fife by Ru (TMP)(0)  138  2  VI  2  IV  2  VI  2  4.3  2  VI  4.4  2  Catalytic activity of Ru (porp)(0) [porp=TMP or TDCPP] towards 0 -oxidation of'PrOH and benzyl alcohol in benzene  148  Oxidation of neat alkenes catalyzed in the presence of Ru (TDCPP-Cl )(CO) or Ru (TDCPP-Cl )(0) under 1 atm  173  VI  2  2  5.1  n  VI  8  0  8  2  xix  2  5.2  Oxidation of methylcyclohexane in the presence of Ru (TDCPP-Cl )(CO) or Ru (TDCPP-Cl )(0) under 1 atm 0  180  IR absorption frequencies for some Ru-porphyrin complexes in the 1000 cm" region  200  Observed variable temperature ^ - N M R chemical shifts for some Ru (TMP)(X) species  206  Values for the parameter A for the oxidation of phenol by Ru (TMP)(0) derived from the expression kobs = A.[phenol]  223  n  YI  g  8  2  2  6.1  1  6.2  IV  2  6.3  .  YI  2  3/2  6.4  Oxidation of W-dimethylaniline catalyzed by Ru^(TMP)(0) under 1 atm air in benzene  XX  2  232  List of Abbreviations [X]  concentration of species X  A or Abs  absorbance  A  angstrom unit (10" m)  ABN  azobis(2-methylpropionitrile); common radical initiator  Ar  aryl group (or argon)  BHT  2,6-ditertbutyl-4-methylphenol  bpy  2,2'-bipyridine  dcbpy  6,6'-dichloro-2,2'-bipyridine  d  day (unit of time)  e  extinction coefficient in UV-visible spectra  EI  electron impact  exp(x)  natural base e raised to the power of x  FAB  fast atom bombardment  FED  flame ionization detector  FT  Fourier Transform  GC  gas chrotomatography  GCMS  tandem gas chrotomatography-mass spectrometry  h  Planck's constant, 6.626 x 10" J s (or hour)  H2TDCPP  /weso-tetra(2,6-dichlorophenyl)porphyrin  FLTMP  /weso-tetramesitylporphyrin  Int  area of integration in 'H-NMR spectrum  K  Kelvin  k„  kinetic rate constant for nth elementary step  k  Boltzman's constant, 1.38x10' J K"  10  34  23  b  kn/ko  kinetic isotope effect  kobs  pseudo-first order rate constant  In  natural logarithm  log  base ten logarithm  xxi  1  M  molarity  m  multiplet, as used in the description of NMR resonances  ivf  parent ion (mass spectrometry)  TM-CPBA  meto-chloroperbenzoic acid  m-H/w'-H  /we/a-proton  M.W.  molecular weight Bohr Magneton  P-eff  effective magnetic susceptibility  mg  milligram  MO  molecular orbital  (m)mol  (milli)mole  V  infrared frequency  nm  nanometer  o-Me  o/Y/20-Methyl group  OEP  dianion of 2,3,7,8,12,13,17,18-octaethylporphryin  7C*  antibonding 71-molecular orbital  P-450  cyctochrome P-450 enzyme system  p-n  para-proton  p-Me  para-Methyl group  Ph  phenyl group  ppm  parts per million  qvib  vibrational partition function  R  alkyl group (or Ideal gas constant)  Ru  ruthenium porphyrin  a  Hammett factor  s  second (unit of time)  S  spin quantum number  t  triplet, as in the description of NMR resonances  %T  percent transmittance, as used in IR spectroscopy  T  temperature  xxii  TDCPP  dianion of /weso-tetra(2,6-dicrilorophenyl)porphyrin  TDCPP-Clg  dianion of /weso-tetra(2,6-dichlorophenyl)-/?octachloroporphyrin  terpy  terpyridine  THF  tetrahydrofuran  TLC  thin layer chromatography  TMP  dianion of /weso-tetramesitylporphyrin  TMS  tetramethylsilane  TPFPP  dianion of /weso-tetra(pentafluorophenyi)porphyrin  TPFPP-Clg  dianion of /weso-tetra(pentafluorophenyl)-/?octachloroporphyrin  TPP  dianion of /weso-tetraphenylporphyrin  TRIZMA® HC1  tris(hydroxymethyl)aminomethane hydrochloride (Sigma Chemicals)  UBC  University of British Columbia  VT  variable temperature  W  Watt  X  mole fraction of nth species  n  xxiii  Acknowledgments This is perhaps the most difficult section to write; perhaps I am not used to committing myself in writing. Clearly, thesis writing is not possible without readily available resources. I have to say that UBC and NSERC have treated me well in the last four years in the form of a scholarship. Without some luck, my work would not have gone as smoothly as it had in the last few years; success is 100% hard work, but luck is the catalyst. To acknowledge specific names would do injustice to those I do not mention. Everyone around me has contributed to this thesis, either though his/her spiritual support or helpful comments/suggestions. (Those who deserve to have a bigger share of my thanks willfindit in some other form!)...If this page does not make any sense, probably it is because BRJ has not edited this page (and I am quite happy that there is ONE page in this thesis that did not undergo any editing); nonetheless, this thesis appears that much more presentable than it was when it wasfirstcompleted is due in no small part to my supervisor...  THANKS !!!  xxiv  Chapter 1  Chapter 1 Ruthenium Complexes as Oxidants for Organic Compounds  1  References on p. 32  Chapter 1  1 Introduction The oxidation of organic functional groups plays an important role in the synthesis of organic compounds in the laboratory and industry. Classical stoichiometric oxidants, 1  such as permanganate and dichromate, used for oxidizing organics are disfavoured because of growing environmental concerns over the disposal of such ecologically harmful metal wastes. High-valent oxoruthenium complexes are competent oxidants, the classic 2  example being RuOu, which found its place in laboratory syntheses in the 1950s. (RuCv 3  is not implied to be environmentally benign.) In this chapter, advances in the last few years pertaining to the development of the oxidation chemistry of ruthenium complexes will be discussed, with particular focus on, but not limited to, alkane hydroxylations. The subject is vast, and this is by no means a complete review; there are several recent reviews on oxoruthenium complexes. The work in the present thesis, which pertains to the 4  catalytic oxidations effected by ruthenium porphyrin species, will be incorporated in the discussion of such recent work where appropriate. Some of the material in this thesis has been published or presented in conference proceedings. 5  6  1.1 Using O2 as a Terminal Oxidant: Nature's Cytochrome P-450 The ideal oxidant satisfies the following criteria: i) economically affordable; ii) naturally abundant; iii) produces clean reaction by-products; iv) high reactivity and v) high selectivity under relatively mild conditions. Usually, only some of these conditions can be satisfied at the expense of others. In recent years, the use of molecular oxygen as an alternative to currently used oxidants has led to intense research. Already, O2 satisfies 7  2  References on p. 32  Chapter 1  thefirstthree criteria out of the five (0 fromair would be more inexpensive than pure 2  0 ); however, 0 exists in a paramagnetic triplet ground state (see Figure 1.1), and thus 2  2  the reaction of 0 with diamagnetic organic molecules is invariably slowed down in 2  overcoming this spin-forbidden barrier. If any reaction with 0 proceeds, it usually 2  operates via a radical (paramagnetic) pathway. Free-radical reactions are usually undesired as they give to little regio- and enantio-selectivity. Strong oxidants such as Ru0 , Os0 and Mn0 " are high-valent, diamagnetic 4  4  4  oxometal species capable of oxidizing a variety of organic substrates. ' The active centre 1 8  in the ubiquitous cytochrome P-450 enzyme (from now on referred to as P-450), found in abundance in the mamallian liver, as well as among many other living organisms, is believed to oxidize substrates via a high-valent oxoiron porphyrin intermediate (see Figures 1.2 and 1.3). This Fe=0 moiety is generated by the reductive activation of 0 9  2  (Eq. 1.1), in which one O-atom is reduced to H 0, while the other O-atom is used for 2  oxidation (Figure 1.3). RH + 0  2  + 2FT + 2e' —  ROH + H 0  (1.1)  2  Nature's P-450 system perhaps represents the optimal conditions for the oxidation of organic substrates. The mechanism of the O-atom transfer with a P-450 oxidation is generally accepted to occur via the "oxygen rebound mechanism", depicted in Figure 1.3.  9,10  The hydrophobic hydrocarbon substrate occupies a binding site in the protein  cavity adjacent to the iron centre and is oxidized as the iron is activated to a high 11  valence. In hydrocarbon hydroxylation a hydrogen atom is thought to be abstracted, and the OH group bound to the Fe-centre is then transferred to, and recombines with, the  3  References on p. 32  Chapter 1  hydrocarbon fragment (R*) before it leaves the protein cavity, hence oxygen rebound. Perhaps a synthetic metalloporphyrin system mimicking the active centre in P-450 may become practical, hence affording the use of O2 (with appropriate reductants) as a clean and inexpensive oxidant without the need of the protein in a natural enzyme.  V  ^N- a /  2  s  ENERGY ^^t-\CT*ls  Figure 1.1  Molecular orbital (MO) diagram for 0 in its ground state. Note that the energy levels are not drawn to scale, and the diagram shows only the relative energies of the orbitals. The ground state electronic configuration is a E state. Two unpaired electrons occupy the highest occupied molecular orbitals (HOMO), a pair of degenerate of n -antibonding orbitals. 2  3  4  References on p. 32  Chapter 1  S = thiolate RS from the cysteine residue of cytochrome P-450 protein  Figure 1.2  The active centre of cytochrome P-450 enzymes is an iron protoporphyrin-IX moiety. The 5th coordination site is occupied by a sulfur-bound thiolate from a cysteine amino acid residue of the P-450 protein.  5  References on p. 32  Chapter 1  ~Fe~"" = iron protoporphyrin-LX moiety  Figure 1.3  Mechanism of the catalytic cycle of the cytochrome P-450 enzyme. The oxidizing species is written as an oxoiron(IV) porphyrin radical-cation species, which is favoured in model studies. ' Two equivalents of reductant are not required if an O-atom donor is used; this bypasses the full P-450 cycle and proceeds via what is known as the shunt pathway. 9 10  6  References on p. 32  Chapter 1  1.1.1 Metalloporphyrins as P-450 Models Generally, synthetic porphyrins fall into three classes or generations when it comes to the description of metalloporphyrin oxidation catalysts (see Figure 1.4).  12  The first  generation metalloporphyrin catalysts are TPP* derivatives (OEP derivatives also have t  been used). Such porphyrins are susceptible to destruction under the oxidizing conditions that exist in the reaction medium, or to deactivation to the thermodynamically more stable p-oxo-dinuclear species;  13  however, the steric bulk present in TMP^ prevents the  formation of p-oxo-diruthenium species, and a derived monomeric trans-Ru (IMP)(0)2 VI  species exhibits a rich array of oxidation chemistry (see Section 1.4.1). The second generation metalloporphyrin catalysts, with the addition of halogens on the /weso-phenyl group for improved stability, are improvements over the first-generation type, and the steric bulk of the 2- and 6- chloro groups of TDCPP also prevents the formation of p5  oxo-dinuclear ruthenium species. To go one step further, the third generation metalloporphyrins have the yff-pyrrolic positions halogenated as well. One can envision the steric repulsion amongst the halogens, especially at the /2-pyrrole positions, and the porphyrin adopts a saddle-shaped conformation to relieve such stress. Crystallographic analyses on some such metalloporphyrins show that they adopt saddle-shaped structures;  14  these results are complemented by theoretical studies which favour a non-planar conformation for such highly halogenated metalloporphyrins.  15  t TPP = dianion of /weso-tetraphenylporphyin (see Figure 1.4). O E P = dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin. T M P = dianion of /neso-tetramesitylporphyrin (see Figure 1.4). T D C P P = dianion of we5o-tetra(2,6-dichlorophenyl)porphyrin (see Figure 1.4). f  ?  5  7  References on p. 32  Chapter 1  C 1 Generation Porphyrins  2nd Generation Porphyrins  3rd Generation Porphyrins  A, B, C, Z = H (TPP) /weso-TetraPhenylPorphyrin  B,C,Z = H; A -CI (TDCPP) we50-Tetra(2,6DiChloroPhenyl)Porphyrin  B,C = H; A,Z = C1 (TDCPP-Clg)  st  A, C = Me; B, Z = H (TMP)  meso-  A,B,C = F; Z = H (TPFPP)  TetraMesitylPorphyrin  mesoTetra(PentaFluoroPhenyl)Porphyrin  A B , C = F; Z = CI (TPFPP-Clg) A,B,C = F; Z = F (TPFPP-F ) 8  A,B,C = F;Z = Br (TPFPP-Br ) 8  Figure 1.4.  Abbreviations and names of some dianions of free-base porphyrins that are based on the tetraphenylporphyrin family mentioned in this chapter and the rest of this thesis. A systematic nomenclature has been developed for porphyrins, but the above abbreviations (or ones similar to those used by other authors) are more convenient.  g  References on p. 32  Chapter 1  Experimentally, the extensive halogenation appears to increase the stability, and above all the reactivity of the metalloporphyrin catalysts.  16  Ruthenium, periodically analogous with iron, was a natural choice in the extension of iron porphyrin chemistry. The active species carrying out the P-450 oxidation is generally accepted to be an extremely unstable and reactive, high-valent oxoiron moiety. ' By switching to ruthenium, it was hoped the chemistry could be "slowed 9 10  down" to allow for mechanistic studies. '  2 13  Also, the wide range of oxidation states  available, as high as 8+, makes ruthenium a potentially powerful oxidant (see Sections 1.2 to 1.8). To date, a number of oxidations carried out by ruthenium porphyrins has been discovered and investigated (examplesfromReferences 2,5,6,7,22-25,2730,32,34,38,51,53,55,59 are discussed in the following sections) but the oxidation chemistry of ruthenium non-porphyrin species is also very rich (examples from References 3,4,17-20,39-50,52,57,61).  1.2 Ruthenium(VHI) Complexes The highest attainable oxidation state for ruthenium is +8. The most well-known and perhaps the only well-defined ruthenium(VIII) complex is RuO/t. ' The potential of 1 3  Ru04 as a laboratory reagent for organic synthesis was not realized until the 1950s, even 3  though the compound had been discovered early in the turn of the century. In the laboratory, Ru0 findswide use in the oxidation of secondary alcohols to ketones, ' ' '  1 3 4 17  4  but the oxidation of primary alcohols almost always over-oxidizes the aldehyde product to the carboxylic acid, diminishing the value of this reagent in this respect. Perhaps Ru0 is 4  9  References on p. 32  Chapter 1  of greater importance in thefieldof carbohydrate chemistry, where the selective oxidation of the hydroxyl groups in carbohydrates to carbonyl groups without oxidizing the other protected groups is possible. Lee and Van den Engh performed mechanistic studies on 1  the stoichiometric oxidation of alcohols by Ru0 , 4  1 7  and found that two different rate-  limiting steps govern the overall rate of the reaction at different pH ranges. At very high acidities, carbenium-ion formation was rate-determining, but at lower acidities (1 to 6 M perchloric acid) hydride abstraction was the slow step. The stoichiometric alcohol oxidation by RuC»4 is represented in Eq. 1.2, and the process can be made catalytic if the tetraoxide is regenerated (Eq. 1.3). Ru0 + 2RR CH OH — 4  1  Ru0 -2H 0 + 2 RRiCO  2  2  Ru0 »2H 0 + 2NaI0 — 2  2  4  (1.2)  2  Ru0 + 2NaI0 + 2 H 0 4  3  (1.3)  2  Hence, instead of using the tetraoxide stoichiometrically, in the presence of excess oxidizing agents such as hypochlorite or periodate, Ru0 can be regenerated catalytically, 4  a definite advantage over using a large, stoichiometric amount of the tetraoxide. Ru0 can also be formedfromlower-valent ruthenium species, such as RuCl3 nH 0. #  4  18  2  More recently, Ru0 generated in situ has been used in the hydroxylation of 4  saturated hydrocarbons. The stoichiometric oxidation of cis and *ra«s-pinane with a 18  RuCl / NaI0 / (CC1 / CH CN / H 0) system showed some interesting mechanistic 3  4  4  3  2  insights. In summary, the bond-breaking in the saturated hydrocarbons was observed mainly to occur at tertiary C-H bonds and was proposed to occur via a two-electron hydride transfer pathway. Of greater interest is that the analysis of the numerous products  10  References on p. 32  Chapter 1  from the oxidation of the pinanes by the in situ RuGu indicated that an unprecedented methyl (1°) C-H cleavage occurred.  1.3 Ruthenium(VII) Complexes The perruthenate ion, RuOY, is the only well-defined oxoruthenium(VlI) complex. Lee and Congson have also carried out some mechanistic studies on the oxidation of alcohols by RuOV, and invoked afree-radicalmechanism, as the oxidation of 19  cyclobutanol cleaved the C-C bond and yielded mainly butanoic acid rather than cyclobutanone. More recently, the same group investigated the oxygen-atom transfer properties of the perruthenate ion to sulfides;  20  here, the active oxidizing species was  proposed to be afive-coordinateoxoruthenium(VII) species formed by coordination sphere expansion (Eq. 1.4).  OH C\ O  X>  OH-  O-  -O O  I £> O-  The oxidation of the thioether substrate was proposed to occur via either direct O-atom transfer or attack of the S lone pair on an empty 7i*-orbital of Ru=0, followed by the release of the S=0 moiety. Both mechanisms have been considered for other O-atom transfer reactions; '  21 29  however, kinetic and mechanistic data are generally lacking in  ruthenium oxidation chemistry, and the O-atom chemistry is not fully understood.  ll  References on p. 32  Chapter 1  1.4 Ruthenium(VI) Complexes Many oxoruthenium(VI) complexes are competent oxidation reagents or catalysts. Examples from both non-porphyrin and porphyrin work are numerous, with the latter emerging in recent years. These complexes contain high-valent ruthenium-oxo moieties capable of oxygen-atom transfer or C-H bond cleavage.  1.4.1 Ruthenium(VI) Porphyrin Complexes The first dioxoporphyrinatoruthenium(VI) complex,fraws-Ru (TMP)(0)2,was VI  discovered independently by Grove's group and this group at UBC. 22  23  The  Ru (TMP)(0)2 complex can be formed by the /weto-chloroperbenzoic acid (/w-CPBA) VI  oxidation of Ru (TMP)(CO), or by the aerobic oxidation of Ru (TMP)(L) ( L = MeCN, n  n  24  2  THF, N or vacant ). More recently, Ru (TMP)(0) was reported to be generated by 25  26  VI  2  2  oxidizing Ru (TMP)(THF) with N 0 . n  2  2  27  The use of TMP as a ligand, with its methyl  substituents on the 2- and 6- positions on the meso-phenyl groups, prevents dimerization of the porphyrin complex to p-oxo-dinuclear ruthenium(IV) species, which are generally regarded as catalytically inactive, thermodynamic sinks. '  2b 13  The use of TMP for catalytic  systems was thus an improvement over the use of unhindered Ru(TPP) species. The Ru (TMP)(0) complex is a versatile, stoichiometric and 02-catalytic oxidant YI  2  (see Figure 1.5). Both of the oxygen atoms in Ru (TMP)(0) can be used for the VI  2b  2  oxidation of substrates, hence this shows that the dioxo species exhibits genuine dioxygenase-type activity. Under air or O2 at mild conditions, the following oxidations catalyzed by Ru (TMP)(0) take place: alkenes ' IY  25 28c  2  12  or steroids ' to corresponding 28a b  References on p. 32  Chapter 1  rt« (MeCN) n  2  O 2 / benzene OEAr /f« (EAr3)  3  EAr  3  R vi(0)  «  n  u  Ru™(Q)  2  Ph,C aldehyde/ketone J?« (OR) IV  Ru (0) w  J  RM (OSR ) 1 1  2  2  2  Ru = Ru(TMP) unit Figure 1.5.  Various oxidations carried out by Ru (TMP)(0) in benzene or toluene; the processes become catalytic in the presence of excess substrate under 1 atm air or 0 . The intermediates and/or products, where indicated, are identified based on spectroscopic or structural evidence. Higher temperatures usually speed up the rate of catalysis; however, the porphyrin decomposes faster under such conditions than at room temperature. vl  2  2  13  References on p. 32  Chapter 1  epoxides, thioethers to sulfoxides, tertiaryarylphosphines, ' ' ' AsPh '  6a,t  SbPh3 '  5a,6a,t  29  5b 6a 24 t  5b  3  5b  6a,t  to the corresponding oxides, alcohols to aldehydes or ketones,  and and the  tertiary alkane Ph CH to Ph COH. Stoichiometrically, Ru (TMP)(0) hydroxylates f  3  VI  3  2  activated mono-substituted aromatic rings, such as phenol ' and jV,A/-dimethylaniline to 29a b  /?-hydroquinone and /?-hydroxy-7V,A'-dimethylaniline, respectively.* Prior to this thesis r  work, mechanistic details and a kinetic database were generally lacking on the Ru (TMP)(0)2 oxidation chemistry, and the present work has sought to study such VI  systems in more detail, as well as to develop catalytic CVoxidation systems based on the dioxo complex. Recently, a catalytic system based on Ru (TMP)(0)2 using pyridine-A'-oxide was VI  developed, with remarkable activity towards the hydroxylation of secondary and tertiary 30  alkanes. For adamantane, up to 14000 turnovers (giving primarily 1-adamantanol) were realized at ambient conditions. Water inhibited the catalytic activity of the system; however, trace anhydrous acid (HC1 or HBr) enhanced the rates of catalysis. Treatment of a benzene solution of Ru (TMP)(0) with HC1 (gaseous or aqueous) has been suggested YI  2  to produce the complex Ru (TMP)(Cl)2, ' ' and the active catalytic species in the above IV  30 31 ¥  system was proposed to be Ru (TMP)(0)(Cl) . VI  + 30  Of note, Ru (TMP)(CO) was an active n  catalyst precursor, and even Ru (TPP)(CO) was shown to be effective in hydroxylations. n  In fact Ru (TPP)(CO) was the most effective catalyst precursor, oxidizing adamantane to n  1-adamantanol and adamantane-1,3-diol, with a trace of 2-adamantanone (68 : 25 : 1), the total turnover being 120000 after heating for 6 h at 80 °C in benzene.  ' Present work to be discussed in later chapters. * The reaction of H X acids with Ru (TMP)(0) will be discussed in Chapter 6. VI  2  14  References on p. 32  Chapter 1  The first chiral picket-fence trans-R.u (poT*)(0) complex was synthesized n  2  recently (por* = chiral porphyrin ligand, see Figure 1.6), and some chiral recognition 32  was observed in the stoichiometric oxidation of R- and S-phosphine mixtures. For the  a,P,a,P isomer of the dioxoruthenium porphyrin, the oxidation of R- and SP(CH Ph)(Ph)(Me) showed that the i?-enantiomer was oxidized more selectively to the 2  phosphine oxide (R.S = 2.4); however, the phosphorus binding-preference in the final Ru(II)-product, Ru (por*)(phosphine) , was the ^-configuration about phosphorus (S.R 33  n  2  = 2.3 preference of binding to Ru).  Figure 1.6.  Thefirstchiral picket-fence dioxoporphyrinatoruthenium(VI) species. The ot,P,oc,P and oc,a,P,P isomers are shown above.  15  References on p. 32  Chapter 1  Some Ru (porp)(0)2 species (where porp = TPP-x and OEP, the non-sterically VI  f  34  hindered porphyrins) have been prepared without the expected formation of the inactive p-oxo-dinuclear ruthenium(IV) species. '  2b 13  The Ru (porp)(CO)(MeOH) precursors were n  oxidized by /w-CPBA in EtOH/CH Cl2, which resulted in the formation of the 2  corresponding dioxo species. A coordinating solvent such as EtOH appears to be crucial in preventing the formation of the p-oxo-diruthenium species. Of note, the dioxo species were reported to be capable of oxidizing stoichiometrically the tertiary alkanes adamantane and methylcyclohexane to the corresponding tertiary alcohols with yields of approximately 20% based on the metal complex. Ethylbenzene was also oxidized to 1phenylethanol and acetophenone. Epoxidations of alkenes were also reported in the studies.  34  In all these cases, it appears that the dioxo species eventually do form p-oxo-  dinuclear ruthenium(IV) species, thought to be due to contamination by water. The fact that these dioxo species also oxidized alcohols leads one to question the true identity of the Ru-product in the alkene oxidation reactions; Ru (TPP)(0)«EtOH or IV  Ru (TPP)(OH) «EtOH was proposed as the Ru-product based solely on 'H-NMR IV  2  spectroscopy in a CD CD OD/CDCl3 solvent system. Studies carried out in this thesis 3  2  work show that a bis(alkoxo)ruthenium(IV) species is the inorganic product of alcohol oxidation with the Ru (TMP)(0)2 species, "' and that excess alcohol can exchange VI  5  63  rapidly with the alkoxo ligands. It seems likely that Ru (porp)(OR)2 [R = CD or IV  3  CD CD )] species are formed in the conditions noted above. 2  3  TPP-x = dianion of weso-tetra(para-substituted-phenyl)porphyrin (see Figure 1.4).  16  References on p. 32  Chapter 1  A most exciting breakthrough in ruthenium porphyrin oxidation chemistry came about with the use of halogenated porphyrins, commencing with /ra«5-Ru (TDCPP)(0)2, VI  which was shown to be a much more robust catalyst than the TMP analogue;  29  an iron-  TDCPP system had been demonstrated earlier to epoxidize alkenes efficiently using Oatom donors.  35  The Ru (TDCPP)(0) species exhibits very much the same chemistry VI  2  described in Figure 1.5, '* generally with higher reactivity than the TMP analogue due to 29  the increased electronegativity on the /weso-phenyl rings. Recently, iron, chromium and manganese complexes of TPFPP were reported to catalyze the aerobic oxidation of light 5  alkanes, such as isobutane and propane under 0 pressures < 1000 psi at temperatures 2  reaching 150 °C.  36  Further halogenation of the eight /^-pyrrole positions lying on the  porphyrin plane led to some remarkably reactive species. The use of Fe (TPFPPm  Br )(Cl)^ as a catalyst precursor afforded a system that oxidized isobutane to ferf-butanol 8  with turnovers of about 13000, again under 1000 psi 0 but now the reaction proceeds at 2  room temperature. Of note, there has been some debate as to whether a genuine oxoiron species is involved, or whether free-radical hydroperoxide decomposition is responsible 36  for the actual oxidation. '  163 37  On the ruthenium front, very little work has been done on  such perhalogenated Ru-porphyrins, except for the recent synthetic/structural studies with TPFPP-Clg systems, and the work to be described in Chapter 5 on the aerobic oxidation 14  of alcohols, alkenes and tertiary alkanes catalyzed by some Ru(TDCPP-Clg) species.  Present work to be discussed in later chapters. TPFPP = dianion of weTO-tetra(2,3,4,5,6-pentafluorophenyl)porphyrin (see Figure 1.4). Refer to figure 1.4 for the abbreviations for these 3rd generation porphyrins.  17  References on p. 32  Chapter 1  The 6+ formal oxidation state is the highest observed to date for ruthenium in any ruthenium porphyrin complex, although a Ru(VT) porphyrin-radical-cation has been formed in the oxidation of Ru (porp)(0) , porp = TMP or OEP, by phenoxathin VI  2  hexachloroantimonate(V). A g-value of 2.002 observed in the ESR spectrum taken at 38  77 K, a blue-shifted Soret band and a broad Q-band are suggestive of the formation of a porphyrin radical-cation. The oxidation of diphenylsulfide and several alkenes by these radical-cation species implied that they are stronger oxidants than the non-radical Ru(VI) counterparts. The removal of one electronfromthe porphyrin ligand likely increased the electrophilicity of the Ru-oxo moieties, and hence, their reactivities as well.  38  1.4.2 Ruthenium(VI) Non-porphyrin Complexes A group of /raws-dioxomthenium(VI) complexes based on tetradentate tetraaza Ndonor macrocycles and tetradentate dioxadiaza N- and O-donor ligands has been extensively studied in recent years. These tetradentate ligands (some are shown in 39  Figure 1.7) behave similarly to porphyrin ligands in their binding mode and the ligand binding geometry forces the two oxo ligands to a trans configuration. These high-valent dioxoruthenium(VI) complexes can oxidize stoichiometrically alcohols to the corresponding ketones or aldehydes in CH Cl , ' ' and under air, some of these systems 39b  2  d  e  2  become marginally catalytic (2 to 3 turns) at ambient conditions. ' Alkenes are also 39d e  oxidized exclusively to epoxides.  398  Of note, large kinetic isotope effects (k /k about 20) H  D  were observed in the stoichiometric oxidation of alcohols by these Ru(VI) complexes, in contrast with thefindingson the alcohol oxidations by Ru (TMP)(0) in the present VI  2  18  References on p. 32  Chapter 1  thesis (Chapter 4). The dioxoruthenium non-porphyrin species are also capable of oxidizing C - H bonds in alkanes.  39c  The oxidation of some aromatic hydrocarbons showed  the following reactivity trend: toluene < ethylbenzene < cumene, the oxidized products being benzaldehyde, acetophenone and 2-phenyl-isopropanol, respectively. A twoelectron hydride or one-electron H-atom abstraction pathway was proposed as a possible mechanistic step. Kinetic isotope effects of k / k > 10 were observed in these alkane H  D  oxidations, indicating that C - H bond-breaking is the rate-determining step.  Me  s  |  -N  | JVle  N-  A^,#'-dimethyl-6,7,8,9,10,ll,17,18-octahydro-5//-dibenzo[e«][ 1,4,8,12]dioxadiazacyclopentadecine  Me  v  |  | jVIe  i—N  N—1  N  N—'  Me  Me  1,4,8,11-tetramethyl1,4,8,11 -tetraazacyclotetradecane meso-2,3,7,11,12-pentamethyl3,7,11,17-tetraazabicyclo [11.3.1]heptadeca-1 (17), 13,15-triene Figure 1.7.  Several examples of tetradentate macrocyclic tetraaza and dioxadiaza N - and N-/0-donor macrocyclic ligands, analogous to porphyrins, that have been used in the synthesis of dioxoruthenium(VI) complexes  19  References on p. 32  Chapter 1  Perhaps the most notable non-porphyrin oxoruthenium(VI) complex is the ruthenate ion, Ru(0)3(OH) ". Once thought to be the tetrahedral RUO4 " anion, the 2  2  2  ruthenate ion is now known to be trigonal pyramidal from crystallographic studies.  40  The  ruthenate ion finds use in the oxidation of alcohols to carboxylic acids or ketones, and the system becomes catalytic in the presence of oxidizing agents such as persulfate.  43  Mechanistic studies by Lee and Congson suggest that a two-electron hydride transfer 19  mechanism is operating in the oxidation of alcohols, which is different from the oneelectron H-atom abstraction mediated by perruthenate noted in Section 1.3. Recently, barium ruthenate has been successfully applied to the stoichiometric oxidation of alkanes at room temperature with remarkable reactivity.  41  Acetic acid  enhanced the reactivity of the reagent toward the hydroxylation of alkanes,  413  and the  tertiary alkanes adamantane and methylcyclohexane were oxidized in CH2CI2 in the presence of acetic acid to the corresponding tertiary alcohols within 2 h, with yields reaching 95 and 42%, respectively. For «-hexane, the oxidation occurred mainly at the secondary C - H bonds, forming 2- and 3-hexanone, with yields reaching 20% and 16%, respectively. The oxidation of cyclohexane yielded 60% cyclohexanone exclusively; no cyclohexanol was observed. The addition of Lewis acids such as ZnCb and FeCl3 reduced the reaction time dramatically to a few minutes, in contrast to a few hours. Cyclohexane was now oxidized to cyclohexanone with the same yield in about 5 min, with some trace cyclohexanol being detected. In another study,  41b  trifluoroacetic acid was used instead of  acetic acid, and such a change resulted in a very reactive system capable of oxidizing the light alkanes ethane and propane to acetic acid (40% yield) and acetone (65%),  20  References on p. 32  Chapter 1  respectively. Benzene was also hydroxylated to /?ara-benzoquinone with a 20% yield. Dioxoruthenium(VI) acetato species were proposed to be the active oxidizing species, the reactivities of which were possibly further enhanced by the presence of Lewis acids. Of interest, the effect of the acids seems to be similar to that of HC1 and HBr in the Ru(porp)/pyridine-iV-oxide systems mentioned earlier in Section 1.4.1, although the role 30  of the acids in either systems is unknown.  1.5 Ruthenium(V) Complexes Oxoruthenium(V) complexes are rare. Griffith and co-workers characterized crystallographically the product from the reaction of [Ru0 ][N"Pr ] and 2-hydroxy-24  ethylbutyric acid as [Ru (0)(0 COCEt ) ][N"Pr ]. v  2  2  2  4  42  4  This oxoruthenium(V) complex is a  mild stoichiometric oxidant that can oxidize primary alcohols to aldehydes and secondary alcohols to ketones. Excess 7V-methylmorpholine-7V-oxide can be used as the primary Oatom source, and the system can produce up to 25 turnovers at room temperature. Che and co-workers have demonstrated recently that [Ru (L)(0)][C10 ] (L = v  4  2  anion of [2-hydroxy-2-(2-pyridyl)ethyl]bis[2-(2-pyridyl)ethyl]amine) was an oxidant strong enough to oxidize cyclohexane to cyclohexanone (60% yield) in acetonitrile.  43  Other tertiary alkanes, such as adamantane and methylcyclohexane were oxidized exclusively to the corresponding tertiary alcohols with yields of 60% and 43%, respectively. A kinetic isotope effect k /k of 5.3 was observed for the oxidation of H  D  cyclohexane, suggesting C-H bond cleavage as the rate-determining step.  21  References on p. 32  Chapter 1  1.6 Ruthenium(IV) Complexes Meyer's group, and a few others, have worked extensively with cisRu(bpy)2)(py)(0) (bpy = 2,2'-bipyridine, py = pyridine) and similar polypyridine 2+  complexes, and have studied alkene epoxidation, alcohol, phenol and para44  45  46  hydroquinone oxidations, as well as O-atom transfer reactions to thioethers and 47  phosphines.  49  48  This type of Ru-complexes is shown in Figure 1.8. These stoichiometric  oxidations usually were carried out in acetonitrile or acetonitrile/water solvent systems. As kinetic and mechanistic studies on Ru-oxo oxidations are rather sparse, the results for the oxidation of alcohols by Ru (bpy)2(py)(0) are particularly relevant with respect to IV  2+  the oxidation of alcohols by Ru (TMP)(0)2 described in this thesis. Although the RuVI  atoms are in different formal oxidation states, 4+ and 6+, respectively, both oxidations are proposed to occur via a two-electron, hydride transfer pathway. Roecker and Meyer  458  observed an unusually large kinetic isotope effect (k /kD = 50) for the oxidation of benzyl H  alcohol, and a kn/ko value of 18 for 'PrOH. The stoichiometric oxidation of 'PrOH in benzene by Ru (TMP)(0) has a much lower value of k /k = 1.9 for the a-C-H bond YI  2  H  D  cleavage. The discussion of this subject will be presented later in Chapter 4. Che and co-workers have varied the Ru(bpy) (py)(0) theme and replaced the 2+  2  polypyridine ligands with substituted polypyridines. Generally the chemistry that can be accomplished (alkene epoxidation, alcohol oxidation, etc.) by these complexes is not much differentfromthat of their unsubstituted analogues.  50  One interesting find was that  Ru (terpy)(dcbpy)(0) (terpy = 2,2':6',2"-terpyridine, dcbpy = 6,6'-dichloro-2,2'iv  2+  bypyridine) (see Figure 1.8) also was capable of oxidizing stoichiometrically alkanes in  22  References on p. 32  Chapter 1  acetonitrile at room temperature. Adamantane was oxidized to 1-adamantanol with a 28% yield after 4 h, while ethylbenzene was oxidized to 70% acetophenone and 31% 1phenylethanol in the same amount of time. The presence of the electron-withdrawing 6 and 6' CI groups likely enhances the reactivity of the Ru=0 moiety.  cw-R lV(bipy) (py)(0)2+ U  2  2+  Ruiv(terpy)(dcbpy)(0) 2 + Figure 1.8.  Two examples of monooxoruthenium(IV) polypyridyl complexes. These complexes have been used to oxidize stoichiometrically a variety of organic substrates (phosphines, thioethers, alcohols, alkenes).  23  References on p. 32  Chapter 1  Earlier work in this laboratory led to the discovery of Ru (OEP' )(0)(Br) (OEP* IV  +  +  = OEP porphyrin radical-cation) formed from the reaction of Ru(OEP)(Br)(PPh ) and 3  PhlO.  The Ru(OEP' )(0)(Br) was proposed as such based on ESR evidence for a  51  +  porphyrin radical-cation, as well as the stoichiometry of O-atom transfer to PPh . Of 3  particular importance is that this oxoruthenium(IV) moiety is isoelectronic with the proposed active Fe^-O intermediate in the P-450 system, and thus for the first time a ruthenium model of the oxoiron(IV) protoporphyrin-IX radical-cation species was available. The oxidation of cyclohexane with this oxoruthenium(IV) species was marginally catalytic on using PhlO as an oxidant, producing cyclohexanol, cyclohexanone and cyclohexylbromide in a 1:8:9 ratio, the total turnover being 1.7 based on the metalloporphyrin. The other often quoted oxoruthenium(IV) porphyrin species is Ru (TMP)(0), a rv  proposed intermediate in various catalytic oxidations: epoxidation of alkenes, '  25 28  oxidative dehydrogenation of alcohols "' and oxidations of tertiaryarylphosphines, ' ' 5  AsPh ' and SbPh . ' 5b  6a  5b  3  63  5b 6a 24  Equally important, Ru (TMP)(0) is the proposed intermediate  6a  IV  3  in the formation of Ru (TMP)(0) from the aerobic oxidation of Ru (TMP)(L) (L = VI  n  2  2  MeCN, THF, N or vacant ), which is believed to proceed via Eqs. 1.5 and 1.6 [Ru = 24  25  26  2  Ru(TMP)]. +Ru\h)  -L  Ru\h)  2  +0  2  —  2  Ru(L)0  2  — -  -2L  (L)Ru(0-0)Ru(L) —2Ru (0) w  (1.5)  -L  + 2L  2 ^ ( 0 ) —  Ru\L)  2  + ^(O),  24  (1.6)  References on p. 32  Chapter 1  The monooxo Ru(IV)-species has yet to be isolated, but 'H-resonances assignable to Ru (TMP)(0) can be observed in situ by 'H-NMR spectroscopy in benzene-ofe during the IV  oxidations of tertiaryarylphosphines, ' ' AsPh ' " and SbPh . ' 5b 6a 24  5b 6  5b  3  The Ru^TMPXO)  6a  3  species is paramagnetic and exhibits shifted 'H-resonances (relative to those, for example, of diamagnetic Ru(II) species) for the TMP ligand characteristic of such Ru(rV )-porphyrin r  24,27,31  species. In non-porphyrin work, monooxoruthenium(IV) species have been shown to undergo proton-coupled equilibria with H 0 in solution to form the trans2  bis(hydroxo)ruthenium(IV) species. This type of equilibrium is likely to occur for 52  Ru (TMP)(0) species (Eq. 1.7), and such a reaction has been invoked to account for the IV  catalytic aerobic oxidation of alcohols. ' 5a  Ru (TMP)(0) + H 0 — IV  2  has been reported by two group s.  The bis(hydroxo) species depicted in Eq. 1.7  6a  Ru (TMP)(0)(OH ) —  Ru (TMP)(OH)  IV  IV  2  29ab  '  53  2  (1.7)  Preliminary work in this laboratory, reported in  1990 on the oxidation of'PrOH, led to the isolation of a complex, which was proposed to be Ru (TMP)(OH) IV  29a 2  ' based mainly on the non-detection of any axial ligand protons by b  H-NMR spectroscopy. In 1993, the same Ru (TMP)(OH) was reported to be isolated IV  2  from the m-CPBA oxidation of Ru (TMP)(CO) in EtOH/CH Cl , with the mention of n  2  unpublished crystallographic data on the complex.  53  2  The isolation of Ru (TMP)(OT r) in IY  J  2  the oxidation of'PrOH by Ru (TMP)(0) in benzene,"'" and the subsequent detailed VI  5  6  2  study and understanding of such alcohol oxidations (Chapter 4) strongly refute the proposal of the isolation of Ru (TMP)(OH) . Indeed, the work described in Chapter 4 IV  2  shows that the axial alkoxo ligands of Ru (TMP)(OR)2 species exchange rapidly with IV  25  References on p. 32  Chapter 1  excess alcohol in solution; therefore, the bis(hydroxo) species, though possibly existing as part of the equilibria of Eq. 1.7, would not be the favoured species when excess alcohol is present. Of interest, the supposed "Ru (TMP)(OH) " reported by Che and co-workers rv  53  2  was reported to be slightly more effective than Ru (TMP)(0)2 for the epoxidation of VI  norborene. Although this author believes that Ru (TMP)(OH) has not been successfully IY  2  isolated under the above-mentioned conditions, recently the Ru (TDCPP)(OH) analogue IV  2  was characterized crystallographically, and a Ru-0 bond distance of 1.78 A was observed, which is extremely short for a Ru-0 bond length for this class of Ru(IV) 54  complexes (1.892 or 1.905 A for Ru (TMP)(OR) , where R = 'Pr ' or l,3-dichloro-2IV  5a  55  2  propyl, respectively) and 1.944 A in [Ru (TPP)(p-OC H Me) ]0. 55  IY  6  4  2  13a  A high degree of  7i-backbonding seems to be shortening the Ru-0 bond to almost a Ru-oxo double bond,  54  which is typically ca. 1.73 (Ru^) to 1.78 (Ru™) A in various dioxo- and oxoruthenium i  4 c 56  complexes. '  1.7 Ruthenium(III) Complexes A RuCl »nH 0 or Ru (Cl) (PPh) / aldehyde system was recently employed to n  3  2  2  3  effect the catalytic 0 -hydroxylation of alkanes under relatively mild conditions.  57  2  Aldehydes are known to form peracids in the presence of 0 , 2  58  and once formed the  peracid can oxidize low-valent ruthenium(II or III) to higher-valent oxoruthenium species. In these systems, elemental iron was more effective as a catalyst precursor than the ruthenium complexes, and under 1 atm 0 , some saturated hydrocarbons (cyclohexane, 2  methylcyclohexane, adamantane, cyclooctane, »-decane and ethylbenzene) were oxidized  26  References on p. 32  Chapter 1  at the secondary and tertiary positions to the corresponding ketones and tertiary alcohols. For the RuCl »nH 0/heptanal/acetic acid/CH Cl2 system, cyclooctane was oxidized to 3  2  2  cyclooctanone and cyclooctanol (3:1) over a period of 15 h, the total turnover being 8.4 based on the starting ruthenium.  1.8 Ruthenium(Il) Complexes Work conducted in this laboratory throughout the 1980s led to the discovery of the production of hydrogen peroxidefromFT and 0 mediated by a ruthenium(II) 2  porphyrin species (Eqs. 1.8 and 1.10). In the presence of a reductant, the Ru(II) species 59  is regenerated (Eq. 1.12), making the production of H 0 catalytic. The in situ generated 2  2  H 0 then can oxidize organic substrates that are present in solution. Phosphines were 2  2  studiedfirstwith this system, but the chemistry can be applied to the oxidation of thioethers. The overall reaction is catalytic in Ru (OEP)(PR ) , FT and OFT. The n  3  2  following mechanism was proposed (Eqs. 1.8 to 1.12): Ru(OEP)(PR ) + 0 3  H 0 — 2  2  2  3  + 2  + 0"  (1.8)  2  (1.9)  H0 —  2  2  Ru(OEP)(PR )  FT + OFT  0 - + ft — H 0  —  2  2  \ H 0  + PR — * H 0 + OPR 3  2  2 Ru(OEP)(PR ) 3  + 2  2  +\ 0  2  (1.10)  2  (1.11)  3  + PR + OFT — - 2 Ru(OEP)(PR ) + OPR + Ff (1.12) 3  3 2  3  For any substrate that can be oxidized by H 0 , the system can, in principle utilize 0 as 2  2  2  oxidant within the above scheme. As mentioned, a reductant is necessary to regenerate  27  References on p. 32  Chapter 1  the Ru(II)-catalyst (Eq. 1.12), and for an "optimum" system this reductant is preferably the substrate itself. The same basic mechanism applies to the oxidation of thioethers, namely, superoxide is first generated by an outer sphere electron transfer (Eq. 1.8), followed by the generation of  H2O2  (Eq. 1.10), which then subsequently oxidizes the  thioether to sulfoxide. Visible light from a tungsten source was necessary to assist in driving equilibria 1.8 and 1.10 to the product side.  Initial turnovers were close to  593  360 h", with total turnovers of about 10000. Slowly, the catalytically less active 1  Ru (OEP)(SR2)(OSR ) species containing S-bound sulfoxide was formed. n  2  The oxidation of primary or secondary alcohols to the corresponding aldehydes or ketones is in essence a dehydrogenation reaction (Eq 1.13). RCH2OH  — - RCHO + {H }  (1.13)  RROO  + {H } — -  (1.14)  2  2  RRCH2OH  The hydrogen, {H }, that is liberated in Eq. 1.13 may or may not be transferred to a 2  hydrogen acceptor R'R"C=0 (Eq. 1.14). The liberation of free H in a dehydrogenation 2  reaction is an endothermic process, e.g. for 'PrOH, AH = + 66.5 kJ^mol" at 327 °C. 1  60  In  the aerobic oxidative-dehydrogenation of alcohols to aldehydes/ketones and H 0 , the end 2  hydrogen acceptor is 0 and the overall reaction becomes exothermic. It is not necessary 2  to use O2 as the hydrogen acceptor; for example, an imine or a ketone can accept the hydrogen from the substrate. The use of O2 as acceptor is generally referred to as oxidation, while the use of other acceptors is usually referred to as transfer hydrogenation. Transfer hydrogenation is more generally concerned with the use of a hydrogen source other than H to effect hydrogenation, and the focus is on reducing the unsaturated 2  28  References on p. 32  Chapter 1  substrate, not the oxidized hydrogen source. In the last few years, Backvall and coworkers have developed ruthenium(II)-based systems for dehydrogenating alcohols by transfer hydrogenation. Imines, ketones and O2 have been used as hydrogen acceptors. 61  With O2, an elaborate catalytic system involving three components was employed (see Figure 1.9).  61a  Secondary alcohols, which are more difficult to oxidize than benzyl  alcohol, were oxidized to the corresponding ketones with high yields. Overall, most alcohols gave turnovers around 30 to 40 h" at 100 °C. Of note, the reactions were more 1  efficient under a low 0 partial pressure, ca. 0.6 -1.5% in 1 atm N , than those under 2  2  higher 0 partial pressures, and this was thought to be due to the sensitivity of the Ru(II)2  catalytic precursor to O2. When both the hydrogenated product and oxidized hydrogen source are valuable chemicals, this kind of transfer hydrogenation can be an extremely useful process.  1.9  Aims and Scope of this Thesis A general overview has been presented and the diverse chemistry of Ru oxidation  reagents and catalysts is very much apparent. The aims of this thesis work were two-fold. The foremost interest in the current research focussed on the use of dioxoruthenium(VT) porphyrin complexes as 02-oxidation catalysts for the oxidation of organic substrates. Secondly, the continual need for detailed kinetic and mechanistic studies was recognized, as they may further the understanding of such oxidation reactions. As the discussion of each individual subject is at hand, the particular aims and scope (as well as success and failure!) will be explored more clearly. Chapter 2 summarizes the general experimental  29  References on p. 32  Chapter 1  Figure 1.9.  Ruthenium-based, aerobic, triple catalytic system for the Ovoxidation of alcohols to aldehydes and ketones. The ruthenium complex {Ru} dehydrogenates the alcohol. Regeneration of the ruthenium catalyst is accomplished by the bulky benzoquinone. A cobalt Schiff base complex is responsible for regenerating the benzoquinone from the reduced /?ara-hydroquinone. O2, is the sole terminal oxidant that oxidizes the reduced cobalt complex, {CoL} d (Ref. 61a). re  30  References on p. 32  Chapter 1  procedures, and preparation and characterization of starting materials. Chapters 3 and 4 present kinetic and mechanistic studies on the stoichiometric and catalytic oxidations of phosphines and alcohols, respectively. Chapter 5 introduces work concerning the O2oxidation of alcohols and neat hydrocarbons catalyzed by ruthenium perhalogenated porphyrins. Chapter 6 includes some preliminary work on the reactions of Ru (TMP)(0)2 VI  with HX acids, mono-substituted aromatics and /?-hydroquinone. Finally, Chapter 7 presents the overall conclusions of the entire thesis work, and suggests research topics that need further study.  31  References on p. 32  Chapter 1  References  1  a) A. H. Haines, Methods for Oxidation of Organic Compounds, Academic Press, Toronto, 1988. b) M. Hudlicky, Oxidations in Organic Chemistry, American Chemical Society, Washington, DC, 1990.  2  a) B. R. James, Fundamental Research in Homogeneous Catalysis, ed. A. E. Shilov, Plenum Press, Vol 1, 1986, p. 309. b) T. Mlodnicka and B. R. James, in Metalloporphyrins Catalyzed Oxidations, eds. F. Montanari and L . Casella, Kluwer Academic Publishers, Dordrecht, 1994, p. 121.  3  R. R. Engle and C. Djerassi, J. Am. Chem. Soc, 75, 3838 (1953).  4  a) W. P. Griffith, Chem. Soc. Rev., 21, 179 (1992) b) W. P. Griffith, Trans. Met. Chem., 15, 251 (1990) c) C.-M. Che and V. W.-W. Yam, Adv. Inorg. Chem., 39, 233 (1992)  5  a) S. Y. S. Cheng, N. Rajapakse, S. J. Rettig and B. R. James, J. Chem. Soc, Chem. Commun., 2669 (1994). b) S. Y. S. Cheng and B. R. James, J. Mol. Cat., in press.  6  a) S. Y. S. Cheng and B. R. James, Proc. of the 78th Can. Chem. Conf, Guelph, Canada, 1995, Abstract IN-447. b) S. Y. S. Cheng and B. R. James, Poster Presentation at the 15th Annual BC Inorganic Research Colloquim, Victoria, Canada, June 18-20, 1993.  7  a) Metalloporphyrin Catalyzed Oxidations, eds. F. Montanari and L. Casella, Kluwer Academic Publishers, Dordrecht, 1994. b) Metalloporphyrins in Catalytic Oxidations, ed. R. A. Sheldon, Marcel Dekker, New York, 1994. c) B. Meunier, Chem. Rev., 92, 1411 (1992). d) T. Mukaiyama and T. Yamada, Bull. Chem. Soc. Jpn., 68, 17 (1995).  8  R. Stewart, Oxidation Mechanisms, W. A. Benjamin, Inc., New York, 1965.  9  a) Cytochrome P-450, eds. T. Omura, Y. Ishimura and Y. Fujii-Kuriyama, Tokyo, 2nd Ed, 1993, Chapter 2. b) N. Rajapakse, M. Sc. Dissertation, University of British Columbia, Vancouver, Canada, 1985.  10  J. T. Groves, J. Chem. Ed., 62, 928 (1985).  32  References on p. 32  Chapter 1  11  T. L. Poulos, B. C. Finzel, I. C. Gunzalus, Wagner and J. Kraut, J. Biol. Chem., 260, 16122 (1985).  12  Reference 7b, p. 113.  13  a) J. P. Collman, C. E. Barnes, P. J. Collins, T. Owaza, J. C. Galluci and J. A. Ibers, J. Am. Chem. Soc, 106, 5151 (1984). b) H. Masuda, T. Tagu, K. Osaki, H. Suzimoto, M. Mori and H. Ogoshi, J. Am. Chem. Soc, 103, 2199 (1981).  14  a) E. R. Birnbaum, W. P. Schaefer, J. A. Labinger, J. E. Bercaw and H. B. Gray, Inorg. Chem., 34, 1751 (1995). b) D. Mandon, P. Ochsenbein, J. Fischer, R. Weiss, K. Jayaraj, R. N. Austin, A. Gold, P. S. White, O. Brigaud, P. Battioni and D. Mansuy, Inorg. Chem., 31, 2044 (1992).  15  a) T. Takeuchi, H. B. Gray and W. A. Goddard III, J. Am. Chem. Soc, 116, 9730 (1994). b) P. Ochsenbein, K. Ayougou, D. Mandon, J Fischer, R. Weiss, R. N. Austin, K. Jayaraj, A. Gold, J. Terner and J. Fajer, Angew. Chem. Int. Ed. Engl., 33, 348 (1994).  16  a) M. W. Grinstaff, M. G. Hill, J. A. Labinger and H. B. Gray, Science, 264, 1311 (1994). b) J. E. Lyons and P. E. Ellis,' Catal. Lett, 8, 45 (1991). c) P. E. Ellis and J. E. Lyons, Coord. Chem. Rev., 105, 181 (1990). d) J. E. Lyons and P. E. Ellis, Catal. Lett, 3, 389 (1989). e) J. F. Bartoli, O. Grigaud, P. Battioni and D. Mansuy, J. Chem. Soc, Chem. Commun., 440 (1991). f) A. M. d'A. R. Gonsalves, R. A. W. Johnstone, M. M. Pereira, J. Shaw and A. J. F. doN. Sobral, Tetrahedron Lett., 23, 1355 (1991).  17  D. G. Lee and M. Van den Engh, Can. J. Chem., 50, 2000 (1972).  18  J. -L. Coudret and B. Waegell, Inorg. Chim. Acta, 222, 115 (1994).  19  D. G. Lee and L. N. Congson, Can. J. Chem., 68, 1774 (1990).  20  D. G. Lee and H. Gai, Can. J. Chem., 73, 49 (1995).  21  R. H. Holm, Chem. Rev., 87, 1401 (1987).  22  T. J. Groves and R. Quinn, Inorg. Chem., 23, 3844 (1984).  33  References on p. 32  Chapter 1  23  M. J. Camenzind, B. R. James and D. Dolphin, unpublished work, Oct. 1984.  24  J. T. Groves and K.-H. Ahn, Inorg. Chem., 26, 3833 (1987).  25  J. T. Groves and R. Quinn, J. Am. Chem. Soc., 107, 5790 (1985).  26  M. J. Camenzind, B. R. James and D. Dolphin, J. Chem. Soc, Chem. Commun., 1137 (1986).  27  J. T. Groves and J. S. Roman, J. Am. Chem. Soc, 117, 5594 (1995).  28  a) M. Tavares, R. Ramasseul, J.-C. Marchon, B. Bachet, C. Brassy and J.-P. Mornon, J. Chem. Soc. Perkin Trans. 2, 1321 (1992). b) J.-C. Marchon and R. Ramasseul, J. Chem. Soc, Chem. Commun., 298 (1988). c) B. Scharbert, E. Zeisberger and E. Paulus, J. Organometallic Chem., 493, 143 (1995).  29  a) N. Rajapakse, B. R. James and D. Dolphin, Stud. Surf. Sci. Catal, 55, 109 (1990). b) N. Rajapakse, PhD Dissertation, University of British Columbia, 1990. c) N. Rajapakse, B. R. James and D. Dolphin, Catal. Lett., 2, 219 (1989).  30  a) H. Ohtake, T. Higuchi and M. Hirobe, Heterocycles, 40, 867 (1995). b) H. Ohtake, T. Higuchi and M. Hirobe, J. Am. Chem. Soc, 114, 10660 (1992).  31  a) C. S. Alexander, Ph. D. Dissertation, University of British Columbia, 1995. b) C. Sishta, Ph. D. Dissertation, University of British Columbia, 1990.  32  P. Le Maux, H. Bahri and G. Simonneaux, J. Chem. Soc, Chem. Commun., 1287 (1994).  33  C. Sishta, M. J. Camenzind and B. R. James, Inorg. Chem., 26, 1181 (1987).  34  a) C.-M. Che and W. H . Leung, J. Chem. Soc. Dalton Trans., 2932 (1991). b) W. H. Leung and C.-M. Che, J. Am. Chem. Soc, 111, 8812 (1989).  35  P. S. Traylor, D. Dolphin and T. G. Traylor, J. Chem. Soc, Chem. Commun., 279 (1984).  36  P. E. Ellis and J. E. Lyons, J. Chem. Soc, Chem. Commun., 1189 (1989); 1315 (1989).  37  J. A. Labinger, Catal. Lett., 26, 95 (1994).  34  References on p. 32  Chapter 1  38  Y. Tokita, K. Yamaguchi, Y. Watanabe and I. Morishima, Inorg. Chem., 32, 329 (1993).  39  a) C.-M. Che, C.-K. Li, W.-T. Tang and W.-Y. Yu, J. Chem. Soc. Dalton Trans., 3153 (1992). b) C.-M. Che, W.-T. Tang, W.-O. Lee, K.-Y. Wong and T.-C. Yu, J. Chem. Soc. Dalton Trans., 1551 (1992). c) C.-M. Che, W.-T. Tang, K.-Y. Wong and C.-K. Li, J. Chem. Soc. Dalton Trans., 3277 (1991). d) C.-M. Che, T.-F. Lai and K.-Y. Wong, Inorg. Chem., 26, 2289 (1987). e) K.-W. Wong, C.-M. Che and F. C. Anson, Inorg. Chem., 26, 737 (1986).  40  M. O. Elout, W. G. Haije and W. J. A. Maaskant, Inorg. Chem., 27, 10 (1988).  41  a) T.-C. Lau and C.-K. Mak, J. Chem. Soc. Chem. Commun., 766 (1993); b) 943 (1995).  42  A. C. Dengel, W. P. Griffith, C. A. O'Mahoney and D. J. Williams, J. Chem. Soc, Chem. Commun., 1720(1989).  43  C.-M. Che, C. Ho and T.-C. Lau, J. Chem. Soc. Dalton Trans., 1259 (1991).  44  L. K. Stultz, R. A. Binstead, M. S. Reynolds and T. J. Meyer, J. Am. Chem. Soc, 117, 2520 (1995).  45  a) L. Roecker and T. J. Meyer, J. Am. Chem. Soc, 109, 746 (1987). b) J. G. Muller, J. H. Acquaye and K. J. Takeuchi, Inorg. Chem., 31, 4552 (1992).  46  W. K. Soek and T. J. Meyer, J. Am. Chem. Soc, 110, 7358 (1988).  47  R. A. Binstead, M. E. McGuire, A. Dovletoglou, W. K. Soek, L. Roecker and T. J. Meyer, J. Am. Chem. Soc, 114, 173 (1992).  48  a) L. Roecker, L. J. C. Dobson, W. J. Vining and T. J. Meyer, Inorg. Chem., 26, 779 (1987). b) J. H. Acquaye, J. G. Muller and K. J. Takeuchi, Inorg. Chem., 32, 160 (1993).  49  a) A. Dovletoglou and T. J. Meyer, J. Am. Chem. Soc, 116, 215 (1994). b) B. A. Moyer, B. K. Sipe and T. J. Meyer, Inorg. Chem., 20, 1475 (1981).  50  C.-M. Che, C. Ho and T.-C. Lau, J. Chem. Soc. Dalton Trans., 1901 (1991)  51  T. Leung, B. R. James and D. Dolphin, Inorg. Chim. Acta, 19, 180 (1983).  35  References on p. 32  Chapter 1  52  C.-M. Che, W.-T. Tang, W.-T. Wong and T.-F. Lai, J. Am. Chem. Soc, 111, 9048 (1989).  53  W.-H. Leung, C.-M. Che, C.-H. Yeung and C.-K. Poon, Polyhedron, 12, 2331 (1993).  54  P. Dubourdeaux, M. Taveres, A. Grand, R. Ramasseul and J.-C. Marchon, Inorg. Chim. Acta, 240, 657 (1995).  55  This thesis, Chapter 4.  56  J. M. Mayer, Inorg. Chem., 27, 3899 (1988).  57  S.-I. Murahashi, Y. Oda and T. Naota, J. Am. Chem. Soc, 114, 7913 (1992).  58  R. A. Sheldon and J. Kochi, Metal-Catalyzed Oxidations of Organic Compounds, Academic Press, Toronto, p. 25, 1981.  59  a) A. Pacheco, Ph. D. Dissertation, University of British Columbia, 1993. b) A. Pacheco, B. R. James and S. J. Rettig, Inorg. Chem., 34, 3477 (1995). c) B R . James, A. Pacheco, S. J. Rettig and J. A. Ibers, Inorg. Chem., 27, 2414 (1988). d) B. R. James, S. R. Mikkelsen, T. W. Leung, G. M. Williams and R. Wong, Inorg. Chim. Acta, 85, 209 (1984). e) B R . James, T. W. Leung, F. W. B. Einstein and A. W. Willis, Can. J. Chem., 62, 1238 (1984).  60  Kirk-Othmer Concise Encyclopedia of Chemical Technology, ed. M. Grayson, D. Eckroth, E. Graber, A. Klingsberg and P. M. Siegel, John Wiley and Sons, Toronto, 1985, p. 13.  61  a) G.-Z. Wang, U. Andreasson and J.-E. Backvall, J. Chem. Soc, Chem. Commun., 1037 (1994). b) G.-Z. Wang and J.-E. Backvall, J. Chem. Soc, Chem. Commun., 980 (1992). c) G.-Z. Wang and J.-E. Backvall, J. Chem. Soc, Chem. Commun., 337 (1992). d) J.-E. Backvall, R. L. Chowdhury and U. Karlsson, J. Chem. Soc, Chem. Commun., 473 (1991). e) R. L. Chowdhury and U. Karlsson, J. Chem. Soc, Chem. Commun., 1063 (1991).  36  References on p. 32  Chapter 2  CHAPTER 2 Experimental Methods  3 7  References on p. 55  Chapter 2  2.1 Materials 2.1.1  Gases CO, Ar, N and 0 2  2  (99.99+  % pure) were supplied by Linde Gas (Union Carbide  Inc.) and used without further purification. The Ar gas used for photolysis was passed through a Ridox column (Fisher Scientific) to remove any trace 0 . Trace moisture 2  present in the gases was removed by passing the gases over activated 5 A molecular sieves (BDH).  2.1.2  Solvents and Reagents Common organic solvents, such as benzene, toluene, CH C1 and CHCU, were 2  2  supplied by Fischer Scientific as reagent or spectroscopic grade. Benzene or toluene, if required to be moisture-free, was dried over sodiunVbenzophenone and stored under N . 2  Other solvents were dried over CaH (BDH) and stored under N . Mesitylene (Aldrich) 2  2  was used without further purification. Deuterated solvents used for NMR studies (D 0, benzene-ok, toluene-dg, CD C1 2  2  2  and CDCI3, all 99.6+% deuterated) were purchased from MSD ISOTOPES or ISOTEC Inc. When needed to be used under anaerobic conditions, these deuterated solvents were dried over ground molecular sieves (5 A, BDH). Subsequently, three tofivefreeze-pumpthaw cycles were applied to remove the air. 'PrOD-dg was purchased from Aldrich. 'PrOD-^i was obtained by mixing 1 mL of'PrOH in 100 mL of D 0, with subsequent 2  distillation of the isopropanol-afi. Any co-distilled D 0 was removed by the addition of 2  38  References on p. 55  Chapter 2  molecular sieves (5 A, BDH). The absence of the -OH functional group in the 'PrOD-di was confirmed by 'H-NMR spectroscopy. Ruthenium was obtained as RuCi3 3H 0 on loanfromJohnson Matthey Ltd. and #  2  Colonial Metals Inc. Ru3(CO)i was prepared from RuCl3»3H 0 by a literature method.  1  2  2  Pyrrole (Aldrich) was distilled prior to use. BF (50 % weight) in MeOH was supplied by 3  Aldrich and was stored in a vacuum desiccator. Mesitaldehyde and 2,6dichlorobenzaldehyde were obtainedfromAldrich. P(p-X-C H4) compounds (X = H, Me, OMe, F, Cl and CF ) (Strem Chemicals) 6  3  3  were recrystallized from EtOH prior to use. Triphenylphosphine oxide (Aldrich, 99% pure) was purified by column chromatography (Activity I neutral alumina), with the impurities first eluted with benzene, and the phosphine oxide subsequently eluted with acetone. The purities of the phosphines and phosphine oxide were determined by TLC analysis and *H and P{ H}-NMR spectroscopies. AsPh and SbPha (Eastman) were 31  X  3  purified by recrystallizationfromEtOH. MeOH, EtOH, 1-PrOH, 'PrOH and benzyl alcohol were spectroscopic grade reagents obtainedfromFischer Scientific, while -R.S-l-phenylethanol and 1,3dichloropropan-2-ol were purchasedfromEastman. All the alcohols were dried over molecular sieves (5 A, BDH) and were used without further purification. Ph CH and 3  adamantane werefromBDH and Aldrich, respectively. The purities of these two alkanes were verified on a gas chromatograph.  PI13COH wasfromEastman,  while 1-adamantanol,  2-adamantanol and 2-adamantanone werefromAldrich. These alcohols and ketone were employed as standards for GC experiments. Methylcyclohexane (Eastman) was found by  39  References on p. 55  Chapter 2  GC analysis to contain no other impurities. 1-Methylcyclohexanol, 2-methylcyclohexanol, 2-methylcyclohexanone, 3-methylcyclohexanone and 4-methylcyclohexanone were purchased from Eastman, and were used as GC standards. Cyclohexene, c/s-cyclooctene (herein referred to simply as cyclooctene), cyclohexene-oxide and cyclooctene-oxide were obtained from Eastman. The alkenes were pre-purified by first passing down neutral alumina (Activity I) before being distilled. Cyclohexene was pure by GC analysis. GC analysis of the distilled cyclooctene showed another compound (~ 4%), presumably an isomer of cyclooctene, to be present; the distilled substrate was used without further purification. Cyclohexene-oxide and cyclooctene-oxide were used as standards without further purification. iV,A-Dimethylaniline (Eastman) was passed down a silica column before being /  atmospherically distilled. Phenol (BDH) was recrystallized twice from petroleum ether before use. p-Hydroquinone and /^-benzoquinone (Aldrich) were used as received.  2.2.  Instrumentation and General Experimental Procedures  2.2.1  UV-Visible Spectroscopy UV-visible spectroscopic data were obtained with a Perkin Elmer 5 52A UV-  Visible Spectrometer or a Hewlett-Packard HP 8452A Diode-Array Spectrophotometer, both equipped with thermoelectric temperature controllers. It should be noted that wavelength readings from the HP 8452A instrument are approximately 2 nm higher than those from the Perkin Elmer 552A instrument; all reported readings within this thesis  40  References on p. 55  Chapter 2  correlate to thosefromthe HP 8452A instrument.* Extinction coefficients, 8, are given in units of M^cm" in parentheses immediately following the reported wavelength maxima, 1  X-  2.2.2  Stopped-flow Kinetic Studies A stopped-flow apparatus capable of achieving mixing within 1 to 2 ms was  manufactured by Applied Photophysics Inc., and was used, for example, to study reactions of /raw5-Ru (TMP)(0) with EAr -type substrates (E = P, As, Sb). The apparatus was VI  2  3  equipped with a monochrometer, and both the in-slit and out-slit widths were set to 0.25 mm. The light source was a 150 W Xe arc lamp. Anaerobic conditions for the instrument, when required, were achieved by bubbling N or Ar into the cooling water. In 2  addition, TRIZMA® hydrochloride (Sigma) and sodium thiosulfite were added to the water to remove dissolved 0 on the surface of the Teflon coils. Data acquisition was 2  computer controlled by an Archimedes 410/1 computer; the software was supplied by Applied Photophysics and was custom-made for the stopped-flow apparatus. Figure 2.1 shows a diagram of the sample handling section of stopped-flow apparatus. The syringes that contain the sample solutions are called the "drive syringes". An electronic trigger releases the 5 atm N pressure to force the drive platform upwards, 2  pushing the drive syringes in the same direction. The samples were mixed rapidly and at the same time the computer acquired 400 data points within a preset time interval (5 ms to 1000 s intervals are possible).  * The UV-visible spectrum of aqueous K M n 0 (Mallinckrodt) obtained on the H P 8452A instrument shows absorption maxima at 508, 526 and 546 nm. 4  41  References on p.55  Chapter 2  Fill syringes  Figure 2.1.  The diagram showing the various parts of the sample-handling section on the stopped-flow apparatus. Benzene solutions of Ru (TMP)(0)2 were loaded into the leftfill-syringevia a disposal syringe from the top, while benzene solutions of ¥(p-X-C(£U)i, AsPh and SbPh werefilledon the right. The drive platform is controlled electronically via a trigger, which starts and stops a flow of pressurized N gas (~ 5 atm). The mixing chamber and observation window lie in perpendicular to the sample handling unit are not shown in the diagram. VI  3  3  2  42  References on p. 55  Chapter 2  Isothermal conditions were maintained within the sample-handling compartment with the use of a thermoelectric temperature controller. The operating range of the stopped-flow apparatus itself was between 5 and 50 °C. Temperatures outside this range tend to make the drive syringe pistons either too loose or too stiff, respectively. In the course of these studies, the temperatures of the cooling source were set typically at 10, 20, 30 or 40 °C, and the exact temperatures were obtained from the digital readout at the sample compartment of the stopped-flow apparatus.  2.2.3  Infrared Spectrophotometer Infrared spectra were taken on an ATI Mattson Genesis Series FTIR instrument.*  The samples were prepared by one of three methods: 1) a Nujol mull sandwiched between KBr plates (referred herein as "Nujol, KBr"), 2) solid compound dispersed within a compressed KBr pellet or 3) dissolved in a solvent and then coated and dried on the surface of a KBr plate (both 2 and 3 will be referred from now as "KBr").  2.2.4  FT-NMR Instruments Solution NMR spectra were obtained on a Bruker AC-200E (200 MHz) or a  Varian XL-300 (300 MHz) instrument in FT modes. Proton chemical shifts are given as 8 in parts per million (ppm) with reference to the solvent residual [CeHg at 7.15,  CHCI3  at  7.24 or CHj-CeHs at 2.09] as the internal standard, relative to TMS. ^P^Hj-NMR chemical shifts are given as 8 referenced to aq.  H3PO4  in a particular solvent.  19  F-NMR  The IR spectrum of a polystyrene film shows absorption at v =c = 1600 cm" . 1  c  43  References on p.SS  Chapter 2  chemical shifts are given as 8 referenced to CF COOH in a particular solvent. The 3  reported 'H-NMR chemical shifts are singlets unless indicated otherwise (d = doublet; t = triplet; m = multiplet). The Varian XL-300 instrument was equipped with a variable-temperature unit, making VT-NMR experiments possible. Toluene-dg was used as the solvent in all the VTNMR studies. Typically the temperature at the NMR probe was lowered at 20 °C intervals, and thermal equilibration was allowed to proceed for 10 min before data acquisition began.  2.2.5 Gas Chromatography Experiments Gas chromatograms were obtained on an HP 5891A instrument, equipped with an HP17 column (cross-linked 50%-Ph-50%-Me Silicone capillary column, 25 m length, 0.32 mm diameter, 0.26 pm thick column coating) and a hydrogen-flame ionization detector (FID). The carrier gas was He, and all gases used were purified by a Supelco gas purifier system (HC 2-2445). The column conditions and temperature programs are listed in Table 2.1 for the elution of various known standards. Sample injection volumes were typically 1 to 2 pL of solution, with typical solute concentrations between 10" to 10" M, although 2  1  concentrations in the order of 10" M presented no difficulties. A split-gasflowrate of 3  ~ 70 mL/min was employed, so that the injected sample would not overload the column.  44  References on p.55  Chapter 2  Table 2.1.  Conditions for the separation of compound mixtures by gas chromatography. Retention times (min) 3.6; 3.2  benzyl alcohol/benzaldehyde  150 °C  Column Head Pressure (kPa) 45  #,S-l-phenylefhanol/ acetophenone  110 °C  40  7.2 8.1  Ph CH / Ph COH  220 °C  45  13.9 24.5  120 °C for 6 min, then 20 °C min" until 200 °C  45  4.9 9.4  cz's-cyclooctene/ cyclooctene oxide  90 °C for 4 min, then 10 °C min' until 140 °C  45  methylcyclohexane/ 1 -methylcyclohexanol, 2-methylcyclohexanone, 3 -methylcyclohexanone, 4-methylcyclohexanone  50 °C for 5 min, then 10 °C min" until 200 °C  45  3.8 9.3 11.4 11.6 11.8  A/^-dimethylaniline  100 °C for 2 min., then 10°C min" until 200°C  45  6.82  Substrate/products  Temperature  0  6  3  3  adamantane/1 -adamantanol  1  1  1  c  .  4.0 9.4  1  ° These compounds were standards, obtained commercially, and were not further purified. Typically, 10" to 10" M solute was dissolved in benzene, and 1 to 2 pL were injected into the injection port, which was always set to 220 °C. The split injection flow rate was appoximately 70 mL/min. A racemic mixture was used. CH2CI2 was used as a solvent. 2  1  b  0  45  References on p. 55  Chapter 2  2.2.6  Elemental Analyses, X-ray Crystallography and Mass Spectral Analyses Elemental analyses were obtained by Mr. P. Borda of this department. X-ray  crystallographic structures were determined in this department by Dr. S. Rettig with a Ragaku X-ray Diffractometer, the X-ray source being Cu-Ka or Mo-Ka radiation. Mass spectral analyses were obtained in this department in a facility headed by Dr. G. Eigendorf. Both electron impact and fast atom bombardment (on thioglycerol and 3 nitrobenzylalcohol matrices) methods of ionization were used.  2.3  Techniques A N -filled glove-box was used to handle air-sensitive compounds. Standard 2  Schlenk techniques were used to carry out air-sensitive reactions and solvent transfers. Flame-sealed tubes attached to vacuum lines were used to prepared anaerobic NMR samples. These standard vacuum techniques and the photolysis procedure to prepare 2  Ru (TMP)(MeCN) have been described elsewhere. ' n  2 3,7  2  2.4  Synthesis and Characterization of Starting Compounds The Ru-porphyrin complexes prepared during the course of this thesis are  described below. Where known, the spectroscopic data are in excellent agreement with thosefromprior studies in this laboratory. Many new porphyrin species were observed in situ, their description will be presented later in the appropriate sections, where their reactivities will also be described in detail.  46  References on p. 55  Chapter 2  H TMP 2  H2TMP, thefree-baseporphyrin weso-tetramesitylporphyrin, was made by a procedure reported by Groves and Nemo, which was a modification of the Rothemund 4  synthesis. The purity of the product was determined by UV-visible and 'H-NMR 5  spectroscopies and TLC analysis. The data are in good agreement with those previously reported.  11  Molecular formula (M.W.)  C 6H  NMR ( H, C D , 25 °C)  8.56 O p y r r o l e - H , 8H), 7.22 (w-H, 8H), 2.58 (p-Me, 12H),  1  6  6  5  5 4  N4  (783.07)  1.80 (o-Me, 24H), -2.54 (N-H, 2H) UV-Visible (CH C1 ) 2  2  422, 516, 550 nm  Ru"(TMP)(CO) Carbonyl(tetramesitylporphyrinato)ruthenium(II), Ru (TMP)(CO), was prepared n  by a modification of a procedure that has been used to synthesize Ru (TPP)(CO). n  6  H TMP (500 mg, 0.063 mmol) was added to 200 mL mesitylene, and the solution was 2  refluxed under a bubbling stream of CO gas. Ru3(CO)i (300 mg, 0.047 mmol) was added 2  in 18 aliquots during the next 6 h. The solution was heated for a total of-24 h, and during this time the reaction was monitored by TLC. At the end o f 24 h, the mixture was rotary evaporated t o remove the mesitylene, and the product was chromatographed on alumina (neutral Activity I). Unreacted TMPH and Ru3(CO)i were elutedfirstwith benzene as 2  2  purple and yellow bands, respectively. Ru (TMP)(CO) was subsequently eluted with 1:1 n  benzene/CH Cl as a red-orange band. Purity was assessed by TLC analysis and UV2  2  47  References on p. 55  Chapter 2  visible and 'H-NMR spectroscopies. Yield 0.30 g, 60 %. The data are in good agreement with those previously reported.  11  Molecular formula (M.W.)  RUC57H52N4O  NMR( H, C D , 25 °C)  8.79 O p y r r o l e - H , 8H), 7.25 (/n-H, 4H), 7.10 (m-H, 4H),  1  6  6  (910.13)  2.48 (p-Me, 12H), 2.20 (o-Me, 12H), 1.83 (o-Me, 12H) UV-Visible(CH Cl )  414, 532 nm  IR (KBr)  v = 1943 cm-  2  2  1  c o  Ru"(TMP)(MeCN)  2  7>a«5-bis(acetonitrile)(tetramesitylporphyrinato)ruthenium(II), Ru (TMP)(MeCN) , was prepared from Ru (TMP)(CO) by a standard photolysis n  n  2  procedure described elsewhere. ' ' Ru (TMP)(CO) (0.10 g, 0.11 mmol) was dissolved in 2 3 7  n  a 5:3 benzene/acetonitrile mixture (80 mL) and the solution was transferred to a glass tube (3 cm wide, 20 cm long) with a narrow neck (1 cm wide, 20 cm long). A water-cooled condenser was fitted over this narrow neck, and the opening was covered with a rubber septum.  2,11  A stainless steel needle was inserted into the solution through the rubber  septum and the solution was purged with Ar for 30 min before it was irradiated with a 450 W Hanovia Hg-vapour lamp for 24 h. After this time a solution sample withdrawn from the mixture showed n o remaining Ru (TMP)(CO) in the IR spectrum (v o = 1943 cm"). n  1  C  The remaining solvent was removed by continuing the Ar-purging without water-cooling. After about 1 h, all the solvent was removed, and the solid was isolated and dried under  48  References on p. 55  Chapter 2  vacuum for 24 h. Yield 0.08 g, 80%. The data are in good agreement with t h o s e previously reported.  11  Molecular formula (M.W.)  RuC H N (964.23)  NMR CH, C D , 25 °C)  8.65 O p y r r o l e - H , 8H), 7.27 (m-U, 8H), 2.54 (p-Me, 12H),  6  6  60  5g  6  2.21 (o-Me, 24H), -1.32 (MeCN, 6H) Analysis, Calculated Found  C, 74.74; H, 6.06; N, 8.72 C, 74.80; H, 6.16; N, 8.56  UV-Visible (CeHe)  410, 506 nm  IR (Nujol, KBr)  v  Ru (TMP)(0) vl  = 2270 cm"  1  CN  2  Ru (TMP)(0)2, ^a«5-dioxo(tetramesitylporphyrinato)ruthenium(VI), can be vl  synthesized by the oxidation of Ru (TMP)(CO) with /neta-chloroperbenzoic acid (mn  CPBA), or by the aerobic oxidation of Ru (TMP)(N ) , Ru (TMP), or 8  n  9  2  Ru (TMP)(MeCN) . n  2  n  n  9  2  In this thesis, Ru (TMP)(0) was produced in situ either by the VI  2  /w-CPBA oxidation of Ru (TMP)(CO), or by the aerobic oxidation of Ru (TMP)(MeCN) n  n  2  in benzene or benzene-fife Two mole equivalents of MeCN were observed by ^ - N M R spectroscopy upon the formation of Ru (TMP)(0) when the bis(acetonitrile) complex VI  2  was used as the dioxo-precursor. Evacuation of the resulting solution gave a quantitative yield of the dioxo complex with no trace of the acetonitrile. The data are in good agreement with those previously reported.  11  Molecular formula (M.W.)  R u C 6 H N 0 (914.12) 5  52  4  2  49  References on p. 55  Chapter 2  NMR ( H, C D , 25 °C) J  6  6  9.01 (/?-pyrrole-H, 8H), 7.10 (m-H, 8H), 2.45 (p-Me, 12H), 1.86 (o-Me, 24H)  M'W ), 516 (22,000)nm 1  UV-Visible (CeHe)  422 (280,000  IR (Nujol, KBr)  v = = 821 cm"  1  Ru  0  H TDCPP 2  The free-base porphyrin H TDCPP, /we50-tetra(2,6-dichlorophenyl)porphyrin, was 2  synthesized by a literature procedure reported for the synthesis of H TMP. The 10  2  modifications to the original literature preparation are described below. 2,6Dichlorobenzaldehyde (10.0 g, 0.058 mol), pyrrole (4.0 mL, 0.058 mol) and chloranil (4.0 g, 0.0016 mol) were added in the above order to 1 L CH C1 , which had been dried, 2  2  distilled and N -purged. When all the aldehyde had dissolved, BF -MeOH (50 % weight 2  3  BF in MeOH) (1.3 mL, 0.014 mol) was added via a syringe to the solution, which was 3  then stirred magnetically at about 25 °C for 10 min. Then NEt (2.0 mL, 0.014 mol) was 3  added to quench the BF catalyst. The resulting solution was rotary evaporated and the 3  black tarry solid was chromatographed on a silica column (BDH 70-230 mesh). The porphyrin was elutedfirstwith benzene as a red-purple band, although substantial amounts of dark green and violet compounds contaminated the porphyrin. MeOH (100 mL) was added to the crude porphyrin, and the solution was left sitting overnight. The purple precipitate of H TDCPP was collected and chromatographed again on a silica column 2  (BDH 70-230 mesh). This time, the dark green and violet impurities that remained in the  50  References on p. 55  Chapter 2  precipitate were retained on the silica column. Yield 0.20 g, 1.6 %. The data are in good agreement with those previously reported. . 11  Molecular formula (M.W.)  C H N C1 (890.30)  NMR ( H, CDC1 , 25 ° C )  8.68 (^pyrrole-H, 8H), 7.80 (m-U, d, 8H),  1  3  44  22  4  8  7.75 (p-U, t, 4H), -2.45 (N-H, 2H) UV-Visible (CgFL)  420, 514, 592 nm  Ru"(TDCPP)(CO) Ru (TDCPP)(CO), carbonyl(tetra(2,6-dichlorophenyl)porphyrinato)ruthenium(II), n  was prepared by the same method as that used for the preparation of Ru (TMP)(CO) n  described above. H TDCPP (160 mg, 0.18 mmol) was added to a 500 mL 3-necked flask 2  containing mesitylene (200 mL), and the solution was refluxed under a bubbling stream of CO for 48 h. Ru (CO)i (200 mg, 0.31 mmol) was added in 5 mg aliquots over this 48 h 3  2  period, and the reaction was monitored by TLC. The mixture was then rotary evaporated to remove the mesitylene and the product was chromatographed on a neutral Activity I alumina column. Unreacted FLTDCPP and Ru (CO)i were elutedfirstwith benzene as 3  2  purple and yellow bands, respectively, and Ru (TDCPP)(CO) was subsequently eluted as n  a red-orange band with 1:1 benzene/CH Cl . The purity of the compound was assessed by 2  2  TLC analysis and UV-visible and ^-NMR  spectroscopies. Yield 80 mg, 50%. The data  are in good agreement with those previously reported.  11  Molecular formula (M.W.)  RuC 5H oN Cl80 (1017.37) 4  2  4  51  References on p. 55  Chapter 2  NMR O H , C D , 25 °C) 6  8.70 (yS-pyrrole-H, 8H), 7.36 (/w-H,d, 4H),  6  7.25 (m'-H, d, 4H), 6.90 (p-K, t, 4H) UV-Visible (CgHe)  412, 532 nm  IR (Nujol, KBr)  -i v o - 1951 cm' C  Ru (TDCPP)(0) v,  2  This species can be prepared either by the aerobic oxidation of Ru (TDCPP)(MeCN) or by the /w-CPBA oxidation of Ru (TDCPP)(CO), in benzene. n  n  11  2  Ru (TDCPP)(0) was prepared via the latter route by mixing Ru (TDCPP)(CO) (40 mg, VI  n  2  0.04 mmol) and w-CPBA (120 mg, 0.12 mmol) in benzene (10 mL). After 15 min, the complete conversion to Ru (TDCPP)(0) was verified by UV-visible spectroscopy and VI  2  the product was purified with on a silica column (BDH 70-230 mesh), with the dioxo species eluted first with benzene. A dark brown band remained unmoved on the column. The complex was pure by TLC analysis and UV-visible and ^ - N M R spectroscopies, and the solid was stored in a vacuum desiccator. Yield 20 mg, 50 %. The data are in good agreement with those previously reported.  11  Molecular formula (M.W.)  RuC44H oN 0 Cl (1021.36)  NMR ( H, C D , 25 °C)  8.90 (pyrrole-H, 8H), 7.85 (m-U, d, 8H), 7.75 (p-H, t, 4H)  UV-Visible (CeHe)  420 (255,000 M^cm' ), 514 (14,000) nm  IR (Nujol, KBr)  v =o = 822 cm"  1  6  6  2  4  2  8  1  1  Ru  52  References on p. 55  Chapter 2  Ru (TDCPP-Cl )(CO) n  8  Ru (TDCPP-Cl )(CO), carbonyl(/^octachloro(/we5o-tetra[2,6-dichlorophenyl])n  8  porphyrinato)mthenium(II) was prepared by Dr. L. Xie from Dr. D. Dolphin's group in a collaborative venture with this laboratory. Ru (TDCPP)(CO) (100 mg, 0.1 mmol) that n  has been prepared by the previously mentioned method (H TDCPP was provided by 2  Dolphin's group) was suspended in MeOH (50 mL). A'-Chlorosuccinimide (300 mg) was then added to the MeOH suspension, and the resulting mixture was refluxed in air for 18 h. After this time, the solid Ru (TDCPP-Cl )(CO) that had precipitated was filteredn  8  off and washed with a small amount of MeOH. Thefiltratewas green and the solid that remained was dark purple. Yield 82 mg, 64%. Molecular formula (M.W.)  RuC 5H,2N OCli (1292.93)  NMR ('H, DMSO-^e, 25 °C)  7.50 (p-K, d, 4H), 7.64 (m-H, t, 8H)  UV-Visible (CH C1 /C H6 1:20)  418 (205,000 M cm"), 540 (17,000) nm  IR (KBr)  v = 1965 cm"  Analysis, Calculated Found  C, 41.80; H, 0.94; N, 4.33 C, 41.79; H, 1.05; N, 4.15  Mass Spec. (EI)  [Ru(TDCPP-Cl )] , 1266 amu; loss of CO ligand  2  2  6  4  6  1  1  1  c o  +  8  Ru (TDCPP-Cl )(0) Vi  4  8  2  The w-CPBA oxidation of Ru (TDCPP-Cl )(CO) in benzene or CH C1 yielded n  8  2  2  Ru (TDCPP-Cl )(0) . Only sufficient dioxo complex (< 5 mg) was made immediately VI  8  2  prior to use as needed. Approximately 10 equivalents of /w-CPBA were added to a suspension.of Ru (TDCPP-Cl )(CO) in CH C1 or benzene, as the carbonyl compound is n  8  2  2  53  References on p. 55  Chapter 2 not very soluble either of the two solvents, and the mixture was stirred rigorously. At the end of 5 min, the completion of the reaction was confirmed by UV-visible spectroscopy. The resulting solution was chromatographed on a silica column (BDH 70- 230 mesh), using either benzene or CH2CI2 as the eluent; with CH C1 some TH-CPBA could be eluted 2  2  as well, as the colourless peracid followed very closely the yellow-brown dioxo complex as they were eluted down the column. With benzene as the eluent, the /w-CPBA was retained by the silica; however, the dioxo complex ( A ^ 430 nm) in the eluent was converted to a new Ru(porp) species characterized by a Soret maximum at 422 and a Qband at 518 nm. This porphyrin species with A™, 422 nm can be readily converted back X  to the dioxo species, almost quantitatively, by the addition of m-CPBA. The transformation of the dioxo complex to this unknown porphyrin species was slower in CH C1 (~ 2 h). Thus, the choice of the eluent was important for the preparation of a pure 2  2  sample of the dioxo species. Even in the solid state, the dioxo species degraded substantially overnight in air, evidenced by the loss of V R „ = O intensity in the YR spectrum. Presumably, Ru (TDCPP-Clg)(0) reacts with impurities in the solvent, or even with the VI  2  solvent itself, to give the species with A™>x 422 nm. Molecular formula (M.W.)  RuC 4Hi2N 0 Cli6 (1296.92)  UV-Visible (CeHe)  430 (200,000  IR (KBr)  v =o = 827 cm"  Analysis, Calculated Found  C, 40.75; H, 0.93; N , 4.32 C, 41.95; H, 1.0 ; N , 4.04  Mass Spec. (EI and FAB)  [Ru(TDCPP-Cl )] , 1266 amu; loss of 2 O-ligands  4  4  2  M" cm ), 516 (16,000) nm 1  -1  1  Ru  +  g  54  References on p. 55  Chapter 2  References  1  a) J. L. Dawes and J. D. Holmes, Inorg. Nucl. Chem. Lett., 7, 847 (1971). b) A. Mantovani and S. Cenini, Inorg. Syn., 16, 47 (1976).  2  C. Alexander, Ph.D. Dissertation, University of British Columbia, 1995.  3  M. Ke, Ph. D. Dissertation, University of British Columbia, 1988.  4  J. T. Groves and T. E. Nemo, J. Am. Chem. Soc, 105, 6243 (1983).  5  G. M. Badger, R. A. Jones and R. L. Laslett, Aust. J. Chem., 17, 1028 (1964).  6  D. P. Rillema, J. K. Nagle, L. F. Barringer and T. J. Meyer, J. Am. Chem. Soc, 103, 56(1981).  7  A. Antipas, J. W. Buchler, M. Gouterman and P. D. Smith, J. Am. Chem. Soc, 100, 3015 (1978).  8  J. T. Groves and R. Quinn, Inorg. Chem., 23, 3844 (1984).  9  M. J. Camenzind, B. R. James and D. Dolphin, J. Chem. Soc, Chem. Commun., 1137(1986).  10  J. S. Lindsey, K. A. MacCrum, J. S. Tyhonas and Y.-Y. Chuang, J. Org. Chem., 59, 579 (1994).  11  N. Rajapakse, B. R. James and D. Dolphin, Stud. Surf. Sci. Catal., 55, 109, (1990).  55  References on p. 55  Chapter 3  Chapter 3 Mechanism of Aerobic Oxidation of EAr  3  (E = P, As, Sb)  56  References on p. 110  Chapter 3  3.1 Introduction Phosphines are readily oxidized to phosphine oxides. In fact, phosphines are O2sensitive, the tertiaryarylphosphines being air-stable only in the solid state and somewhat 1  air-oxidizable in solution. Phosphines are easily oxidized and they can serve as useful test f  substrates for oxidation studies; a transition-metal complex to be used as an (Voxidation catalyst can be tested initially for the oxidation of phosphines. Moreover, the oxidation by oxometal species is a relatively simple process, an oxygen-atom transfer to the phosphorus atom, compared to other organic oxidations which might involve breakage or formation of more than one bond. An oxygen-atom transfer generally is defined as a reaction of the 2  type represented in Eq. 3.1. This is the simplest DO + A n  D " + A  m  (n  2)  (m+2)  0  (3.1)  representation where D O is the O-atom donor and A is the acceptor. The O-atom does n  m  not change in its oxidation state, while the donor's and acceptor's oxidation states change by -2 and +2, respectively. For example, the O-atom transfer reaction of interest between oxoruthenium species and PPh involves only cleavage of the Ru=0 bond and formation 3  of the 0=P bond, unlike alcohol or alkane oxidations where O-H and C-H bonds are also involved. As a result, mechanistic studies can be carried out more easily when phosphines are used as test-substrates. In addition, the oxidation of phosphines by an oxometal species is likely to proceed via an intermediate in which the phosphine oxide product is bound to the metal before dissociating into solution. ' Rate constants for such 3a b  ' P P h and Pip-X-CetUh are slightly air-sensitive in solution. These phosphines (in benzene solutions at ~10" M ) under 1 atm air at room temperature are oxidized to approximately 5% of the corresponding phosphine oxide in 24 h. AsPh and SbPh are not oxidized to their respective oxides under the same conditions. 3  2  3  3  57  References on p. 110  Chapter 3  dissociation reactions of phosphine oxide may be of value in the design of homogeneous catalysts that make use of hemi-labile chelating ligands, similar to the phosphine-ether bidentate type ligands used in some homogeneous catalysis systems. The oxidizable 4  nature of phosphines allows one to determine the stoichiometry of an O-atom transfer reaction with an oxometal species, and the number of active oxo-moieties can be readily determined, thus providing a useful diagnostic tool.  3.1.1 Aims of Phosphine Oxidation in Current Work Previous studies in this laboratory on the 0 -oxidation of thioethers catalyzed by 2  zraw5-Ru (TMP)(0)2 (1) [from now on simply referred to as Ru (TMP)(0) ] led to VI  VI  2  interesting observations. Thioethers with longer alkyl chain lengths were more rapidly 5  oxidized, the faster rates being due to more favourable AS* values for the longer chain thioethers. One mechanistic suggestion was that the O-atom transfer from oxoruthenium species to the sulfur was induced via strong Ru=0 vibrational coupling, and for the case 30  of the Ru=0 moiety on the porphyrin a bulkier substrate was considered to be entropically more favourable.  5  Tertiaryarylphosphines can be easily handled in the solid state as well as in solution. In addition, a whole range of P(p-X-C H4)3 compounds are available 6  commercially, allowing for kinetic studies of the O-atom transfer from Ru (TMP)(0)2 to VI  give a direct comparison with the earlier thioether oxidations. Also an earlier study on the same Ru (TMP)(0) /PPh system implied that the phosphine oxide was nonYI  2  3  coordinating; however, the kinetic studies in the present work showed the presence of 6  58  References on p. 110  Chapter 3  OPPh to be important in the overall reaction. The compounds PPh , AsPh and SbPh 3  3  3  3  were oxidized stoichiometrically by (1), and the rate constants and activation parameters were obtained. The para substituent on the phenyl group within a series of P(p-X-C6FL0  3  [X = OMe, Me, H, F, CI and CF ] was systematically varied so that electronic effects were 3  also studied.  3.2 Sample Preparation and Data Analysis 3.2.1 Sample Preparation Freshly distilled benzene was used to prepare the phosphine, arsine and stibine substrate solutions. The stopped-flow spectrophotometer was prepared for anaerobic conditions as described in Section 2.2.2. The sample solutions were purged with Ar and dried over molecular sieves (5 A), but samples treated in this manner gave the same kinetic data as samples that were simply prepared with freshly distilled benzene without subsequent Ar purging. The procedure required for anaerobic sample handling is timeconsuming, and thus all the stopped-flow kinetic runs were performed aerobically. Solutions of Ru (TMP)(0) were prepared by aerobically oxidizing VI  2  Ru (TMP)(MeCN) in freshly distilled benzene or by adding solid Ru (TMP)(0) directly n  VI  2  2  (Chapter 2). Complete conversion to the dioxo species from the bis(MeCN) precursor was ensured by monitoring the UV-visible spectrum from 350 to 650 nm, and the resulting concentrations in the dioxo species, determined spectrophotometrically (Chapter 2), were of the order of 10' M. Solutions of P(p-X-CeH4) , AsPh and SbPh were prepared by 6  3  3  3  dissolving appropriate weights of the compound in freshly distilled benzene, with  59  References on p. 110  Chapter 3  concentrations typically ~10" M ([SbPh ] ~ 10" M). Solutions of Pf/J-X-CeFLOs 3  4  3  containing OPPh were prepared in the same way, with the appropriate weights of OPPh 3  3  added as well ([OPPh ] ~ If/ M). 3  3  The above solutions [(1) and substrate] werefilledinto the stopped-flow apparatus via disposal 2.5 mL syringes (Aldrich). Isothermal conditions were maintained by a watercooled temperature controller, with the temperature at the sample compartment maintained at ± 0.1 °C for the temperature range between 5 °C and 45 °C. A computer was triggered electronically to acquire the data immediately after the porphyrin and substrate solutions were mixed. The absorbances were monitored at wavelengths of 422, 430 and 412 nm, which correspond to the loss of the dioxo species, loss of an intermediate and appearance of the product, respectively (see Figure 3.2, p. 67). For the catalyzed C«2-oxidations, benzene-fife solutions containing ~10' M (1) were 4  prepared, and their concentrations were determined by UV-visible spectroscopyfromthe known extinction coefficient of (1) (Chapter 2). P(p-X-C H4) [X = OMe, H, F, Cl] stock 6  3  solutions were prepared by dissolving appropriate weights of the phosphines in 1.00 mL benzene-fife. All catalysis experiments were carried out in NMR tubes by adding 0.40 mL solution of (1) first. Then the NMR tubes were capped with rubber septa and secured with Parafilm. Appropriate volumes of the phosphine stock solutions subsequently were added with a 250 pL syringe (Unimetrics), so that thefinalconcentrations of the phosphines were 0.014 and 0.027 M for the experiments under 1 atm O2. An O2 atmosphere (1 atm) in these NMR tubes was created by bubbling a stream of 0 with a 2  stainless steel needle into the benzene-fife solutions for 10 min. The catalytic oxidations of  60  References on p. 110  Chapter 3  PPh and P(p-F-C6H4) were also studied under 1 atm air. Blank solutions with the same 3  3  phosphine concentrations but containing no species (1) were prepared and purged with 0*2 (or left under 1 atm air), so that the contributions from the autoxidation could be taken into account in the calculation of the total turnover numbers. All of the NMR samples were kept at room temperature, 24 ± 2°C, for the duration of the experiment.  3.2.2 Data Analysis Absorbance-time data for each phosphine oxidation run were transferred to an IBM-compatible computer as an ASCII text file. Sigma Plot for Windows on an IBM PC was used to function fit the data as a first-order exponential decay of the form represented by Eq. 3.2, of which the derivation can be found in Appendix B. A = ( A ) - A )exp(-k bst) + Ax,, where t = time (seconds) and A = absorbance X)  The parameters  0  A o , kob  S  and A*, ( A > = initial absorbance,  kobs  (3.2)  = observed pseudo-lst-order  rate constant and A*, = absorbance at completion of reaction) were determined by the function-fitting program in Sigma Plot. Values twice the standard errors of regression were taken to be the error estimates for the individual rate constants. Pseudo-first-order rate constants, kobs, obtainedfromfunctionfittingwere compared to  kobs  values obtained  by the Guggenheim method and semi-log analysis (where A o and A* were known), and 7  the resultsfromall three cases were in perfect agreement (see Appendix A). The raw data from the stopped-flow experiments, if in numerical form (400 data points for each absorbance-time trace), would be too voluminous to list in the present thesis. Hence, the kinetic data for the oxidations of all the substrates are tabulated in Appendix A as pseudo-  61  References on p. 110  Chapter 3  first-order rate constants for the corresponding absorbance-time traces. Samples of the actual PPh oxidation absorbance-time traces are shown in Appendix A. 3  At the outset of the kinetic studies on the stoichiometric oxidation of PPh by (1), 3  a fast (10" to 10" s) phase, followed by a slow phase(10 to 10 s), in the overall reaction 2  1  1  2  was observed. In the presence of excess PPh , the slow kinetic phase exhibited non-first3  order behaviour in (1):  kobs varied  as [(1)] was adjusted and exponential-decay,  absorbance-time traces were not observed. The addition of excess OPPh alleviated the 3  above two problems. For the fast kinetic phase, the kinetic data exhibited first-order behaviour in (1), with and without added excess OPPh . Evidently, OPPh plays an 3  3  important role in the slow phase of the reaction between PPh and (1). For the 3  stoichiometric oxidation of the phosphine series, P(p-X-C6H4) , excess OPPh was added 3  3  when the slow kinetic phase was monitored (see Table 3.4). For the catalytic aerobic oxidation experiments, the ratios of oxide product to phosphine substrate in every NMR sample (including the blank solution systems) were determinedfromintegration areas on the NMR spectra. The autoxidation contributions to the overall conversion of phosphine to the phosphine oxide within the sample solutions were taken to be equal to that of the appropriate blank solutions, and the percentages due to the blanks were subtractedfromthe percentages in the samples to ensure an accurate determination of the turnover numbers. For PPh , P(p-OMe-CoFl4) and Vlp-CX-C^U)*, 3  3  integrations in the P{ H}-NMR spectra were used. A pulse delay of 1.0 s was 31  1  implemented initially. These relative integrations then were compared to the spectrum obtained immediately afterwards with a pulse delay of 4.0 s when the ratio of the  62  References on p. 110  Chapter 3  integration areas varied by approximately 7%. The process was repeated with the implementation of a 8.0 s pulse delay. No further change in the integration intensities was observed, indicating that a pulse delay of 8.0 s was sufficient to allow the P nuclei to 31  relax and allow for consistent integrations. For Vip-V-C^U)^ the integration areas on the 19  F-NMR spectra were used to determine the product/reactant ratios. Pulse delay  experiments were performed similarly to the P{ H}-NMR experiments, and it was found 31  1  that the product/reactant ratios were independent of pulse delay times. Of note, F-NMR 19  spectroscopy has the convenience of a more rapid data acquisition over that of P{ H}3,  1  NMR spectroscopy.  3.3 Overview of the Mechanism of Tertiaryarylphosphine Oxidation The first mention in the literature of the oxidation of PPh by Ru (TMP)(0) (1) VI  3  2  was in 1987 by Groves and Ann. The experiment involved a stoichiometric "H-NMR 6  titration which monitored the conversion of (1) first to Ru (TMP)(0) and OPPh , and IV  3  then to Ru (TMP)(PPh ) and 2 OPPh , as one and three equivalents of PPh were added, n  3  3  3  respectively. A successive O-atom transfer mechanism was implied in the report. Of note, the experiment was described to have taken place in benzene-^, although examination of the 'H-NMR spectrum indicated that the experiment most likely took place in CD2CI2, as indicated by the solvent residual peak at 5 ~ 5.3 ppm, whereas the solvent residual for 8  benzene-^is at 8 ~ 7.15. The results from the stoichiometric titrations implied a noncoordinating OPPh , with no possible role of the phosphine oxide in the oxidation 3  mechanism. The simple stepwise O-atom transfers suggested by the "H-NMR titrations  63  References on p. 110  Chapter 3  were found to be an inadequate description once kinetic studies were undertaken in this laboratory. The mechanism of phosphine oxidation is presented first (see Figure 3.1), and the supporting data will be presented in the upcoming sections. This choice of presentation is for the benefit of the reader, as the mechanism involves several interrelated steps. The mechanism is summarized in Eqs. 3.3 to 3.6 [Ru = Ru(TMP), L = PPh ]. 3  Jfoi^Ofc + L  Ru™(0)(OL)  Step 2: OL Dissociation:  /?« (0)(OL)  Ru (0)  Step 3: Disproportionate  2Ru™(0)  Step 4: Ligation of L:  Ru + L  Step  1: Initial O-atom Transfer:  IV  -  w  "  (3.3)  + OL  (3.4)  Ru + Ru^O^  (3.5)  Ru\h)  (3.6)  n  n  The oxidation mechanism in Figure 3.1 equally applies to the other phosphines within the series P(p-X-C H4) [X = OMe, Me, F, Cl and CF ]. When AsPh and SbPh 6  3  3  3  3  were used as substrates, only their initial O-atom transfer reactions with (1) (Step 1) were monitored. Step 1 involves the O-atom transferfromRu (TMP)(0)2 to PPh . This fast VI  3  step, the fast kinetic phase referred to in Section 3.2.2, isfirst-orderin (1) and PPh , and 3  zero-order in OPPh . Step 2 is the reversible dissociation of the OPPh productfromthe 3  3  intermediate species, Ru (TMP)(0)(OPPh ) (2), to form Ru (TMP)(0) (3). Step 3 is the IV  IV  3  disproportionate of (3) to (1) and Ru (TMP) (4). In Step 4, PPh readily coordinates to n  3  (4) to form Ru (TMP)(PPh ) (5). Species (1) formedfromthe disproportionate in Step n  3  3 can oxidize PPh , and the cycle repeats to oxidize 2 equivalents of phosphine with 3  complete formation of (5).  64  References on p. 110  Chapter 3  Oxygen-atom Transfer followed by Disproportionation  ki  (2)  O-atom transfer faster step  reversible k2 dissociation of phosphine oxide  —Ry n  +L,k4  — R u — + —Ru^— n  L  O  (4)  f<5)  — R u — (3) IV  Disproportionation  + 0=L  ^-(1)  Regeneration of Catalyst (see Section 3.4)  *P  + L  b=o: y  L = L*, used to denote an exchange process  Figure 3.1.  +  L  a series of steps  (1)  Mechanism of oxidation of P(p-X-C6H4) , AsPh and SbPh by Ru (TMP)(0)2 (1). The overall reaction involves the transfer of the O-atom from (1) followed by the disproportionation of Ru (TMP)(0). Under air or 0 the process becomes catalytic, but the catalysis occurs at a much slower time-scale (see Section 3.4). 3  3  3  VI  IV  2  65  References on p. 110  Chapter 3  Steps 2, 3 and 4 were observed as an isosbestic set of UV-visible spectra, referred to in Section 3.2.2 as the slow kinetic phase, with the Soret maximum shiftingfrom430 to 412 nm. Figure 3.2 shows UV-visible/time traces of a benzene solution, initially containing (1) (5 x 10" M). In the presence of 0.1 M OPPhj, addition of 10 equivalents of 6  PPh rapidly shifted the 422 nm Soret band [characteristic of (1)] to 430 nm (Step 1). 3  Within the next few minutes, the spectrum's 430 nm Soret maximum shifted to 412 nm (Steps 2, 3 and 4), corresponding to that of (5) (see Section 3.4). Addition of only 1 equivalent of PPh , again in the presence of 0.1 M OPPh . shifted the Soret band to 430 3  3  nm, and then there was no further change in the position of the Soret maximum. As Groves and Ann's 'H-NMR studies suggested that (3) was formed on the addition of 1 6  equivalent of PPh to (1), it is reasonable to assign the 430 nm Soret band to 3  Ru (TMP)(0)(OL) (2) with the OPPh still coordinated to Ru. Isosbestic points at 382, IV  3  420, 484 and 538 nm for the second spectral change [(2) to (5)] are consistent with no other intermediates being formed in any significant quantity during the conversion to the product. The experiment involving the addition of 1 equivalent of PPh to (1) (~10' M) 3  3  in benzene-fife under vacuum, similar to that performed by Groves and Ahn, gave a H 6  1  NMR spectrum that showed 'H-resonances corresponding to those offreeOPPh and 3  Ru (TMP)(0) (3). The UV-visible spectrum of the same sample had absorption maxima IV  at 424 and 518 nm. These results further support the assignment of the species with A™,* 430 nm as Ru (TMP)(0)(OPPh ) (2) (with coordinated OPPh ). Of note, species (3) in IV  3  3  the benzene-fife solution had decomposed when the sample was analyzed again by H !  NMR and UV-visible spectroscopies after 24 h.  66  References on p. 110  Chapter 3  16  T  J Ru (TMP)(0) (1) VI  2  Fast O-atom transfer step; appearance of intermediate at 430 nm  Ru (TMP)(0)(OPPh) (2) V I  3  Dissociation of OPPh , di sproporti onati on, followed by L ligation; 1 slower step; loss of intermediate at 430 nm 3  350  Figure 3.2.  400  450 500 Wavelength (nm)  550  600  UV-visible/time traces monitoring the conversion from Ru (TMP)(0) (1) (422 nm) to Ru (TMP)(PPh ) (5) (412 nm). In the presence of -0.1 M OPPh , addition of 10 equivalents of PPh forms an intermediate at 430 nm before proceeding to form the product (5) at 412 nm. Total time < 5 min. Isosbestic points can be seen clearly at 382, 420, 484 and 538 nm. [(1)] = 5 x 10' M in benzene at room temperature under 1 atm air. Xma (e, IVT'cm') values for (5) in benzene: 412(230,000) and 504(20,000) nm. VI  n  2  3  3  3  6  1  X  67  References on p. 110  Chapter 3 The rate expressions derived from the proposed mechanism in Figure 3.1 are represented in Eqs. 3.7 and 3.8 (see Appendix B for their derivation). O-atom transfer:  rate = - - ^ ^ = - ^ ^ = ki[(l)][L]  (3.7)  OL dissociation followed by disproportionation: r a t p =  r a i e  dJi2yi d[(5yi =  " dt  k k4K rLir(2)l 1/2  =  dt  2  3  k. [OL] + (ki+k4)K [L] 1/2  2  3  Under 0 or air, the oxidation becomes catalytic. The rate-determining step is the 2  regeneration of the catalyst, and the catalysis occurs on a much slower time-scale. The catalysis will be discussed in Section 3.4 after the mechanism of phosphine oxidation by Ru (TMP)(0) has been discussed in detail. VI  2  3.3.1  Oxygen-atom Transfer In the present study, the fast UV-visible spectral change from 422 to 430 nm  (Figure 3.2) corresponds to the initial O-atom transfer step that forms (2) as the phosphine adds to the oxo ligand. The slower, second spectral change from 430 to 412 nm, resulting in the formation of thefinalproduct (5), was inhibited by added excess OPPh (Section 3  3.3.2). This suggests that the phosphine oxide product initially formed in fact remains coordinated to the metal centre, and that the OPPh can reversibly coordinate and 3  dissociate. Thus, the O-atom transfer reaction between (1) and PPh is thought to result 3  initially in the formation of Ru (TMP)(0)(OPPh ) (2). Of note, no evidence from H or IY  X  3  3I  P{ H}-NMR experiments was found to support the existence of a bound phosphine 1  The kobs values were the same for monitoring the loss of (2) or production of (5) at 430 and 412 nm, respectively (see Appendix A).  t  68  References on p. 110  Chapter 3 oxide species in the absence of added excess OPPh (Section 3.4 and Ref. 6), and 3  unfortunately similar NMR experiments in the presence of ~0.1 M OPPh are not feasible; 3  however, that phosphine oxides bind at axial positions of Ru(II) and Ru(IV) centres within an equatorial N -ligand set as observed in other systems, ' and that OPPh slows the rate 3a b  4  3  of reaction in the present system, suggest strongly the formulation of the intermediate species (2) as Ru (TMP)(0)(OPPh ). Furthermore, that Ru (TMP)(0) (3) absorbs IV  IV  3  differently in the UV-visible spectrum (see Section 3.3) supports the formulation of (2) as Ru (TMP)(0)(OPPh ). IV  3  Plots of  kobs  (observed pseudo-first-order rate constant for the initial O-atom  transfer) versus [L] are linear throughout the concentration range studied (5 x 10" to 5  4 x 10" M for the case of PPh ). Figure 3.3 shows the kinetic data for PPh . The values 3  3  3  for the second-order rate constants, k i , are given in Table 3.1 for the oxidation of all the substrates. The activation parameters for the O-atom transfer reaction to PPh are 3  AHi* = 18 ± 1.4 kJ moi" and ASi* = -94 ± 5 J mo^K" (Table 3.2), calculatedfromthe 1  1  slopes of the Eyring plots (Figure 3.4). The AHi* value is lower than that for the t  thioether oxidations (AH* ~ 50 kJ moi" ), suggesting that PPh is perhaps a better 1  5  3  nucleophile than thioethers. The ASi* values are comparable, showing that both coupling reactions are unfavourable in terms of activation entropy. No trend was found for AHi* on goingfromPPh to AsPh to SbPh (Table 3.2). 3  3  3  AHi* increases by 50% on goingfromPPh to AsPh . On the other hand, the AHi* value 3  3  for SbPh is about half that for the PPh system. AHi* is the key factor governing the k i 3  t  Eyring Equation: ln ^ r  3  -  = (- -pr) ^ + (  +  69  ln ^  ). See Ref. 20.  References on p. 110  Chapter 3  Table 3.1.  Second-order rate constants, ki, for the initial O-atom transfer from Ru (TMP)(0) (1) to various phosphines, AsPh and SbPh substrates in benzene. VI  2  3  Substrate P(/?-X-C H4) 6  ki x l O ^ M V at 10, 20 30, and 40°C, respectively 8.14 + 0.08 10.9 + 0.02 14.8 + 0.02 19.2 + 0.02 4.29 + 0.07 5.88 + 0.07 7.69 + 0.18 10.0 + 0.3 3.95 + 0.14 5.7 ± 0 . 3 7.18 + 0.14 9.38 + 0.15 7.62 + 0.13 10.6 + 0.02 14.2 + 0.2 18.1+0.4 9.17 + 0.11 12.8 + 0.2 16.9 + 0.2 22.3 ± 0.03 6.38 + 0.17 9.10 + 0.3 12.7 + 0.3 16.6 + 0.4 0.945 ± 0.02 1.38 + 0.04 2.00 + 0.08 2.87 + 0.08 0.0623 ± 0.0007 0.0940 ± 0.0006 0.147 + 0.001 0.212 + 0.001 285 + 30 303 +35 325 +30 362 + 35  3  X = OMe  X = Me  X=H  X=F  X = C1  X = CF  3  3  (dichloro)(triphenylphosphine)(tris(2pyridyl)phosphine-A')ruthenium(II)  AsPh  3  SbPh (10, 15, 20,and25°C) 3  70  References on p. 110  Chapter 3  0  0.0005  0.001  0.0015  0.002  0.0025  0.003  0.0035  0.004  0.0045  [PPh ] (Molar) 3  Figure 3.3.  Plot of kobs, pseudo-first-order rate constant, as a function of [PPh ] in benzene. k o corresponds to the rate constant for the initial O-atom transferfromRu (TMP)(0) (1) to PPh . Inset shows the data at 20 °C at a lower value of [PPh ]. [(1)] = 4.2 x 10" M (1.6 x 10 M for the data in the inset). A tabulation of k o values can be found in Appendix A for all the different substrates listed in Table 3.1. 3  b s  VI  2  3  6  -6  3  b s  71  References on p. 110  Chapter 3  F i g u r e 3.4.  Eyring plots, ln(!jf) versus ^ , and T l n ( ^ f ) versus T. From the slopes of these lines the activation parameters, AFT.* and ASi*, are derived, respectively.  72  References on p. 110  Chapter 3  Table 3.2.  Activation parameters, AHf and ASr, for the initial O-atom transfer from Ru (TMP)(0) (1) to phosphine, arsine and stibine substrates. VI  2  Substrates  AHi* (kJ moi ) and ASi* (J moi" K" ), respectively 18 + 1 -87 ± 5 1  1  P(p-X-C H4) 6  3  X=OMe  1  X = Me  18± 1 -92 ± 5  X=H  18 ± 1.4 -94 ± 5  X=F  18.9 + 1 -84 ± 4  X = C1  19.4 ± 1.6 -81+5  X = CF  21 + 1.4 -78 + 5  3  (dichloro)(triphenylphosphine)(tris(2pyridyl)phosphine-AOruthenium(II)  25.7+1 -78 ± 5  AsPh  28.7 + 1 -90 + 3  SbPh  10.2 ± 2 -85 ± 10  3  3  73  References on p. 110  Chapter 3  values for the oxidations of PPh , AsPh and SbPh by (1), as the ASi* values are similar in 3  3  3  all three cases. The following are some periodic trends within the series EPh (E = P, As, 3  Sb):  9  1) a donor strength decreases in the order P > As > Sb; 2) steric effects due to E  increases in the order P < As < Sb; 3) steric effects due to the Ph groups decreases in the order P > As > Sb. That such effects should contribute to the activation enthalpy seems feasible, but nofirmconclusions can be drawn based on the current data. An attempted Hammett correlation plot for the k values for the P(p-X-CeH4) t  3  substrates versus a values is shown in Figure 3.5. The non-linearity observed is usually 10  considered to indicate a change in the reaction mechanism, but this would seem unlikely 11  for this series of phosphine substrates. Hammett analysis is a type of linearfreeenergy relationship, where the activationfreeenergy, AG*, is being correlated with the para substituent. More precisely (and especially in this case) the correlation is between the purely electronic effect brought about by a change in the para substituent on the P-atom, and the numerical value, o. A conventional Hammett plot of logj^ versus a can be linear only if the change in the para substituent results in one of the following three scenarios: 1) AHi* = constant, implying that A(ASi*) oc a; 2) ASi* = constant, implying that A(AHi*) oc a; 3) A(AH!*) oc A(ASi*) oc a. As a non-linear Hammett plot is observed for the present systems, the logical alternative is to look at how the activation parameters, AHi* and ASi*, are affected by the para substituents. Consideration of the different contributions of AHi* and ASi* (Table 3.2) suggests that the change in the values might indeed be independent of one another, and hence the phosphine systemsfitnone of the above three situations. The AHi* values do increase  74  References on p. 110  Chapter 3  -r 0 35 40.4  • CI  0.3 - •  • F  OMe  0.25 0.2 - •  •  CF  3  0.15 - 0.1  Me •  H  /  0.05  -+ -0.4  0.2  -0.2  0.4  0.6  a (Hammett factor)  Figure 3.5.  Hammett plot for logr values for the ki step at 20 °C (a values taken -  fromRef. 10).*  * A supervisory member of my Ph.D. committee, M . Tanner, has suggested that the p-substituent effects are small, and that the Hammett plot may be horizontal.  75  References on p. 110  Chapter 3  with increasing electron-withdrawing groups (see Figure 3.6 for the modified Hammett plot). If one considers an electrophilic attack of a Ru=0 moiety of (1) on the lone-pair of electrons on P(p-X-C6H4) , then withdrawal of electron density from phosphorus by X 3  should tend to increase AHi*. In terms of ASi*, no correlation can be seen with a, although ASi* generally becomes more favourable, i.e. less negative, as the mass of the phosphine, arsine or stibine substrates increases (see Figure 3.7). An earlier suggestion has been made that if the Oatom transfers are induced via strong Ru=0 vibrational coupling, the effect is perhaps 3  reflected in a more favourable activation entropy with bulkier substrates. To test the 5  effect of the mass of the phosphine on ASi*, the complex (dichloro)(triphenylphosphine)(tris[2-pyridyl]phosphine-iV)ruthenium(II) (Eq. 3.9) was used as an oxidizable phosphine substrate, as the phosphorus on the coordinated tris(2-pyridyl)phosphine ligand can be oxidized to the phosphine oxide. The identities of the two species in Eq. 3.9 are known from prior work carried out in this laboratory.  12  O  (3.9)  php"; 3  76  References on p. 110  Chapter 3  24 -j 23 22 -  16 15 14 13 -0.4  -0.2  0.0  0.2  0.4  0.6  a (Hammett factor)  Figure 3.6.  Modified Hammett plot, AHi* versus o.  77  References on p. 110  Chapter 3  Molecular Mass of P ( p - X - C H ) 3 and Related Substrates (gram moi ) -75 H 1 1 1 1 1 6  4  650  750  {P(2-pyridyl)3}(PPh )(Cl) Ru 3  2  ASx* moi K Y 1  Figure 3.7.  Plot of molecular mass of P(p-X-C6Fi4)3 and related substrates versus ASi*.  78  References on p. 110  Chapter 3  The value of ASi* perhaps reaches some limiting value as the mass is increased; this is not surprising as the coupling reaction between (1) and L is expected to be entropically unfavourable. The tris(2-pyridyl)phosphine complex is very different structurally from the EPh -type substrates, and within this set an almost linear trend is 3  established. Intuitively, one may envision this quantum mechanically in terms of the vibrational energy levels of the transition state becoming closer together as the mass becomes larger* A non-linear Hammett plot has been observed for the oxidation of p- and msubstituted styrenes by Ru (porp)(0)2 (porp = OEP and TPP). vl  13  The non-linearity was  ascribed to a shift in the electron density on the alkene C=C double bond, as the substituent on the phenyl ring variedfromelectron-withdrawing (NO2) to electronreleasing (OMe) groups, and this was suggested to lead to a change in the electronic structure of the transition state. Of note, the Hammett plot was concaving upwards, with the unsubstituted styrene at the minimum of the plot. If there was some change in the electronic structure in the C=C bond, this would not necessarily occur when the substituent was H, although this was invoked in order to explain the observed experimental results. A look at the activation parameters would be more insightful in this case.  T  Vibrational Entropy <x In q , where the vibrational partition function, q,* = [1 - exp(vib  )]"' for a  simple harmonic oscillator (Ref. 21). The vibrational frequency, v « u," , where \x = reduced mass. As the mass of phosphine substrate increases, the reduced mass also increases, leading to an decrease i n the vibrational energy gaps, and hence a greater number of vibrational levels. A greater number of vibrational levels leads to an increase in vibrational entropy in the transition state; the macromolecules in the present system are, of course, much more complicated than the species considered in the Transition State Theory. 1/2  79  References on p. 110  Chapter 3  Vip-X-C^U)?, compounds, compared to other substrates such as alkenes or thioethers, yield the largest span of molecular mass differences, and thus this effect is perhaps the most pronounced for this series. The rates of O-atom transfer from Ru (TMP)(0)2 to phosphines are clearly governed by both AHi* and ASi*: AHi* becomes VI  more favourable as the electron density around phosphorus increases, while ASi* is more favourable with more massive substituents. The increased bulk at the para position should not increase any steric hindrance, and should have minimum effects on 14  the activation parameters in terms of steric considerations. The O-atom transfer is probably similar to the process in thioether oxidations, and occurs via strong Ru=0 vibrational coupling, with a more massive phosphine giving rise to a more favourable AS i via a larger vibrational entropy. 1  In terms of the actual mode of O-atom transfer, the phosphine could initially coordinate to Ru, followed by O-atom transfer to the phosphorus; however, the steric constraint presented by the TMP ligand makes this unlikely. The redox process could conceivably involve two successive one-electron transfers; this would be difficult to distinguish mechanistically from a single two-electron O-atom transfer pathway, although rates arising from single-electron transfers would perhaps be more likely to adhere to a Hammett correlation. The non-Hammett behaviour of this system, as well as the strong AS* dependence on the substrate mass, are consistent with a single two-electron O-atom transfer pathway.  80  References on p. 110  Chapter 3  3.3.2 Disproportionation of Ru (TMP)(0) 1  Figure 3.2 shows that two separate processes occur on different time-scales. The shift in the Soret maximumfrom422 to 430 nm has been discussed, and corresponds to the O-atom transfer to form Ru (TMP)(0)(OPPh ) (2). The shift of the Soret maximum IV  3  from 430 to 412 nm occurs on a slower time-scale and is thought to correspond to the dissociation of OPPh from(2), followed by a disproportionation equilibrium driven to the 3  product side by the formation of the stable Ru (TMP)(PPh ) (5) (see Figure 3.1). The n  3  disproportionation reaction mechanism was summarized previously in Eqs. 3.3 to 3.6, with the resulting rate equation given in Eq. 3.8. In agreement with this mechanism for the slower second step, the rate is first-order in [(2)], first- to zero-order in [PPh ], and 3  shows an inverse dependence on [OPPh ] (see Figure 3.8). The analysis of the kinetic 3  data will be considered later. An alternative simpler, but less favoured, mechanism can be proposed for the second step by assuming that the second UV-visible spectral change corresponds to a second O-atom transfer starting with dissociation of OLfrom(2), followed by oxidation of L by (3), and ending with the formation of (5) via rapid PPh ligation, Eq. 3.10 3  (j = rate constants). A steady state approximation applied to the series of reactions in n  +L / -OL *. Ru\L) fast  (3.10)  (5) Eq. 3.10 yields the rate law shown in Eq. 3.11 which is of the same form as Eq. 3.8.  ibs  ; j. [OL]+j [L] 2  (3.11)  3  81  References on p. 110  Chapter 3  0.00138M OPPh.3  0.00271M  0.00399M  0  0.001  0.002  0.003  0.004  0.005  [PPh ] (Molar) Plots of k o b s (2nd slower UV-visible spectral change from 430 to 412 nm) versus [PPh ] at various [OPPh ] values in benzene at 20 °C. [ ( l f e a i = 4.2 x l O " M . 3  Figure 3.8.  3  3  6  82  References on p. 110  Chapter 3  Rearrangement of Eq. 3.11 to the form represented by Eq. 3.12 facilitates the J-2  analysis of the kinetic data to yield values for j and • . Figure 3.9a shows the plot of 2  Kobs  J2  J2J3  [L]  '  v  1 [OL] j.2 1 T— versus - , for L = PPh at 20 °C, with the slope giving r~r and the y-intercept —. rT  Kobs  3  L M  J2  J?)3  (Figures 3.9b to f show similar plots for the other P(p-X-C H4) substrates). The y6  3  intercept is near 0, hence the value obtained for J2 is unreliable. It is possible to obtain j  2  by a different method. As [L] is increased, j [L] > j.2[OL], and eventually 3  j. [OL] becomes negligible. In essence, the rate-determining step is now the dissociation 2  of the OL ligand. 1.3 x 10" M OL was present (instead of ~10" M in typical experiments 5  3  as described in Section 3.2.1) in order to minimize the competition by the j. [OL] term. 2  The expected saturation kinetics are observed with the values of  kobs  leveling-off as [L]  increases to nearly 0.05 M (Figure 3.10). Rearrangement of Eq. 3.12 to the form represented in Eq. 3.13 allows the value of r- to be determined from the slope of the plot J2  of  Kobs  versus [L] (Figure 3.11). The values of j are obtained under various 2  ^ Kobs  = ~ [L] + ^constant, forfixed[OL] J2  (3.13)  J2j3  temperatures (Table 3.3), and the following activation parameters may be obtained (Figure 3.12): AH  = 39 ± 13 kJ mol" and As/ = -85 ± 4 0 J mol" K" ; however, the Eyring 1  j2  1  2  1  plots are unsatisfactory (see below).  83  References on p. 110  Chapter 3  8  T  7+ 6 + 5 +  (s)  4 +  3 +  2 + 1 +  0  0.5  1  +  1.5  +  2  2.5  3  3.5  4  4.5  [PPh ] 3  Figure 3.9a. 6  Plot of r~ versus^^^r for the kinetic data of the Soret shift from 1  kob  [PPh ]  S  3  430 to 412 nm at 20 °C, corresponding to the slower 2nd step in the overall reaction between Ru (TMP)(0) ( 1 ) and PPh . The kobs values are pseudo-first-order rate constants under the conditions of added excess PPh and OPPh . [ ( 1 ) ] ^ = 4.2 x 10 M. k o values for all P(p-X-C H4) substrates are tabulated in Appendix A. VI  2  3  -6  3  3  b s  84  6  3  References on p. 110  Chapter 3  10  15 FOPPh ]  20  25  30  3  [P(p-OMe-C H ) ] 6  4  3  Figure 3.9b. Plot of 7^~~ versus 7^7—7^T~~^77TT for the kinetic data of the Soret shift kobs [PO-OMe-CeFLO ] from 430 to 412 nm (see also Appendix A). 6  3  120 -  10 °C  100 - • 80 i< > s  60" 40 20 +  +  0 0  10  +  20  30 fOPPh l [P(/>-Me-C H ) ]  40  50  3  6  Figure 3.9c. 6  4  3  Plot of r~ versus / ^ T U T ^ L \ i for the kinetic data of the Soret shift kobs  [P(p-Me-C H4) ] m  6  3  from 430 to 412 nm (see also Appendix A).  85  References on p. 110  Chapter 3  30 - • 25 - • 20 - •  10 - • 5  "  +  0 -0  10  15  20  [OPPh l [Pi>F-C H ) ] 3  6  Figure 3.9d. Plot of ir— versus kobs  6  /^*^]  ro  [P">-F-C H4)3]  f  or  4  3  the kinetic data of the Soret shift  6  from 430 to 412 nm (see also Appendix A).  40  10 °C  35 30 25 - •  1  20 - • ;< >i5-s  40 °C  10 • • 5  o -•  +  + 10  •H 20  15  25  30  •lOPPhal [P(p-Cl-C H ) ] 6  Figure 3.9e. 6  4  3  ^^T^vl \  Plot of r~ versusr r t / -, for the kinetic data of the Soret shift kobs [P^-Cl-CeFLOs] from 430 to 412 nm (see also Appendix A).  86  References on p. 110  Chapter 3  20 °C  20 [OPPh l  10  30  40  3  [P(p-CF3-C H )3] 6  Figure 3.9f. 6  Plot of r— versus kobs  v n r  4  ^J^I^IT \ ^ for the kinetic data of the Soret shift  [P(p-CF3-C H4)3] 6  from 430 to 412 nm (see also Appendix A).  87  References on p. 110  Chapter 3  18 " 16 " 14 " 12 " 10 kobs 8  <*V4 " 2"  0 0  0.01  0.02  0.03  0.04  0.05  [PPh ] (Molar) 3  Figure 3.10. Plot of kobs versus [PPh ] for the kinetic data of the Soret shiftfrom430 to 412 nm at 20.5 °C, corresponding to the slower 2nd step in the overall reaction between Ru (TMP)(0) (1) and PPh . The kobs values are pseudo-first-order rate constants under the conditions of added excess PPh and OPPh . The k o values at other temperatures are tabulated in Appendix A. [OPPh ] = 1.3 x 10" M, [ ( l ) ] ^ = 2 x 10" M 3  YI  2  3  3  3  b s  5  6  3  88  References on p. 110  Chapter 3  Table 3.3.  Values of j , dissociation of O P P h from R u ( T M P ) ( 0 ) ( O P P h ) . lv  2  3  3  Temperature (°C)  j (s" )  11.2 20.5 30.1  18.7 + 1 22.7 ± 1  40.1  82 + 25  1  2  55.7 ±9  89  References on p. 110  Chapter 3  Figure 3.12.  j 1 j Eyring plots, ln(y-) versus j , and Tln(^ ) versus T. From the 2  2  slopes of these lines the activation parameters, A H j derived.  90  2  and A S j , are 2  References on p. 110  Chapter 3  The large negative ASj value would thus correspond to the loss of OPPh , a 2  3  dissociation reaction. This is unusual, but could be ascribed in part to solvent effects, perhaps due to some solvation of the transition state, if its geometry approximates that of Ru (TMP)(0). As written, this second O-atom transfer follows the dissociation of OL IY  from (2), while the coordination of OL inhibits the O-atom transfer. This is contrary to the mechanism suggested for thioether oxidations by (l), where Ru (TMP)(0)(OSR ) is IY  5  2  considered more active than (1) as an O-atom transfer agent (see later). The disproportionation mechanism (Eqs. 3 . 3 to 3 . 6 ) is favoured for the phosphine oxidation reaction as explained below. First, the disproportionation of Ru (TMP)(0) to rv  Ru (TMP) and Ru (TMP)(0) , although not directly established, presents a "consistent" n  VI  2  explanation for the Ru (TMP)(0) oxidation chemistry demonstrated for a range of VI  2  different systems studied. The 0 -oxidation of alkenes catalyzed by (1) has been proposed 2  to involve a disproportionation process ' as depicted below. 15 16  Ru (TMP)(0) + alkene  - Ru (TMP)(0) + epoxide  VI  IV  2  2 Ru^TMPXO)  = 5 = = S 5  Ru (TMP) + Ru (TMP)(0) n  VI  2  The generation of Ru (TMP)(0) from Ru (TMP)(MeCN) upon exposure to air ' also VI  n  5 6  2  2  has been suggested to occur via the disproportionation of Ru (TMP)(0). In addition, the IV  catalytic 0 -dehydrogenation of primary and secondary alcohols to aldehydes and ketones, 2  respectively (Chapter 4), is proposed to involve this disproportionation reaction. According to the disproportionation mechanism, the pseudo-first-order rate constant,  ko  D S  ,  assumes the form represented in Eq. 3 . 8 , and the observed saturation  91  References on p. 110  Chapter 3  kinetics yield not j (the OL dissociation rate constant), but rather the combination of rate 2  k lC4 2  constants, k' = ^  +  ^ , where k alone represents the OL dissociation rate constant (see 2  Appendix B). The Eyring plots in Figure 3.12 are performed on k', and the observed AS* value of -85 J mor'K" is probably not meaningful. The Eyring equation applied to k' is 1  not expected to yield a linear plot, and the scatter of the data in Figure 3.12 suggests that the Eyring plots are probably non-linear. The dissociation of OL from Ru (TMP)(0)(OL) is a necessity within the disproportionation mechanism, as a vacant IV  site is required for the disproportionation of Ru (TMP)(0) to take place. IV  16  k.  2  The slope from the plot in Figure 3.9a gives the value of k" = I I K C2  C4  1 / 2 3  A T  20 °C  for the PPh system [the values at other temperatures, as well as those for other P(/?-X3  C6H4) systems, are listed in Table 3.4]. Excess OPPh was used throughout each study, 3  3  as the dominant oxide present would then be OPPh regardless of the phosphine substrate. 3  The inhibition of the rates of reaction by OPPh in all the P(p-X-C6H4) systems (see data 3  3  in Appendix A and the linear r~ versus [ J J ^ ^ Q F L ^ ] plots, Figures 3.9b to 3.9f) implies that the k and L steps involve a rapid replacement of OPQj-X-CelUh by excess 2  2  OPPh , and hence the reversible dissociation and coordination reactions involve mainly 3  OPPh . K is independent of the phosphine substrate as well. Thus, the smaller the value 3  3  k-  2  of i k K ' ' 1/  C2  4  3  2  l g the relative value of IQ. From Table 3.4, the relative rate of a r  e r  binding of L to Ru(II) follows the order: CI > F > CF ~ OMe > H ~ C H at 10 °C. 3  92  3  References on p. 110  Chapter 3  Table 3.4.  Values of, ,  v  1/2 obtainedfromthe kinetic data for the spectral change  K2K4IV3  of the Soret maximumfrom430 to 412 nm. P(p-X-C H4)3, X=  k.2  6  k k4K 2  1/2  "at 10, 20 30 and 40°C  3  OMe  1.52 + 0.2 0.92 ± 0.07 0.63+0.08 0.48 ±0.08  Me  2.25 + 0.17 1.27 + 0.1 1.05 + 0.06 0.846 + 0.07  H  2.16 + 0.2 1.62 + 0.09 1.26 + 0.1 1.06 + 0.1  F  1.38 + 0.06 0.864 + 0.06 0.628 ± 0.06 0.536 + 0.05  Cl  1.12 + 0.1 0.69 + 0.06 0.52 + 0.054 0.38 ±0.045  CF  1.48 + 0.3 0.94 ±0.14 0.444 ± 0.09 0.31 ±0.07 k , k- and K are considered to be the same for every reaction (see text). Excess OPPh was used in every study to allow for a comparison of kj between different phosphine systems. 3  0  2  2  3  3  93  References on p. 110  Chapter 3  The orders are slightly different at other temperatures: C l > F > O M e > C F > C H > H at 3  3  20 °C, C F > C l > F > O M e > C H > H at 30 °C, and C F > C l > O M e > F > C H > H at 3  3  3  3  40 °C. The data suggest that the electron-rich groups tend to give the smaller relative IQ values. Perhaps the electron-rich Ru(II)-centre favours rc-acceptor ligands; for example S-bound sulfoxides are generally favoured over O-bound sulfoxides in Ru(JJ)A more electron-deficient phosphine may act as a better 7t-acceptor. The  complexes. '  5 17  coordination o f L to Ru(II) may well be the driving force for the effective disproportionation o f R u ^ T M P ^ O ) . In hindsight, the two-stage oxidation of thioethers may follow the same mechanism as the phosphines, via disproportionation, rather than via two successive O-atom transfers. The time-scale of the O-atom transfer from (1) to aliphatic thioethers is o f the 5  order o f hours, and any R u ( T M P ) ( 0 ) that may have formed should have rapidly I V  disproportionated. The scheme represented in E q . 3.14 [Ru = R u ( T M P ) , S = SEt2; O and S imply oxygen- and sulfur-bonding sulfoxides, respectively] is the mechanism o f thioether + SEt *"  V I  (°)2  (1)  + SEt  2  2  l b w ~ *" (0)(QS) I S T * * " ( Q S ) IV  n  (6)  2  —  i?« (OS)(OS) — *« (OS) n  n  (8)  (7)  2  (3.14)  (9)  oxidation proposed in Reference 5. M o r e careful examination o f the data in Reference 5 shows that the formulation of species (7) as the bis(0-bonded sulfoxide) complex may be incorrect. In Reference 5a, the ' H - N M R spectrum o f Ru (TMP)(SEt2)2, produced in situ n  from the reaction of R u ( T M P ) ( M e C N ) and excess S E t , is found to be identical to that n  2  2  assigned to (7). This also possibly suggests that the formulation for species (8) as written in E q . 3.14 is also incorrect, and it might be the Ru (TMP)(SEt )(OSEt2) species. This n  2  94  References on p. 110  Chapter 3  chemistry would be consistent with the labile nature of an O-bound Et2SO ligand in the Ru(TMP) system. A plausible route to these Ru(II) thioether and S-bound sulfoxide 5  species is from the disproportionation of Ru (TMP)(0) to Ru (TMP) and (1), followed IV  n  by rapid ligation of thioether and sulfoxide to the Ru(II)-centre.  3.4  Ru"(TMP)(L) Species and Catalytic Aerobic Oxidation of Phosphines  3.4.1  Ru"(TMP)(L) Species Stoichiometric 'H-NMR titrations (see Section 3.3) performed by Groves and Ahn  6  showed Ru (TMP)(PPh ) (5) along with 2 equivalents of OPPh , to be the products of the n  3  3  reaction between Ru (TMP)(0)2 (1) and 3 equivalents of PPh . It was assumed initially VI  3  that perhaps the bis(phosphine) complex, Ru (TMP)(PPh ) , would form if more than 3 n  3  2  equivalents of PPh were added to (1), as Ru (TMP)(P Bu ) and Ru (OEP)(PPh ) have n  n  n  3  3  2  3  2  been synthesized previously in this laboratory; however, H and ^P^HJ-NMR 18  1  experiments showed that only (5) was formed even when more than 3 equivalents of PPh  3  reacted with (1). Figure 3.13 shows the ^ - N M R spectrum of (5), the product from the reaction of (1) with 3 equivalents of PPh in benzene-^. That two distinct ortho-Me ^-resonances 3  are observed is indicative of (5) possessing C symmetry. Of note, addition of 1 5  4 v  equivalent of PPh to Ru (TMP)(MeCN) yields a product giving a ^ - N M R spectrum n  3  2  identical to that of (5), with production of free MeCN. This rules out the possibility that OPPh coordinates to the Ru-centre [as Ru (TMP)(L)(OL) also exhibits C symmetry] n  3  4 v  when (5) is produced via PPh oxidation by (1), where 2 equivalents of OPPh is produced. 3  3  95  References on p. 110  Chapter 3  Thus, the formulation of (5) as the mono-phosphine complex Ru (TMP)(PPh ) is correct. n  3  Also shown in Figure 3.13 is the 'H-NMR spectrum of the same benzene-fife solution at room temperature containing (5), formed via the reaction between (1) and 30 of equivalents PPh . The two ^ - N M R spectra for the systems containing no excess PPh and 3  3  excess PPh are generally the same, except that the ortho-Me protons of TMP were 3  exchanged broadened and the signals of the coordinated PPh protons had disappeared for 3  the system containing the excess PPh . Most likely, rapid PPh exchange via nucleophilic 3  3  attack at the Ru centre is causing the broadening of the ortho-Me protons signals. The ligand exchange process of (5) with excess PPh was verified in variable 3  temperature 'H and ^PjTiJ-NMR studies. Figure 3.14 shows the H and P{TiJ-NMR !  31  spectra in benzene-fife of (5) formedfromthe reaction of (1) with 60 equivalents PPh . At 3  10 °C, the ortho-Me signals were exchange broadened, and the signals of the PPh protons 3  disappeared. At -78 °C, 'H-resonances due to the two inequivalent ortho-Me groups, as well as 'H-resonances for the protons on the coordinated PPh , were detected, as the ligand 3  exchange rate at the lower temperature was decreased. Also at -78 °C, the P{ H}31  1  resonance for the coordinated PPh was observed (Figure 3.14). These results clearly 3  suggest that afive-coordinatemono-phosphine complex is favoured. That no other Ru (TMP) species can be detected in these NMR studies indicates that the bis(phosphine) n  species is present only in a trace amount needed to effect phosphine ligand exchange,  96  References on p. 110  Chapter  o  r-r-i  cfl  (3D  o 'r»5  E a a.  < .=> -e " 3 w E cd  —'  * 3 o  Vi[  oc"  E-H  fa  s  WD  97  References on p. 110  Chapter 3  'H-NMR spectra l  Me  10 °C  toluene toluene  p-Me  Coordinated PPh  9.0  8.0  7.0  -40 °C  3  -78 °C  3.0  6.0 5.0 4.0 Chemical Shift (ppm)  2.0  Free PPh  3  M  P{'H}-NMR  spectra  10 ° c  Coordinated PPfc ted PPh  3  45  I Free Fro OPPh,  35  15  25  Chemical shift (ppm)  Figure 3.14.  Variable-temperature H and P{ H}-NMR (300 MHz) spectra of Ru (TMP)(PPh ) (5) (5 x 10" M) containing excess PPh (3 x 10" M) in toluene-dg. Species (5) was formed by reacting (1) with 60 equivalents of PPh , andfreeOPPh is observed in the P{'H}-NMR spectra. The partial P{ H}-NMR spectrum at 10 °C shows only OPPh ; the signal due to the coordinated PPh is not observed. !  31  n  1  4  3  3  2  31  3  3  31  l  3  3  98  References on p. 110  Chapter 3  which would make the ortho-Me protons become equivalent (Eq. 3.15 [Ru = Ru(TMP)]). The UV-visible spectrum of (5) (Figure 3.2) did not change when more Ru\L)  +V  Ru (V)(L)  ====  ===== Ru (L*) + L  n  (3.15)  a  phosphine was added (up to ~0.1 M), a strong indication that there is no significant amount of Ru (TMP)(PPh ) in solution, if any. n  3  2  Ru (TMP)(L) [L = PO-X-CeFLOs, X = OMe, Me, F, CI and CF ] species can also n  3  be formed from the reaction of (1) with 3 equivalents of L, and the NMR data obtained for these species produced in situ are tabulated in Table 3.5. The reaction of (1) with 3 equivalents of EPh (E = As and Sb) also afforded the Ru (TMP)(EPh ) species. The 'Hn  3  3  NMR spectra of the solutions containing excess phosphine L show the same exchange broadening of the ortho-Me protons and non-detection of the coordinated ligand phenyl protons, as observed for the PPh system, showing that the phosphines within the P(p-X3  CeH4) series do not form complexes of the type Ru (TMP)(L) . It seems that only n  3  2  stronger rj-donor phosphines such as P"Bu can form the Ru (TMP)(P"Bu ) complex in n  3  3  2  solution; however, the second P"Bu ligand within the complex can be removed at 3  270 °C under a vacuum of ~ 10" torr. 5  3.4.2  18  Catalytic Aerobic Oxidation of Phosphines Ru (TMP)(0), Ru (TMP)(0) and Ru (TMP)(L) were observed in benzene-^ w  VI  n  2  solutions of Ru (TMP)(L) (initially made from (1) + 3 L) [L = P(p-X-C H4) , AsPh and n  6  3  3  SbPh ] when these solutions were exposed to air for approximately 2 min. Free L was not 3  observed during the reaction, and within 10 min OL and (1) were the only species in  99  References on p. 110  Chapter 3  Table 3.5.  "H and P{"H}-NMR data for various Ru (TMP)(L) species (L = substituted phosphine, AsPh or SbPh ). 31  n  3  Ru (TMP)(L)°  3  8.42  2.41  Chemical shifts, '" 8 Me H Ho 2.18, 1.40 6.32 4.80  L = P(p-OMe-C6H4)  8.45  2.41  2.32, 1.41  6.07 4.88  -  -  L = P->-Me-C H4)  8.45  2.43  2.23, 1.70  6.25  -  29.6  8.38  2.43  2.23, 1.29  6.10 4.64  N/A  31.7  8.37  2.43  2.23, 1.28  6.39 4.57  N/A  35.1*  8.37  2.43  2.19, 1.20  6.65  4.69  N/A  29.5  3  8.28  2.38  1.92, 1.78  6.54  5.35  6.67  N/A  3  8.55  2.38  2.25, 1.55  6.38  5.18  6.52  N/A  8.45  2.63  2.47, 1.72  n  6  Hp  L = PPh  3  3  6  3  L = V(p-F-C n ) 6  4  3  L = P(p-Cl-C H4) 6  3  L = P->-CF -C H4) 3  L = AsPh  6  3  L = SbPh  Ru (TMP)(P"Bu ) n  e  3  a  H  m  4.86  31 p  P{-H)  6.44  35.3^  d  N/A  53.09  -0.38 8.43 2.48 2.4/ N/A Ru (TMP)(P"Bu ) Ru (TMP)(L) species produced in situ from the reaction between Ru (TMP)(0)2 and 3 equivalents of L. H relative to TMS; P{ H} relative to H P 0 a q ) ; 200 MHz machine at 25 °C in benzene-tfk unless indicated otherwise. Legend: Porphyrin protons (singlets) Me , 2 sets of 12 inequivalent H Me„ 12 H; Hp, 8 H X = P, As, Sb H , , around 7 ppm region, buried beneath solvent, L and OL protons n  e  3  a  b  2  n  l  VI  31  J  3  4(  0  0  me  a  Ligand Protons (multiplets) H , 6 H; H , 6 H; H , 3 H e  d  e  f  m  p  Temperature at -68 °C in toluene-dg on a 300 MHz instrument. Reference 18. Singlet for the ortho-Ms "H-resonance is indicative of the complex possessing Z) h symmetry. 4  100  References on p. 110  Chapter 3  solution. Figure 3.15 shows the ^ - N M R spectrum of a benzene-ofe solution of Ru (TMP)(AsPh ) [formedfrom(1) reacting with 3 AsPh ], which has been exposed to n  3  3  air for approximately 2 min. Other substrate systems generally give the same type of HX  NMR spectrum under the corresponding conditions: namely, Ru (TMP)(0), rv  Ru (TMP)(0) and Ru (TMP)(L) are observed. For the spectrum of the AsPh system VI  n  2  3  shown in Figure 3.15, an unassigned upheld ^-resonance at 8 ~ -8 ppm that is not present in the spectra of the other systems is observed. This broad signal disappeared in the spectrum that was acquired after a total time of ~ 4 min of exposure to air. This unassigned 8 value could resultfroma species formedfromthe binding of OAsPh to 3  Ru^fTMPXO). If Ru (TMP)(0)(OAsPh ) is indeed present, the ligand binding is IV  3  expected to be weak, and the 'H-chemical shifts of Ru (TMP)(0) moiety generally might IV  not be perturbed to a great extent; nonetheless, the perturbation on the yff-pyrrole-H signal might be large enough to be detected. The yS-pyrrole-H signals of the paramagnetic Ru (porp) ' ' species are very sensitive to the environment about the ruthenium and IV  5 19 t  might possible discriminate between Ru^TMPXO) and Ru (TMP)(0)(OAsPh ). IV  3  As the exposure of Ru (TMP)(L) species to air in solution regenerates n  Ru (TMP)(0)2 (1), oxidizing L catalytically with 0 is clearly viable. Initial qualitative VI  2  The ^pyrrole protons within Ru (TMP)(OR) (R = Me, CgHj, 'Pr, Et) species exhibit very different chemical shifts (-21.8, -30.45, -11.95, -17.6 ppm, respectively), while the M e a n d Me 'H-chemical shifts differ by ~ 0.3 ppm. See Chapter 4. f  IY  2  pflrfl  101  ortho  References on p. 110  Chapter 3  102  References on p. 110  Chapter 3  experiments showed that PPh can be 02-oxidized using (1) as the catalyst, with total 3  turnovers of approximately 20 at the end of 24 h at room temperature under 1 atm air. The turnover frequency of about 1 h" (exclusive of the initial 2 equivalents of phosphine 1  oxide formedfromthe stoichiometric reaction) is low considering that the O-atom transfer and disproportionation steps to form Ru (TMP)(PPh ) (5) are complete within a few n  3  minutes. The relatively slow regeneration of (1)from(5) most likely is initiated via 0  2  attack at the vacant axial site in (5) (Figure 3.1), and the excess PPh competes against 3  this 02-binding. Catalysis studies were done on various phosphine systems under 1.0 atm O2 and/or air (Table 3.6 and Figs. 3.16a to d). The catalytic activity of (1) generally is higher under 1 atm O2, but the turnovers obtained are not too much greater than those obtained under 1 atm air, especially during the initial 24 h of the catalytic runs. The diffusion of O2fromthe gas phase into the benzene-fife solutions within the NMR tubes to replenish the consumed 02 is expected to be slow and dependent upon various factors, and thus no firm conclusions regarding the effect of O2 on the rate of catalysis can be drawnfromthe current data; indeed diffusion may be rate-limiting. There is generally little effect of the concentration of phosphine on the catalytic activity, especially when the experimental errors are taken into consideration. A possible exception might be the P(p-Cl-C6H4)  3  system, which gave higher turnovers at a higher value of [phosphine]. Again, the 0 2  diffusion problem precludes any discussion regarding the effect of [phosphine], as the key step in the catalytic process, that of the regeneration of (1), must depend on both phosphine and O2 binding to (5).  103  References on p. 110  Chapter 3  Table 3.6.  Total turnovers of various phosphines catalytically oxidized at 24 °C in benzene-^ under 1 atm 0 in the presence of Ru^(TMP)(Q) (1). Blank Substrate (Molar) Time Turnovers based contributions on (hours) ([Ru (TMP)(0) ] in parentheses) (% of initial L) Ru (TMP)(0) PPh 64 excess; 0.0147 M (2.3 x IO" M) 22 3.5 31 ± 3 64 excess; 0.0147 M*(2.0 x I O M) 3.0 22 21+3 128 excess; 0.0257 M (2.3 x 10" M) 5.0 22 36 + 5 22 5.5 128 excess; 0.0257 M (2.0 x 10' M) 14 + 3 2  2  VI  2  VI  2  a  3  4  - 4  4  6  P(p-F-C H4) 6  4  3  175 excess; 0.0148 M (8.5 x IO" M) 5  350 excess; 0.0274 M (7.8 x 10" M) 5  155 excess; 0.0278 M (1.8 x I O M) 6  -4  310 excess; 0.0515 M (1.7 x 10" M) 6  P(p-OMe-C H4) 6  4  -5  332 excess; 0.0272 M (8.2 x 10" M) 5  6  0.8 1.4 2.3 1.3 2.7 4.2 1.5 3.4 7.6 3.0 7.0 15.0  9+ 2 82 + 4 96 + 5 14 + 2 80 + 3 112 + 6 11+2 27 + 3 40 + 4 13+2 32 + 3 40 + 4  19.75 48.75 60 19.75 48.75 60  1.7 4.2 5.6 3.4 8.5 11.5  24 + 3 131 ± 10 166 + 12 19 + 2 180+15 190 + 20  20 48 62.5 20 48 62.5  1.4 3.0 4.0 2.4 5.9 6.2  7+1 64 + 5 71+6 15+2 110 + 10 115 + 10  3  166 excess; 0.0144 M (8.7 x I O M)  P(p-Cl-C H4)  19 48 62 19 48 62 22 49 70 22 49 70  3  180 excess; 0.0150 M (8.3 x I O ' M) 5  360 excess; 0.0275 M (7.6 x 10' M) 5  " Autoxidation by 0 has been taken into account in these reported turnover numbers. Refer to Section 3.2.2 on the quantification of OL and L. Experiment done under 1 atm air (-0.20 atm 0 ) 2  b  2  104  References on p. 110  Chapter 3  40 - i  0  5  10  15  20  25  Time (hours)  Figure 3.16a. Catalytic oxidation of PPh in the presence of Ru (TMP)(0)2 (~ 2 x 10" M) under 1 atm air or 0 in benzene-afe at 24 °C. Linear dependences are assumed, based on related systems-see Figs. 3.16b to d. 3  4  2  105  References on p. 110  Chapter 3  Legend  1 2 0  H  V(p-F-C6R ) 4  0.0274 M 350 excess 1 atm 0 2  i  3  H  0.0148 M 175 excess 1 atm 0 2  Total 80 -| Turnovers  0.0274 M 350 excess 1 atm air  1 0 0  60  40  0.148 M 175 excess 1 atm air H  2 0  if "i  0  1 0  2 0  r-  1  30 40 50 Time (hours)  60  70  80  Figure 3.16b. Catalytic oxidation of P(p-F-C H4) in the presence of Ru (TMP)(0) (1) under 1 atm air and 0 in benzene-£& at 24 °C. [(1)] ~ 2 x 10" M for experiments under 1 atm air and ~ 8 x 10" M under 1 atm 0 . VI  6  3  2  4  2  5  2  106  References on p. 110  Chapter 3  200  H  P(p-OMe-C H ) 6  1 atm 0  4  0.0272 M 332 excess  3  X j  2  0.0144 M 166 excess  150  Total Turnovers -JQQ J  50  H  o4 0  1  1  10  20  r-  1  30 40 Time (hours)  50  60  70  Figure 3.16c. Catalytic oxidation of P(p-OMe-C H4) in the presence of Ru (TMP)(0) (~ 8 x 10" M) under 1 atm 0 in benzene-de at 24 °C. VI  6  3  2  5  2  107  References on p. 110  Chapter 3  140 - i P(p-Cl-C H ) 6  120  H  4  3  i  1 atm O2  0.0275 M  100  360 excess  Total Turnovers 8 0 0.0150 M 180 excess  60  40 H  20 H  0 -W 0  1  1  10  20  r—  1  30 40 Time (hours)  50  60  70  Figure 3.16d. Catalytic oxidation of P(p-Cl-C H4) in the presence of Ru (TMP)(0) (~ 8 x 10" M) under 1 atm 0 in benzene-^ at 24 °C. VI  6  3  2  5  2  108  References on p. 110  Chapter 3  3.5.  Conclusions This chapter presented some kinetic data for the O-atom transfer from trans-  Ru (TMP)(0)2 to tertiaryarylphosphines, AsPh3 and SbPh . The increasing AHi* for the VI  3  O-atom transfer upon withdrawing electron density around phosphorus suggests that the Ru-oxo moieties are electrophilic in nature, and that the reaction proceeds via an electrophilic attack of the Ru=0 moieties on the lone pair of phosphorus. Alternatively, a nucleophilic attack of the phosphorus lone pair on the empty Ru=0 7r*-orbital, with the phosphorus atom coordinating to Ru, as suggested for O-atom transfer reactions with organic sulfides within non-porphyrin Ru=0 systems, is also a possibility, but unlikely 22  due to the steric constraints presented by the mesityl groups on TMP.  Furthermore, the  O-atom transfer appears to occur via strong Ru=0 vibrational coupling, as reflected in the trend found for ASi*. In contrast to the conclusions drawn for the thioether oxidations, a successive two 5  O-atom transfer mechanism is not favoured for the phosphine systems. Rather, an initial O-atom transfer from Ru (TMP)(0)2, followed by a disproportionation reaction of the VI  Ru(IV) formed to generate Ru(II) and Ru(VI), is favoured. This type of disproportionation is more consistent in explaining Ru(TMP) oxidation chemistry in general, for example, in alkene ' and alcohol oxidations (Chapter 4). Indeed, the 13 14  thioether oxidations may also proceed via the same disproportionation mechanism as that for the phosphine oxidations; the reported kinetic data could equally well be rationalized 5  in terms of the disproportionation mechanism, as discussed in Section 3.3.2.  109  References on p. 110  Chapter 3  References 1  R. A. Sheldon and J. K. Kochi, Metal-Catalyzed Oxidations of Organic Compounds, Academic Press, Toronto, 1981, p. 395.  2  R. H. Holm, Chem. Rev., 87, 1401 (1987).  3  a) B. A. Moyer, B. K. Sipe and T. J. Meyer, Inorg. Chem., 20, 1475 (1981). b) A. Dovletoglou and T. J. Meyer, J. Am. Chem. Soc, 116, 215 (1994). c) L. Roecker, J. C. Dobson, W. J. Vinning and T. J. Meyer, Inorg. Chem., 26, 779 (1987).  4  E. Lindner and M. Haustein, Coord. Chem. Rev., in press.  5  a) N. Rajapakse, Ph. D. Dissertation, University of British Columbia, 1990. b) N. Rajapakse, B. R. James and D. Dolphin, Stud. Surf. Sci. Catal., 55, 109 (1990).  6  J. T. Groves and K.-H. Ahn, Inorg. Chem., 26, 3831 (1987).  7  B. Borderie, D. Lavalire, G. Levy and J. C. Michaeu, J. Chem. Ed., 67, 459 (1990).  8  DeuteratedNMR Solvents-Handy Reference Data, Merck and Co., Quebec, Canada, 1992.  9  F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, 5th edition, John Wiley and Sons, Toronto, 1988, p. 432.  10  C D . Johnson, The Hammett Equation, Cambridge University Press, Chapter 1, 1973.  11  P. R. Wells, Chem. Rev., 62, 171 (1962).  12  R. Schutte, Ph. D. Dissertation, University of British Columbia, 1995.  13  C. Ho, W.-H. Leung and C.-M. Che, J. Chem. Soc, Dalton Trans., 2933 (1991).  14  a) C. A. Tolman, Chem. Rev., 77, 313 (1977). b) P. B. Dias, M. E. Minas de Piedale and J. A. Martinho Simoes, Coord. Chem. Rev., 135/136, 737 (1994).  15  J. T. Groves and R. Quinn, J. Am. Chem. Soc, 107, 5790 (1985).  110  References on p. 110  Chapter 3  16  J. T. Groves and J. S. Roman, J. Am. Chem. Soc, 117, 5594 (1995).  17  a) D. T. T. Yapp, J. Jaswal, S. J. Rettig, B. R. James and K. A. Skov, Inorg. Chim. Acta., 177, 199 (1990). b) D. T. T. Yapp, J. Jaswal, S. J. Rettig, B. R. James and K. A. Skov, J. Chem. Soc, Chem. Commun., 1528 (1992).  18  C. Sishta, M. J. Camenzind, B. R. James and D. Dolphin, Inorg. Chem., 26, 1181 (1987).  19  S. Y. S. Cheng, N. Rajapakse, S. J. Rettig and B. R. James, J. Chem. Soc, Chem. Commun., 2669 (1994).  20  H. E. Avery, Basic Reaction Kinetics and Mechanisms, Macmillan Education, London, 1974, p. 66.  21  G. M. Barrow, Physical Chemistry, 4th Edition, McGraw-Hill, Toronto, 1979, p. 228.  22  D. G. Lee and H. Gai, Can. J. Chem., 73, 49 (1995).  Ill  References on p. 110  Chapter 4  Chapter 4 Catalytic Aerobic Oxidation of Alcohols and Alkanes  112  References on p. 155  Chapter 4  4.1  Introduction The recent developments in the use of ruthenium complexes in the oxidation of  saturated hydrocarbons were discussed in Chapter 1. Most of the complexes discussed were represented by examples from non-porphyrin oxoruthenium species. Attention is 1  now turned to the discussion of the oxidation of alcohols and alkanes catalyzed by dioxoruthenium(VI) complexes containing porphyrin ligands that were studied in the present thesis. Work carried out as a part of this thesis led to the development of a ruthenium porphyrin-based system exhibiting remarkable activity for the catalytic aerobic oxidation of alcohols. The complexes Ru (porp)(0) [porp = TMP (la) and TDCPP (lb)] VI  2  catalyzed the aerobic oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones, respectively, under mild conditions. An intermediate in the oxidation of'PrOH to acetone was identified to be a bis(alkoxo)ruthenium(IV) species, Ru (TMP)(0'Pr) (2a), which was characterized crystallographically. To the best of the rv  2  2  author's knowledge, this represents the first structurally characterized, monomeric alkoxo complex of ruthenium porphyrins; the results clarify earlier proposals by this group and 3  others that the intermediate was possibly the bis(hydroxo) species, Ru (TMP)(OH) . 4  IV  2  The ability of some dioxoruthenium porphyrins similar to (la) and non-porphyrin 5  oxoruthenium species to hydroxylate tertiary alkanes stoichiometrically prompted further 6  studies on (la) and (lb) in their abilities to oxidize alkanes. Species (la) catalyzes the aerobic oxidation of Ph CH to Ph COH, while species (lb) [but not (la)] also catalyzes 3  3  the aerobic oxidation of adamantane to 1-adamantanol, although the rates were slow and  113  References on p. 155  Chapter 4  the overall turnovers were low. The question regarding whether (la) or (lb) can oxidize alkanes; either stiochiometrically or catalytically, has been raised, and the catalytic 3b  aerobic oxidation of the above tertiary alkanes clearly answers that question, as well as demonstrating some significant chemistry within these ruthenium porphyrin systems.  4.1.1  Scope of Alcohol Oxidations in Current Work As mentioned, the nature of the intermediate in the stoichiometric oxidation of  'PrOH by Ru (TMP)(0) (la), tentatively proposed in previous studies to be VI  2  Ru (TMP)(OH) , ' was unresolved, and it was the initial goal to establish its identity. IY  3 4  2  Also, it was hoped that a better understanding of the oxidation mechanism could be realized through kinetic studies and deuterium-isotope labeling experiments. Furthermore, in the initial thesis work the Ru (TMP)(0)/PrOH system was found to be marginally VI  catalytic under 1 atm air (Section 4.3), and thus a considerable effort was devoted to enhance the lifetime and reactivity of the catalyst.  4.2  Sample Preparation and Data Analysis  4.2.1  Sample Preparation The kinetics for the stoichiometric oxidation of'PrOH and benzyl alcohol were  followed by ^ - N M R spectroscopy. In typical experiments, solutions of (la) (made from the aerobic oxidation of Ru (TMP)(MeCN) , Chapter 2), 1 to 5 x 10" M in benzene-^ n  4  2  (0.30 to 0.40 mL), were purged with Ar for 30 min. During this time, the NMR probe was preset at the desired temperature, between 18 and 35 °C. At the end of this time,  114  References on p. 155  Chapter 4  'PrOH or benzyl alcohol, dried over molecular sieves (5 A, BDH), was injected (1 to 5 pL) into the benzene-^ solution, with resulting concentrations of the alcohol between 10"  2  and IO" M. 1  The catalytic aerobic oxidations of'PrOH and benzyl alcohol were generally carried out at 24 or 50 °C (± 2) under 1 atm air. Typical solutions of (la) 10" to 10" M 4  3  in benzene-^ (0.40 mL) were prepared, and the alcohols were added via syringe (Unimetrics), with resulting concentrations between 10" and 10" M. The conversions of 2  1  the alcohols to the ketone or aldehyde were monitored periodically (usually between 24 h intervals) by "H-NMR spectroscopy, with the relative amounts of the reactant to product determined from the integration intensities of Me2CHOH ('PrOH), Me^CO (acetone), PI1CH2OH (benzyl alcohol) and PhCHO (benzaldehyde) at 3.68, 1.58, 4.31 and 9.62 ppm, respectively. In gas chromatography experiments, the aerobic oxidations of benzyl alcohol and 1-phenylethanol were carried out at 50 °C under 1 atm air. Benzene solutions (0.40 mL) of (la) or (lb) [see Chapter 2 for the preparation of (la) or (b)] in the concentration range between 10" and 10" M were prepared in screw-capped glass vials. The caps were 6  4  lined with Teflon tape to ensure that the benzene did not evaporate. The vials then were immersed in an oil-bath, which was maintained at a temperature of 50 ± 2 °C. At the end of approximately every 24 h, a sample (1 to 2 pL) of the solution was withdrawn and analyzed by a gas chromatograph to determine the total turnover number. The retention times of the various substrates and the column conditions of the GC runs are tabulated in Section 2.2.5, Table 2.1.  115  References on p. 155  Chapter 4  For the above catalysis studies, the deuterated and non-deuterated benzene solvents were not dried and were used directlyfromthe bottle. The concentration of F£ 0 2  in benzene-fife directlyfromthe bottle that has not been pre-dried was determined to be approximately 4 x 10" Mfromthe ' H - N M R spectra using MeCN as the standard. The 3  concentration of H 0 in benzene directlyfromthe bottle was assumed to be of the same 2  order of magnitude as in benzene-fife. H 0 saturated benzene-fife (with H 0/benzene-fife as 2  2  a two-phase system) was found to have a water concentration of 1.0 x 10" M in the 2  organic phase. In both the NMR and GC catalysis experiments, no additional water, 50 pL water, or 50 pL 3.0 M aqueous KOH was added to the benzene or benzene-fife solutions. The catalytic hydroxylations of Ph CH by (la) and Ph CH and adamantane by (lb) 3  3  were studied in benzene solutions at 24 ± 2 °C under 1 atm air in the same type of vials that were used for the catalytic oxidation of alcohols. Complex (la) [1.2 x 10" M in 0.40 4  mL benzene generatedfromthe bis(acetonitrile) precursor] was prepared and 50 pL 0.026 M Ph CH in benzene solution was added to the solution of (la). The resulting excess of 3  alkane over (la) was 29-fold. Complex (lb) (2.4 x 10" M in benzene) was prepared by 4  the /n-CPBA oxidation of Ru (TDCPP)(CO) (Chapter 2). 25 pL of 0.10 M adamantane n  in benzene was added to 0.40 mL of benzene solution containing (lb), giving rise to a 26fold excess of alkane over (lb). 25 pL of 0.074 M Ph CH in benzene was added to 0.40 3  mL benzene solution containing (lb), giving rise to a 19.4-fold excess of alkane over (lb). X-ray quality crystals of Ru (TMP)(0'Pr) (2a) and Ru (TMP)(0'CH(CH Cl) ) IV  IV  2  2  2  2  (2b) were obtained from concentrated benzene-fife solutions that were used for 'H-NMR  116  References on p. 155  Chapter 4  analyses of the stoichiometric oxidations of the 'PrOH and l,3-dichloro-2-propanol substrates. Extended evacuation of these solutions to dryness at ambient temperatures yielded crystals suitable for X-ray diffraction.  4.2.2  Data Acquisition and Analysis The kinetics of the stoichiometric oxidations of'PrOH and benzyl alcohol under 1  atm Ar were followed by the integrations of the para-methyl protons of (la) and the product Ru^TMPXO'Pr^ (2a) or Ru (TMP)(OCH Ph) (2c), respectively. The IY  2  2  combined integrations of (la) and (2a) or (2c) were normalized to 100%, since no porphyrin intermediates* were observed by NMR, ESR or UV-visible spectroscopies. The natural logarithm of the mole fraction of (la), lnfJGa), was plotted versus time. For the 'PrOH oxidations, the half-lives were 3 to 4 h in typical experiments, and it was practical to follow only one of the reactions for more than three half-lives to establish first-order dependence in (la) (see Figure 4.1). Subsequent reactions, where the concentrations for both (la) and 'PrOH or benzyl alcohol were systematically varied (Appendix C), were monitored only for 1 to 2 h. Of note, H-NMR spectroscopy, rather than UV-visible !  spectroscopy, was chosen as the method to follow the kinetics for the stoichiometric oxidation of alcohols, because the concentration of (la) in UV-visible experiments is ~ 10" M. The alcohol oxidations become catalytic in the presence of 0 , and removing 0 6  2  2  ' i) Species (la) and (2a) were the only ones observed in solution during the reaction, as monitored by ' H - N M R spectroscopy, ii) A frozen benzene-cfe solution of "(la) + 'PrOH" under A r at 110 K showed no ESR signals (see later), iii) Previous work (Ref. 3) followed the conversion of (la) to (2a) by UV-visible spectroscopy in benzene, and the set of spectra showed isosbestic points, suggesting that (la) and (2a) are the dominant species in solution.  117  References on p. 155  Chapter 4  Time (s)  Chemical Shift, ppm Figure 4.1.  The kinetics of the stoichiometric oxidation of 'PrOH by Ru (TMP)(0) , (la), in benzene-c/e under 1 atm Ar at 18.2 °C followed by H-NMR spectroscopy (300 MHz) in the 2 to 3 ppm region. Inset shows the plot of lnCYi ) versus time (Xu = mole fraction of starting porphyrin (la) = Intp.Me{Ru(vi))/[InVMe(Ru(vi)) + 1/3 Intp+ -Me(Ru(iv))]), the slope of which gives the pseudo-first -order rate constant, k o b . [(la)] = 4.0 x IO M; ['PrOH] = 0.0568 M. VI  2  X  a  0  9  -4  118  References on p. 155  Chapter 4  to the extent that it becomes less than 10" M, such that (la) does not regenerate, is not 6  feasible. The catalytic oxidations of 'PrOH and benzyl alcohol were followed by "H-NMR spectroscopy and GC analysis, with results in agreement. The products of oxidation were solely acetone and benzaldehyde, respectively; benzaldehyde was not further oxidized to benzoic acid under the conditions described in Section 4.2.1. In both ^ - N M R and GC experiments, the identities of the products were determined with the use of known standards. The combined integrations of the alcohols and products were normalized to 100%, and subsequently the percentage conversions were calculated. Knowledge of the initial ratios of substrates to the catalyst (la) or (lb) allowed the catalytic turnovers to be determined as the reactions progressed. The catalytic hydroxylations of adamantane to 1-adamantanol and  PI13CH  to  Ph COH by (la) and (lb) in benzene were followed by GC analysis. The retention times 3  of the solutes were determined from authentic samples of the starting alkanes and alcohol products (Chapter 2, Table 2.1). The response factors of adamantane and 1-adamantanol to the FID detector were proportional to the molar concentrations of the analyte. The same also applies to the Ph CH/Ph3COH, benzyl alcohol/benzaldehyde and 13  phenylethanol/acetophenone systems. In the GC analyses, the starting alkanes and tertiary alcohol products accounted for all the organics present, and thus the conversions were calculated based on the relative intensity of the alkane and alcohol signals. The kinetic data for the stoichiometric oxidation of'PrOH and benzyl alcohol by (la) are tabulated in Appendix C. The data from the catalytic oxidation of benzyl alcohol  119  References on p. 155  Chapter 4  are also tabulated in Appendix C. The alkane hydroxylation data can also be found in Appendix C. The supplementary data for the crystal structures of (2a) and (2b) are given in Appendix D.  4.3  Stoichiometric Oxidation of Alcohols by Oxoruthenium Species Kinetic and mechanistic studies on the stoichiometric oxidation of alcohols by  monooxoruthenium(IV) and dioxoruthenium(VI) complexes have been reported, mainly by the groups of Meyer, Lee, Griffith and Che ' ' . Nonetheless, further detailed 7  8  1  6a 9 15  kinetic and mechanistic studies on the oxidation of alcohols by oxoruthenium complexes are invaluable in order to understand better such oxidations in general; this can aid in the design of better oxidation catalysts. Further, the Ru-porphyrin catalysts reported in this thesis are thefirstto utilize effectively 0 as the oxidant in alcohol oxidations. 2  4.3.1  Bis(aIkoxo)porphyrinatoruthenium(IV) Species The kinetic studies on the stoichiometric oxidation of'PrOH to acetone and benzyl  alcohol to benzaldehyde by (la) were studied, and the proposed mechanism will be discussed in the next section. The metalloporphyrin products in these alcohol oxidations were the corresponding bis(alkoxo) species, Ru (TMP)(OR) [R = 'Pr (2a) or CH Ph IV  2  2  (2c)]. For the stoichiometric oxidation of'PrOH by (la), the Ru-porphyrin product proposedfrompreliminary work in this laboratory was Ru (TMP)(OH) , the underlying IV  2  reason being mainly the non-detection of axial 'PrO ligand protons by 'H-NMR  120  References on p. 155  Chapter 4  spectroscopy. This proposal now seems incorrect. Previously in this laboratory, (2a) 3  33  was prepared following the scheme represented in Eq. 4.1 (not balanced). 1) Ambient temp.,  Ru^(TMP)(0) + xs 'PrOH  — ^  2  4  Ru^TMPXO'POa + acetone  h  (4.1)  2) rotary evap.  (la)  (2a)  In the earlier work, " the removal of solvent and excess 'PrOH by rotary 3  evaporation gave a compound, the elemental analysis (C 68.87; H 5.76; N 5.55%) corresponding neither to that calculated for Ru (TMP)(0'Pr) (C 74.45; H 6.65; N IY  2  5.60%) nor Ru (TMP)(OH) (C 73.42; H 5.94; N 6.12%); however, the non3a  IV  2  detection of the axial ligand protons and magnetic susceptibility measurement (p ff = 2.96 3  e  p, ; S = 1) favoured the formulation of (2a) as Ru (TMP)(OH) at the time. In the IV  B  2  present thesis work, the preparation of (2a) in an NMR tube from which the solvent and excess 'PrOH were removed completely under vacuum overnight gave a "H-NMR spectrum that showed the chemical shifts for the axial 'PrO ligand protons (Figure 4.2). Heating the sample (> 100 °C) under vacuum to remove the solvent and 'PrOH led to decomposition of the complex, while pumping under vacuum at a lower temperature was not always effective in removing all of the 'PrOH (see also Section 4.3.3). A satisfactory elemental analysis of (2a) still is not obtained, presumably due to the above-mentioned difficulties; however, the fact that the axial ligands were alkoxo, and not hydroxo, was shown unambiguously through the X-ray structural analyses of (2a) and its bis(l,3dichloro-2-propoxo) analogue (2b). Thus, the earlier incorrect proposals from this group  3  and others that Ru (TMP)(OH) existed in the presence of excess alcohol were clarified. 4  IV  2  121  References on p. 155  Chapter 4 o  in  o vi  a <w  so  0) >- , Ol n o  on  O  <a  w  o  s a  o  S u  <u -a  O  </->  o  o  r-~'  h o oo  122  s WO  References on p. 155  Chapter 4  Of note, the TDCPP analogue, Ru (TDCPP)(OH) , recently has been characterized IV  2  crystallographically (see Section 4.3.3). X-ray analyses of (2a) and (2b) revealed structures with inversion centres, with the Ru-atom being essentially octahedral, sitting in the centre of the porphyrin plane with coordinated axial 'PrO or l,3-dichloro-2-propoxo ligands (Figures 4.3 and 4.4). The tetramesityl groups on the porphyrin ring are perpendicular to the porphyrin plane and the Ru(TMP) moiety essentially has the same dimensions as those found in Ru (TMP)(MeCN) . There are no significant non-bonding interactions between the axial n  3  2  alkoxo ligand and the porphyrin in either (2a) or (2b) less than 3.6 A (see Appendix D). The crystal structures of (2a) and (2b), even though exhibiting disorder about the axial ligands due to high thermal motion, unambiguously show the complexes to contain axial alkoxo ligands. In terms of the Ru-0 distances, 1.892(3) A in (2a) and 1.905(6) A in (2b), these values lie within the range found for similar Ru(IV)-porphyrin complexes [1.929(9) A within Ru (TMP)(OEt) and 1.944 A within the coordinated /?ara-cresol for IV  t  2  [Ru (TPP)(p-OC6H Me)] 0, although the latter is a Ru(IV) diamagnetic species]. On IY  10  4  2  the other hand, the average Ru(III)-0 bond length for the coordinated ethanol/ethoxo in Ru (OEP)(OEt)(EtOH) is longer at 2.019 A . ffl  11  The marginally longer Ru-0 bond length  in (2b) over that in (2a) is presumably due to the inductive electron-withdrawing effect of the two chlorine atoms, which reduces the extent of 7i-backbonding from the oxygen to the ruthenium. Such backbonding is evident in the large Ru-O-C bond angles  ' The axial ligand was unidentified due to severe disorder in the axial ligands, but the axial ligand was most likely ethoxo. See Reference 4.  123  References on p. 155  Chapter 4  Figure 4.3.  The structure of Ru (TMP)(0 Pr) (2a) (H-atoms omitted for clarity). Selected bond lengths (A) and angles (°): Ru-O(l) 1.892(3), av. Ru-N 2.033, 0(1)-C(29a) 1.18(3), 0(1)-C(29) 1.34(1), C(29)-C(31) 1.55(2), C(29a)-C(31) 1.47(3), C(29)-C(30) 1.56(1), C(29a)-C(30) 1.66(3); Ru-0(1)-C(29) 139.7(5), Ru-0(1)-C(29a) 155(1), 0(1)-C(29)-C(31) 103(1), O(l)-C(29)-C(30) 100(1), O(l)-C(29a)-C(30) 101(1), 0(1)-C(29a)-C(31) 117(2). At the Ru, all c/s-angles are 90 ± 1.2°. Additional crystallographic data can be found in Appendix D. IV  /  2  124  References on p. 155  Chapter 4  Figure 4.4.  The structure of Ru (TMP)(OCH(CH Cl)2)2 (2b) (H-atoms omitted for clarity). Selected bond lengths (A) and angles (°). Ru-O(l) 1.905(6), RuN(av.) 2.036; Ru-0(1)-C(29) 146(1), Ru-0(1)-C(29a) 150(2). Additional crystallographic data can be found in Appendix D. IY  2  125  References on p. 155  Chapter 4  of 139.7 and 155° in (2a) and 146 and 151° in (2b), and in both complexes the bond angles deviate significantly from the ideal value of a sp hybrid expected at the O-atom of 3  the alkoxo ligand. Unfortunately, the disorder problem precludes any direct comparison between the bond angles of (2a) and (2b), and masks the information pertaining to the difference in degree of backbonding as a result of the two chlorines. The ability of Ru (TMP)(0)2 (la) to oxidize alcohols was tested with some VI  primary and secondary alcohols, and the spectroscopic evidence suggests that the Ruporphyrin intermediates are the corresponding bis(alkoxo) species, Ru (TMP)(OR)2 (see IV  later, Table 4.1). The products of the stoichiometric oxidation of these alcohols are aldehydes or ketones, and the reactions are most likely general for any primary or secondary alcohol, although the methanal and ethanal productsfromthe oxidations of MeOH and EtOH, respectively, are not identified by 'H-NMR spectroscopy, as the characteristic aldehyde H-resonances for the two aldehyde products are not observed. ]  The non-detection of the methanal and ethanal products is likely due to polymer formation, which is known to occur with these aldehydes, and as the stoichiometrics of 11  the 'PrOH and benzyl alcohol oxidations have been established (see Section 4.3.2), no further attempts were made to detect the methanal and ethanal products. The 'H-NMR chemical shifts of various Ru (TMP)(OR) species are reported in IV  2  Table 4.1. These Ru (TMP)(OR) species [R = Me, Et, 'Pr, 1-Pr, PhCH , (CH C1) CH, IV  2  2  2  2  PhCH(Me)] were observed in situ in benzene-afe under 1 atm Ar in ^ - N M R studies when the corresponding primary and secondary alcohols were oxidized by (la) to the aldehyde and ketone, respectively. The data for these Ru (TMP)(OR) species are entirely IV  2  consistent with Ru(IV) species possessing £ ) h symmetry, as all known Ru (TMP)(X) IV  4  126  2  References on p. 155  Chapter 4  Table 4.1  'H-NMR data" for /ra/75-Ru (TMP)(OR) species. IY  2  OR* =  meta-H  para-Mt  ortho-Me  pyrrole-H  7.52  2.85  2.90  -11.95  0  O'Pr (2a)  e  d  1,3-dichloropropoxo (2b)  7.69  OMe  7.40  2.93  2.70  -21.8  OEt*  7.40  2.85  2.76  -17.6  1-PrO  7.49  2.78  2.93  -16.4  benzoxo (2c)  7.48  2.74  2.92  -20.6  7.66, 7.60  2.91,2.83  3.00, 2.96  -19.4  7.63  3.00  2.90  -30.5  7.63  3.00  2.90  -30.45  1-phenylethoxo* phenoxo'* para-OC a OB'  k  6  4  -28.8  not observed^  ° Chemical shifts, 5 ppm, in benzene-ak relative to TMS at -25 °C. * These bis(alkoxo) species are typically generated in situ by the addition of corresponding excess alcohol (1.0 x 10" M) to (la) (~ 5.0 x 10" M) under 1 atm Ar in benzene-^. Excess alcohol is present, which generally leads to exchange broadening and non-observance of axial ligand protons. Extended heating under (~ 100 °C) vacuum can remove all the alcohol, but this leads to decomposition of the complex as well (see text). Axial ligand "H-chernical shifts are reported if observed. Single meta-H peak indicates a £>4h symmetry about the porphyrin plane. Single meta-Me peak indicates a £> h symmetry about the porphyrin plane. Axial ligand protons observed after removal of excess 'PrOH: -OCH, 2H, -14.22; CH(CH3) , 12 H, -15.2. The 'H-chemical shifts for the free alcohol are in the - 3 ppm range and overlap with those for the bis(alkoxo) complex. Ligand protons observed after removal of excess EtOH: -OCEb, 4H, -7.48; -CH3, 6H, -12.90. * Racemic 1-phenylethanol was used, leading to a mixture of 3 isomers: a 1:1 enantiomeric mixture of Ru(TMP)(OR*)(OR*) and Ru(TMP)(OR )(OR ) accounts for 50%; Ru(TMP)(OR )(OR ) accounts for the other 50%. Two sets of axial ligand *Hchemical shifts, unassigned, are observed (excess alcohol not removed) in the NMR spectra of the solution containing the above set of compounds: -18.9 and -18.4; 7.91 and 8.02; 15.2 and 13.9. ' Generated in situ in benzene-^ under 1 atm Ar from "(2a) + excess phenol" (see text). Axial ligand protons (excess phenol not removed): para-H, 2H, -71.9; ortho-H, 4H, 2  4  c  d  4  e  2  f  g  5  s  s  /?  68.2; meta-H, 4 H, 49.7. j  Axial ligand protons: para-OU, 2H, -71.85; ortho-H, 4H, -68.19; meta-H, 4 H, 49.68 (Ref. 3). * The bis(p-hydroquinoxo) complex has been incorrectly assigned as such (Ref. 3) and is in fact the bis(phenoxo) complex (see Section 6.4.1).  127  References on p. 155  Chapter 4  species belonging to the D h point group exhibit single meta-H and ortho-Me signals. ' '  3 4 12  4  Previously in this laboratory, the ^-chemical shifts for the bis(isopropoxo) and bis(phenoxo) species have been measured between -60 and +60 °C.  3a  The isotropic H 1  chemical shifts for the TMP ligand within these paramagnetic Ru(IV) species, and also within other paramagnetic Ru (TMP)(X)2 species ' (X = Cl and Br), vary with inverse IV  4 12  temperature, showing the existence of a single spin state over this temperature range. The paramagnetic nature of the Ru (TMP)(OR) complexes suggests bonding similar to that IV  2  found in Ru(porp)(X) species (X = Cl, Br), which accommodate two unpaired electrons 2  in a closely spaced t set (with either dxy or d^yz being lowest in energy).  12  2g  Among the complexes listed in Table 4.1, only the protons of the axial EtO, 'PrO, 1-phenylethoxo, and phenoxo ligands within the Ru (TMP)(OR) species are observed by IV  2  ^ - N M R spectroscopy. In general, the alkoxo ligands exchange readily with the corresponding alcohol in solution, leading to line-broadening in the 'H-NMR spectra and undetectable axial ligand chemical shifts, although the 1-phenylethoxo and phenoxo ligands could be detected even in the presence of the corresponding alcohols. The increased steric bulk of the 1-phenylethoxo ligand perhaps slows the rate of exchange, while for the phenoxo ligands, the slow exchange may be due to steric as well as possible electronic effects of the aromatic ring. The exchangeability of the 'PrO ligands was used to prepare the bis(phenoxo) analogue in situ. Phenol (~ 50-fold excess) was added to an Ar-purged benzene-ofe solution of (2a) (~ 5 x 10" M). Within the time required to acquire 4  a ^ - N M R spectrum (-15 min), quantitative axial ligand exchange, with the liberation of free 'PrOH, was observed, with no trace of (2a). Of note, the product from the above-  128  References on p. 155  Chapter 4  mentioned phenol exchange shows ^-resonances nearly identical to those of a complex previously proposed to be Ru (TMP)(p-OC6H40H) (Table 4.1); the significance of this 3  rv  2  will be discussed in Chapter 6. The exchange of the 'PrO ligands with alcohol in solution was observed readily when (2a) (~ 10" M) was dissolved in benzene containing ~10' M 6  3  EtOH or MeOH; almost instantaneous shifts (within seconds) of the Soret band of (2a) from 412 to 408 and 406 nm were observed, respectively, indicating formation of the different Ru (TMP)(OR)2 species in solution. The UV-visible data for these IV  Ru (TMP)(OR) species in benzene are [ W n m (e/lO^MW )]: R = 'Pr, 412 (240), IV  1  2  522(29.0); R = Et, 408(230), 520(25.4); R = Me, 406(200), 520(26.7).  4.3.2  Mechanism of Alcohol Oxidation by Ru (TMP)(0) VI  2  Previous work in this laboratory, in addition to the knowledgefromthe 3  crystallographic structure of the metalloporphyrin product (2a) from the 'PrOH oxidation, allow the overall stoichiometry of the oxidation reaction to be established (Eq. 4.2). One equivalent of acetone and two equivalents of water were observed by ^ - N M R 33  spectroscopy upon complete formation of (2a). Ru (TMP)(0) + 3 'PrOH VI  2  (la)  Ru (TMP)(0'Pr) + 2 H 0 + Me C=0 (2a) IV  2  2  2  (4.2)  The oxidation of benzyl alcohol presumably follows the same stoichiometry as that for 'PrOH; again, one equivalent of benzaldehyde was observed by 'H-NMR spectroscopy, although no special precautions were taken to remove all the waterfromthe system, and the water stoichiometry was assumed to be the same as in Eq. 4.2. Thus ( l a )  129  References on p. 155  Chapter 4  in reaction 4.2 is an overall two-electron oxidant, similar to other oxoruthenium(VI or IV) complexes. " ' ' 5  9 13 15  The kinetics o f PrOH oxidation by (la) under 1 atm Ar showed a first-order dependence in (la) (see Figure 4.1 in Section 4.2.2). Thefirst-orderdependence was also assured, as the kinetics monitored for ['PrOH] = 0.218 M were independent of [(la)] (2.0 vs. 4.0 x 10" M; see Appendix C). Under pseudo-first-order conditions at about 18 °C, 4  the 'PrOH dependence isfirst-orderat ['PrOH] values below 0.3 M (Figures 4.5). In this linear range, the use of'PrOD-cfe showed that a kinetic isotope effect of 1.9 ± 0.3 is exhibited at the a-C-H bond, while the use of'PrOD gave no kinetic isotope effect. The kobs  versus ['PrOH] plot for the oxidation o f PrOH by (la) tends to level-off at ['PrOH]  values beyond 0.4 M (see later); that is, the oxidation of'PrOH by (la) exhibits saturation kinetics as the concentration of'PrOH increases. The oxidation of benzyl alcohol by (la) is more rapid; the concentration range studied (Figure 4.6) is lower than that for 'PrOH, and there is no obvious fall-off of  fromafirst-orderdependence on [benzyl alcohol].  kobs  Regarding the non-linear k o b s versus ['PrOH] plot (Figure 4.5), the phenomenon is likely due to solvent effects. Addition of an inert alcohol, BuOH, to simulate the high f  'PrOH content, slows the rate of oxidation of'PrOH by (la). At 18.2 °C with [TPrOH] = 0.130 M, the k o  value for the 'PrOH oxidation is (4.2 ± 0.5) x 10" s". At the 5  b s  same value of ['PrOH], but with [ BuOH] = 0.177 and 0.530 M, f  ko  1  = (9.2 ± 0.7) x 10" s" 6  b s  1  and (3.6 ± 0.5) x 10" s", respectively. Hence, it seems very likely that the levelling-off of 6  1  the k o b s values as the 'PrOH content increases is attributed to some solvent effect.  130  References on p. 155  Chapter 4  0.0002 - 0.00018 - 0.00016 - 0.00014 0.00012 + (s ) 0.0001 + 1  1.5  0.5 ['PrOH] (Molar)  Figure 4.5.  Pseudo-first-order rate constant, kobs, as a function of excess 'PrOH concentration in benzene-ok under 1 atm Ar at 18.2 °C. A kinetic isotope effect of kn/ko = 1.9 ± 0.3 was observed at low concentrations of alcohol (< 0.3 M). The kobs values for both 'PrOH and v4 - l 'PrOD-dg at higher [alcohol] values level-off at about 1.3 x 10" See Appendix C for a list of the raw data. g  131  References on p. 155  Chapter 4  0.0025 T  [benzyl alcohol] (Molar)  Figure 4.6.  Pseudo-first-order rate constant, kobs, as a function of [benzyl alcohol] at various temperatures in benzene-^ under 1 atm Ar.  The following mechanism [Eqs. 4.3 and 4.4; Ru = Ru(TMP)] for the oxidation of alcohols by (la) is favoured by the experimental evidence, which will be further presented after the introduction of the mechanism.  132  References on p. 155  Chapter 4  hydride transfer 0=/?K =0  •P Ru —OH =  V I  V}  (4.3) proton transfer/fast /?u (OH) IV  2  alcohol exchange fli# (OH) + 2 'PrOH IV  2  Ru^iOPrh  +  2H 0  (4.4)  2  A hydride transfer pathway seems appropriate (Eq. 4.3) because the addition of KOH/'PrOH and KO'Bu/'PrOH increases the rate of oxidation (see Table 4.2). The electrophilic Ru=0 moiety (Chapter 3) would favour attack of the a-C-H bond of the 'PrO over that of'PrOH. In the presence of base, (la) attacks the a-C-H bond of an alkoxide, followed by stepwise hydride and proton transfers to the oxo ligands to generate Ru (TMP)(OH)2 (Eqs 4.5, 4.6; B" = OH" or 'BuO"). w  B + 'PrOH  H 0=Ru  vl  =0  ^  (4.5)  HB + 'PrO"  hydride transfer i)=Ru —OH VL  (4.6) HB  proton transfer  /to (OH) IV  133  2  + B"  References on p. 155  Chapter 4  T a b l e 4.2.  Selected pseudo-first-order rate constants, k o for the stoichiometric oxidation of 'PrOH to acetone by Ru (TMP)(0) ( l a ) . D S  VI  2  ['PrOH] (M)  KOH/PrOH* KO'Bu/'PrOH  pseudo-lst-order rate  0.0568 0.131  -  -  (1.87 ± 0.1) x 10" (4.21 +0.5) x 10"  0.0408 0.0408 0.0816  4x 1 0 M K O H 2x 1 0 M K O H 4x 10" MKOH  (0.9 ± 0.2) x 10" (1.2 ± 0.2) x 10" (1.1 ± 0 . 2 ) x 10"  0.130 0.130  1.2 x 10- MKO'Bu 1.6 x 10" MKO'Bu  (5.4 ± 0.8) x 10" (5.6 ± 0.8) x 10"  a  c  c  constant, k o  (s ) 1  bs  5  5  6  4  5  4  6  4  4  4  3  3  * [Ru (TMP)(0) ] = 10 to 10 M in benzene-dfe at 18.2 °C under 1 atm Ar. * Various solutions of'PrOH with dissolved KOH or KO Bu were prepared and injected into the benzene-afe solutions, and the [base] values refer to those in the diluted solutions. The approximately constant rate of oxidation, apparently independent of the concentrations of KOH and 'PrOH, is likely due to the insolubility of KOH in benzene such that a saturation concentration has been reached. Hence, a maximum increase of rate is reached. See Figure 4.5 for the k o b versus ['PrOH] plot and Appendix C for the raw data. VI  -4  3  2  f  c  s  That KOH or KO'Bu accelerated the rate of oxidation suggests bond cleavage by the Ru=0 moiety at the a-C-H bond (Eq. 4.5). At lower ['PrOH] values where the k^s versus ['PrOH] plots are linear, the kn/kn ratio is approximately 1.9. The oxidation of 'PrOH by (la), based on the observed kinetic isotope effect, also seems reasonably consistent with the cleavage of the alcohol a-C-H bond by a Ru=0 moiety as the initial oxidation step (Eq. 4.3), although the isotope effect of 1.9 is clearly very small, especially considering that a k /k value is expected to be -6.9, if VC-H and VC-D zero point energies H  D  are the only factors under consideration. In non-porphyrin systems, the oxidations of alcohols by oxoruthenium(IV) ' ' and ^*a«5-dioxoruthenium(VI) complexes have been 7a 9 13  15b  observed to give kinetic isotope effects larger than the theoretical value of 6.9, including  134  References on p. 155  Chapter 4  k /k values as high as 50 and 18 for the oxidations of benzyl alcohol and 'PrOH, H  D  respectively.  73  The data for the 'PrOH oxidation at 18.2 °C (Figure 4.5) show that the  kobs  versus [alcohol] plots for 'PrOH and 'PrOD-dg both level-off at approximately the same value of  kobs  ~ 1.3 x 10' s", which means that the under such conditions, the k /k ratio is 4  1  H  D  approximately 1.0. The levelling-off of the k o b s values has been shown to be an artifact resulting from a solvent effect at the high 'PrOH concentration (see earlier). It is not known why the oxidation of'PrOH by (la) exhibits such a small kinetic isotope effect if a-C-H bond cleavage is involved, or why the k /k values becomes ~ 1.0 at higher 'PrOH H  D  concentrations. One interpretation of thefindingsis that significant solvent effects (perhaps due to the alcohol content itself), in addition to direct a-C-H bond cleavage by the Ru=0 moiety, may be involved in the oxidation reaction. An alternative explanation for the levelling-off of the k o b s values (saturation kinetics) is the operation of a preassociation step, forming a {Ru-alcohol} adduct prior to the actual oxidation step, which has been invoked in alcohol oxidations by non-porphyrin oxoruthenium(IV) species. Roecker and Meyer studied the stoichiometric oxidation of 73  some alcohols using Ru (bpy) (py)(0) as the oxidant in MeCN solutions, and they IV  2+  2  observed non-linear k o b s versus [benzyl alcohol] plots which were attributed to a preassociation step; however, a linear plot was observed once the solution ionic strength 73  in MeCN was rendered constant by the addition of 0.10 M TEAP or when the reaction took place in H 0. Neither the Ru (TMP)(0) nor Ru (byp) (py)(0) VI  2  IV  2  2+7 3  2  system shows  any spectroscopic evidence for the formation of a preassociation complex in the respective oxidation reactions. Hence, the observed levelling-off of the k^s values, at least in the  135  References on p. 155  Chapter 4  Ru (TMP)(0)2 system, is considered due mainly to a solvent effect caused by high 'PrOH VI  concentrations used. As for the formation of the bis(alkoxo) product (2a), a likely path is via a metathesis reaction of'PrOH with Ru (TMP)(OH) (Eq. 4.4). There is no evidence for IV  2  the existence of Ru (TMP)(OH) , nor is there any direct proof regarding the rapid IY  2  exchange of the hydroxo ligands with the alcohol in solution to form (2a), although rapid alcohol exchange with the axial alkoxo ligands within the Ru (TMP)(OR) species has rv  2  been observed (Section 4.3.1); it is feasible that the formation of Ru (TMP)(OH) is IV  2  disfavoured over that of (2a) in the presence of excess 'PrOH. There is indirect support that Ru (TMP)(OH) exists in solution, as the bis(hydroxo) analogue of TDCPP, IV  2  Ru (TDCPP)(OH) , has been characterized crystallographically recently; of interest the IV  14  2  complex was isolatedfroma toluenefiltratesolution (that had been left standing at -25 °C) obtained during the preparation of Ru (TDCPP)(0) . The stoichiometric oxidations vl  2  of alcohols by some non-porphyrin *ra«s-dioxomthenium(VI) species have been shown, based on UV-visible data, to form oxo(aquo)ruthenium(IV) species.  15b  These Ru(IV)  species also have been suggested to isomerize to the bis(hydroxo)-Ru(IV) species via proton migration. Of note, ^-resonances assignable to Ru (TMP)(0) were detected in 15  IV  the 0 -oxidation ofp-hydroquinone to p-benzoquinone catalyzed by (la) (Section 6.4.1). 2  As for the present Ru (TMP)(0) /'PrOH system, ^-resonances corresponding to VI  2  Ru (TMP)(0) or Ru (TMP)(0)(OH ) were not detected; the only observable UIV  IV  1  2  resonances in the 'PrOH system corresponding to Ru(TMP) species are those assignable to (la) and (2a). Although Ru (TMP)(0) has not been detected in the 'PrOH system (but IV  136  References on p. 155  Chapter 4  as Ru (TMP)(0) has been detected in the /?-hydroquinone system), it can still be IV  envisaged that the initial hydride transfer (Eq. 4.3) yields Ru (TMP)(0), while the IV  Ru (TMP)(OH) could form subsequently via reaction of Ru (TMP)(0) and H 0 similar IY  IV  2  2  to that proposed in the Ru(IV) non-porphyrin systems (see also Section 4.4.3 regarding 15  the role of H 0 in a Ru (TMP)(0) /alkene oxidation system). VI  2  2  The slopes of the lines in Figures 4.5 and 4.6 give the second-order rate constants, k , for the stoichiometric oxidation of'PrOH and benzyl alcohol by ( l a ) (Table 4.3). The 2  Eyring plots derived for these k values, Figures 4.7 and 4.8, give the following activation 2  parameters: AH * = 45 ± 7 and 65 ± 11 kJ mol" , and AS * = -167 ± 10 and 1  2  2  -70 ± 20 J mof'K" for 'PrOH and benzyl alcohol, respectively, a marked difference being 1  noted. The rates of alcohol oxidations in the Ru (TMP)(0) system are limited by large vl  2  and negative AS * values, and that benzyl alcohol is oxidized approximately 10 times faster 2  than 'PrOH is due entirely to a more favourable AS *; indeed, the relative AH * values 2  2  favour oxidation of 'PrOH. In comparison, the activation parameters for the oxidation of 'PrOH and benzyl alcohol by Ru (bpy) (py)(0) in MeCN are AH* = +33.5 and +24.2 kJ IV  2+  2  mol" , and AS* = -176 and -160 J mol" K" , respectively; 1  1  1  although the AS* values are  73  large and negative, as in the Ru (TMP)(0) systems, the AH* term is the major factor VI  2  affecting the differences in the rate constants. An alternative mechanism for the stoichiometric 'PrOH oxidation by (la) involves oxidative addition of the alcohol a-C-H bond across the Ru=0 moiety of (la), leading to an organoruthenium intermediate (as proposed for a Ru03 7alcohol system), although the 2  8  lack of cis sites at the Ru makes this unlikely. The Ru=0 moiety of (la) could perhaps  137  References onp, 155  Chapter 4  abstract a hydrogen atom from the a-C-H bond to form Ru (TMP)(0)(OH) and an inv  cage organic radical Me2C"-OH; a single-electron transferfromMe2C*-OH to Ru (TMP)(0)(OH), followed by loss of H"fromMe C=OH , will give the same products v  +  2  as those shown in Eq. 4.3. This hydrogen abstraction path is disfavoured somewhat as no ESR signals due to either an organic radical and/or a Ru(V) paramagnetic species were observed at 110 K in a frozen benzene solution of (la) and 'PrOH; however, as the organic radical and Ru(V) species might be unable to escapefromeach other in a solvent cage in the frozen environment, an electron transferfromthe radical to the Ru(V) species may have occurred prior to the attempted detection of the radicals by ESR spectroscopy, and thus the hydrogen abstraction mechanism cannot be ruled out completely.  Table 4.3.  Second-order rate constants, k , for the stoichiometric oxidations of'PrOH and benzyl alcohol in benzene-de by Ru (TMP)(0) (la). 2  VI  2  Temperature (Kelvin) [for benzyl alcohol]  k ( M s")" 1  1  2  PrOH  benzyl alcohol  291.4 [291.2]  3.8 x 10"  2.6 x 10"  301.7 [302.7]  7.4 x 10"  4  3  46  7.6 x 10"  3  1.4 x 10" 308.7 1.05 x lO * T307.7] ° The kinetics were monitored by ^ - N M R spectroscopy in benzene-afe under 1 atm Ar. These k2 values were derivedfroma single kobs value determined at ['PrOH] = 0.161 and 0.174 M at 301.7 and 308.7 K, respectively. These [PrOH] values are well within the linear region of the kobs versus [alcohol] plots (Figures 4.5 and 4.6), and hence are deemed reliable in the calculation of k2. -3  2  b  138  References on p. 155  Chapter 4  Figure 4.7.  Eyring plots for the stoichiometric oxidation of'PrOH by Ru (TMP)(0)2 under 1 atm Ar in benzene-^. VI  139  References on p. 155  Chapter 4  Figure 4.8.  Eyring plots for the stoichiometric oxidation of benzyl alcohol by Ru (TMP)(0)2 under 1 atm Ar in benzene-ok. vl  140  References on p. 155  Chapter 4  4.3.3 Aerobic Oxidations of Alcohols to Aldehydes and Ketones The implication for ( l a ) to function catalytically in the aerobic oxidation of alcohols was noticed in 'H-NMR experiments where excess 'PrOH was added to a vacuum-degassed sample of ( l a ) [generated in situ in benzene-ak from the aerobic oxidation Ru (TMP)(MeCN) (3)]. Complete conversion of ( l a ) to (2a) and the n  2  formation of one equivalent of acetone after about 24 h under vacuum, in accordance with Eq. 4.2, were observed by 'H-NMR spectroscopy. After an additional 48 h, the same sample was analyzed again by 'H-NMR spectroscopy, and 'H-resonances characteristic of species (3) (-10%) were detected (j0-pyrrole-H, 8.65; o-Me, 2.21; p-Me, 2.54; MeCN. -1.32 ppm). At the end of 2 weeks, when no further noticeable changes were observed in the 'H-NMR spectrum of the sample, greater than 90% of (2a) was converted to (3). Also, almost two, instead of the original one, equivalents of acetone were detected. This regeneration of (3), coupled with the fact that (3) under air or 0 can reform ( l a ) 2  (Chapter 2), suggests that the 0 -oxidation of alcohols can be catalyzed by ( l a ) . 2  The mechanism for the aerobic oxidation of alcohols catalyzed by ( l a ) is proposed to follow the pathways represented in Eqs. 4.7 to 4.11 [Ru = Ru(TMP)], and the evidence suggesting the operation of these pathways will be presented below. 1/2 O  Ru (MeCN) (3) a  2  2  Ru \0) l  l  (4.7)  + 2 MeCN  (4)  2 MeCN  *. «« (MeCN) +  (4) J t o ^ O f c + 3 'PrOH (la)  Ru \0)  n  2  (3)  /?« (0)  (4.8)  VI  2  (la)  Ru (0^r) (2a) w  2  141  + Me C=0 + 2 H 0 2  2  (4.9)  References on p. 155  Chapter 4  RtT'(0'Pr) (2a)  + 2H 0  2  /fc* (OH)  Ru \0)  IV  (4.11)  + H 0  l  2  (4.10)  ^ ( 0 ^ 2 + 2'PrOH  2  2  (4)  The formation of Ru (TMP)(MeCN) (3), as well as the production of an n  2  additional equivalent of acetone in vacuum, observed in the previously mentioned H !  NMR experiment, can be accommodated by the proposed catalytic mechanism (Eqs. 4.7 to 4.11). In the absence of 0 , Eq. 4.7 is removedfromthe scheme for the catalytic 2  oxidation, and the 1/2 equivalent of Ru (TMP) formedfromthe disproportionation of 1 n  equivalent of (4) can no longer regenerate (la). Thus only 1/2 equivalent of (la) oxidizes the excess 'PrOH, and in the next cycle the 1/2 equivalent of (4) disproportionates to reform only 1/4 equivalent of (la), and so forth. All the cycles added together as an infinite sum* would yield exactly one additional equivalent of acetone and one equivalent of Ru (TMP) [which is coordinated readily by MeCN to form (3)]; the net, overall n  reaction is given in Eq. 4.12, Ru = Ru(TMP). J t o ^ O f c + 2 'PrOH  + 2MeCN  /?« (MeCN) +2Me C=0 + 2 H 0 n  2  2  2  (4.12)  Evidence for reaction 4.10 can be inferredfromthe following experiment, where an isolated sample of (2a) dissolved in benzene-afe and exposed to air regenerated (la), with acetone forming concurrently, as monitored by 'H-NMR spectroscopy. Moisture was crucial in the regeneration of (la), as (2a) dissolved in benzene-afe containing dry 0  2  gave no reaction. During the regeneration of (la), nofree'PrOH was observed at any  f  2  +  (  2  )  2 +  (  2  )  3  +  •  =  2  (  —  T  )  =  !>  R  e  f  e  r  e  n  c  e  2  7  -  142  References on p. 155  Chapter 4  time [-30 min for complete regeneration of (la)]. Of note, the complete removal of 'PrOH from (2a) was a problem (mentioned earlier in Section 4.3.1), and as high as 10 equivalents of acetone have been observed on one occasion when a sample of (2a) was exposed to air. Typically less 'PrOH is present, although usually more (3 to 6 equivalents) than the expected two equivalents of acetone are formed. The slightly excess 'PrOH was not observed in the 'H-NMR spectrum, presumably due to the rapid exchange of the axial alkoxo ligands with the alcohol (Section 4.3.1). Because water is crucial in the regeneration of the active catalyst (la) from (2a), H 0 is proposed to exchange with the axial alkoxo ligands of (2a) to form 2  Ru (TMP)(OH) , followed by conversion to Ru (TMP)(0) (4) (Eqs. 4.10 and 4.11, IV  IV  2  respectively). Species (4) then disproportionates (cf. Eq. 4.8) to (la) and Ru (TMP). n  The pathways shown in Eqs. 4.7 and 4.8, although not fully established, generally represent the accepted mechanism for generating (la) from the aerobic oxidation of 16  Ru (TMP)(L) species (L = THF, MeCN, N or vacant ), with the disproportionation n  17  18  2  19  2  of (4) to (la) and Ru (TMP) (cf. Eq. 4.8) occurring via attack of the Ru=0 moiety on the n  vacant site of another molecule of (4).  20  In addition, (4) is also the supposed intermediate  in the catalytic epoxidation of alkenes by (la). ' ' 17  20  21  Of note, a recent study showed that the addition of water promoted the catalytic 0 -oxidation of alkenes by (la). 2  21  No explanation was offered by the authors; however,  noting the above observations in the present 'PrOH system, two possible proposals may explain the H 0 effect. The rate-determining step in the epoxidation of alkenes catalyzed 2  by (la) appears to be the dissociation of the epoxide product from  143  References on p. 155  Chapter 4  Ru (TMP)(0)(epoxide) (Figure 4.9), as the catalysis is independent of alkene concentration and O2 partial pressures. Hence, water could displace the epoxide from 17  the Ru-centre and speed up the disproportionation of (4) to (la) and Ru (TMP). The lack n  of a trans or cis site leaves a seven-coordinate associative mechanism as the only possibility for a water-assisted dissociation of epoxide, but considering the steric constraints presented by the TMP mesityl groups, an associative mechanism is unlikely. Another potential role of water might be its participation in the disproportionation reaction shown in Eq. 4.12 [Ru = Ru(TMP)]. Such reactions (and their reverse reactions) /?« (0) + /?i# (0)(OH ) 1V  lv  2  Ru\OU ) 2  (4)  (4.13)  + ^ ( 0 ) 2 (la)  are suggested to be proton-coupled, electron transfer processes (the FT comingfromH 0 ) 2  in the non-porphyrin oxoruthenium(III, IV, V, VI) systems, '' based on electrochemical 71  15  studies. If H 0 can speed up the disproportionation of (4), the rates of epoxidation will 2  also be increased. The results for the aerobic oxidation of'PrOH and benzyl alcohol catalyzed by (la) and (lb) are tabulated in Table 4.4. Complex (la) is a far more effective catalyst than (lb) for the oxidation of benzyl alcohol. This was initially surprising as (lb) is generally more reactive than (la) due to the presence of the electron-withdrawing Cl-groups on the TDCPP ligand. That (lb) is less reactive than (la) is due to the former being more 3  susceptible to deactivation during the catalysis, to form the inactive Ru (TDCPP)(CO) n  species, as evidenced by the appearance of UV-visible and IR absorption bands characteristic of the carbonyl complex (Chapter 2). Species (la) is also deactivated, as  144  References on p. 155  Chapter 4  well as decomposed, but more slowly (see later); the formation of Ru (TMP)(CO) is a n  problem not only in alcohol oxidations, but also in epoxidations of alkenes. '  17 21  Ruthenium(II) is known to have a strong affinity for CO and otherrc-acidligands (e.g. Sbound is favoured over O-bound sulfoxides), ' ' whererc-backbondingstabilizes the 3 22 23  Ru(II) centre. Decarbonylation of carbonyl-containing organic compounds by Ruporphyrins is not without precedent; for example, earlier workfromthis laboratory showed Ru(TPP)(phosphine)2 species to be competent catalysts in the thermal decarbonylation of aldehydes.  23  X  Figure 4.9.  —  RU  II— /  ^ - 1/2 0  2  Mechanism of alkene epoxidation catalyzed by Ru (TMP)(0)2. The dissociation of the epoxide from the Ru(IV) centre is interpreted as being the rate-determining step, as the rate of catalysis is the insensitive to the alkene concentration and O2 partial pressure (Ref. 17). VI  145  References on p. 155  Chapter 4  The data in Table 4.4 show that (la) is a far more effective catalyst for oxidizing benzyl alcohol than 'PrOH. The aerobic oxidation of 1-phenylethanol to acetophenone catalyzed by (la) and (lb) also was studied briefly, and as with 'PrOH, only a few total turnovers were achieved at room temperature (~ 20 °C); carbonylation of the catalyst to Ru (porp)(CO) (porp = TMP and TDCPP) within 24 h was the main deactivation n  pathway, as evidenced by ^ - N M R and UV-visible spectroscopies. Benzyl alcohol is an order of magnitude more reactive than 'PrOH and, under the optimum conditions, a total turnover of 2000 was achieved in a period of 13 d. The presence of water which created a two-phase system enhanced the rates of catalysis, and the addition of 3.0 M aqueous KOH increased, at least for benzyl alcohol, the turnovers even further (Figure 4.10). Of note, the turnover numbers were independent on the O2 partial pressure (1 atm air versus 1 atm 0 ; see Table 4.4). 2  Figure 4.10 shows the turnovers in the initial 24 h as a function of [benzyl alcohol], while Figure 4.11 shows the progress of the aerobic oxidation of benzyl alcohol catalyzed by (la) as a function of time. The daily turnovers in Figure 4.10 show that an upper limit in the effectiveness of the catalyst (in terms of turnover numbers) is reached beyond certain [benzyl alcohol] values (> 0.2 M); therefore, it is plausible that the rate-limiting step in the catalysis, when [benzyl alcohol] values are below 0.2 M, is the alcohol oxidation step (Eq. 4.9). As the [benzyl alcohol] values increase, the turnovers per day versus [benzyl alcohol] plots level-off, and one of the processes (Eqs. 4.7, 4.8, 4.10 or 4.11) involving the regeneration of (la) may become the rate-limiting step in the catalytic cycle. The generation of (la) from Ru(II)-porphyrin species, when exposed to air or 0 , 16  2  146  References on p. 155  Chapter 4  is known to occur rapidly (usually within minutes, see also Chapter 3); therefore, the ratelimiting step is likely reaction 4.10 or 4.11. Figure 4.11 shows that the activity of the system slowly degrades over time and, as mentioned earlier, the catalyst becomes carbonylated to Ru (TMP)(CO) at 24 °C; the aldehyde or ketone product is presumably n  decarbonylated, but this was not checked experimentally. At 50 °C, the Ru(TMP)(OR)2 species in the 'PrOH and benzyl alcohol systems also decompose, as evidenced by the disappearance of the 'H-resonances in the NMR spectrum characteristic of the TMP ligand; the relative contributionsfromcarbonylation of versus destruction of Ru(TMP) species are not known, although at 24 °C deactivation to Ru (TMP)(CO), as evidenced by n  'H-NMR spectroscopy, was the primary deactivation pathway. It is not obviousfromthe data or graphs, but an important point is that the presence of aqueous KOH extended the catalytic activity of (la) to over 10 d and, although the addition of H 0 increased the 2  turnover numbers, the catalyst did not survive for more than 4 d in typical experiments. A finding relevant to this is that substantial decomposition of (la) occurs in a benzene solution under 1 atm air overnight,* with the instability thought to be due to the presence of trace acid impurities. In direct support of this postulation, addition of-25 pL 3.0 M 3  aqueous KOH to -5 x 10" M benzene solution of (la), again in air, led to the preservation 6  of the 422 nm Soret band of (la) overnight, while solutions of (la) without added base lost this characteristic Soret band (a new band appears at 414 nm).  At room temperature under 1 atm air, a substantial portion of (la) (~ 10" M ) decomposes in the benzene solution overnight. Under the same conditions (lb) converts to Ru (TDCPP)(CO) in solution, as well as in the solid state, via an unknown process (see Chapter 5). x  6  n  147  References on p. 155  Chapter 4  Table 4.4. Catalytic activity of Ru"(porp)(0) [porp = T M P (la) and TDCPP (lb) towards Q -oxidation of 'PrOH and benzyl alcohol under mild conditions in benzene. 2  2  [(la)or(lb)]  fl  [alcohol]  (M)  (M)  turnovers within 1st 24 h*  total turnovers; % conversion [time]  H 0 , or NONE  3.0 M K O H  ( a q )  , 1  2  c  (la) 20 °C  PrOH  4.0x10^  0.033  1.5 ±0.1  -  NONE  7.0 x l O ' 2.0 x 10" * 2.0 x IO" '  0.242 0.0325 0.0325  6.0 ±0.5 10.6 ± 1 6.3 ±0.5  -  NONE  20 °C  PhCH OH  0.0242 0.0484 0.121  30 ±2.5 . 40 ± 3 50 ± 4  -  NONE  -  NONE  -  NONE  1.5xl0^ 1.5 xlO" * 1.5 x l O " ' 2.35 x IO" 8.33 x 10" 8.33 x 10" 8.33 x IO" 2.1 x IO" 2.0 x IO" 8.33 x IO" 2.0 xlO" 7.5 x 10" 7.5 x IO" 2.63 x 10" 2.63 x IO" 2.63 x IO" 2.63 x 10"  0.0242 0.0242 0.0483 0.121 0.00083 0.00167 0.0321 0.0321 0.121 0.138 0.362 0.362 0.725 0.121 0.241 0.483 0.876  24 ± 2 28 ± 2 42 ± 3 50 ± 4 5.5 ±0.4 14 + 1 28 ± 5 34 ± 3 77 ± 6 72 ± 6 137 ± 9 101 ± 8 113 + 9 111 ± 9 274 ± 22 297 ± 25 272 ± 22  122; 77% (67.5 h)  NONE  -  H 0  -  H 0  -  H 0  (lb) 50 °C  PhCH OH  50 °C 6  4  4  H 0 2  D 0 2  2  2.0 x IO"  46  50 °C e/  4  4  46  5  5  5  4  4  5  4  5  5  5  5  5  5  NONE NONE NONE 2  2  H 0 2  H 0 2  H 0 2  H 0 2  H 0 2  2  440; 9.5% (259 h) 950; 10% (234 h) 1860; 10%(334h) 2000; 5.3% (308h)  H 0 2  KOH KOH KOH KOH  2  H 0 complete loss of 0.121 9.0 x IO" 10 + 1 H 0 catalytic activity 0.242 9.0 x 10" 18 + 1.5 KOH 0.0966 after about 2.19 x IO" 15 + 1.2 KOH 2d 2.19 x 10^ 0.387 20 + 1.6 " In benzene, under 1 atm air, followed by GC analysis, unless otherwise indicated. Turnovers are typically obtained during a period between 18 to 25 h and are normalized to 24 h. At 50 °C, (la) decomposes gradually and the systems loses its catalytic activity. Benzene directly out of the bottle contains H 0 at a concentration of the order of 10" M , and "JVeWZT' means that no further H 0 has been added. Addition of H 0 (or KOHaq) to benzene creates a 2-phase system, with the benzene phase containing H 0 at ~10" M (Section 4.2.1). Followed by ' H - N M R spectroscopy in benzene-d Under 1 atm 0 . 5  2  5  2  4  6  c  d  3  2  2  2  2  2  e  /  6  148  2  References on p. 155  Chapter 4  350  T  [benzyl alcohol] (Molar)  Figure 4.10.  Daily turnovers versus [benzyl alcohol] for the aerobic oxidation of benzyl alcohol catalyzed by Ru (TMP)(0) (la) at 50 °C. [(la)] ~ 10" M in benzene (see also Table 4.4). VI  2  4  149  References on p. 155  Chapter 4  2000  j 0.8791VL*  1800 +  0.483M  1600 + 1400 + 1200 + Total TwnoverslOOO f  ^.^--  m  0.242M  0.121M  50  ure 4.11.  100  150 200 Time (hours)  250  300  350  Total turnovers versus time for the aerobic oxidation of benzyl alcohol (concentrations indicated) catalyzed by Ru^TMPXO^ (la) at 50 °C. [(la)] = 2.63 x 10" M in benzene (see also Table 4.4). 5  150  References on p. 155  Chapter 4  Of note, a recent report on the use of the same catalysts, namely Ru (porp)(0) VI  2  species (porp = TMP and TDCPP), using pyridine-iV-oxides as oxidants, demonstrated efficient catalytic activity for the oxidation of alcohols, with total turnovers for the conversion of benzyl alcohol to benzaldehyde being -140 (80 % yield).  24  The oxidation of  adamantane in the same Ru (TMP)(0)2/pyridine-A -oxide system was more impressive; VI  r  up to 14000 total turnovers were realized. Active species other than Ru (porp)(0)2 must VI  account for such high activities, as the studies described in Section 4.4 show that the dioxo species are only barely able to oxidize the more active alkanes adamantane and Ph CH. Acids such as HC1 and HBr were present in the pyridine-N-oxide system, and 3  were essential for the enhanced reactivity, and Ru (TMP)(0)(X) species (X = Cl, Br) VI  +  have been suggested to be the active oxidant; the coordination of the pyridine-A -oxide 23  r  to the ruthenium centre may play a role in the system's high catalytic reactivity. In addition, a Ru-porphyrin catalyzed decomposition of pyridine-TV-oxide to generate perhaps an O-atom, and thus initiate a possible radical-chain reaction, might lead to such high activities.  4.4  Aerobic Oxidation of Tertiary Alkanes Catalyzed by Ru (porp)(0) Species VI  2  At 24 °C under 1 atm air in benzene, (la) catalyzes the aerobic oxidation of Ph CH to Ph COH, while (lb), but not (la), can also catalyze the aerobic oxidation of 3  3  adamantane to 1-adamantanol; however, the reactions are sluggish (< 1 turnover per day). As the dioxoruthenium(VI) species are subject to degradation, particularly (la), kinetic studies were deemed to be impractical, and no kinetics studies were undertaken on  151  References on p. 155  Chapter 4  these alkane systems. In 'H-NMR studies in benzene-^6, 'H-resonances corresponding to (la) (~10" M) can still be detected after 24 h (i.e. not all of (la) at this higher 3  concentration has decomposed after this time, see end of Section 4.3.3); 'H-resonances corresponding to Ru (TMP)(0) (see Section 3.4.2) also can be observed [~ 5 % of the IV  total Ru]. The progress of the catalyses is shown in Figure 4.12. The presence of electron-withdrawing Cl-groups makes (lb) more reactive, and almost four times the turnovers are achieved for the Ph CH oxidation catalyzed by (lb) over that by (la). The 3  addition of 2,6-ditertbutyl-4-methylphenol (BHT, 0.01 M) to the Ru (TMP)(0)2/Ph CH f  YI  3  system does not inhibit the oxidation, and thus the oxidation most likely is due to direct attack of the tertiary C-H bond by the Ru=0 moiety. The mechanism of oxidation is proposed to occur via Eq. 4.14 [Ru = Ru(TMP) or Ru(TDCPP)]; whether the reaction in Eq. 4.14 proceeds via an 0=Ru =0 vl  + R-H  ^ 0=/?M(OH)'R*  + R-OH  ^ 0=Ru  w  (4.14)  H-atom abstraction followed by electron transfer is unknown. For example, oxidation of alkanes by Fe(TMP)(Cl)(0) species has been proposed occur via a hydride transfer pathway, while oxidations by non-porphyrin oxoruthenium species have been proposed 25  to undergo a homolytic H-atom abstraction pathway. For the Ru (TMP)(0)2 system, a 6b  VI  homolytic cleavage of the tertiary C-H bond by a Ru=0 moiety to initiate the alkane oxidation reaction, with the *OH being transferred to the R* fragment within a solvent cage, is consistent with the results in Chapter 5, where the catalytic oxidation of hydrocarbons occurs via radical-chain pathways, possibly initiated by a homolytic C-H  The addition of B H T (~ 0.01 M ) to Ru (TMP)(0) (~ 10" M ) in benzene, under 1 atm air, gave no reaction, as evidenced by UV-visible spectroscopy. 1  VI  6  2  152  References on p. 155  Chapter 4  16  X  0  3.5  10  20  30 Time (days)  40  50  T  Time (days)  Figure 4.12.  Total turnovers versus time for the aerobic oxidations of a) Ph CH and b) adamantane catalyzed by Ru (porp)(0) [porp = TMP (la) and TDCPP (lb)] at 24 ± 2 °C in benzene. a) TMP: [(la)] = 1.2 x IO" M; [Ph CH] = 2.89 x 10" M TDCPP: [(lb)]-2.4 x 10" M; [Ph CH] = 4.64 x IO" M b) [(lb)] = 2.4 x IO M; [adamantane] = 6.28 x 10° M. VI  3  2  4  3  3  4  3  3  -4  153  References on p. 155  Chapter 4  bond cleavage by Ru=0 moieties. Eq. 4.14 corresponds to the oxygen-rebound mechanism proposed for the ubiquitous cytochrome P-450 enzyme, where the *OH 26  group is transferred to the R* fragment before the substrate leaves the protein cavity.  4.5  Conclusion The description and plausible mechanism of an efficient catalytic aerobic system  based on /raw5-dioxoporphyrinatoruthenium(VI) species, capable of oxidizing benzyl alcohol, 'PrOH and 1-phenylethanol to the corresponding aldehydes and ketones, have been presented. The initiation of the oxidation via a hydride transferfromthe alcohol aC-H bond was proposed. At 50 °C under 1 atm air, benzyl alcohol was oxidized selectively to benzaldehyde with daily turnovers up to 300 d", and total turnovers reaching 1  2000 in 13 d. This is among the most efficient of Ru-based catalyst systems for the aerobic oxidation of alcohols. The Ru (porp)(0) species (porp = TMP and TDCPP) 1  VI  2  can also catalyze the aerobic oxidations, although slowly, of Ph CH to Ph COH and 3  3  adamantane to 1-adamantanol under 1 atm air at 24 °C.  154  References on p. 155  Chapter 4  References  1  W. P. Griffith, Chem. Soc. Rev., 21, 179 (1992).  2  a) S. Y. S. Cheng, N. Rajapakse, S. J. Rettig and B. R. James, J. Chem. Soc, Chem. Commun., 2669 (1994). b) S. Y. S. Cheng and B. R. James, Proc. of the 78th Can. Chem. Conf, Guelph, Canada, 1995, Abstract IN-447.  3  a) N. Rajapakse, Ph. D. Dissertation, University of British Columbia, 1990. b) N. Rajapakse, B. R. James and D. Dolphin, Stud. Surf. Sci. Catal, 55, 105 (1990) .  4  W.-H. Leung, C.-M. Che, C.-H. Yeung and C.-K. Poon, Polyhedron, 12, 2331 (1993).  5  a) C.-M. Che and W. H. Leung, J. Chem. Soc. Dalton Trans., 2932 (1991). b) W. H. Leung and C.-M. Che, J. Am. Chem. Soc, 111, 8812 (1989).  6  a) C.-M. Che, C. Ho and T.-C. Lau, J. Chem. Soc. Dalton Trans., 1259 (1991). b) M. S. Thompson and T. J. Meyer, J. Am. Chem. Soc, 104, 5070( 1982).  7  a) L. Roecker and T. J. Meyer, J. Am. Chem. Soc, 109, 746 (1987). b) M. S. Thompson and T. J. Meyer, J. Am. Chem. Soc, 104, 4106 (1982).  8  D. G. Lee and L. N. Congson, Can. J. Chem., 68, 1774 (1990).  9  C.-M. Che, W.-T. Tang, W.-O. Lee, K.-Y. Wong and T.-C. Lau, J. Chem. Soc Dalton Trans., 1551 (1992).  10  J. P. Collman, C. E. Barnes, P. J. Brothers, T. J. Collins, T. Ozawa, J. C. Galluci and J. A. Ibers, J. Am. Chem. Soc, 106, 5151 (1984).  11  R. J. Fessenden and J. S. Fessenden, Organic Chemistry, 3rd Edition, Brookes/Cole, Monterey, 1986, p: 523-524.  12  a) C. Sishta, M. Ke, B. R. James and D. Dolphin, J. Chem. Soc, Chem. Commun., 787 (1987). b) M. Ke, C. Sishta, B. R. James and D. Dolphin, Inorg. Chem., 30, 4776 (1991) . c) C. S. Alexander, Ph. D. Dissertation, University of British Columbia, 1995.  13  J. G. Muller, J. H. Acquaye and K. J. Takeuchi, Inorg. Chem., 31, 4552 (1992).  155  References on p. 155  Chapter 4  14  P. Dubourdeaux, M.Taveres, A. Grand, R. Ramasseul and J.-C. Marchon, Inorg. Chim. Acta., 240, 657 (1995).  15  a) C.-M. Che, W.-T. Tang, W.-T. Wong and T.-F. Lai, J. Am. Chem. Soc, 111, 9048 (1989). b) C.-K. Li, C.-M. Che, W.-F. Tong and T.-F. Lai, J. Chem. Soc. Dalton Trans., 813 (1992).  16  T. Mlodnicka and B. R. James, in Metalloporphyrins Catalyzed Oxidations, eds. F. Montanari and L. Casella, Kluwer Academic Publishers, Dordrecht, 1994, p. 121.  17  J. T. Groves and R. Quinn, J. Am. Chem. Soc, 107, 5790 (1985).  18  J. T. Groves and K.-H. Ahn, Inorg. Chem., 26, 3833 (1987).  19  M. J. Camezind, B. R. James and D. Dolphin, J. Chem. Soc, Chem. Commun., 1137(1986).  20  J. T. Groves and J. S. Roman, J. Am. Chem. Soc, 111, 5594 (1995).  21  B. Scharbert, E. Zeisberger and E. Paulus, J. Organometdllic Chem., 493, 143 (1995).  22  a) D. T. T. Yapp, J. Jaswal, S. J. Rettig, B. R. James and K. A. Skov, Inorg. Chim. Acta., Ill, 199 (1990). b) D. T. T. Yapp, J. Jaswal, S. J. Rettig, B. R. James and K. A. Skov, J. Chem. Soc, Chem. Commun., 1528 (1992).  23  G. Domazetis, B. Tarpey, D. Dolphin and B. R. James, J. Chem. Soc, Chem. Commun., 939 (1980).  24  a) H. Ohtake, T. Higuchi and M. Hirobe, Heterocycles, 40, 867 (1995). b) H. Ohtake, T. Higuchi and M. Hirobe, J. Am. Chem. Soc, 114, 10660 (1992).  25  J. T. Groves and T. E. Nemo, J. Am. Chem. Soc, 105, 6243 (1983).  26  J. T. Groves, J. Chem. Ed, 62, 928 (1985).  27  J. F. Hurley, Intermediate Calculus, Saunders College, Philadelphia, 1980, p. 682.  156  References on p. 155  Chapter 5  Chapter 5 Reactivities of Ru(TDCPP-CI ) Species 8  157  References on p. 187  Chapter 5  5.1  Introduction The development of metalloporphyrins as catalysts in 02-oxidations of organic  compounds, a particular aim being the oxidation of light alkanes, entered a new stage with the introduction of the so-called third-generation porphyrins (See Section 1 . 4 . 1 ) . The methodology behind the development of this class of compounds is based on the extensive halogenation of the TPP ligand at its ^-pyrrole positions and on the /weso-phenylringsto stabilize the porphyrin against oxidative destruction in the oxidizing medium of the reaction mixture. Furthermore, the saddle shape conformation for these extensively 1  halogenated metalloporphyrins favours monomelic structures and prevents their "dimerization" to p-oxo-dinuclear species, a cause for catalyst deactivation. Adding to 2  these properties a very reactive oxometal moiety due to the addition of electronwithdrawing halogen groups (if the systems indeed generate M=0 moieties as the active catalytic centres), a potentially powerful reagent is thus available for oxidizing organic compounds. Of particular significance is the work of Lyons and Ellis on the 02-oxidation of light alkanes catalyzed by Fe(porp) species [porp = octa-/?-fluoro, chloro and bromotetra(pentafluorophenyl)porphyrins] under mild conditions; for example, total turnovers for an isobutane system exceeded 1 0 0 0 0 moi" . One of the aims of the present thesis is to 1 3  extend the periodic analogy of Fe to Ru and examine the reactivity of similar Ruporphyrins of the third generation. One difficulty is the insertion of ruthenium into the free-base porphyrins having a large number of electron-withdrawing halogens. Collaboration with Dolphin and Xie led to successful preparation of one of the first  158  References on p. 187  Chapter S  perhalogenated Ru-porphyrin complexes, Ru (TDCPP-Cl )(CO) (TDCPP-C1 = dianion of n  g  8  octa->S-chloro-tetra(2,6-dichlorophenyl)porphyrin], whose reactivity is the subject of this chapter.  5.1.1  Ru-Perhalogenated Porphyrins: Aims and Scope Although a wide range of transition metals across the periodic table has been  inserted into free-base porphyrins, the metallation of the highly-halogenated thirdgeneration porphyrins, to the best of the author's knowledge, has been limited until very recently to the first row transition metals. Metalloporphyrins of such type, particularly 4  iron porphyrins, have been shown to exhibit high activity in the hydroxylation of alkanes.  3  Only recently have there been reports on the second row (Ru) congeners, '* although no 5  catalysis studies on these Ru-porphyrins are yet reported. The metallation of Ru into these highly-halogenated porphyrins is non-trivial. The common procedure of Ru-insertion is to reflux Ru (CO)i2 and the free-base porphyrin (eg. 3  TPP) in a high-boiling organic solvent, such as mesitylene under 1 atm CO for extended 6  periods of time, or more recently, heating Ru(DMF)  3+ 6  and water-soluble free-base  porphyrins in DMF. Initial attempts in this thesis work to metallate H TPFPP (which 7  2  contains twenty F-groups, and does not have any yff-pyrrole-halo groups) via the Ru (CO)i2 route [see Chapter 2 regarding the preparation of Ru (porp)(CO), where porp n  3  = TMP and TDCPP] gave low yields of Ru (TPFPP)(CO) (<10% approximated by n  spectrophotometry and TLC), and the application of the Ru (CO)i route to other highly3  2  * Work described in the present thesis was being carried out when the papers of Ref. 5 appeared i n the literature.  159  References on p. 187  Chapter 5  halogenated porphyrins was assumed to be similarly difficult. Recently, Murahashi et al.  8  reported the reaction of Ru (CO)i and H TPFPP in decalin to give Ru (TPFPP)(CO) in a n  3  2  2  49% yield; this solvent was also used in the preparation of Ru (TDCPP)(CO) by n  Dubourdeaux et al  9  Also, Birnbaum et al. reported the insertion of ruthenium into 5  H TPFPP-Clg, the reaction involving heating Ru (CO)i and thefree-baseporphyrin in 2  3  2  refluxing perfluorobenzene to form Ru (TPFPP-Clg)(CO). Clearly, the choice of the n  5  solvent for the Ru (CO)i route is critical for the successful preparation of Ru-porphyrins 3  2  containing a large number of electron-withdrawing groups. Again, at the time when the current research was in progress, the reports of Birnbaum etal. were unpublished, and an 5  alternative route to obtain the highly-chlorinated Ru-porphyrin, Ru (TDCPP-Cl8)(CO), n  (1), was discovered in a collaborative effort with Dolphin and Xie (Chapter 2). Following the successful preparation of (1), /ra«5-Ru (TDCPP-Clg)(0) , (2), was obtainedfromthe VI  2  /w-CPBA oxidation of (1). (1) and (2) were tested as catalyst precursors in the 0 2  oxidations of alcohols, alkenes and alkanes.  5.2  Sample Preparation and Data Analysis  5.2.1  Sample Preparation in Catalysis Studies The catalytic 0 -dehydrogenations of benzyl alcohol and 1-phenylethanol (up to 2  0.58 M) were studied at 50 °C in benzene under 1 atm air using an experimental procedure similar to that outlined in Section 4.2.1. Concentrations of (2) were 10' - 10" 5  4  M in benzene, these being determined spectrophotometrically using the extinction coefficient of the complex (Chapter 2). The aerobic oxidation of Ph CH (~10' M) to 2  3  Ph COH catalyzed by (2) (~10" M) in benzene also follows the same setup as that 4  3  160  References on p. 187  Chapter 5  described in Section 4.2.1. The 02-oxidations of neat c/'s-cyclooctene (referred to as cyclooctene), cyclohexene and methylcyclohexane were studied under 1 atm O2. The 1 atm O2 environment created by the continual purge of O2 into the neat hydrocarbons resulted in some solvent losses in the cyclohexene and methylcyclohexane systems, and the experimental setup shown in Figure 5.1 was employed to minimize the evaporation of the hydrocarbons. The reactions were done in a 25 mL, three-neck, conicalflasktopped with a water-cooled (10 °C) condenser, although under such an experimental setup, -20% losses of methylcyclohexane and cyclohexene were still observed over the time of the experiment,* typically < 24 h. Alkane or alkene (5 mL) was added into theflask,and subsequently -0.5 mg (1) or (2) was added into the hydrocarbons. A 25 uL aliquot of the neat hydrocarbon containing the Ru-porphyrin was diluted in 1 mL benzene, and the diluted concentration of (1) or (2) was determined spectrophotometrically in the benzene solution; typical concentrations of the Ru-porphyrin in the original neat hydrocarbons, where significant catalysis occurred (see Sections 5.4 and 5.5), were calculated to be - 3 x 10' M. The reaction vessel was submerged into an oil-bath heated by an electric hot5  plate, with the desired temperature (35 to 100 °C) maintained within ± 1 °C. 0 was 2  introduced into the solution through a stainless steel needle, with the gas continually purging through the solution at -5 mL min". 1  Physical changes were observed approximately 1 h after the cyclooctene system was heated to 93 °C. The darker brown colour of the alkene solutions due to the presence  * The 20% losses in volumes were assumed to contain mostly methylcyclohexane and cyclohexene, as they are the most volatile component in the respective systems.  161  References on p. 187  Chapter 5  10 ° c  cooling water  /o  2  Stainless steel needle  Neat Alkane/Alkene with Dissolved Ru-porphyrin  Electrically heated oil-bath  Figure 5.1.  Experimental setup for the oxidations of neat cyclohexene, cyclooctene and methylcyclohexane under 1 atm O2. The constant purge of O2 necessitated the use of a water-cooled condenser. -20% losses of cyclohexene or methylcyclohexane (see text) were observed over a period of-24 h.  162  References on p. 187  Chapter 5  of (2) turned greenish-yellow after this time; however, a Soret absorption, although gradually disappearing as the reaction progressed, was still observed at 422 nm at this time. Of note, the Soret Xma for (2) is at 430 nm; however, (2) reacts with the neat X  cyclooctene almost immediately at room temperature, and the resulting Ru-porphyrin species absorbs at 422 nm. At the end of 24 h, < 30% of the intensity of the Soret maximum at 422 nm remained, indicating that a substantial amount of the Ru-porphyrin had decomposed. After 55 h, a very small (< 5%) Soret absorption was still observed in the cyclooctene system, but a large UV-visible absorption, presumably due to the organic products (starting from ~ 420 nm and rising steeply below this wavelength), made an accurate determination of the amount of intact porphyrin difficult. The methylcyclohexane system showed no oxidation after 2 h of heating at 90 °C; however, the solution became bleached after 24 h, when no Soret absorbances were evident.  5.2.2  Preparation of <ra«s-Ru (TDCPP-Cl )(0)2 VT  8  That /raw5-Ru (TDCPP-Clg)(0) (2) contains two oxo ligands is shown by its YI  2  ability to oxidize 2 equivalents of P^-F-CeUt^ to the corresponding phosphine oxide in CDCI3 VR =O U  under 1 atm Ar, as observed by F-NMR spectroscopy.* The IR absorption due to 19  within (2) is observed at 827 cm" (solid KBr), in agreement with values for other 1  ?raw5-Ru (porp)(0)2 species (porp = TMP, TDCPP, OEP and TPP ), whose v =o VI  10  11  12  Ru  values range between 820 and 823 cm". Hence a trans geometry for the oxo ligands in (2) 1  5 equivalents of POJ-F-QJLOS (2.5 x 10" M) were added to a C D C 1 solution of (2) (5.0 x 10" M) under 1 atm Ar, and the amount of oxide product was determined from integrations on the F - N M R spectrum (acquired ~ 30 min after the addition of the phosphine): OPip-F-CetUh and Pip-F-CetUh at 8 = -30.7 and -36.4, respectively (see also Chapter 3). 1  3  4  2  2  1 9  163  References on p. 187  Chapter 5  seems reasonable. Purification of (2) by column chromatography (activity I neutral alumina) using benzene as the eluent gives a product with Soret and Q-bands at 430 and 516 nm, respectively (Chapter 2); however, when species (2) is left in benzene, within 1 h the Soret maximum shifts to 422 (e ~ 150,000 M" cm") and the Q-band to 518 nm (e ~ 1  1  14,000 M" cm"). Using CH2CI2 as the eluent leads to the same Soret and Q-band shifts, 1  1  although the time for the transformation is typically longer (~ 2 h) than that in benzene. The loss of the dioxo ligands in these solution species is certain, as the Soret shift from 430 to 422 nm is accompanied by the loss of the 827 cm" absorption band in the IR 1  spectrum of a recovered solid sample. Of note, the addition of ~ 10 equivalents of mCPB A to the benzene solution containing the unknown Ru(porp) species with A™, 422 nm x  regenerates almost quantatively (2). Addition of 0.50 mL HCl-saturated benzene solution to afreshbenzene solution of (2) (~ 4 x 10" M, 5.00 mL), within 1 min, yielded a new species which absorbed at 424 6  and 528 nm, with e values of 140,000 and 14,000 M^cm" , respectively. The reaction of 1  HC1 with Ru (porp)(0)2 species, which will be discussed in Chapter 6, gives VI  Ru (porp)(Cl)2 products. The benzene solution was pumped to dryness, and the solid IV  that remained was analyzed by mass spectrometry (Figure 5.2); the mass peak at 1336 amu corresponds to the parent peak for [Ru (TDCPP-Clg)(Cl) ] , which suggests that the IV  +  2  bis(chloro) species was present in the solid. This reaction of (2) with HC1 gives further indirect evidence that (2) is the dioxo species.  164  References on p. 187  Chapter 5  Chapter 5  The identity of the Ru(TDCPP-Clg) species with a Soret maximum at 422 nm is unknown. Most likely the sixteen Cl-groups on the porphyrin makes the Ru=0 moieties within (2) extremely reactive, and (2) perhaps react with any trace impurities in the solvents* presumably to form reduced, lower-valent Ru-species. When a solution (benzene or CH2CI2) of (2) is left standing for 1 week in air, the Soret maximum shifts further to 418 nm, and at this time an IR absorption due to Vco can be observed at 1965 cm". Even more remarkable is that a solid sample of (2) left exposed to air for 1 month 1  shows the presence of an IR stretch at vco  5.2.3  =  1965 cm". 1  Data Acquisition and Analysis The progress of all the catalytic oxidations (alcohol and hydrocarbon systems) was  monitored by GC analysis. The procedure and methodology have been described already in Sections 2.2.5 and 4.2.2. Known standards, when available, were used to identify the oxidation products (Chapter 2). In addition, GC-MS analyses were employed to ascertain the identities of some of the products from the neat cyclohexene, cyclooctene and methylcyclohexane systems, where known standards were unavailable for all of the oxidation products. The GC-MS data are compiled in Appendix E, as are the raw data from the GC analyses for the catalysis studies on these neat hydrocarbons systems.  ' The benzene and CH2CI2 eluents used were H P L C grade solvents from Fisher, and were used without further purification.  166  References on p. 187  Chapter 5  5.3  Catalytic Aerobic Oxidation of Alcohols Ru (TDCPP-Cl )(0) (2) was tested as a catalyst for the aerobic oxidation of VI  8  2  alcohols. In Chapter 4, the aerobic oxidation of alcohols in benzene catalyzed by the Ru (porp)(0) species (porp = TMP and TDCPP) was discussed, and the TDCPP VI  2  analogue was more susceptible to deactivation via decarbonylation pathways (total loss of catalytic activity within 24 h). The activity of (2) is of the same order of magnitude as that of Ru (TMP)(0) (Chapter 4); this is surprising as the reactivity of (2) had been thought VI  2  to resemble that of the TDCPP analogue, also highly chlorinated, and (2) was expected to be similarly susceptible to deactivation. That (2) does not lose catalytic activity as rapidly as Ru (TDCPP)(0) under similar conditions suggests perhaps that the highly distorted VI  2  and sterically crowded environment about the ruthenium prevents decarbonylation of the aldehyde or ketone products (Chapter 4); however, inspection of the 1-phenylethanol system after ~ 7 d shows the presence of Ru (TDCPP-Cl )(CO), as evidenced by the n  8  presence of V c o at 1965 cm" in the IR spectrum. 1  The aerobic oxidations of benzyl alcohol and 1-phenylethanol catalyzed by (2) are shown in Figures 5.3 and 5.4. About 1200 turnovers are obtained for benzyl alcohol after 15 d; no benzoic acid is detected under the conditions described below. The conditions used in this system are the optimum ones found for the Ru(TMP)/benzyl alcohol system: addition of 3.0 M aqueous KOH (50 pL) to benzene (0.40 mL) and moderate reaction conditons (1 atm air at 50 °C). Of interest, the unknown species with a characteristic Xmax 422 nm described in Section 5.2.2 gives almost the same turnover numbers as those by (2) (see later).  167  References on p. 187  Chapter 5  Time (hours)  1400 - • 1200 • •  (b)  [(2)] = 3 . 5 x 1 0 " M 5  £.580M  1000 - | 800 - • o  0.290M  1600 1400  •  •  +  200 +  •  0 100  0  +  +  200  300  400  500  Time (hours) Figure 5.3.  Aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by R u ( T D C P P - C l ) ( 0 ) (2) under 1 atm air in benzene at 50 °C (2-phase system containing 0.40 m L benzene/50 u L 3.0 M aqueous K O H , see text). The unknown Ru-porphyrin species with characteristic Soret absorption at 422nm (a) exhibits almost the same activity as (2) (b). YI  g  2  168  References on p. 187  Chapter 5  0  Figure 5.4.  50  100 Time (hours)  150  200  Aerobic oxidation of R, S- 1-phenylethanol to acetophenone catalyzed by Ru (TDCPP-Cl )(0) (2) under 1 atm air in benzene at 50 °C (2-phase system containing 0.40 mL benzene/50 pL 3.0 M aqueous KOH, see text). [(2)] = 2.1 x 10-*M VI  g  2  169  References on p.  187  Chapter 5  Addition of the common radical inhibitor, 2,6-ditertbutyl-4-methylphenol (BHT, 0.1 M) to the benzyl alcohol system did not hinder the oxidation, thus ruling out the operation of a radical-chain mechanism. The selective oxidation of benzyl alcohol to benzaldehyde without further conversion to benzoic acid also strongly suggests a mechanism not involvingfree-radicals.The catalytic process most likely is analogous to that of the Ru (TMP)(0)2 system, which has been fully discussed in Section 4.3.3, and is VI  summarized again in Eqs. 5.1 through 5.4 [Ru = Ru(TDCPP-Clg)]. ^(0)2  + 3RR'CHOH  /?ii (OCHRR')2 + IV  /^(OFfy 2Ru (0) w  » Jta^COCHRR'fc + R R ' C O + 2 H 0 (5.1) 2  2H 0  + 2 RR'CHOH  Ru (OH) w  2  2  (5.2)  ^"^(O) + H 0  (5.3)  2  ~Ru  n  + Ru^iOh  (5.4)  Of note, the addition of 10 pL of benzyl alcohol (1 x 10" M) to (2) (3.0 x 10" M 2  6  in benzene under air), after -30 min, gives a Ru-species which absorbs at 422 and 518 nm; this spectral change is the same, and occurs on the same timescale, as that observed with (2) alone in benzene solution (see earlier). If the present system exhibits chemistry similar to that of the TMP system (Chapter 4), the Ru-product in the benzyl alcohol reaction is expected to be Ru (TDCPP-Clg)(OCH Ph) . IY  2  2  That the unknown Ru(TDCPP-  Clg) species with A™* 422 nm formedfrom(2) alone in benzene exhibits almost the same reactivity as that of (2) implies that it is an equally effective catalyst precursor, presumably exhibiting similar chemistry as (2) (Eqs. 5.1 to 5.4); this suggests that the ^  170  422 nm  References on p. 187  Chapter 5  species is similar in nature to Ru™(0), Ru (L) or J?« (L') species (L, L' = ligands that TY/  n  2  2  are labile or exchangeable with water or alcohol; see Chapter 4). The catalytic activity of (2) is vastly superior to that of Ru (TDCPP)(0) and is VI  2  comparable to that of Ru (TMP)(0) for the aerobic oxidation of benzyl alcohol. In IV  2  addition, (2) gives -130 turnovers for the catalytic aerobic oxidation of 1-phenylethanol to acetophenone, while Ru (porp)(0) species (porp = TMP or TDCPP) give only a few VI  2  turnovers before being deactivated completely (Chapter 4). Hence, (2) might offer a greater potential as an alcohol oxidation catalyst, and possibly is more useful for a greater range of alcohol substrates.  5.4  Oxidation of Alkenes The 0 -oxidations of cyclohexene and c/'s-cyclooctene catalyzed by (2) give total 2  turnovers of the order of 10 when the neat alkenes are used without any solvent. The 5  epoxide is the main product ih the cyclooctene oxidation; however, cyclohexene-2-ol and cyclohexene-2-one, allylic C-H bond cleavage compounds, are the main products in the cyclohexene oxidation. Table 5.1 lists the results from the oxidation of cyclohexene and cyclooctene catalyzed by (1) and (2). The addition of BHT (either 0.01 or 0.1 M) completely inhibits oxidation in both alkene systems, and both active systems test positive (Kl/starch) for the presence of organic peroxides. The BHT experiment and the predominant production of allylic C-H bond cleavage products within the cyclohexene system suggest a free-radical oxidation mechanism. It is clear from blank studies at higher temperatures that (1) and (2) are necessary in these alkene oxidations, and a reasonable  171  References on p. 187  Chapter 5  conclusion is that the Ru-porphyrins are involved in the decomposition of organic peroxides to propagate a radical-chain process at a lower temperature (see later, Figure 5.7). The Ovoxidations of alkenes using radical initiators have been well-studied, and 13  the reactions generally follow the mechanism outlined in Figure 5.5. Two main propagating pathways, addition of R0 * to alkenes (Eq. 5.7) and H-abstraction from 2  alkenes by R0 * (Eq. 5.9), are identified within this mechanism, with the former leading to 2  epoxides as products (Eq. 5.8). Clearly, for every equivalent of epoxide formed, one equivalent of alkoxyl radical must be accounted for (Eqs. 5.8, 5.10, 5.11 and possibly 5.12); therefore, the maximum yield of epoxide should never exceed 50%, if addition is the only epoxide yielding path. Mayo mentioned the possibility of an alkoxyl radical giving directly an epoxide (Eq. 5.12);  13c  however, how such a reaction can proceed was  not indicated in the report and the actual mechanism for such an epoxide forming route is not obvious. The yields of the various products in the cyclohexene system are consistent with radical pathways in operation; however, the cyclooctene system gives as high as 87% cyclooctene-oxide among the products (see also Figure 5.6), which is far higher than the expected maximum of 50% based on an addition pathway alone. Cyclooctene is known to be an unusual substrate in autoxidation studies in that it is not as autoxidizable compared to its cyclohexene, cyclopentene and cycloheptene homologues.  13b  A most intriguing, and still unexplained, observation by de Roch and  Balaceanu was that the autoxidation of cyclooctene at 106 °C in the presence of  172  References on p. 187  Chapter 5  Table 5.1.  Oxidation of alkenes catalyzed by Ru (TDCPP-Cl )(CO) (1) and Ru (TDCPP-Cl )(0) (2) under 1 atm 0 . n  8  YI  8  Substrate  2  2  Products (% of starting alkene) [% Distribution of oxidation products]  0"  OH  d  o  d  f  OOH  e,  6  6  Total Products (% of starting alkene)  O O +other dimers"  Blank 24 h [(l)f = 3.15 x 10" M 23 h 5  0.012 [2.8]  0.16 [37]  0.23 [54]  0.0032 [0.74]  0.023 [5.4]  0.42 ±0.1  1.05 [3.6]  13.4 [45]  12.8 [43]  0.031 [1.0]  2.1 [7.0]  29.6 ± 1 [92000 turnovers]  5  o  a  Blank 23 h  o c  [(2)] = 5.0 x 10' M 26 h 5  d  -C=0, -OH and -OOF/containing and rearrangement products 6  8.2 [73]  3.1 [27]  11.3 ± 1  35.8 [87]  5.4 [13]  41.2±4 [63000 turnovers]*'  7  " Reaction conditions: 5 mL neat alkene under 1 atm 0 ; 35 ± 1 °C for cyclohexene and 93 ± 1 °C for cyclooctene, unless indicated otherwise. * Similar conversion were obtained in qualitative studies under the same conditions using (2) as the catalyst. Again, cyclohexene-2-ol and cyclohexene-2-one were the major products. 110± 1 °C Identification of product from the correlation of retention times with known standards, as well as by GC-MS (Appendix E). Formulation of product identity based on GC-MS only (Appendix E). Presence of hydroperoxides suggested from a positive Kl/starch test result. * Turnovers based on [neat cyclohexene] = 9.86 M. * Turnovers based on [neat cyclooctene] = 7.69 M. ' Progress of this reaction beyond 26 h is shown in Figure 5.6. 2  c  d  e  f  173  References on p. 187  Chapter 5  Initiation  RH  " R* + H*  Peroxide formation  R* + O2  (5.5)  R0 *  (5.6)  2  O2R ADDITION  RCV + /  &  \  / — \  0R  O / - A + RO'  2  ox Epoxide formation rirmatrnn  ABSTRACTION  Fates of RO*  >—( /  — \  /  RO + JJ—/  5 ?  )  (5.8)  \  \  ?  RO*  (  R0 H + / ~ \ (5.9) 2  \  ROH + /  \  (510)  H  RQ RO* +  / ~ \  »  —  / ~ \ Q  (5-11) " (5.12)  Figure 5.5.  Radical-chain mechanism proposed for the oxidation of alkenes (Ref. 13). Chain propagation proceeds through either an ADDITION or ABSTRACTION pathway.  174  References on p. 187  Chapter 5  cobalt(II) stearate gave over 7 0 % yield in the epoxide.  14  A t about the same time, V a n  Sickle et al. conducted similar experiments (ABN-initiated autoxidation) and found that only 4 0 % cyclooctene-oxide was obtained at 70 °C;  13b  the high epoxide yield observed by  de R o c h and Balaceanu was viewed with skepticism. The present cyclooctene system using (2) as the catalyst yields 87 % epoxide among the oxidation products after 26 h; there is no doubt that a > 50 % yield of epoxide is generated. Approximately 60000 turnovers per day are realized at 93 °C when (2) is added to the cyclooctene, and the catalytic activity does not decrease much as the reaction proceeds (see Figure 5.6). A s < 3 0 % of the starting Ru-porphyrin remains in the cyclooctene system after 24 h (Section 5.2.1), the almost linear turnover versus time plot suggests that Ru-porphyrin species are not solely responsible for the catalytic activity (see Section 5.5 later). Worth noting is that the reaction involving cyclooctene and (2) is relatively clean and that the epoxide content among the products remains almost constant throughout the reaction (Figure 5.6). Autoxidation at 93 °C in the absence of (2) is negligible (< 0.4 % product after 24 h), but at 110 °C some 11 % cyclooctene autoxidation is evident (blank study, Table 5.1); the amount of epoxide obtained at 110 °C (blank study) is 73 ± 4 % of the total products, which is close to the distribution seen when (2) is present as a catalyst at 93 °C. Earlier work by M a y o ' s group on the ABN-initiated autoxidation of cyclohexene at 60 °C (closed system initially under ~5 atm 0 ) achieved a 6.15 % overall conversion in 2  13.5 h; among the products observed were cyclohexene-2-peroxide (80.4 %), cyclohexene-2-ol (7.0 %), cyclohexene-2-one (4.7 %), cyclohexene-oxide (0.9 %) and  175  References on p. 187  Chapter 5  dimers (7.0 %).  13b  In comparison, the present cyclohexene system catalyzed by (1) shows  a higher activity (30 vs. 6 % conversion) at a lower temperature (35 vs. 60 °C) and pressure (1 vs. 5 atm O2).  Thus, (1) and (2) are effective catalyst precursors, and are even  more effective than some free-radical initiators (e.g. ABN) in promoting the free-radical propagated 0 -oxidation of cyclohexene and cyclooctene. 2  At lower temperatures (24 and 50 °C) under 1 atm air in benzene solvent [~10" M 2  alkene, ~ 5 x 10" M (1) or (2)], (1) is completely inactive as a catalyst, while (2) shows 4  marginal activity in the epoxidation of cyclohexene and cyclooctene. Under such  90% T  Time (hours) Figure 5.6.  0 -oxidation of cyclooctene under 1 atm 0 at 93 ± 1 °C catalyzed by R u ^ T D C P P - C l g ) ^ (2). [(2)] = 5.0 x 10' M. Excess of alkene to (2) corresponds to 150000 : 1. 2  2  5  176  References on p. 187  Chapter 5  conditions, approximately 1 turnover per day is realized (total turnovers -10) for either alkene when ( 2 ) is employed as the catalyst, and the turnovers obtained are invariant with temperature. Under 1 atm 0 at 35 °C, ( 2 ) (3.5 x 10" M in benzene) also gives only 1 5  2  turnover after 16 h for the oxidation of cyclohexene (1.5 x 10" M) to cyclohexene-oxide. 2  The Soret intensity at 422 nm has not changed when the solution is inspected after 24 h, unlike in the reactions involving the neat cyclooctene, indicating that the Ru-porphyrin remains intact in the reaction medium. The oxidation of both cyclohexene and cyclooctene, at dilute concentrations in benzene, produces exclusively the corresponding epoxides, a direct contrast with the neat alkene systems. An O-atom transfer mechanism, suggested by the specificity for epoxide formation, is most likely in operation in the case where the alkenes are dilute in the benzene solutions.  5.5  Oxidation of Alkanes Lyons and Ellis have suggested that their isobutane and propane oxidations  (~ 13000 turnovers for isobutane) catalyzed by Fe(TPFPP-Br )(Cl) occur via a high-valent 8  oxoiron intermediate, with the Fe=0 moiety attacking the hydrocarbon C-H bonds.  3  Recent work by Grinstaff et al., however, demonstrated that the oxidations involve the 15  decomposition of organic peroxides by Fe-porphyrins via a radical-chain mechanism (Figure 5.7). The inhibition of any oxidation in the presence of 0.01 M BHT, as well as the >99% selectivity for the tertiary C-H bond, led to the conclusion that the main reaction pathway was a free-radical one.  15  Also, computer simulation studies based on free-radical  177  References on p. 187  Chapter 5  propagation of oxidation via Fe(porp) decomposition of hydroperoxides closely accounted for the actual experimental observations.  16  ROH  — M — = metalloporphyrin  Figure 5.7.  Radical-chain mechanism for the oxidation of alkanes via peroxide decomposition catalyzed by Fe-porphyrin species. Adapted from Ref 15. Ru(TDCPP-Cl ) species can be considered to undergo similar chemistry, catalyzing the decomposition of hydroperoxides. g  178  References on p. 187  Chapter 5  In the present study, (1) and (2) are also effective in initiating the 02-oxidation of methylcyclohexane at 90 °C via a radical-chain pathway, likely via a mechanism similar to the one proposed by Grinstaff et al. (Figure 5.7).  15  The results for the methylcyclohexane  oxidation catalyzed by (1) and (2) are listed in Table 5.2. A blank study conducted at 100 °C under 1 atm 0 shows that the autoxidation gives only 0.67% oxidized products, which 2  are distributed between 57 % 1-methylcyclohexanol, 26% secondary alcohols and 17% ketones. The selectivity for oxidation at the tertiary C-H bond over secondary ones normalized on a per bond basis* is approximately 12.4 for the autoxidation within the the blank solution. When (1) or (2) is present, a similar tertiary bond selectivity of 13 ± 3 (average of the three runs involving (1) and (2) in Table 5.2) is observed. Hence, the presence of (1) or (2) does not have any effect on the selectivity of oxidation, and the role of Ru-porphyrin species in the oxidation likely involves the catalytic decomposition of organic peroxides, similar to that of Fe-porphyrins in the scheme shown in Figure 5.7. Although the systems containing (1) or (2) give the same distribution of products as that in the blank, the Ru-porphyrin species are clearly effective in promoting oxidation of the methylcyclohexane by about 10-fold (Table 5.2). Of note, when BHT (0.01 M) was added, (1) and (2) were completely ineffective in promoting the autoxidation of methylcyclohexane, this result being consistent with a free-radical mechanism.  + S 3 products * no. 3° C H bond = 1; no. 2° C H bonds = 10; bond selectivity = „ p * 100  £  179  2  r o d u c t s  References on p. 187  Chapter 5  60  60  u  .12 £Pi  o  £ -S o  C >D NO o  o  1/3  o P  +1  +1  t-  CN VI  o  t-i  -4—*  o o o  60  1  CO  1  1  CO L-  > o oe +1  •4->  00  o o m  CN  CO  > O  <u  3 o  3 co  1 — 1 +1 ON  ON'  e  o o  t_ T3  v> CN  ON  1—'  w  CD  CD 15  CL  I;  3  -S  CO  s  -*-*  CD  J 2  til NO  NO  CN  r. -1  o  vi  ON  IT)  ON  o r".  P O o o  ON  1  CO RJ  O CO «J  e CO  8  X>  g o  ON  i * •S  c 15  co  o  O  o  €^  o  CO  o  NO  vi  ^  CN  NO  NO  T3  c CD CD  t3  X>  CD  3 CO  u o NO  CN O ,—,  o  NO  V)  ° oo' o „  .22  V>  m  d 00  d NO  o  -t>  o o  ,__, 00 NO  o  , , <—'CN  d  NO ON  ON i , ON  VI  d  o  r_1  ON  d  ON NO  d  1  CX  •  (U  6a ^a. Cu  <a  o  vi r  _  r - 00 V)  d  vi  i  !  NO  o CN o o" m V) d  CN 1  V>  d  o  1  CN  CN m  V>  O  O vi v f p-J"  o O CN  ^  d ^ oo" rfr °\ v i o m  , ON  NO  cW  ^  x  '  o  t/3  ON  O c o  o  X!  »/-)  v>  T3  ii co  u  CQ  i-f CN  o  i  II J=  II J3  V)  i—i v>  1  CN r -  CN  180  CN <N  co  CO  O  cd  CD  3°  IT  co  0)  fc o o  +1 <o  CN  s£ o  o  a, >  •a ts  o  s a"  J3 U "u  O  •3 s  « to  00 ' S r~ O P o  i  ,  ON  O I-;  a>  •  18  O  o  <U C  vi  C«1  V)  d  X «J CO  e  o  c5  O  „ r<-> OO  o  CN  co"  CD  '+->  8 ^ S « 1  6  o  §  3  C —  O  U o -H  o o  o p o o «  c  1  CX CX u-  1  o T3  °- £ cna .2 o to  15 <u <u • o > c O-  _  co 4>  „  PM  B 3 H  References on p. 187  Chapter S  As a further test for catalytic activity, Ru (TMP)(0) (1.5 x 10' M) was added to VI  4  2  neat methylcyclohexane, and the solution heated at 93 °C under 1 atm 0 . At the end of 2  16 h, approximately 3.6 % of oxidation products were present, with product distribution (52 % 1-methylcyclohexanol, 9 % secondary alcohols, 34 % ketones and 5 % other products) similar to that shown for systems containing (1) or (2) (see Table 5.2). An important observation is that after 16 h the brown colour due to Ru (TMP)(0)2 was VI  completely bleached, and a small amount of black residue was present in the solution. In an attempt to increase the amount of the black residue formed, 5 mg Ru (TMP)(0)2 (10" VI  3  M) was added to 5 mL methylcyclohexane and the procedure was repeated; however, almost no oxidation occurred after 16 h, and the oxidation products accounted for approximately 0.1% of the total organics (~ 8 turnovers), an amount even less than that for the blank study (Table 5.2). Also in this case, by visual inspection the colour of Ru (TMP)(0) was still present and no black residue was formed. A similar experiment, VI  2  performed by adding 5 mg (1) (10" M) to 5 mL methylcyclohexane under corresponding 3  conditions, also showed negligible oxidation after 16 h. These "ineffective oxidation" experiments involving Ru (TMP)(0)2 and (1) VI  correspond to porphyrin concentrations of approximately 10" M, while experiments that 3  generated oxidation products have porphyrin concentrations that are 1 to 2 orders of magnitude more dilute. The reduced forms of the Ru-porphyrins, when present at higher concentrations, may react with the hydroperoxides to form Ru(porp)(0)2 species, rather 6  than decomposing them according to the scheme in Figure 5.7, and thus the radical-chain does not propagate (see below).  181  References on p. 187  Chapter 5  Ru(TMP) species are known to decompose hydroperoxides. Hansen studied the decomposition of cyclohexyl hydroperoxide catalyzed by Ru(porp) species (porp = TMP, TDCPP and TPP), and the following results are particularly relevant to the present 17  TDCPP-Clg system: i) the Ru (porp)(CO) precursors are initially oxidized to the n  corresponding Ru (porp)(0)2 species by the cyclohexyl hydroperoxide; ii) the VI  decomposition rate of the cyclohexyl hydroperoxide is almost linear for about 120 min, although ~ 90 % of the Ru(TDCPP) species are destroyed in about 30 min; iii) the use of the radical scavenger, galvinoxyl, slows the rate of decomposition of hydroperoxides to 54% that of the reaction without any added radical scavenger; and iv) ESR studies show that the system contains ESR-active species which give rise to g-values of 2.0023 and 2.35, with the latter suggested to belong to a Ru non-porphyrin species. In the present TDCPP-Clg system, an almost linear rate in the cyclooctene oxidation was observed (Figure 5.6), although > 70% of the Ru(TDCPP-Clg) species had been destroyed in thefirst24 h. This result suggests that Ru-porphyrin species are not solely responsible for the catalytic oxidation within the neat hydrocarbon systems; complementing this proposal are Hansen's studies, which suggest that Ru non-porphyrin 17  species are responsible, at least partly, for the decomposition of cyclohexyl hydroperoxide. Dioxoruthenium(VI) porphyrin species may act as initiators for oxidation via a radicalchain pathway (Eqs. 5.13 and 5.14, [Ru = Ru(porp)]) by initially producing R' (and thus RO2') radicals; in Chapter 4, the oxidation of tertiary alkanes by Ru (TMP)(0) was VI  2  RH  Ru \0) v  2  (5.13)  {/?II(0)(OH)}{R-}  {/?«(0)(OH)}{R-}  RU(0)(OH) + ( R '  182  fast  ROV)  (5.14)  References on p. 187  Chapter 5  discussed, and a homolytic C-H cleavage was proposed as a possible mechanism (Eq. 5.13). When the Ru(porp) (porp = TDCPP-Clg and TMP) concentrations are ~ 10" M, 3  which are ineffective in initiating any oxidation, the hydroperoxides formed (Eq. 5.14) may not be decomposed according to the scheme in Figure 5.7, but rather, the reduced Ru(porp) species react with the hydroperoxides preferentially to give the corresponding dioxo complexes. '  6 17  When the Ru(porp) concentrations are lower (10' to 10' ), the 4  5  systems become effective, operating via radical-chain pathways, for the oxidation of methylcyclohexane and cyclooctene; in these active systems, the destruction of the Ru(porp) species is noted. Hence, it is feasible that Ru non-porphyrin, decomposition 17  products, not Ru(TDCPP-Clg) species, are responsible for mediating the radical-chain pathways depicted in Figure 5.7. As the Ru(porp) species are clearly destroyed during the oxidations, the usefulness of the porphyrin ligands is questionable (see below). The black residue mentioned above is most likely RuC>2, but this as yet is unsubstantiated; demetallation of Ru-porphyrin species to give Ru0 under oxidizing 2  conditions has been demonstrated in this laboratory. It is difficult to increase the amount 18  of Ru-porphyrin to give more decomposition product as the metalloporphyrin itself, when present at a higher concentration, inhibits the oxidation (and the demetallation seems to occur as the oxidation progresses). Of note, the essentially insoluble RuCl »3H 0 (5 mg, 3  2  -20 pmol, in 5 mL methylcyclohexane at 90 °C under 1 atm 0 for 20 h) gives 2  approximately 2% oxidation products for the methylcyclohexane system [35 % 1methylcyclohexanol, 5.4 % secondary alcohols, 29.3 % ketones and 30.3% other products; cf. Table 5.2]. It is plausible that some RUCI3 is oxidized to Ru0 under the 2  183  References on p. 187  Chapter 5  above conditions, and the dioxide in turn can catalyze the generation and decomposition of hydroperoxides similar to a recently used RuCl /aldehyde/saturated hydrocarbon 023  oxidation system, where the formation of high-valent Ru-oxo species was invoked. In 19  this thesis work, RuCl »3H 0 and Ru0 2H 0, although essentially insoluble in neat #  3  2  2  2  cyclooctene, were also found to be effective in catalyzing the oxidition of the alkene: after 16 h at 92 °C, the RuCl »3H 0 system gave an 8% conversion (with 72% epoxide 3  2  formation), while the Ru0 2H 0 system gave a 16% conversion; after 56 h, the latter #  2  2  system showed almost 80% conversion (with 86% epoxide formation). At room temperature (24 °C) under 1 atm air, the aerobic oxidation of Ph CH to 3  Ph COH in benzene catalyzed by (2) is similar to that catalyzed by Ru (porp)(0) species VI  3  2  (porp = TMP and TDCPP) (Section 4.4). Figure 5.8 shows the progress of the aerobic oxidation of Ph CH catalyzed by (2). The catalytic activity is marginal, and at the end of 3  20 d three turnovers are realized. As BHT (0.01 M) does not inhibit the oxidation, the mechanism most likely does not involve hydroperoxide decomposition, and is presumably similar to that described for the TMP and TDCPP systems (Chapter 4).  184  References on p. 187  Chapter 5  5.6  Conclusions That Ru(TDCPP-Clg) species can catalyze 0 -oxidations of hydrocarbons via a 2  radical-chain propagation pathway is clearly demonstrated in this chapter; however, the Ru-porphyrin species are completely destroyed in the methylcyclohexane system, as the colour of the Ru-porphyrin is completely bleached. For the neat cyclooctene system ~ 70% of the initial porphyrin most certainly disappears after 24 h. Among the oxidations discussed in this chapter, the oxidation of alcohols to aldehydes or ketones in benzene catalyzed by (2) appears to be the only efficient oxidation  185  References on p.  187  Chapter 5  that proceeds via a high-valent oxoruthenium species. The Ru(TMP and TDCPP) systems were well-studied (Chapter 4) and the activity of Ru (TDCPP-Cl )(0) resembled that of v,  8  2  the TMP analogue. The exclusive production of benzaldehyde from benzyl alcohol without further oxidation to benzoic acid, as well as the fact that BHT has no effect on the catalysis, suggest a process not involving a radical-chain pathway. The higher activity of (2), over that of the TMP and TDCPP analogues (Chapter 4), in catalyzing the aerobic oxidation of 1-phenylethanol suggests that (2) may be potentially more useful in the oxidation of other alcohols.  186  References on p. 187  Chapter 5  References 1  P. Ochsenbein, K Ayougou, D. Mandon, J. Fischer, R. Weiss, R. N. Austin, K. Jayaraj, A. Gold, J. Terner and J. Fajer, Angew. Chem. Int. Ed. Engl. 33, 348 (1994).  2  a) J. P. Collman, C. E. Barnes, P. J. Collins, T. Owaza, J. C. Galluci and J. A. Ibers, J. Am. Chem. Soc, 106, 5151 (1984). b) H. Masuda, T. Tagu, K. Osaki, H. Suzimoto, M. Mori and H. Ogoshi, J. Am. Chem. Soc, 103, 2199 (1981).  3  a) J. E. Lyons and P. E. Ellis, Catal. Lett., 8, 45 (1991). b) P. E. Ellis and J. E. Lyons, Coord. Chem. Rev., 105, 181 (1990). c) J. E. Lyons and P. E. Ellis, Catal. Lett., 3, 389 (1989).  4  T. P. Wijesekera and D. Dolphin, in Metalloporphyrins in Catalytic Oxidations, ed. R. A. Sheldon, Marcel Dekker, Inc., New York, p. 218, 1994.  5  a) E. R. Birnbaum, W. P. Schaefer, J. A. Labinger, J. E. Bercaw and H. B. Gray, Inorg. Chem., 34, 1751 (1995). b) E. R. Birnbaum, J. A. Hodge, M. W. Grinstaff, W. S. Schaefer, L. Herding, J. A. Labinger, J. E. Bercaw and H. B. Gray, Inorg. Chem., 34, 3625 (1995).  6  N. Rajapakse, B. R. James and D. Dolphin, Stud. Surf. Sci. Catal, 55, 109 (1990).  7  C. J. Ware, M. Sc. Thesis, University of British Columbia, 1994.  8  S.-I. Murahashi, T. Naota and N. Komiya, Tetrahedron Lett, 36, 8059 (1995).  9  P. Dubourdeaux, M. Taveres, A. Grand, R. Ramasseul and J.-C. Marchon, Inorg. Chim. Acta., 240, 657 (1995).  10  J. T. Groves and R. Quinn, Inorg. Chem., 23, 3844 (1984).  11  N. Rajapakse, Ph.D. Dissertation, University of British Columbia, 1990.  12  a) C.-M. Che and W. H. Leung, J. Chem. Soc. Dalton Trans., 2932 (1991). b) W. H. Leung and C.-M. Che, J. Am. Chem. Soc, 111, 8812 (1989).  13  a) F. R. Mayo, Acc. Chem. Research, 1, 193 (1968). b) D. E. Van Sickle, F. R. Mayo and R. M. Arluck, J. Am. Chem. Soc, 87, 4824 (1965). c) F. R. Mayo, J. Am. Chem. Soc, 80, 2497 (1958).  14  I. S. de Roch and J. C. Balaceanu, Bull. Soc. Chim. Fr., 1393 (1964).  187  References on p. 187  Chapter 5  15  M. W. Grinstaff, M. G. Hill, J. A. Labinger and H. B. Gray, Science, 264, 1311 (1994).  16  J. A. Labinger, Catal. Lett., 26, 95 (1994).  17  a) C. B. Hansen, Ph.D. Dissertation, Utrecht University, Netherlands, 1991. b) C. B. Hansen, F. P. W. Agterberg, A. M. C. van Eijndhoven and W. Drenth, J. Mol. Cat., 102,117(1995).  18  B. R. James, S. R. Mikkelsen, T. W. Leung, G. W. Williams and R. Wong, Inorg. Chim. Acta, 85, 209 (1984).  19  S.-I. Murahashi, Y. Oda and T. Naota, J. Am. Chem. Soc, 114, 7913 (1992).  188  References on p. 187  Chapter 6  Chapter 6 Preliminary Work: Reactions of Ru^CTMPKO^ with HX Acids and Oxidation of Phenol and A^-Dimethylaniline  189  References on p. 235  Chapter 6  6.1  Introduction The formation of Ru (TMP)(X) species (X = Cl, CF COO and CHCl COO) from IV  2  3  2  the reaction represented in Eq. 6.1 (reaction not balanced) [Ru - Ru(TMP)] was /fo^(0) + excess HX  b e n z e n  2  -  Ru (X)  (6.1)  W  2  discovered in the course of this thesis work. The effects of acids and bases on the rates of oxidation of alcohols (Chapter 4) were examined, and the above-mentioned acids were found to react with Ru (TMP)(0) (1) instead of giving a possible rate enhancement VI  2  effect, as observed for the BaRuOs/HOAc and Ru(porp)/pyridine-JV-oxide systems used 1  2  for the hydroxylation of hydrocarbons. Some preliminary data on the characterization of these Ru (TMP)(X) species are discussed in this chapter; they are unexpected products IV  2  and are characterized mainly in situ. Preliminary studies have been carried out earlier in this laboratory on the stoichiometric oxidation of phenol by (1), and the Ru-porphyrin product was thought to be a bis(hydroquinoxo)ruthenium(IV) species. The mechanism represented in Eqs. 6.2 to 3  6.4 was proposed based on the evidence available at the time [Ru = Ru(TMP)].  fli^O),  + C H OH -£T5w 6  /f« (0)(p-HOC6H OH)  (6.2)  IY  5  4  (1)  (2)  /?a (p-HOC6H40H)(0) +C H OH IV  6  TasT"  5  ^ V H O C e r L j O H ^  (2)  (3) 1  /?«V-HOC H40H) 6  (6.3)  2  fast  + JO2  /?« 0?-OC H4OH) + H2O IV  6  (3)  2  (6.4)  (4)  190  References on p. 235  Chapter 6  While the intermediate (2) [or the analogous Ru (TMP)(0)] was not observed, *HIV  resonances characteristic of Ru (TMP) and Ru^TMP) species, tentatively formulated as n  (3) and (4) in Eq. 6.4, respectively, were observed under anaerobic conditions in an approximately 2:3 ratio. Under 1 atm O2 or air, only 'H-resonances due to the 3a  paramagnetic Ru (TMP) species (4) were detected. This phenol system is re-examined, IV  and compared to the chemistry of Ru(TMP) species within the phosphine and alcohol systems (Chapters 3 and 4). The use of TV.JV-dimethylaniline as a mono-substituted aromatic substrate seemed a logical step in testing the reactivity of (1), and preliminary work showed that (1) oxidizes iV,iV-dimethylaniline to /?-hydroxy-A/,./V-dimethylaniline both stoichiometrically, and in the presence of air, catalytically.  6.2  Experimental: Sample Preparation and Data Analysis The reactions of (1) with FfX acids (X = CI, CF COO and CHCl COO) were 3  2  studied in situ by 'H-NMR, ESR and UV-visible spectroscopies. Ru (TMP)(CF COO) IY  3  2  (5) was isolated and subjected to mass (by FAB ionization) and elemental analyses. Ru (TMP)(MeCN) (10 mg, 0.01 mmol) was dissolved in air in 5 mL benzene until the n  2  aerobic oxidation to (1) was complete (< 30 min). Subsequently C F 3 C O O H (10 pX, 0.13 mmol) was added, when an instantaneous darkening (from brown to dark green) of the solution was observed. After 10 min the solvent and excess acid were removed by pumping under vacuum, and the solid (5) that remained was dried at 100 °C under vacuum for a further 24 h. Ru (TMP)(CHCl COO) (6) was prepared in situ in benzene IV  2  191  2  References on p. 235  Chapter 6  (1 mL) in an NMR tube by adding CHC1 C00H (1 pL, 0.012 mmol) to (1) (formed from 2  the aerobic oxidation of Ru (TMP)(MeCN) , 0.001 mmol), when an instaneous darkening n  2  of the solution was observed. After 10 min, the solvent and excess acid were removed under vacuum at room temperature for 12 h. Toluene-dg (1 mL) was then vacuum transferred to the NMR tube containing (6), which was used in ^ - N M R experiments (see later, Figures 6.6, 6.8 and Table 6.2). A sample of (5) for NMR studies was prepared in the same way as that for (6); however, the solvent and excess CF COOH were removed 3  with heat (100 °C) under vacuum, instead of at room temperature. This sample did not exhibit any characteristic TMP 'H-resonances, implying that compound (5) had decomposed. Subsequently, (5) was prepared in situ by adding C F 3 C O O H (1 pL, 0.013 mmol) to (1) (from bis(MeCN) precursor, 0.001 mmol) in toluene-dg (1 mL) under 1 atm air, and the excess acid was not removed. Attempts to purify compound (5) by column chromatography were unsuccessful, as the compound moved down the column in streaks using either benzene or CH C1 as the eluent. Elemental analysis of (5), compared with 2  2  the theoretical formulation as Ru (TMP)(CF COO) , gave the following data: IV  3  2  Analysis, calculated for CeoHs^CvFgRu Found  C, 65.03; H, 4.73; N, 5.06 C, 57.21; H, 4.92; N, 5.13.  Mass spectral analysis of (5) (FAB ionization in a 3-nitrobenzylalcohol matrix) showed the following ion mass peaks: [Ru(TMP)(CF COO) ] at 1108, [Ru(TMP)(CF COO)f at +  3  2  3  995 and [Ru(TMP)] at 822 amu (see Figure 6.1). Afrozenbenzene solution of (5) at +  110 K did not show any ESR signals, suggesting that Ru(III) or Ru(V) species are absent. The kinetics of the stoichiometric oxidation of phenol by (1) in benzene were monitored by UV-visible spectroscopy, using an HP 8452A Diode-Array instrument for  192  References on p. 235  Chapter 6  experiments involving [phenol] < 0.1 M and a stopped-flow spectrophotometer for [phenol] values between 0.1 and 1.0 M. The experimental setup, sample preparations and data analysis for the phosphine oxidations have been described in Sections 2.2.2 and 3.2, and these procedures are equally applicable to the phenol oxidation kinetics monitored on the stopped-flow instrument. For the kinetic experiments using the HP 8452A instrument, phenol solutions (1.00 mL) of the appropriate concentrations (0.001 to 0.1 M) were prepared in benzene and added to a UV-visible quartz cell (1 cm path-length), which were then equilibrated thermally at 20 + 1°C. After 10 min, appropriate volumes of a benzene solution containing (1) (~10" M) were added to the cell to arrive at diluted concentrations 3  of ~ IO" M, and the kinetics were monitored over the 340 - 650 nm range. Figure 6.2 6  shows a typical isosbestic set of spectra acquired during a kinetic run (0.0943 M phenol; (1) 5 x IO" M; 1 atm 0 at 20 °C). The values of the pseudo-first-order rate constants, 6  2  kobs,  were derived from the absorbance changes at the Soret maximum for (1) at 422 nm  for all the kinetic experiments. The kinetic data and kobs values are tabulated in Appendix F. The reaction of (1) with A^N-dimethylaniline under 1 atm air or 1 atm Ar was studied in situ by 'H-NMR spectroscopy. The Ru-porphyrin product from the reaction of (1) with A^N-dimethylaniline in benzene-di; under air was isolated by pumping off the solvent (see also Section 6.5), and the solid that remained was analyzed by mass spectrometry (Figure 6.3). The data from the mass spectrum suggest a mixture of compounds to be present (see later, Section 6.5). The catalytic oxidation of N,Ndimethylaniline in benzene employed the same procedure as that used for the alcohol oxidations, which has been described previously in Sections 4.2 and 5.2.  193  References on p. 235  Chapter  Chapter 6  Chapter 6  100—1  3-Nitrobenzylalcohol Matrix  t iV r \ 100  i .1 '| "i1 I  i—i—i——i—r^l—i—(-1—i  200  300  400  500  600  [Ru(CO) + 2H]+  [Eu]+/  Relative intensity  i  882  i  ' i r 1  700  i j i 800  T-  /  [&y(U)]+  l  1003  912  |  fML2)]+  '  ^|019  I  1  I  1 1 1 1  1200  1300  100—i  Thioglycerol Matrix  T 100  4  I  1  I  i 300  400  1 1  '  500  1  I ' '" 600  100-  [Ru]+  [Ru(CO) + 2H]+  882 ^  L 0  ^ rRu(L2) H] +  0  +  +  ,1020  Ai s  0—' 700  too  i*f *t 'i*  900  1000 1000  .  I  1 1  r t | i—r • i • 1200 i-  1  1  I 1300  1100  M/Z  Figure 6.3  Mass spectra of solid sample isolated from the reaction between Ru (TMP)(0) and /V-dirnethylaniline in benzene-ak under 1 atm air. The results suggest a mixture of Ru (TMP)(/?-NMe2-C6H -X) species, where X = H (Ll) and OH (L2), to be present. (FAB ionization of the compound supported in (a) 3-nitrobenzylalcohol and (b) thioglycerol matrices). See also Section 6.5. VI  2  n  4  196  References on p. 235  Chapter 6  6.3  R u ( T M P ) ( X ) Species IV  2  Ru (TMP)(X) species (X = Cl and Br) have been synthesized and characterized IY  2  previously in this laboratory. The preparation of these compounds follows the scheme 4  represented in Eq. 6.5 [Ru = Ru(TMP) and X = Cl or Br]. The presence of air or 0 has 2  /?« (MeCN) + excess HXanhydrom/benzene n  1 W C C  2  »  Ru (X)  (6.5)  IV  2  been noted to accelerate the rate of the reaction as depicted in Eq. 6.5, if the air or 0 is 2  introduced into the system after the FIX has been added. Recently the formation of 4b  Ru (TMP)(Cl) , via the reaction of Ru (TMP)(0) (1) with anhydrous HC1 in benzene, IV  VI  2  2  was reported, and it was found independently during the course of this thesis work that 2  exposure of a benzene solution of (1) to gaseous HC1 or 12 M aqueous HC1 gives Ru (TMP)(Cl) quantitatively, the reaction being complete within a few minutes at room IV  2  temperature, as evidenced by 'H-NMR and UV-visible spectroscopies. Furthermore, the addition of the strong organic acids, CF COOH and CHCl COOH, to benzene solutions of 3  2  (1) produces rapid changes in the UV-visible spectra (Figure 6.4); the expected products are bis(substituted-acetato)-Ru(IV) complexes (see below). Of note, the oxidation products in the reactions between (1) and HX, presumably derivedfromthe acids themselves, are presently unknown; one way to balance reaction 6.1 is to consider H 0 2  2  as the oxidation product [Eq. 6.6; /?«=Ru(TMP)], but this is unlikely chemically. ^11^(0)2 (1) + 2 HX  • Ru (X) w  2  197  + H 0 2  2  (6.6)  References on p. 235  Chapter 6  0.18T  402  nm  0.16"  CHCl COOH added 2  0.14-• (b)  400  350  Figure 6.4.  500 450 Wavelength (nm)  600  550  650  UV-visible spectra of Ru (TMP)(0) , (1), in 1 mL benzene at 25 °C followed by the addition of 5 pL (a) CF COOH and (b) CHCl COOH. [(1)] = 6.4 x 10" M in (a) and 1.1 x 10" M in (b). VI  2  3  7  6  2  198  References on p. 235  Chapter 6  The 1000 cm" region in the IR spectra of Ru(TMP) complexes contains what is 1  known as the "oxidation state marker", the name arisingfromthe strong IR signal which varies depending upon the oxidation state of the ruthenium centre. This property has been used by other workers ' to demonstrate a change in the oxidation state of the Ru within 5 6  Ru-porphyrin complexes; however, the IR database has been somewhat limited to a few complexes. Earlier work carried out in this laboratory led to the preparation of a variety of alkoxo (Chapter 4), alkyl and haloruthenium(IV and III) TMP complexes, and thus a 4  larger number of complexes has become available andfirmercomparisons may be drawn (Table 6.1, see also Figures 6.9 and 6.10 later). The TR datafromTable 6.1 are consistent with assigning an oxidation state of 4+ for the Ru-centre in the proposed bis(acetato)ruthenium(IV) species. A sample of (5), generated in situfromthe reaction of (1) and excess CF COOH in benzene-c/6 for 'H3  NMR experiments, exhibits a solution magnetic susceptibility value of p ff = 2.5 p e  B  measured by the Evan's method. The p ff value suggests a Ru(IV) S = 1 spin state. 7  e  The ^ - N M R spectrum of (5) in toluene-c/ is shown in Figure 6.5 and that of the 8  CHCI2COO analogue, Ru (TMP)(CHCl COO)2 (6), in Figure 6.6. Single w-H and o-Me IY  2  'H-resonances of the TMP ligand in (5) and (6) are indicative of these species possessing Z) symmetry, ' and coordination of two acetate ligands would give the observed single 3 4  4h  w-H and o-Me ^-resonances. The F-NMR spectrum of (5) (Figure 6.5 inset) clearly 19  indicates the presence of coordinated CF COO at 5 25.4. The upfield-shifted /2-pyrrole 3  'H-resonances at -61.10 for (5) and -63.33 ppm for (6) at -290 K are reminiscent of those of the paramagnetic Ru (TMP)(X) (X = Br and Cl ) complexes. IV  4a  4b  2  199  References on p. 235  Chapter 6  Table 6.1.  IR absorptionfrequenciesfor some Ru(TMP) complexes in the 1000 cm" region. IR Absorption Frequency (cm ) 1000*  Reported Source  1001(1003)*  this thesis (Groves et al. )  1000  Huang etal.  1004  Huang etal.  1005  this thesis  1004  this thesis  Ru (TMP)(0)  1011*  Groves etal.  Ru^CTMPXO'POz  1010  this thesis  Ru (TMP)(OEt)  1010(1011)  this thesis (Leung et al. )  6  1007  this thesis  Ru^TMPXMe)/  1007  this thesis  Ru (TMP)(Ph)  1007  this thesis  1011  this thesis  1011  this thesis  1016  Huangef a/.  Ru (TPP)(0)(NH 'Bu)  1016  Huang et al.  Ru (TMP)(0)  1019*  Groves etal.  Ru (TPP)(0)  1017  Leunge/a/.  1019  Huang etal.  Ru(TMP) species  0  1  Ru (TMP)(PPh ) n  3  Ru (TMP)(MeCN) n  2  Ru (TPP)(NH T3u) n  2  2  Ru [(MeO)i TPP](NH 'Bu) n  2  2  c  2  Ru (TMP)(NH )(Cl)  d  Ru (TMP)(NH )(Br)  d  ra  3  m  3  IV  IV  Ru^fTMPXCl)/  IV  2  rf 2  Ru (TMP)(CF COO) IV  3  2  Ru^TMPXCHC^COO)/ Ru [(MeO)i TPP](0)(NH 'Bu) IV  2  c  2  IV  2  VI  2  VI  2  Ru [(MeO) TPP](0) VI  12  c 2  Groves etal.  5  5  6a  60  5  6b  6c  6c  5  6a  6a  " IR spectra in this thesis are obtained in Nujol mulls in KBr plates, unless indicated otherwise. IR spectra reported by other workers are in Nujol mulls, unless indicated otherwise. * Solution IR in benzene. (MeO)i TPP = dianion of /weso-tetra(3,4,5-MeO-phenyl)porphyrin. These compounds were prepared by Dr. C. S. Alexander (Ref. 4b) of this laboratory. Prepared by the reaction of (1) with HCl . IR spectrum obtainedfroma benzene solution, which was dried on a KBr plate, initially containing (1) and added CHCl COOH (see Section 2.2.3). 0  2  d  e  (g)  f  2  200  References on p. 235  Chapter 6  202  References on p. 235  Chapter 6  Ru^TMP) paramagnetic species delocalize the spin density to the empty 4e(7i*) orbitals 4  on the porphyrin through Ru(dxz,yz) -> porpfjr*) charge transfer. This interaction is 8  reflected in the inverse temperature dependence of the 'H-chemical shifts within the TMP ligand, with the y9-pyrrole ^-resonances within Ru (TMP) species varying most IV  noticeably with temperature. '  3 4  The 'H-chemical shifts of the TMP ligand in (5) and (6) vary with inverse temperature (see Figures 6.7 and 6.8), suggestive of a single spin state for (5) and (6) over the observed temperature range. Of interest, the m-H and o-Me ^-resonances are more strongly temperature-dependent, as well as being much more downfield-shifted than those of the analogous Ru (TMP)(X) complexes (X = Cl, Br; Table 6.2). In contrast, the 'HIV  2  resonances of the TMP ligand in Ru (TMP)(OR) species (R = C H and *Pr) are IV  3  2  6  5  relatively temperature-insensitive except those for the /^-pyrrole hydrogens. The CO stretching frequencies for the acetate groups within (5) and (6) show that the coordinated acetates have vco values shifted to lower wavenumbers than those of the correspondingfreeacids. In (5), v o = 1670 cm" with a weaker shoulder at 1709 cm", 1  1  C  while for thefreeacid Vco  =  1783 cm" (Figure 6.9). In (6), Vco 1  weaker shoulder at 1667 cm* , while for thefreeacid vco 1  =  =  1648 cm" with a 1  1732 cm" (Figure 6.10). 1  An acetate ligand is expected to give two v o absorptions (vc=o and v -o), and the C  C  difference between the two reflects its bonding mode within the complex. For example, the difference between the two v o absorptions for thefreeCH COO" ion is 144 cm' , and 1  C  3  a coordinated CH3COO" is considered to be V-monodentate if the difference between the  203  References on p. 235  Chapter 6  40  Figure 6.7.  Inverse temperature plot, 'H-chemical shifts (300 MHz) versus T for Ru (TMP)(CF COO)2 (5) in toluene-dg (same sample as for Figure 6.5). 1  IY  3  204  References on p. 235  Chapter 6  Figure 6.8.  Inverse temperature plot, 'H-chemical shifts (300 MHz) versus T for 1  Ru (TMP)(CHCl COO)2 (6) in toluene-d (same sample as for Figure 6.6) IY  2  8  205  References on p. 235  Chapter 6  Table 6.2.  Observed variable temperature 'H-NMR chemical shifts" for selected Ru (TMP)(X) species. rv  2  Ru (TMP)(X) X= Ct* IV  Br  2  fc  0'Pr  c  CF COO (5)  e  3  Temp. (Kf  /2-pyrrole H  meta-H*  ortho-Mt  para-Me  223.55 274.65 291.15  -79.75 -59.35 -55.42  14.44 12.82 12.50  4.41 3.93 3.83  4.71 4.19 4.07  204 243 303  -63.29 -54.22 -43.24  16.20 14.69 13.15  5.37 4.84 4.27  4.93 4.40 3.88  213.15 253.15 293.15  -13.22 -12.70 -11.92  7.79 7.69 7.59  3.12 3.10 2.90  3.35 3.10 2.91  213.15 253.15 298.15  -45.44 -36.88 -29.89  8.13 7.87 7.60  3.69 3.15 2.79  3.49 3.19 2.98  216.05 236.25 256.65 277.15 292.45  -76.44 -73.30 -69.61 -64.53 -61.10  32.62 27.27 23.13 21.33 20.25  10.82 8.92 7.55  4.93 4.58 4.29 4.12 4.00  h  6.72  _ 4.67 8.09 25.46 215.95 4.37 22.40 236.15 -81.41 4.16 6.66 -74.20 20.77 256.15 4.02 19.55 6.36 276.25 -67.38 6.16 3.92 18.79 290.45 -63.33 " In toluene-fifo; data acquired on a 300 MHz instrument. Selected data for X = Br and CI from Ref. 4a and 4b, respectively. Selected data from Ref. 3 a. This species is shown in the present thesis work to contain OCoHs axial ligands, rather than/7-OC6H4OH ligands (see Section 6.4.1). [(5)] = 1.0 x 10" M in situ, [CF COOH] = 1.5 x 10" M, in toluene-dg under 1 atm air (see Section 6.2). [(6)] = 1.0 x 10" M in situ, under vacuum without any excess acid (see Section 6.2). * Uncertainty in T = ± 0.5 K. * Single ^-resonance indicates £> symmetry for these Ru(TMP) species.  CHCl COtf (6) 2  b  c  d  e  3  2  3  f  3  4h  206  References on p. 235  Chapter 6  T  50  40  V  •1 I.'  I  •  1  (a)  %T  30  1783 cm"' Free CF COOH 3  i  I  20  1800  1600  1400  1200  1000  800  ^11.  50  1  /  40  (b)  %T 30  20  t rJ  7/ \  1  's  r .1  A  I  ,".' I;i  :'  J  ty  V  1709 Coordinated 1670 CF COO  1011 "Oxidation State Marker"  3  10  1800  1600  1400  1200  1000  80cT  Wavenumber (cm ) 1  Figure 6.9.  Infrared spectra of (a) free C F 3 C O O H and (b) RiT (TMP)(CF COO) (5), obtained as Nujol mulls in KBr plates. 3  207  2  References on p. 235  Chapter 6  A  60  \i M^/  %T (a)  50  i 1  40 .-1 1732 cm" Free CHCl COOH 2  1500  2000  1000 .' II!  70  11  (b)  I I  II  ion  65  Free  55  '  Oxidation State Marker"  %T 60  '.  CHCl COOH J 1732 V 2  il !  I  I  I  1667 1648 Coordinated CHCl COO 2  2000 1800  1600 1400 1200  1000 800  Wavenumber (cm ) Figure 6.10. Infrared spectra of (a) free CHCl COOH and (b) Ru (TMP)(CHCl COO) (6), obtained as Nujol mulls in KBr plates. 1  2  IV  2  2  208  References on p. 235  Chapter 6  two Vco absorptions is lower than that of the free acetate, and r| -bidendate if the 2  difference is larger. Ru(CH COO) (CO) (PPh )2, with V-acetate ligands, has v o 9  3  2  2  3  C  absorptions at 1613 and 1315 cm", corresponding to a difference of 289 cm"; 1  1  RuCl(CH COO)(CO)(PPh ) , with one r| -acetate, has v 2  3  3 2  c o  absorptions at 1507 and 1465  cm", corresponding to a difference of 42 cm" . Hence, a large difference between the two 1  1 9  Vco absorptions relative to that of the free acetate is indicative of V-monodentate binding mode for the acetate, and vice versa. Consideration of the steric constraints presented by the TMP ligand and the expected six-coordinate Ru(IV) centre in (5) and (6) imply the presence of r\ ^acetates; however, the IR data for (5) and (6) suggest ri -acetates, as 2  differences between the vco absorptions (main peak and shoulder) are 39 and 19 cm", 1  respectively. Nevertheless, an r| -binding mode would require both complexes to contain 2  the unlikely, eight-coordinate ruthenium centres. The solution magnetic susceptibility, MS, IR, H and F-NMR data all support the X  19  formulation of (5) as Ru (TMP)(CF COO) . The elemental analysis of (5) gives IV  3  2  agreeable values for H and N (Section 6.2); however, the extremely low C content, which cannot be explained, is not consistent with solvated acid, solvent or water, or the presence of axial ligands other than CF COO. The poor elemental analysis is likely due to 3  decomposition of (5) when the excess acid and solvent are removed with heat. Nonetheless, all the spectroscopic data point to the formulation of Ru (TMP)(X) IY  2  (X = CF COO and CHCl COO) for the Ru-porphyrin products from the reactions 3  2  between (1) and HX acids.  209  References on p. 235  Chapter 6  6.4  Oxidation of Phenol by Ru (TMP)(0)2  6.4.1  Stoichiometric Oxidation of Phenol  w  The stoichiometric and catalytic oxidations of phosphines (Chapter 3) and alcohols (Chapter 4) have been discussed, and a key step in both systems is believed to involve the disproportionation of Ru (TMP)(0) to Ru (TMP)(0) (1) and Ru (TMP). Also the IV  VI  n  2  reaction of Ru (TMP)(0) and H 0 to give Ru (TMP)(OH) (herein referred to as the IV  IV  2  2  reaction involving the "conversion to a bis(hydroxo) species"), followed by alcohol metathesis to form Ru (TMP)(OR) species, is implicated from the reaction conditions IY  2  required for the catalyzed 0 -oxidation of alcohols (Chapter 4). That Ru (TMP)(0) IV  2  prefers to react via disproportionation or conversion to a bis(hydroxo) species, rather than acting as an O-atom transfer agent is suggested in both the phosphine and alcohol systems; therefore, the initially proposed phenol oxidation mechanism (Eqs. 6.2 to 6.4) was re3  examined in this thesis work. In fact, experimental results now disfavour the successive two-step oxidation mechanism presented in Eqs. 6.2 to 6.4. Previous work in this laboratory showed that the reaction between (1) and phenol under 1 atm air gives 1 equivalent of a paramagnetic Ru (TMP) species, tentatively IV  formulated from ^ - N M R data as Ru^TMP^-OCeF^OH);, (4), 0.5 equivalent of p-benzoquinone and 1.3 equivalents of H 0 [Eq. 6.7, Ru = Ru(TMP)]; however, the 3  2  expected reaction stoichiometry according to the proposed mechanism (Eqs. 6.2 to 6.4) is shown in Eq. 6.8. Ru^Oh + xs C H O H -SIT.. Ru"'(p-OC H40H) 6  5  6  ( ! )  6  5  2  6  2  (6.7)  t .  < * )  (1) + 2 C H O H + \o  + 0.5 /?-OC H40 + 1.3 H 0  2  (4) + H 0 2  210  (6.8)  References on p. 235  Chapter 6 The successive two-step oxidation mechanism (Eqs. 6.2 to 6.4) can account for the formation of the suggested Ru-porphyrin product (4), but cannot adequately explain the formation of the /?-benzoquinone. Moreover, the data from the present thesis work, particularly the mass spectrum of (4) (Figure 6.11), show it to contain axial OCeH , rather 5  than /^-OCeFLjOH, ligands, and thus (4) is more favourably formulated as Ru (TMP)(OC H )2. In addition, the metathesis reaction between Ru (TMP)(0'Pr) and IV  JV  5  6  2  phenol (50-fold excess) in benzene-^ under 1 atm Ar gives a product with an in situ H 1  NMR spectrum identical to that obtained for isolated (4).* A small amount of product assignable to Ru (TMP)(p-OC6H OH)2 is formedfromthe metathesis reaction between rv  4  p-hydroquinone (1.5 x 10" M) and Ru (TMP)(0'Pr)2 (1 x 10" M) in benzene-</; the *H3  IV  3  6  chemical shifts (/?-pyrrole-H, -34.7; o-Me, 2.99; p-Me, 3.04; m-U, 7.55; axial ligand, 14.4, -21.6, -23.8)  (Figure 6.12) of the new compound are distinctively different from  those of (4)} Hence, (4) is now considered to be Ru (TMP)(OC H )2. Of note, the rv  6  5  preliminary work carried out in this laboratory included the attempted purification of (4) 33  by column chromatography, and the isolated compound gave elemental analysis data (C, 74.55; H,5.63;  OC H40H) 6  2  N, 5.11; 0, 5.40) which agreed with those calculated for Ru^TMP)^-  (C68H62N4RUO4;  C, 74.22; H, 5.67; N, 5.09; 0,5.82); those calculated for  Ru (TMP)(OC H )2 (CegHedS^uOz) are: C, 76.45; H, 5.85; N, 5.24; O, 3.00. IY  6  5  H-NMRdatafor(4)inbenzene-rf : >3-pyrrole-H, -30.5; m-H, 7.60; o-Me, 2.90; p-Me, 3.00; axial ligand, 49.7, -68.2, -71.9 (Chapter 4, Table 4.1). O f note, almost no p-hydroquinone is detected (Fig. 6.12), but some p-benzoquinone and (1) can be seen. /?-Hydroquinone is likely oxidized by (1), which can be reformed from the reaction of Ru (TMP)(0'Pr) with H 0 (Chapter 4). Although the metathesis reaction is not complete, the ' H signals assignable to Ru (TMP)(p-OC6H OH)2 clearly show that (4) is not the bis(hydroquinoxo) species. f  1  6  t  IY  2  2  IY  4  211  References on p. 235  Chapter 6  A  E  3  3  >  v 0>  1  c o <U on  8 2  c  £ S  E C  t8  U  O  o  •  L8  .  ©  o X  5x-J-  5\  - °  ^ D. « B <u  H. §  +-»  s  a o o o 03 o G  3  6  c o  &> J3 to  O  N  <U  >  •a o i o . j a-*5  " H  — i  2  5?V 11..i|i• i M i • • 111• M• •  • • •'• I  |• • • • |• • • • I 8  8 88R 88! 882  o t  1  t  |  ,\ 8 "  8 8 8 R 8 8 ? 8 8 2 »*  vo v u 3  M)  212  References on p. 235  Chapter  > o •8  t u  o oo  .2  ©  •a o 3  e  <<  CL  &  j-  oj  H  T3  u  5 o o  o o  r-'  p 00  ffi  SB  fS  s en  213  References on p. 235  Chapter 6  In the present thesis work, attempts to purifry (4) by the reported column chromatography procedure were unsuccessful in removing the />-benzoquinone product, and hence, 33  elemental analysis was not obtained for (4); however, the 'H-NMR data, the metathesis reaction and the mass spectral data all suggest (4) to be the bis(phenoxo) complex. The good elemental analysis determined for the supposed Ru (TMP)(p-OC6H40H)2, IV  particularly the oxygen content, was probably fortuitous, and might have resulted from /7-benzoquinone impurity; the compound could have been Ru (TMP)(OC6H )2 2H 0, IY  ,  5  which would give an elemental analysis  2  C, 73.96; H, 6.02; N, 5.07;  (C68H66N4RUO4;  O, 5.79) equally agreeable with that reported earlier. The phenol oxidation mechanism 33  needs to be reconsidered to account for the formation of the bis(phenoxo) species (4), as well as the production of /?-benzoquinone. The observed /?-benzoquinone is undoubtly formed via the oxidation of p-hydroquinone, which is initially producedfromthe oxidation of phenol by (1) via reaction 6.2. That (1) oxidizes, in fact catalytically under O2, />-hydroquinone to p-benzoquinone in benzene is demonstrated in separate experiments. Under 1 atm O2 with fc-hydroquinone] = 1.5 x 10" M and [(1)] = 5.5 x 10" M, 8 equivalents of 3  5  p-benzoquinone were produced in 20 min (0.4 turnover min"). Under 1 atm O2 with 1  [>-hydroquinone] = 1.5 x 10" M and [(1)] = 5.5 x 10" M, 200 equivalents of 3  6  /?-benzoquinone were produced when the benzene solution was analyzed by GC after 22 h. Of note, no noticeable continuation of the catalysis was observed in the solution after 22 h, possibly due to the deactivation or decomposition of (1) via some unknown pathway. Species (1) clearly catalyzed the 02-oxidation of/j-hydroquinone, as no  214  References on p. 235  Chapter 6  /?-benzoquinone was formed in the absence of (1) under corresponding conditions. The C»2-oxidation of/?-hydroquinone catalyzed by (1) is likely initiated by the reaction represented in Eq. 6.9 [Ru = Ru(TMP)], and Ru (TMP)(0) can then regenerate (1) via IV  disproportionation (Chapters 3 and 4). ^ ^ ( 0 ) 2 + P-HOC6H4OH  - Ru™(0)  + /J-OC6H4O + H 0  (6.9)  2  The reaction between (1) andp-hydroquinone (-1:2 ratio) under 1 atm air at room temperature was monitored by H-NMR spectroscopy, and after approximately 2 X  min, the spectrum showed that mainly (1) was present (Figure 6.13). Ru (TMP)(0) and IV  a Ru(II) species, possibly Ru (TMP)0-HOC6H40H) (~ 10%), can also be detected. At n  f  2  this time nofree/?-hydroquinone was present in the benzene-^ solution, implying that the oxidation of hydroquinone by (1) is rapid; furthermore, the - 90% reconversion to (1) suggests that the disproportionation of Ru (TMP)(0) [and the aerobic oxidation of the IV  Ru(II) species to (1)] is also fast (Chapter 3). No special precautions were taken to dry the benzene-ok solvent, and as such the H 0 stoichiometry in Eq. 6.9 cannot be 2  determined, although 1 equivalent of H 0 is expected to be present by mass balance. The 2  mechanism for the stoichiometric oxidation of/»-hydroquinone by (1) cannot be determinedfromthe current preliminary data; a hydride transfer mechanism analogous to that suggested for the alcohol oxidation (Chapter 4) is plausible, although two successive one-electron transfer/deprotonation steps can equally apply.  A /J-pyrrole-H signal at 8.5 ppm shows that a Ru (TMP) species is present in solution; however, the ' H - N M R data (Ref. 3a) for a Ru (TMP) species proposed as the bis^-HOCeKtOH) complex are different: y8^pyrrole-H, 8.64; o-Me, 2.50; p-Me, 1.70. As only the ^pyrrole signal at 8.5 ppm can be clearly observed, and the other signals are presumably buried beneath those of (1), the identity of the R u ( T M P ) species is unclear. After 10 min, only (1) and p-benzoquinone are present. f  n  n  n  215  References on p. 235  Chapter 6  216  References on p. 235  Chapter 6  The production of 0.5 equivalent of/^-benzoquinone, which cannot be explained by the scheme in Eqs. 6.2 to 6.4, provides a key insight into the phenol oxidation mechanism. The /?-benzoquinone was observed by both 'H-NMR spectroscopy * and in this thesis 3  work by gas chromatography experiments ([(1)] = 2.0 x 10" M and [phenol] = 5 and 83  fold excesses in the respective studies). Attempts to detect the intermediate /7-hydroquinone by GC analysis were unsuccessful. The ti/2 value for the reaction between phenol and (1) under NMR experimental conditions (~ 10" M and 10* M, respectively) is 2  3  approximately 16 min (estimated from kobs = 0.069 I V r V X 0.01 M = 0.00069 s" ), while 1  1  3  the ti/2 value for the reaction between /?-hydroquinone (~ 10' M) and (1) is approximately 3  0.1 min (a rough estimate of ti/2 of - 0.08 min is made using 5 ti/2 = 1 turnover = 0.4 min). That no /?-hydroquinone is detected by GC is certainly a consequence of the faster reaction of (1) with /?-hydroquinone than with phenol, and any /?-hydroquinone produced from the initial oxidation of phenol will be oxidized at a faster rate by any species (1) that remains in solution. In essence (1), a 2-electron oxidant, oxidizes phenol to pbenzoquinone via the /?-hydroquinone intermediate, which is a 4-electron process; this explains the formation of 0.5 equivalent of/?-benzoquinone for every equivalent of (1). A proposed mechanism for the oxidation of phenol involving the Ru (TMP)(0)/Ru (TMP)(OH) interconversion, the chemistry of which is consistent IV  IV  2  within that of the Ru(TMP)/alcohol systems (Chapter 4), is outlined in Figure 6.14;  217  References on p. 235  Chapter 6  Figure 6.14. Phenol oxidation mechanism based on the reversible interconversion of Ru (TMP)(0) to a bis(hydroxo) species and phenol metathesis reactions. The reaction of (1) and phenol produces /?-hydroquinone, which is further oxidized to /^-benzoquinone at a faster rate compared to the rate of the phenol oxidation. Disproportionation of Ru (TMP)(0) to (1) and Ru (TMP) is a competing pathway, and under anaerobic conditions, some Ru(II)-species can be detected (see text). IV  IV  n  218  References on p. 235  Chapter 6  according to the scheme, the overall reaction should produce 0.5 equivalent ofpbenzoquinone and 1.5 equivalents of H 0 [Eq. 6.10; Ru = Ru(TMP)]. The stoichiometry 2  of reaction 6.10 closely accounts for the experimentally observed 0.5 quinone and 1.3 H 0.  3  2  ^ ( 0 ) 2 (1) + | C H OH 6  / f c i ^ O C s H ^ + \ p-OCsFLO  5  +1 H 0 2  (6.10)  A Ru-porphyrin species formulated from ^ - N M R data as Ru (Tlvff )(p-HOC H40H) ( 3 ) has been observed in the reaction between ( 1 ) and excess n  6  2  phenol under anaerobic conditions; however, ( 3 ) only accounted for ~ 4 0 % of the 33  reaction products, with the other - 6 0 % being (4). The large percentage of (4) was explained within the successive two-step oxidation mechanism (Eqs. 6.2 to 6.4), with *  trace 0 being the cause for the formation of 2  (4).  3A  This is now considered unlikely  considering that the concentration of (1) was 4 x 10" M , and even with only one freeze3  3 a  pump-thaw cycle the system should not have contained enough dissolved 0 to give rise 2  to the large amount of observed (4). Furthermore, the fact that (4) is the bis(phenoxo) complex, not the bis(p-hydroquinoxo) complex as proposed initially, invalidates the above "trace 0 " explanation. The reaction of (1) and phenol under anaerobic conditions was 2  repeated in this thesis work, and the formation of (4) was always observed in excess of 90%, with ( 3 ) accounting for < 10% of the inorganic products. That (4) is produced even in the absence of 0 is inconsistent with the formerly 2  suggested mechanism (Eqs. 6.2 to 6.4). The production of (4) via the bis(hydroxo) species, within the present mechanism (Figure  6.14),  is expected to occur if H 0 is 2  present, and to inhibit the conversion to the bis(hydroxo) species is impossible, as the  219  References on p. 235  Chapter 6  oxidation reaction produces H 0. Even under initially dry conditions, the conversion to 2  the bis(hydroxo) species can occur once some FJ 0 forms, and subsequently (4) is 2  produced via the metathesis reaction with Ru (TMP)(OH) . Under anaerobic conditions, IV  2  the disproportionation of 2 Ru (TMP)(0) to (1) and Ru (TMP), followed by ligation of IV  n  p-hydroquinone and/or phenol to the Ru(II) centre provides a plausible explanation to account for the formation of the Ru(II) species (3). As the disporportionation pathway accounts for < 10% of the loss of Ru (TMP)(0) (see above), its contribution to the IV  reformation of (1) is insignificant; therefore, disproportionation is not considered to be one of the main reactions followed by the kinetics monitored for the loss of (1) (see Section 6.4.2)  6.4.2  Kinetic Studies When (1) (4 x 10" M) reacted with phenol (2 x 10" M) in benzene-<i under 1 atm 3  2  6  air or 0 , no other intermediates were observed in the H-NMR spectrum of the solution !  2  en route to the product (4).  3a  The kinetic data in the present thesis work for the  stoichiometric oxidation of phenol by (1) under 1 atm air at various temperatures are shown in Figure 6.15. The reaction is first-order in (1), as demonstrated by a linear semilog plot (inset of Figure 6.2); this first-order dependence is also confirmed, as the same kobs values are obtained with varying amounts of initial (1) at the same [phenol] value of 0.0381 M (see Figure 6.16 and Appendix F). The kinetic data are independent of 0  2  partial pressure, as kinetics obtained under 1 atm 0 or air were identical. Also, purging 2  the solutions with N for 10 min did not affect the kinetics (Appendix F). 2  220  References on p. 235  Chapter 6  0.90  T  [phenol] (M) Figure 6.15.  Plots of k o versus [phenol] for the oxidation of phenol by Ru (TMP)(0)2 (1) in benzene under 1 atm air at various temperatures. [(1)] ~ IO" M. kobs values are tabulated in Appendix F. Kinetic data were obtained on a stopped-flow spectrophotometer. VI  b s  6  i+  Stopped-flow data  [phenol] (M) Figure 6.16.  Plot of kobs versus [phenol] for the oxidation of phenol by Ru (TMP)(0)2 in benzene at 20.0 °C under 1 atm air, except for the point labelled "1 atm 0 ". [(1)] ~ IO" M. The raw data are listed in Appendix F. Kinetic data were obtained on the HP 8452A Diode-Array instrument, except for the point indicated as "Stopped-flow data". VI  6  2  221  References on p. 235  Chapter 6  The non-linearity in the plots of kobs versus [phenol] can be seen readily, illustrating a non-first-order dependence in phenol. Earlier preliminary work in this laboratory was carried out at a lower [phenol] region (up to 0.14 M) and less data were obtained. The 3  kinetic experiments were repeated in this thesis work at the lower [phenol] region (see Figure 6.16), and while the kobs values obtained at [phenol] = 0.0381 M agreed reasonably well with that obtained in the preliminary work, the other datafromthe earlier work clearly do not agree with those obtained in the present studies. This reason for this nonagreement is not known, but only the new curved-dependence data will be considered in the following discussion. The log(kobs) versus log[phenol] plots are linear with slopes averaging 1.51 ± 0.09 (Figure 6.17), which suggest a 3/2 order dependence in phenol. A log-log plot is generally somewhat misleading, as a reaction with ko goingfrom1st- to 2nd-order kinetics with bs  increasing added reagent (cf. Figure 6.15) might exhibit an average apparent order of 3/2; however, the plot for the data at 20 °C (Figure 6.17) is linear over 2 orders of magnitude of [phenol] values. The linearity of a log-log plot for a 1st- to 2nd-order dependence system is unlikely to extend over such a large concentration range (0.01 to 1.0 M), and hence the kobs expression may indeed take the form k o b s A.[phenol] (see Table 6.3). =  3/2  The curvature in the kobs versus [phenol] plots could possibly be ascribed to "solvent effects", as the [phenol] corresponds to ~ 10% molefractionfor the case of the highest concentration used; however, the curvature is considered to be real as the non-linearity starts at [phenol] values as low as ~ 0.04 M for the data at 20 °C.  222  References on p. 235  Chapter 6  Table 6.3.  Values for the parameter A for the oxidation of phenol by (1), derived from the expression kobs = A.[phenol] . The activation energy, AE*, is also calculated from the values of A from the Arrhenius plot (Figure 6 . 1 8 ) . 3/2  Temperature  A (lvr V) 3  1 0 . 2 °C  0.362  1 5 . 0 °C  0.425 + 0.03  ±0.03  2 0 . 0 °C  0.583  ± 0 . 0 4  3 0 . 5 °C  0.98  ± 0 . 0 7  AE* = 3 9 ± 2 k J mol" precollision factor" = (5.1 ± 0.3) x 1 0 s" Calculated at every temperature and then averaged. 1  6  223  1  References on p. 235  Chapter 6  ln(A) 0.0033 1  0.2 - -  0.0035 1  0.0034  T  0 --0.2 - T  -0.4 - -  1  < >-0.6Kl  -0.8 - -1 - -1.2 - Figure 6.18.  Arrhenius plot, ln(A) versus T" , for the parameter A for the reaction between (1) and phenol. The values for A are listed in Table 6.3. 1  According to the mechanism proposed in Figure 6.14, the following reaction pathways [Eqs. 6.11 to 6.15; ^i#=Ru(TMP)] are expected to play a role in the rate law for the phenol oxidation reaction. Ru (0) m  2  + C H OH 6  5  -A*  IV  ^(0)2  Ru (0) w  i y  4  k ==gj-  /?« (0)(p-HOC6H40H)  =  2  l  Ru (0)  6  (6.13)  2  (6.14)  Ru™(OH)  + H 0 = ^ 2  2  +C6H OH/-H 0 2  /?« (OH)(OC H ) IV  IV  6  5  C6H OH/+H 0 5  (6.12)  + /?-OC H40 + H 0  w  6  5  + p-HOCeFLOH  Ru \0)  ==  + /7-HOC H40H  /?K (OH)2  (6.11)  ^M (O)0?-HOC6H OH)  6H5QH ^11^(006^)2  +C  (6.15)  -H 0  2  2  The [(1)] values were ~ 10" M in 'H-NMR and GC studies (see earlier, Section 3  6.4.1), and the oxidation by (1) of the /?-hydroquinone formed (~ 10' M) was shown to be 3  224  References on p. 235  Chapter 6  faster than that of phenol (~10" M). In the kinetic studies, the [(1)] values were three 2  orders of magnitude lower (-10" M), while [phenol] values were higher (0.01 to 1 M); 6  therefore, the rate of oxidation of the /7-hydroquinone formed (~ 10" M) might not have 6  been faster than that of phenol. In addition, the reversible coordination and recoordination reactions of/?-hydroquinone (Eq. 6.12) may contribute to the overall rate law, as similar reactions with OPPh are found to be significant within the phosphine systems (Chapter 3  3). Clearly, more work is necessary to arrive at a rate law which can accommodate the experimental data, namely the curvature in the kobs versus [phenol] plots. The Arrhenius plot (Figure 6.18) for the parameter A gives an activation energy, AE*, of 39 ± 2 kJ moi" and a precollision factor of (5.1 ± 0.3) x 10 s". The paramter A is 1  6  1  presumably comprised of various rate constants and equilibrium constants for the reaction pathways (Eqs. 6.11 to 6.15), but they are still useful for indicating the general ease of the phenol oxidation reaction. The AE value is similar to the AH* value of 45 kJ moi" (which 1  1  corresponds to AE* ~ 48 kJ moi") for the 'PrOH oxidation by (1) (Chapter 4), implying 1  perhaps that cleavage of the aromatic C-H bond requires approximately the same energy as that for the a-C-H bond in 'PrOH.  6.5  0 -Oxidation of Av\-Dimethylaniline Catalyzed by R u ^ T M P K O ^ 2  Following the oxidation of phenol, other mono-substituted aromatics (N,Ndimethylaniline, methoxybenzene, toluene, chlorobenzene, bromobenzene and nitrobenzene) were tested as potential substrates. Only A^,A/-dimethylaniline, which contains the electron releasing NMe2 group, was oxidized by (1). Under 1 atm air the  225  References on p. 235  Chapter 6  oxidation of A,A-dimethylaniline is catalytic, producing a hydroxy-A^-dimethylaniline, as /  /  shown by GC-MS analysis (Appendix G), and the oxidation presumably occurs at the para position based on analogy with the phenol system (Section 6.4.1). Figure 6.19 shows the proposed scheme for the oxidation reaction.  Ru^TMP)(0) (1) 2  ^^-NMe  |  ^HO  2  NMe  2  Ru (TMP)(0) (2a) IV  + H2O H2O  Ru™(TMP)(OH)2 ^  " Ru^(TMP)(0-(f~yNMe2) +2H2O  Ru^TMP) — N =  +2N  X-^Qr-NMQ , 2  2N  \=/  (4a)  -  Ru (TMP)(N) n  2  (7)  where X = OH and/or H  d denotes a disproportionation reaction Figure 6.19. Proposed scheme for the oxidation of A^JV-dimethylaniline catalyzed by Ru (TMP)(0) (1) under 1 atm air. Trace H 0 was present, as the benzene-d was not dried; in any case FJ 0 is generated during formation of (4a) from (1). YI  2  6  2  2  226  References on p. 235  2  Chapter 6  Figure 6.20 shows the 'H-NMR spectra recorded on monitoring the reaction between (1) and  Af-dimethylaniline (1:4) in benzene-fife under 1 atm air. After 1 min,  Ru^TMPXO) was not detected, but 'H-resonances for the TMP ligand characteristic of those within a bis(alkoxo)-Ru(IV) species, (4a), were seen (o-Me, 2.99; p-Me, 2.90; m-H 7.60; yS-pyrrole-H, -22 ppm) (see Chapter 4, Table 4.1), and these are assigned to Ru (TMP)(/?-OC H NMe2)2. Of note, the axial /?-OC H4NMe2 ligand protons within (4a) tv  6  4  6  are not detected by 'H-NMR spectroscopy, while those of the OCeHs ligands within the analogous complex (4) (Table 4.1) are clearly detectable. The reason for the nondetection of the /7-OC H4NMe2 ligands is not substantiated; however, one factor for the 6  non-detection of the alkoxo ligand protons by 'H-NMR spectroscopy can be the rapid exchange of the alkoxo ligands with excess alcohol in solution (Section 4.3.1). The amount of species (4a) increases over time (Figure 6.20) and, unlike in the reaction between (1) and phenol, 'H-NMR signals corresponding to Ru(II) species (7) and a Ru(TMP)(CO) species (D) were observed as well after 30 min. After a total of 60 min, the benzene-fife solvent was removed under vacuum, and the solid residue was analyzed by mass spectrometry (Figure 6.3). Species (7) is thought to be a mixture of Ru (TMP)(p-NMe C H4X)2 species n  2  6  (where X = H or OH). The mass spectral data in Figure 6.3 suggest that Ru(TMP) species containing either one NMe2C H or one /?-NMe C H40H ligand are present, with 6  5  2  6  mass peaks at 1003 and 1019 amu, respectively. In solution, (7) is likely a six-coordinate, bis(amine)ruthenium(II) species, rather than thefive-coordinatecomplex suggested from the mass spectra. The sixth ligand is perhaps labile and readily dissociates when (7) is  227  References on p. 235  Chapter 6  benzene  1 minute  Legend: Ru = Ru(TMP) N =NMe C6H 1 =^(0)2 4a = Ru (p-OC6H4NMe2)2 7 =Rjj (N) 4a D = "Ru (C0)" see text U = Organic product accompanying the formation of D 2  IV  N  4a  5  4a  //  n  2  n  1  5 minutes  N 4a  Porphyrin 'H-resonances at 25 °C 7 D 4a ppm -22 8.30 8.66 8.36 7.60 Hn 1.67 2.99 2.18 2.08 1.88 1.85 2.90 2.41 Me,, -  4a  30 minutes  4a  i  4a  11.0 10.0  9.0  8.0  7.0  6.0  5.0  4.0  3.0  2.0  -22.0  ppm  Figure 6.20.  H-NMR (200 MHz) spectra for the reaction "Ru (TMP)(0) + 4 A^iV-dimethylaniline" in benzene-fife at 25 °C under 1 atm air. [(1)] = 2.0 x 10" M.  J  VI  2  3  228  References on p. 235  Chapter 6  I  1 minute  benzene  N  N  •  I • 9.0  '  '  •  .  I 8.0  1  I i 7.0  i  i  i  1  6.0  i  •  '  •  I  S.O  3.0  4.0  2.0  • i• 1.0  PPM  benzene N 10 minutes  N  J  '  I 9.0  1  '  '  '  1'  8.0  2a  2a 1  I • 7.0  1  '  •  I 6.0  '  5.0 PPM  I  1  '  '  4.0  '  I  1  '  3.0  u  '  '  1 ' ' 1  2.0  2a(p-pyrrole-H)  •  1  I '  -6.0  1  -8.0  N  benzene 20 minutes  N 2a 4a 2a(P-pynole-H)  • i •• ' •i ••' • i » •• • i • • • ' i v• ••i ••• •i• ' ••i • t.O  Figure 6.21.  •.0  7.0  6.0  S.S  4.0  S.O  (.0  i""  i -o.o  -a.o  'H-NMR (200 MHz) spectra monitoring the reaction "Ru (TMP)(0) + 10tyN-dimethylaniline"in benzene-* at 25 °C under 1 atm argon. [(1)] = 1.0 x 10" M. Refer to the legend in Fig. 6.20 for the identities of the observed Ru(TMP) species. 2a = Ru (TMP)(0). VI  2  3  IV  229  References on p. 235  Chapter 6  ionized by the fast atom bombardment ionization method in the MS experiment. In a separate experiment, Ru (TMP)(MeCN) was added to a benzene-ak solution containing n  2  excess AfN-dimethylaniline (aniline:Ru = 10:1), and ^-resonances corresponding to a new Ru(II) species were assumed to be those of Ru (TMP)(HMe C6H ) (yS-pyrrole-H, n  2  5  2  8.34; o-Me, 2.05; p-Me, 2.45 ppm; axial ligand protons were not observed, presumably due to rapid exchange of the ligands withfreeA/,7V-dimethylaniline); the data support the suggestion of (7) (/"-pyrrole-FL ~ 8.3 ppm; see Figure 6.20) as species containing coordinated NMe C H and/or />-NMe C H40H ligands. The 'H-NMR data for (7) in 2  6  5  2  6  Figure 6.20 (at 30 min) show more than one set of o-Me "H-resonances, which can result from three different coordination environments about the Ru(II) centre where two dimethylaniline, one hydroxy-dimethylaniline and one dimethylaniline, and two hydroxydimethylaniline, ligands are present, respectively. The solid residue that had been subjected to mass analysis was also analyzed by IR spectroscopy, and a band at 1942 cm" is assignable to a Ru (TMP)(CO) species (D) (vco 1  n  = 1943 cm", Chapter 2); however, the ^ - N M R signals assignable to (D) in Figure 6.20 1  do not correspond well (except for the yS-pyrrole ^-signal) to those of Ru (TMP)(CO) n  itself (/i-pyrrole-H, 8.79; o-Me, 2.20, 1.83; p-Me, 2.48 ppm; Chapter 2). Nonetheless, the mass spectrum (Figure 6.3) of the solid sample, which also contains (D), shows a mass peak centred around 912 amu, consistent with the presence of a Ru (TMP)(CO) species n  (MW = 910 g moi"). Accompanying the formation of (D) is an organic product (U), 1  which exhibits ^ - N M R signals in the 5.5 to 6 ppm region (Figure 6.20). The identities of (D) and (U) are not known.  230  References on p. 235  Chapter 6  Of note, the reaction between (1) and  N-dimethylaniline under 1 atm Ar, unlike  the reaction under 1 atm air, produced some Ru (TMP)(0) after 10 min; Ru^TMP)^IV  OCeH4NMe2)2 (4a) was not observed at this time, and was only seen after about 20 min (Figure 6.21). Also, the 'H-resonance at 8.66 ppm attributable to the ^-pyrrole-H of the TMP ligand within (D) was observed after 20 min. Unlike the reaction under 1 atm air, the reaction under Ar, after ~ 40 min, showed decomposition of the Ru-porphyrin species in the benzene-afe solution, as suggested by the disappearance of the characteristic TMP ^ - N M R signals for all the species in solution. The natures of the Ru (TMP)(CO) n  formation and Ru(TMP) decomposition reactions are not known. The 'H-NMR spectra (Figure 6.21) for the reaction under Ar showed that Ru (TMP)(0) was first detected, followed by (4a). For the reaction under air (Figure IV  6.20), 'Ff-resonances corresponding to (7) appear after those for (4a). This chronological order in which the Ru-porphyrin species are detected supports the mechanism presented in Figure 6.19. Of note, the formation of the Ru(II) species (7) (Figure 6.20) provides a potential pathway for regenerating Ru (TMP)(0)2 under air or O2, the criterion being that VI  the axial aniline ligands are labile. Indeed, the oxidation of NMe C6H to /?-NMe C6H40H 2  5  2  by (1) is catalytic in air, although only marginally with less than 10 total turnovers (Table 6.4). Of note, the oxidation of phenol to p-hydroquinone by (1) is not catalytic, as the product Ru (TMP)(OC6H )2 (4) does not regenerate (1) under air in wet benzene. IY  5  231  References on p. 235  Chapter 6  Table 6.4.  Aerobic oxidation of N, N-dimethylarriline catalyzed by Ru (TMP)(0) (1) under 1 atm air in benzene. % conversion to /»-hydroxyTime (hours) Reaction Conditions A^A^-dimethylaniline* [total turnovers] 24 °C [(l)] = 3.3xlO" M 47% [2.5] 28.5 [aniline] = 0.0158 M H 0 added" 2  3  2  [(l)] = 3.3xl0" M [aniline] = 0.0316 M H 0 added"  29.0  33% [3.1]  [(I)] = 3.3xl0- M [aniline] = 0.0316 M NO H 0 added"  29.0  19.7% [2.1]  18.0  12.7% [5.4]  18.5  8.4% [9.1]  36.5  8.8% [9.4]  [(I)] = 7.4xl0- M [aniline] = 0.0631 M H 0 added"  18.5  8.6% [7.3]  [(l)] = 7.4x lO^M [aniline] = 0.126 M H 0 added"  18.5  4.9% [8.4]  3  2  3  2  50 °C [(1)] = 7.4 x IO M [aniline] = 0.0316 M H 0 added" -4  2  [(l)] = 3.0x lO^M [aniline] = 0.0316 M H 0 added" 2  4  2  2  " 50 u.L H 0 was added to 0.50 mL benzene solutions, otherwise benzene (HPLC grade) was used directly. * An hydroxy-A ,A-dimethylaniline is suggested from GCMS analysis (Appendix G), and incorporation of the O-atom at the para position is based on analogy with the phenol system (see text). 2  A  /  232  References on p. 235  Chapter 6  6.6  Conclusions A reaction between Ru (TMP)(0) (1) and strong organic acids (CF COOH, YI  2  CHCI2COOH)  3  was discovered and the Ru products are bis(acetato)ruthenium(IV) type  species. Such reactions are of interest because acids have been observed to enhance the reactivity within systems used for the stoichiometric and catalytic hydroxylation of alkanes. ' The oxidation product from the reaction between (1) and HX, when identified, 1 2  will reveal the nature of the reaction. The preliminary study conducted earlier in this laboratory on the oxidation of phenol by (1) was re-examined in this thesis. A new mechanism is proposed consistent 3  with the oxidation chemistry of (1) discovered within the phosphine and alcohol systems (Chapters 3 and 4); Ru (TMP)(0) is no longer considered to be an active oxidant. IV  Rather, a Ru (TMP)(0)/Ru (TMP)(OH)2 interconversion, and disproportionation of 2 IV  IV  equivalents of Ru (TMP)(0) to Ru (TMP) and Ru (TMP)(0) , are considered to be the IV  n  VI  2  significant reaction pathways for Ru (TMP)(0). Kinetic studies for the phenol system w  reveal a non-first-order (betweenfirstand second) dependence on the phenol, which cannot be satisfactorily accommodated within the formerly successive two-step oxidation  3  or the current single O-atom oxidation and Ru (TMP)(0)/Ru (TMP)(OH)2 IV  IV  interconversion mechanisms. Preliminary work on the oxidation of AyV-dimethylaniline suggests the process to be similar to the phenol oxidation. GC-MS analysis suggests the product from the oxidation reaction to be a hydroxy-N, N-dimethylaniline; a larger scale reaction should be carried out so that the organic product could be isolated and its identity confirmed. Unlike the phenol system, the A^A'-dimethylaniline system is catalytic (< 10  233  References on p. 235  Chapter 6  total turnovers) under 1 atm air in benzene; however, the catalytic activity of (1) is lost, involving decomposition of Ru(TMP) species and formation of a Ru (TMP)(CO) species, n  of which the natures are unknown at this time.  234  References on p. 235  Chapter 6  References 1  T.-C. Lau and C.-K. Mak, J. Chem. Soc, Chem. Commun., 766 (1993); 943 (1995).  2  a) H. Ohtake, T. Higuchi and M. Hirobe, Heterocycles, 40, 867 (1995). b) H. Ohtake, T. Higuchi and M. Hirobe, J. Am. Chem. Soc, 114, 10660 (1992).  3  a) N. Rajapakse, Ph.D. Dissertation, University of British Columbia, 1990. b) N. Rajapakse, B. R. James and D. Dolphin, Stud. Surf. Sci. Catal, 55, 109 (1990).  4  a) C. Sishta, Ph.D. Disseratation, University of British Columbia, 1990. b) C. S. Alexander, Ph.D. Dissertation, University of British Columbia, 1995.  5  J. T. Groves and K.-H. Ahn, Inorg. Chem., 26, 3833 (1987).  6  a) W. H. Leung and C.-M. Che, J. Am. Chem. Soc, 111, 8812 (1989). b) W.-H. Leung, C.-M. Che, C.-H. Yeung and C.-K. Poon, Polyhedron, 12, 2331 (1993). c) J.-S. Huang, C.-M. Che and C.-K. Poon, J. Chem. Soc, Chem. Commun., 161 (1992).  7  a) D. F. Evans, J. Chem. Soc, 2003 (1959). b) D. H. Live and S. I. Chan, Anal. Chem., 42, 791 (1970).  8  G. N. La Mar and F. A. Walker, in The Porphyrins, ed. D. Dolphin, Volume 4, Academic Press, New York, Chapter 2, 1979.  9  K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, 3rd Ed., John Wiley and Sons, Toronto, 1978, p. 232.  235  References on p. 235  Chapter 7 Conclusion and Recommendations for Future Work  236  Chapter 7 7.1  General Conclusions The stoichiometric and catalytic 0 -oxidations of a variety of organic substrates 2  (phosphines, alcohols, alkenes and alkanes) effected by fra«5-Ru (porp)(0) species (porp YI  2  = TMP, TDCPP and TDCPP-Cl ) were presented in the preceding chapters. The t  8  preparation of the Ru(TDCPP-Clg) species was a collaborative joint effort with Xie from Dolphin's group. The kinetic data for the oxidation of EAr substrates (E = P, As, Sb) by 3  Ru (TMP)(0) (1) in benzene reveal a characteristic two-phase reaction, with the faster VI  2  stage occurring on a timescale ~ 1 0 ' s and the slower ~ 1 0 s. The faster reaction is 2  1  considered to be an O-atom transfer involving the electrophilic attack of a Ru=0 moiety of (1) on the lone pair of electrons on the E-atom, to form initially Ru (TMP)(0)(OEAr ). A plot of A H i * (but not logr* ) for the O-atom transfer versus IY  3  the Hammett factorCTwas close to linear, suggesting that a more electron-withdrawing para substituent gives a more favourable, lower value AHi*. The ASi* values for the Oatom transfer reactions correlate with the substrate molecular masses, with bulkier substrates giving more favourable, less negative ASi* values, an indication that the O-atom transfers occur via strong Ru=0 vibrational coupling. The slower stage of the reaction of (1) with EAr is thought to involve the dissociation of OEAr from 3  3  Ru (TMP)(0)(OEAr ) to form Ru (TMP)(0), which then disproportionates to (1) and IV  IV  3  Ru (TMP); EAr readily coordinates to the latter species to form the 5-coordinate n  3  T M P , TDCPP and TDCPP-C1 = dianions of mero-tetramesityl, /nero-tetta(2,6-dicMorophenyl) porphyrins and meTO-tetra(2,6-cuchlorophenyl)-y3K)ctachloroporphyrin, respectively. +  8  237  Chapter 7  Ru (TMP)(EAr3) product. The oxidation of EAr3 becomes catalytic under air or O2, and n  preliminary data show that the catalysis is slow compared to the stoichiometric reaction; approximately 1 turnover h" is obtained for the PPh system at ambient conditions. 1  3  The paramagnetic Ru(IV) species formed from the reaction of (1) with 'PrOH was formulated as Ru (TMP)(OH) in previous preliminary work in this laboratory; it is now IY  2  reformulated as Ru (TMP)(0'Pr) from crystallographic and spectroscopic studies in the IV  2  present thesis work. The oxidation of the alcohol is proposed to involve an initial cleavage of the a-C-H with transfer of a hydride to a Ru=0 moiety. The oxidation of 'PrOH to acetone by (1), under air in wet benzene, is catalytic, and (1) can also oxidize benzyl alcohol to benzaldehyde (without further oxidation to benzoic acid); in a benzene/3.0 M aq. KOH 2-phase system, 2000 equivalents of benzaldehyde are produced in ~ 13 d at 50 °C. Species (1) can also oxidize Ph CH to Ph COH catalytically under air. 3  3  Ru (TDCPP)(0) is slightly more reactive and can also oxidize adamantane to 1VI  2  adamantanol, although both systems give only a few total turnovers. That these dioxo complexes use solely 0 as the oxidant for these alkane systems demonstrates some 2  remarkable chemistry. For the first time, Ru(TDCPP-Clg) species are prepared and used as catalyst precursors for the 0 -oxidation of alcohols, alkenes and alkanes. The oxidation of benzyl 2  alcohol catalyzed by Ru (TDCPP-Clg)(0) is about as effective as that by (1) under VI  2  corresponding conditions, and the mechanism is presumably the same. The oxidations of neat cyclohexene, cz's-cyclooctene and methylcyclohexane operate via free-radical  238  Chapter 7  pathways to give turnovers of ~ 10 , probably based on hydroperoxide formation and 5  decomposition mediated by Ru(TDCPP-Clg) species. The reactions of (1) with H X acids (X = Cl, CF COO, CHCl COO) are found to 3  2  give Ru (TMP)(X) products, as established by NMR and IR spectroscopies and mass IV  2  spectrometry. The bis(acetato)ruthenium(IV) species are similar to the paramagnetic bis(halo)ruthenium(IV) complexes that have been characterized previously in this laboratory. The stoichiometric oxidation of phenol by (1) in benzene was proposed from previous preliminary work in this laboratory to form Ru™(TMP)(p-OCoH40H) . The 2  present data favour the formulation of the Ru(IV) product as Ru (TMP)(OC6H ) ; IY  5  2  furthermore, the reaction mechanism is proposed to involve a Ru (TMP)(0)/Ru (TMP)(OH) interconversion, followed by phenol metathesis with the IV  IV  2  bis(hydroxo) species. The Ru (TMP)(0) intermediate is not considered to be an active IV  oxidant; the species either undergoes the disproportionation or interconversion pathways (see above). Species (1), under air, also catalytically oxidizes JV^A'-dimethylaniline, presumably to /?-HOCeH4NMe (see Section 7.2); however, less than 10 total turnovers 2  are obtained in 1 d.  7.2  Recommendations for Future Work A wide area of 0 -oxidation chemistry mediated by Ru(porp) species was opened 2  up in this thesis work. The potential of these Ru-porphyrin species, particularly the TDCPP-Clg type, as 0 -oxidation catalysts has yet to be determined. The 0 -oxidation of 2  2  239  Chapter 7  a wider variety of substrates (alkenes and alkanes) catalyzed by the Ru(TDCPP-Clg) species deserves greater study to establish the scope of the usage of such metalloporphyrins. The following experiments are suggested as starting points in answering some questions raised in Chapter 6. Although the reaction of (1) with HX acids undoubtedly gives Ru (TMP)(X) species, the reaction mechanism is not understood; furthermore, the rv  2  product from the HX species is not known. Stoichiometric titration studies are obviously needed to elucidate the nature of these reactions. The scheme proposed in Chapter 6 for the oxidation of phenol by (1) is consistent with the experimental observations, as well as with the chemistry of Ru(TMP) species within the phosphine and alcohol systems; however, the mechanism does not accommodate satisfactorily the observed kinetic data, which show a non-first-order (-1.5) dependence on phenol. An initial step would be to acquire more kinetic data over lower [phenol] values (< 10" M) to determine whether the non-first-order dependence is 2  valid over a greater concentration range. The GCMS data show that the O-atom is incorporated into the substrate during the oxidation of N, A^-dimethylaniline by (1); the product is presumably /7-HOC6H4NMe , 2  and that the oxidation occurs at the para position is based on analogy with the phenol system. More direct identification of the oxidation product is necessary, and a larger scale reaction, followed by product separation, would be one way to confirm that /?-HOC H4NMe2 is formed. 6  240  Appendix A  Appendix A . Kinetic Data for the Oxidation of E A r . 3  Abs  A Q  I  0.7 4-  4.05xl0" M 3  0.6 0.02  0.00  —r—  H—  0.04  0.06  0.10  0.08  Time (s) Fi2ure A . l .  Absorbance-time traces monitored at 4 2 2 nm by stopped-flow spectrophotometry for the reaction of Ru (TMP)(0) ( 4 . 2 x 10" M in benzene) and PPh . vl  2  3  l^AfA,*,)  or  Figure A.2.  -2 5  +  Semilog and Guggenheim plots for [PPh ] = 4 . 0 5 x 10' M trace in Figure A . l above, where A< = absorbance at time t, A» = final absorbance, and At = 0 . 0 0 7 5 s. Slope = kobs = 2 1 6 ± 1.7, 2 2 0 ± and 2 2 7 ± 2 by semilog, Guggenheim and curve-fitting analyses, respectively. 3  3  241  1.7  Appendix A  2  4  6  8  10  Time (s) Figure A.3.  Absorbance-time traces monitored at 430 nm by stopped-flow spectrophotometry for the loss of the intermediate Ru^TMPXOXOPPlb) via further reaction with PPh (3.9 x 10° M) (initial [Ru (TMP)(0) ] = 4.2 x 10" M in benzene). 3  vl  5  2  0  0.5  Time ( s ) 1.5  1  -1  2 "  2.5 •  3  -1.5 ln(A -A„) t  or  -2  ln(A -A ) t  A t  -2.5 -3 -3.5 Figure A . 4 .  Semilog and Guggenheim plots for [PPh ] = 3.83 x 10' M, 3  3  [OPPh ] = 3.93 x 10' M trace in Figure A . 3 above. At = absorbance at 3  3  time t, A*, =finalabsorbance, and At = 1.0 s. Slope = k'ob, = 0.686 ± 0.01, 0.739 ± 0.01 and 0.713 ± 0.008 by semilog, Guggenheim and curve-fitting analyses, respectively.  242  Appendix A  Figure A.5.  Time (s) Absorbance-time traces monitored at 412 nm by stopped-flow spectrophotometry for the accumulation of the product Ru (TMP)(PPh ) (initial [Ru (TMP)(0) ] = 4.2 x 10' M in benzene). [PPh ] = 3.9x 10° M. n  Y1  3  6  2  3  lnCAt-A.) -1.5 f or ln(A t  Guggenheim  -2.5 - • -3 -3^5 A "  -4.5 Figure A.6. Semilog and Guggenheim plots for [PPh ] = 3.83 x 10*"* M, [OPPh ] = 3.93 x 10" M trace in Figure A.5 above. At = absorbance at time t, A * = final absorbance, and At = 1.0 s. Slope = k'ob, = 0.693 ± 0.011, 0.809 ± 0.02 and 0.748 ± 0.009 by semilog, Guggenheim and curve-fitting analyses, respectively. 3  3  3  243  Appendix A  Table A. 1 . 1 .  Pseudo-1 st-order rate constants for the oxidation of PPh by 3  Ru (TMP)(Q) ( 1 ) . w  2  [(Di  fpphji (10  3  M)  [opphii  k,*, (s )"  k' , ( -y  (IO M)  (O-atom transfer)  (Slower 2 n d reaction)  3  1  6  S  0.985  4.05  35.2 ±0.2  0.101 10.002 [0.0961]  1.00  2.75  38.3 ±0.3  0.18610.003 [0.183]  1.01  1.40  36.110.2  0.274 10.004 [0.274]  1.04  -  37.210.2  -  1.95  4.01  69.710.5  1.99  2.72  76.410.5  0.38910.6 [0.352]  2.03  1.39  74.7 10.6  0.613 ±0.009 [0.571]  2.07  -  74.5 10.6  2.90  3.97  1091 1  0.374 10.007  2.95  2.70  1161 1  0.57510.009  3.01  1.37  1371 1  0.71210.01  3.07  -  1371 1  -  3.83  3.93  1 5 3 1 1.4  0.495 10.008  3.90  2.67  15611.5  0.662 10.009  3.97  1.36  1581 1.5  1.1710.03  4.05  -  1481 1.4  -  0.0501  _  2.9010.02  20.0 °C 1.59 x 10' M  ob  0.0501  1.43  2.83 10.02  0.119  -  6.23 10.03  0.298 10.005 [0.286]  -  -  6.35 10.05 0.169  9.35 10.6  -  10.4410.8 52.010.4  0.14210.004  0.985  4.05  1.00  2.75  1.01  1.40  1.04  -  -  1.95  4.01  8610.7  0.32010.005  1.99  2.72  2.03  1.39  -  .0.752 10.008  2.07  -  2.90  3.97  2.95  2.70  3.01  1.37  3.07  -  3.83  3.93  22712  0.713 10.008  3.90  2.67  22912  0.937 1 10.009  3.97  1.36  245 12  1.2710.02  4.05  -  227 12  -  1 0 3 1 1  1801 1.5 1 6 1 1 1.2  244  0.242 10.005 0.34010.005  0.43810.007  0.493 10.007 0.685 10.009 1.1010.02  -  Appendix A  Table A. 1.1 continued... iTPhjl KD1 (10" M ) 0.985 30.7 °C 1.00 4.2 x 10" M 1.01 1.04 1.95 1.99 2.03 2.07 2.90 2.95 3.01 3.07 3.83 3.90 3.97 4.05  ,  3  -5  -  -  _  4.01 2.72 1.39 _  3.97 2.70 1.37  .  .. ( -y (Slower 2nd reaction) 0.179 ±0.003 0.337 ±0.005 0.475 ± 0.008 k'  _  -  4.01 2.72 1.39  182 ±2 187 ±2 181 ±2  -  -  3.97 2.70 1.37  268 ±2 280 ±3 275 ±2  -  -  o b  ,  S  0.498 ± 0.006 0.642 ± 0.007 0.946 ±0.01  -  0.808 ±0.01 0.935 ±0.02 1.33 ±0.02  1.18 ±0.03 1.31 ±0.03 1.88 ±0.04  0.207 ± 0.006 0.367 ±0.008 0.470 ±0.008  94.7 ±0.8 102 ± 1 98.0 ±0.9  4.05 • 2.75 1.40  0.985 1.00 1.01 1.04 1.95 1.99 2.03 2.07 2.90 2.95 3.01 3.07 3.83 3.90 3.97 4.05  1  kob,  3  6  40.2 °C 4.2 x l O M  3.93 2.67 1.36  (s )" (O-atom transfer) 62.6 ±0.5 80.5 ±0.9 74.6 ±0.7 71.9 ±0.7 143 ± 1 147 ± 1 144 ± 1 144 ± 1 218 ±2 223 ±2 217 ± 2 207 ± 2 274 ±2 286 ±3 273 ±3  [OPPtbl (10- M) 4.05 2.75 1.40  -  0.549 ±0.009 0.682 ±0.01 0.847 ±0.01  -  0.892 ±0.02 1.04 ±0.02 1.42 ±0.03  -  3.93 2.67 1.36  380 ±4  1.14 ±0.02 1.28 ±0.02 1.67 ±0.03  -  -  -  -  ' Monitored at 422 nm for the loss of (1). * Monitored at 430 nm for the loss of Ru (TMP)(0)(OPPh3). Values in [] were obtained at 412 nm for the appearance of the product Ru (TMP)(PPh ). lv  D  3  245  Appendix A  Table A.  1.2.  Pseudo-1 st-order rate constants for the oxidation of PPh by 3  k' ,  [PPh l  fl  (M)  ob  3  (Slower 2nd  0.0184  11.2 °C  0.0323  0.0462  (sT reaction)  14.97 15.13 15.13 18.56 16.97 16.93 17.64 16.58  ±0.5 ±0.4 ±0.5 ±0.4 ±0.4 ±0.3 ±0.2 ±0.2  20.5 °C  0.0114 0.0323 0.0462  10.09 15.42 17.25 17.43  ±0.4 ±0.5 ±0.6 ±0.7  30.1 °C  0.0184  15.21 16.94 16.97 22.37 22.81 23.46 27.4 28.79 28.79  ±0.3 ±0.4 ±0.4 ±0.3 ±0.4 ±0.4 ±0.5 ±0.7 ±0.6  0.0323  0.0462  16.86 ±0.6 17.98 ±0.4 17.0 ±0.5 32.32 ±0.6 29.77 ±0.4 31.9 ± 0.8 35.5 ±0.6' 35.63 ±0.8  0.0162  40.1 °C  0.0323  0.0462 " [OPPh3] = 1.3 x 10' M in all the runs. [(1)] = 2 x 10" M . * Monitored at 412 nm for the appearance of the product Ru (TMP)(PPh ). 5  6  D  3  246  Appendix A  Table A.2.  Pseudo-1 st-order rate constants for the oxidation of P ^ - M e O - C e R t ^ (L) by R u ( T M P ) ( 0 ) (1). v,  2  10.1 °C  l(L)] (1Q- M) 1.07  2.5 x 10* M  2.12  KD1  4  [OPPh,l (O-atom transfer)  (IP M) -3  4.21  8.25  1.16 1.18 2.30 2.35 3.44 3.50 20.4 °C  (Slower 2nd reaction)  8.60 ± 0.07 8.62 ±0.07 8.65 ±0.07 16.8 ±0.15 16.9 ±0.15 16.9 ±0.2 33.7 ±0.3 33.6 ±0.4 33.2 ±0.3 67.8 ±0.6 68.3 ±0.6 66.8 ±0.7 0.0248 ±0.0005 0.0365 ±0.0007 0.0503 ±0.001 0.0770 ±0.001 0.0749 ± 0.002 0.113 ±0.003  2.90 1.48 2.89 1.47 2.88 1.47 12.2 ±0.1 12.7 ±0.1 12.6 ±0.1 22.9 ±0.2 22.8 ±0.2 22.8 ±0.2 45.3 ±0.4 45.4 ±0.4 45.8 ±0.4 89.2 ±0.9 89.0 ±0.9  1.07  2.12  4.21  8.25  91.1 ± 1 1.16 1.18 2.30 2.35 3.44 3.50  0.0391 ±0.0008 0.0625 ±0.001 0.0732 ± 0.002 0.108 ±0.003 0.101 ±0.003 0.164 ±0.005  2.90 1.48 2.89 1.47 2.88 1.47  247  Appendix A  Table A.2 continued. I(L)1 [(1)1 (lO^M) 1.07 30.1 °C  2.5 x 10"* M  39.9 °C  kob.ts )" (O-atom transfer) 17.3 ±0.2 17.0 ±0.2 17.4 ±0.2 30.3 ±0.4 30.4 ±0.5 31.0±0.4 45.3 ±0.6 45.4 ±0.7 45.8 ±0.6 89.2 ± 1 89.0 ± 1 91.1 ± 1 -  [OPPM (IO" M) -  1  3  2.12  4.21  -  8.25  -  1.16 1.18 2.30 2.35 3.44 3.50  2.90 1.48 2.89 1.47 2.88 1.47  1.07  _  2.12  -  4.21  -  8.25  -  1.16 1.18 2.30 2.35 3.44 3.50  2.90 1.48 2.89 1.47 2.88 1.47  23.3 ±0.3 21.9±0.4 21.7 ±0.3 38.8 ±0.4 40.3 ± 0.6 38.5 ±0.5 78.7 ±0.9 78.8 ±0.7 78.5 ±0.8 160 ± 1.4 160 ±1.7 159 ± 1.5 -  -  " Monitored at 422 nm for the loss of (1). * Monitored at 430 nm for the loss of Ru (TMP)(0)(OPPh ). IY  3  248  k'ob. ( • ' ) *  (Slower 2nd reaction) -  -  -  0.0549 ±0.0009 0.0773 ±0.001 0.0988 ± 0.002 0.140 ±0.003 0.142 ±0.003 0.202 ± 0.004 -  -  -  0.0728 ±0.001 0.0961 ±0.001 0.129 ±0.002 0.177 ± 0.003 0.194 ±0.004 0.270 ± 0.006  Appendix A  Table A.3.  Pseudo-1 st-order rate constants for the oxidation of P(p-Me-C<£Uh (L) by R u ( T M P ) ( Q ) (1). [OPPh,] [(L)j kob. ( i - ' r ((1)1 (O-atom transfer) (IO M) (10" M ) 2.05 8.25 ±0.09 10.1 °C 8.52 ±0.1 8.22 ±0.08 17.1 ±0.2 4.08 2.5 x H T M 17.2 ±0.2 17.2 ±0.2 35.3 ±0.3 8.08 35.3 ±0.3 34.1 ±0.4 53.8 ±0.6 12.0 53.0 ±0.5 53.0 ±0.6 4.89 1.02 10.3 °C 2.49 1.04 4.88 1.52 2.49 1.55 4.86 2.53 2.48 2.58 w  2  4  20.4 °C  - 3  2.05  0.00906 ±0.0001 0.0154 ±0.0003 0.0133 ±0.0002 0.0245 ± 0.0003 0.0250 ± 0.0004 0.0404 ± 0.0006  12.3 ±0.1 12.2 ±0.1 12.2 ±0.14 24.2 ±0.3 24.1 ±0.3 24.6 ±0.2 47.7 ±0.5 49.7 ±0.5 48.1 ±0.4 71.7 ±0.9 72.4 ±0.7 70.7 ±0.9  4.08  8.08  12.0  1.02 1.04 1.52 1.55 2.53 2.58  k'ob. (sV (Slower 2nd reaction)  0.0152 ±0.0002 0.0249 ± 0.0004 0.0202 ± 0.0003 0.0343 ±0.0005 0.0339 ±0.0005 0.0631 ±0.0008  4.89 2.49 4.88 2.49 4.86 2.48  249  Appendix A  Table A3 continued..  30.1 °C  2.05  [OPPh,] (i<r M) -  2.5 x l O ^ M  4.08  -  8.08  -  12.0  -  30.0 °C  1.02 1.04 1.52 1.55 2.53 2.58  4.89 2.49 4.88 2.49 4.86 2.48  -  39.9 °C  2.05  _  4.08  -  8.08  -  12.0  -  21.4 ±0.3 22.1 ±0.3 21.6 ±0.35 38.3 ±0.5 37.3 ±0.45 39.3 ±0.5 81.9±0.8 81.7 ± 0.9 81.0 ± 1 130 ± 1.5 129 ± 1.7 126 ± 2  1.04 1.55 2.58 1.02 1.52 2.53  2.49 2.49 2.48 4.89 4.88 4.86  [(1)1  l(L)l (10" M) 4  (s ) (O-atom transfer) 1  kob,  3  16.2 ±0.2 16.3 ±0.2 16.4 ±0.16 32.2 ±0.5 31.8 ±0.4 32.0 ±0.5 66.2 ±0.8 65.1 ±0.9 66.0 ±0.8 93.2 ±1 95.7 ± 1 99.8 ± 1  -  " Monitored at 422 nm for the loss of (1). * Monitored at 430 nm for the loss of Ru (TMP)(0)(OPPh ). tv  3  250  (s / (Slower 2nd reaction) k'  o b  1  .  -  -  0.0185 .0.0322 0.0254 0.0433 0.0447 0.0718  ±0.0003 ± 0.0005 ±0.0004 ± 0.0007 ± 0.0005 ±0.0009  -  -  -  -  0.0384 0.0510 0.0862 0.0228 0.0300 0.0547  ± 0.0004 ±0.0006 ± 0.0009 ± 0.0003 ± 0.0004 ±0.0007  Appendix A  Pseudo-1 st-order rate constants for the oxidation of ?{p-?-C^U)i (L) by Ru (TMP)(Q) (1). [OPPhjl kob. (s ) l(L)l [(1)1 (O-atom transfer) (lO^M) (10 M ) 0.609 4.84 ±0.03 9.9 °C 1.7 x l O ^ M 1.21 10.6 ±0.07 2.40 18.5 ±0.1 4.71 36.2 ±0.2 1.57 2.72 10.3 °C 1.60 1.38 2.34 2.70 2.39 1.38 2.69 3.11 3.17 1.37 0.609 6.96 ±0.05 20.4 °C 13.3 ±0.1 1.21 2.40 26.0 ±0.2 4.71 49.8 ±0.4 1.57 2.72 1.60 1.38 2.70 2.34 2.39 1.38 2.69 3.11 3.17 1.37 0.609 9.26 ±0.08 30.1 °C 17.6 ±0.1 1.21 33.3 ±0.2 2.40 65.0 ±0.5 4.71 1.57 2.72 1.38 1.60 2.70 2.34 1.38 2.39 2.69 3.11 1.37 3.17 12.3 ±0.09 0.609 39.9 °C 23.3 ±0.2 1.21 44.0 ±0.4 2.40 81.4±0.7 4.71 1.57 2.72 1.38 1.60 2.70 2.34 1.38 2.39 2.69 3.11 1.37 3.17  Table A.4.  2  1  3  Monitored at 422 nm for the loss of (1). * Monitored at 430 nm for the loss of Ru (TMP)(0)(OPPh ). 4  rv  3  251  •  (sY  k'ob.  (Slower 2nd reaction)  0.0396 ± 0.0004 0.0808 ± 0.002 0.0592 ± 0.0006 0.100 ±0.001 0.0783 ± 0.0007 0.143 ±0.001  0.0596 ±0.0006 0.104 ±0.001 0.0873 ± 0.0007 0.141 ±0.002 0.124 ±0.001 0.187 ±0.002  0.0788 ± 0.0008 0.134 ±0.001 0.128 ±0.001 0.185 ±0.002 0.152 ±0.001 . 0.243 ± 0.002  0.0914 ±0.0008 0.145 ±0.001 0.135 ±0.001 0.203 ± 0.002 0.173 ±0.002 0.272 ± 0.003  Appendix A  Table A.5.  Pseudo-1 st-order rate constants for the oxidation of P(p-Cl-C£h)i (L) by Ru (TMP)(0)2 (1). kob. (s' ) [OPPh,] 1(L)1 (O-atom transfer) (IP" M) (lO^M) 9.72 ±0.05 1.00 9.90 ± 0.04 9.44 ±0.05 17.8 ±0.1 1.98 18.0 ±0.1 17.9 ±0.1 27.0 ±0.2 2.94 26.9 ±0.2 27.1 ±0.2 44.2 ±0.3 4.81 43.4 ±0.4 43.0 ±0.4 3.59 1.25 1.83 1.27 3.57 1.86 1.82 1.90 3.55 2.47 1.81 2.52 vl  l  KDl  a  3  9.8 °C  2.5 x 1(T  M  10.3 °C  20.2 °C  2.94  4.81  1.25 1.27 1.86 1.90 2.47 2.52  o b  .  (• V  0.0277 ±0.0003 0.0457 ± 0.0005 0.0427 ±0.0005 0.0625 ±0.0007 0.0492 ± 0.0006 0.0998 ±0.001  15.8 ± 0.1 14.8 ±0.1 15.0 ± 0.1 26.1 ±0.2 26.0 ±0.3 24.8 ±0.2 36.5 ±0.4 37.1 ±0.3 37.4 ±0.4 61.5 ±0.5 61.5 ±0.6 60.0 ± 0.6  1.00  1.98  20.3 °C  k'  (Slower 2nd reaction)  0.0429 ±0.0005 0.0680 ± 0.0008 0.0542 ± 0.0006 0.0899 ±0.001 0.0770 ± 0.0009 0.121 ±0.002  3.59 1.83 3.57 1.82 3.55 1.81  252  Appendix A  Table A.5 continued..  30.4 °C  I(L)1 (lO^M) 1.00  2.5 x 10* M  1.98  Id)]  [OPPh,] (IO M)  ko , (••')• 0  (O-atom transfer)  3  4.81  1.25 1.27 1.86 1.90 2.47 2.52  39.9°C  1.00  0.0562 ± 0.0007 0.0888 ±0.001 0.0812 ±0.0009 0.115 ±0.001 0.107 ±0.001 0.172 ±0.002  3.59 1.83 3.57 1.82 3.55 1.81 23.9 ±0.3 24.5 ±0.2 24.7 ±0.2 43.8 ±0.4 43.3 ±0.5 43.3 ±0.4 66.8 ±0.6 68.6 ±0.6 64.3 ±0.7 105 ± 1 106 ± 1 106 ± 1  1.98  2.94  4.81  40.0 °C  1.25 1.27 1.86 1.90 2.47 2.52  1  18.210.1 18.3 ±0.2 17.9 ±0.2 34.4 ± 0.3 34.4 ±0.4 34.0 ±0.4 50.5 ±0.6 49.2 ±0.5 48.1 ±0.5 79.4 ±0.7 82.5 ±0.8 78.4 ±0.8  2.94  30.0 °C  (s )* (Slower 2nd reaction) k'.„.  0.0715 ±0.001 0.112 ±0.002 0.109 ±0.002 0.147 ±0.003 0.137 ±0.002 0.186 ±0.003  3.59 1.83 3.57 1.82 3.55 1.81  " Monitored at 422 nm for the loss of (1). * Monitored at 430 nm for the loss of Ru (TMP)(0)(OPPh ). IY  3  253  Appendix A  Table A.6.  Pseudo-1 st-order rate constants for the oxidation of P(p-CF -C6l-Lt) (L) by Ru (TMP)(Q) (1). [OPPtaj] k ' b , (»•')* kob. (s ) I(L)1 (Slower 2nd reaction) (O-atom transfer) (lO^M) (10 M ) 3  3  vl  2  [(1)1  1  0  3  10.1 ° c 4.4 x l O ^ M  1.33 1.35 1.98 2.02 2.63 2.68  4.11 2.10 4.10 2.09 4.07 2.08  9.05 ± 0.04 9.24 ±0.04 12.6 ±0.05 13.5 ±0.06 17.7 ±0.1 16.6 ±0.1  0.0194 ±0.0003 0.0299 ± 0.0005 0.0354 ±0.0004 0.0513 ±0.0006 0.0464 ± 0.0005 0.0670 ± 0.0009  20.3 °C  1.33 1.35 1.98 2.02 2.63 2.68  4.11 2.10 4.10 2.09 4.07 2.08  12.9 ±0.1 13.4 ±0.1 19.4 ±0.1 17.2 ±0.1 25.1 ±0.2 24.8 ±0.2  0.0310 ±0.0005 0.0501 ±0.0006 0.0512 ±0.0007 0.0707 ± 0.0007 0.0675 ±0.0008 0.119 ±0.001  30.0 °C  1.33 1.35 1.98 2.02 2.63 2.68  4.11 2.10 4.10 2.09 4.07 2.08  17.1 ±0.1 17.6 ±0.1 27.0 ±0.3 25.8 ±0.2 34:6 ±0.3 34.3 ±0.4  0.0543 ± 0.0006 0.0732 ± 0.0007 0.0795 ±0.0009 0.102 ±0.001 0.105 ±0.001 0.140 ±0.0016  39.9 °C  1.33 1.35 1.98 2.02 2.63 2.68  4.11 2.10 4.10 2.09 4.07 2.08  23.9 24.0 34.4 33.8 44.0 42.9  0.0764 ±0.001 0.0997 ±0.001 0.114±0.001 0.148 ±0.0013 0.150 ±0.0017 0.191 ±0.002  " Monitored at 422 nm for the loss of (1). * Monitored at 430 nm for the loss of Ru (TMP)(0)(OPPh ). tv  3  254  ±0.2 ±0.2 ±0.3 ±0.4 ±0.4 ±0.3  Appendix A  Table A.  7.  Pseudo-1 st-order rate constants for the oxidation of [P(2-pyridyl)3](PPh3)(Cl) Ru (L) by Ru^CTMPXO); (1) 2  [(DI  [(D) (10' M)  10.4 °C 1.5 x l O ^ M  2.19 4.38 6.58 8.77 11.0  0.205 ± 0.005 0.248 ± 0.006 0.513 ±0.01 0.508 ± 0.009 0.664 ±0.01 0.665 ±0.01 0.886 ±0.012 0.925 ±0.014 1.04 ±0.02 1.05 ±0.016  20.3 °C  2.19 4.38 6.58 8.77 ' 11.0  0.383 ± 0.008 0.677 ±0.01 0.982 ±0.02 1.27 ±0.02 1.55 ±0.03  30.0 °C  2.19 4.38 6.58 8.77 11.0  39.9 °C  2.19 4.38 6.58 8.77 11.0  kob. (s- ) 1  s  4  (O-atom transfer)  0.403 ± 0.009 0.687 ±0.01 0.984 ±0.02 1.26 ±0.02 1.52 ±0.03  0.571 ±0.01 0.576 ±0.009 0.960 ±0.013 0.940 ±0.01 1.35 ±0.02 1.31 ±0.03 1.77 ±0.04 2.02 ±0.04 2.31 ±0.05 2.19 ±0.04 0.828 ±0.01 1.36 ±0.02 1.96 ±0.04 2.62 ±0.05 3.22 ±0.06  " Monitored at 422 nm for the loss of (1).  255  0.826 ±0.01 1.39 ±0.03 2.03 ±0.04 2.66 ±0.05 3.28 ±0.08  Appendix A  Table A.8.  Pseudo-lst-order rate constants for the oxidation of AsPh and SbPh , (L), by R u ( T M P ) ( 0 ) (1). yi  3  3  2  [AsPhj] ( 1 0 M ) J  [(1)1  9.9 °C 2.3 x 10" M 6  19.8 °C  30.1 °C  39.9 °C  0.928 1 0.008 1.75 ±0.01 2.68 ±0.01 3.29 ±0.016 1.30 ±0.01 2.60 ±0.01 4.10 ±0.022 5.32 ±0.03 69.0 ±0.4 2.21 ±0.01 4.07 ± 0.02 6.55 ±0.05 8.19 ±0.04 3.06 ±0.02 6.02 ±0.07 9.06 ± 0.06 12.1 ±0.1  1.48 2.91 4.36 5.61 1.48 2.91 4.36 5.61 75.0 1.48 2.91 4.36 5.61 1.48 2.91 4.36 5.61  KD1  [SbPh j (IO" M )  9.7 °C 3.0 x l O ^ M  1.14 2.19 3.17 4.08 1.14 2.19 3.17 4.08 1.14 2.19 3.17 4.08 1.14 2.19 3.17 4.08  14.5 °C  20.3 °C  25.4 °C  kob. (••')• (O-atom transfer) 1.06 ±0.01 1.78 ±0.006 2.69 ±0.014 3.49 ±0.02 1.32 ±0.01 2.69 ±0.014 4.10 ±0.015 5.43 ±0.03 66.4 ±0.5 2.21 ±0.02 4.06 ± 0.02 6.13 ±0.04 8.26 ±0.03 3.20 ±0.02 6.21 ±0.03 9.08±0.08 11.8 ±0.1 kob. ( s - y (O-atom transfer) 423 ± 10 647 ± 30. 820 ± 40 • 1216 ±100 445 ± 30 673 ± 50 872 ± 70 1300 ±120 464 ± 40 700160 933 ±85 14101130  4  3  713 1 6 0 1080 1 100 15701 150  * Monitored at 422 nm for the loss of (1). * Monitored at 430 nm for the appearance of Ru (TMP)(0)(OSbPh ). rv  3  256  1.8410.014 2.7710.03 3.6810.03 2.75 1 0 . 0 1 7 3.9610.03 5.2610.09  -  2.33 1 0 . 0 1 4.3510.03 6.4710.03 8.54 1 0 . 0 6 2.9910.02 6.2410.04 9.5410.09 11.9 ±0.1  Appendix B  Appendix B. Mathematical Derivation for the Equation Reflecting the Observed lst-Order Absorbance-Time Changes in the Oxidation of PPh3 by Ru^fTMPXOJa  B.l  O-atom Transfer (Faster Kinetic Phase) The O-atom transfer is a simple (1)  - (2) reaction. If the reaction follows  first-order kinetic behaviour, the absorbance contributions due to (1) and (2) are the following:  a = aoexp(-kob,t); b = b„ - bcoexp(-kob5t), where a^ = initial absorbance of  (1), bo =finalabsorbance due to complete formation of (2),  kobs  = pseudo-1 st-order rate  constant and t = time. Thus the absorbance observed at any time, t, is Abs = a + b = (ao - boo)exp(-kobst) + b». A semilog plot of ln(Abs - b*) versus t should give a straight line with slope = - k o b s in the case where ao >  boo-  When ao < b the absorbances r  arerising,and In | Abs - bco I should be used instead.  B.2.  Dissociation of OL Followed by Disproportionation (Slower Kinetic Phase) The following mechanism was proposed in Chapter 3 . (2)  (B.l)  ===== (3) + O L  2(3)  (B.2)  (l) + (4)  J * ^  (1) + L  k. ,  (2)  (B.3)  (4) + L  let  (5)  (B4)  r  257  Appendix B  Only (2) and (5) were observed in 'H-NMR studies during this stage of the reaction [(1) has been completely consumed in the faster O-atom transfer reaction]. The observed rate expression is represented by Eq. B.5. - ^ j p = M(2)] - M0L][(3)] - k,[L][(l)] =  = k4[L][(4)]  (B.5)  [(1)] = [(4)] = K [(3)], as the only source of (1) is via the disproportionation reaction, 1/2  3  Eq. B.2. Upon substitution of (1) and (4) by K [(3)] into Eq. B.5, we obtain Eqs. B.6, 1/2  3  3.7 and B.8. k [(2)] - k_ [OL][(3)] - k,K [L][(3)] - k4K [L][(3)] = 0 ,/2  2  2  [< » 3  =  =  3  M O L l + k.Ka^rLl + k - J C , ^ ] k K M O L ] + k,K  1/2 3  (B.6)  1/2  3  [ ( 2 ) ]  (  B  7  )  1 / 2  [L] + k K 4  1/ 3  U]  C ( 2 ) 1  (  B  8 )  Thus, the rate expression (Eq. B.5) becomes Eq. B.9. k  dt  ' -  r  m  l  k 2 [ ( 2 ) ]  + +  k. k [0L] k. [OL] + k,K " [L] k4K3 [L] 2  2  2  2  +  1/2  [ ( 2 ) ]  +  3  kik K 2  1/2 3  rL]  M O L ] + k!K " [L] + k4K [L] 2  ty2  3  [ ( 2 ) ]=  3  - '«"»t(2)], where k  •  (B.9)  k k4K ' rL] /2  2  k'obs  3  = ie [OL] + (ki+k4)K [L] ' ^ P 1/2  2  n  e  r e s e n c e  3  °^  e x c e s s  [L] and [OL]. As only (2) and  (5) are present in any significant quantities, the relationship between the observed rate and absorbance changes follows the same derivation as in the previous section.  258  Appendix C  Appendix C. Oxidation of Alcohols and Alkanes by Ru (TMP)(0) C.l  2  Kinetic Data for the Stoichiometric Oxidation of Alcohols under 1 atm Ar.  Table C . l . l .  ['PrOH] = 0.0435 M in benzene-*. [Ru^(TMP)(0) ] = 4.0 x 10" M. Temperature " 18.2 °C. Integration of o-Me of Integration of Time (s) Ru (TMP)(0) p- and o-Me groups of (Arbitrary Units) Ru (TMP)(0/Pr)2 (Arbitrary Units) 100 0 0 208.2 82.2 2115 138.0 80.8 3825 60.7 49.9 5395 57.1 55.0 8955 88.4 91.2 11130 64.7 90.0 14280 73.5 126.8 18075 47.6 120.6 21315 46.8 135.4 25350 23.4 73.2 28360 2.0 x 10" s" kobs 4  2  vl  2  IV  5  Table C.l.2.  1  ['PrOH] = 0.0568 M in benzene-*. [Ru (TMP)(0) ] = 4.0 x IO" M. Temperature = 18.2 °C. Integration of p-Me of Integration of Time (s) Ru (TMP)(0)2 p- and o-Me groups of (Arbitrary Units) Ru (TMP)(0'Pr) (Arbitrary Units) 100 0 0 109.8 12.9 1340 79.76 14.2 3600 76.0 23.9 4620 54.56 30.4 8380 62.7 46.2 11785 56.3 50.4 14700 35.6 44.3 17575 17 200 68610 kobs = 1.9 x 10" s' vl  4  2  %a  ,v  2  5  259  1  Appendix C  Table C.1.3. ['PrOH] = 0.131 M in benzene-^. [Ru (TMP)(0) ] = 4.0 x 10" M. Temperature = 18.2 °C. Integration of p-Me of Integration of Time (s) Ru' (TMP)(0) p- and o-Me groups of (Arbitrary Units) Ru (TMP)(0'Pr) (Arbitrary Units) 100 0 0 163.4 65.1 1805 200.4 93.6 3560 87.3 67.4 5025 64.6 91.6 8640 96.5 130.9 10860 58.2 107.2 13980 58.6 131.1 17925 41.1 128.4 21120 40.2 136.9 25110 4.2 x l O s " kobs vl  4  2  q  2  IV  2  - 5  1  Table C.1.4. ['PrOH] = 0.174 M in benzene-^. [Ru^(TMP)(0) ] = 3.8 x 10" M Temperature = 18.2 °C. Time (s) Integration of Integration of p-Me of p- and o-Me groups of Ru (TMP)(0) Ru (TMP)(0'Pr) (Arbitrary Units) (Arbitrary Units) 0 0 10 930 3.9 7.95 1795 6.0 9.0 koh, = 8.0 x 10' s' 4  2  v1  2  IV  2  5  1  Table C.1.5. ['PrOH] = 0.435 M in benzene-^. [Ru^(TMP)(0) ] = 3.8 x 10" M. Temperature = 18.2 °C. Integration of p-Me of Integration of Time (s) Ru (TMP)(0) p- and o-Me groups of (Arbitrary Units) Ru (TMP)(OPr) (Arbitrary Units) 10 0 0 5.2 2.45 540 . 5.1 3.1 1200 6.3 7.0 2340 4.55 7.7 3540 kobs =1.2 x 1 0 - V 4  2  vl  2  IV  2  260  Appendix C  Table C.1.6. ['PrOH] = 0.435 M in benzene-afe. [Ru (TMP)(0) ] = 5.2 x 10" M Temperature = 18.2 °C Integration of para-Mt of Integration of Time (s) Ru^fTMPXOk para and ortho-Mt's of (Arbitrary Units) Ru (TMP)(0'Pr) VI  4  2  IV  2  10 6.15 • 5.9 6.5 6.3 36  0 3.6 5.1 7.4 8.2 51  0 600 1260 2280 3240 5280  1^ = 1.2 x 10-V  Table C.1.7. ['PrOH] = 0.871 M in benzene-^. [Ru (TMP)(0) ] = 5.2 x 10" M. Temperature =18.2 °C. Integration of p-Me of Integration of Time (s) Ru (TMP)(0) p- and o-Me groups of (Arbitrary Units) Ru (TMP)(0'Pr) v,I  4  2  vl  2  IV  2  10 5.15 5.25 2.25 6.3 5.6  0 1.35 1.3 4.72 3.2 5.15  0 900 1800 2700 3600 4500  lc^ = 1.37 x l O - V Table C.1.8. ['PrOH] = 0.161 M in benzene-fife. [Ru^TMPXO^] = 4.0 x 10 M Temperature = 28.5 °C. Integration of p-Me of Integration of Time (s) Ru^TMPXOfc p- and o-Me groups of (Arbitrary Units) Ru (TMP)(0'Pr) (Arbitrary Units) 10 0 0 8.1 4.1 540 6.0 4.1 1155 7.0 7.1 1750 6.1 7.7 2910 7.0 11.0 4230 -4  ,v  2  ie*,=i.2o xio-y  261  Appendix C  Table C.1.9. ['PrOH] = 0.174 M in benzene-*. [Ru^fTMPXOfc] = 4.0 x 10 M. Temperature = 35.5 °C. Integration of p-Me of Integration of Time (s) Ru^fTMPXOk p- and o-Me groups of (Arbitrary Units) Ru (TMP)(0'Pr) ,v  2  10 4.2 4.3 5.0 5.0 3.8  0 1.75 3.8 4.3 5.3 5.4  0 850 1320 1920 3440 4320  kobs  = 1.82 x l O - V  Table C.1.10. [T>rOH] = 0.218 M in benzene-*. [Ru (TMP)(0) ] = 4.0 x 10 M. Temperature = 18.2 °C. Mole Fraction of Ru^CTMPXOV 1 0 0.912 750 0.832 2485 0.698 4285 v,  2  kobs  + \ "Integrationp.o-MeCRuav))] The data from Table C. 1.1 "S5" "»''/>.  jr=Integration . e(Ru(vi))/[lntegration ,.MefRu(vi))p  M  /  = 8.0 x l O ' V  r  l  3  1.9 were converted to mole fractions to derive kob, (see Chapter 4)  Table C.1.11. ['PrOH] = 0.218 M in benzene-*. [Ru^TMPXO^] = 2.0 x IO M. Temperature = 18.2 °C. Time (s) Mole Fraction of Ru^fTMPKOk 0 1 1040 0.922 2660 0.846 4200 0.80 -4  kobs = 7.8  262  x lQ-y  Appendix C  Table C.1.12. ['PrOH] = 0.218 M in benzene-*. [Ru (TMP)(0) ] = 4.0 x 10" M. Temperature = 18.2 °C. Mole Fraction of Ru (TMP)(0) Time (s) 1 0 0.584 4665 0.586 6005 0.495 7555 U s = 9.2 x 1 0 - V YI  4  2  VI  2  Table C.1.13. ['PrOD-*] = 1.74 M in benzene-*. [Ru (TMP)(0) ] = 4.0 x 10" M. Temperature = 18.0 °C. Mole Fraction of Ru (TMP)(0) Time (s) VI  4  2  vl  2  1 0.89 0.806 0.7865 0.77 0.741  0 780 1680 2580 3480 4380  kobs = 1.3  x  10-V  Table C . l . 14. [PrOD-*] = 0.327 M in benzene-*. rRu^(TMP)(0) ] = 4.0 x 10" M. Temperature = 18.0°C. Mole Fraction of Ru (TMP)(0) Time (s) 4  2  vl  2  1 0.87 0.865 0.84 0.81 0.763  0 720 1320 2280 2940 4800  kobs = 6.66  263  x 10  -5  s"  1  Appendix C  Table C.1.15. ['PrOD-*] = 0.131 M in benzene-*. [Ru (TMP)(0) ] = 4.0 x IO" M. Temperature = 18.0 °C. , Time (s) Mole Fraction of Ru^(TMP)(0) Y1  4  2  2  0 600 1200 1800 3000 4920  1 0.935 0.922 0.933 0.911 0.878  . •  kobs = 3.1  x  .  1Q-V  Table C.l.16. ['PrOH] = 0.0408 M in benzene-*. [KOH] = 4 x 10* M. [Ru (TMP)(0)2l = 4.0 x IO M. Temperature = 18.2 °C. Mole Fraction of Ru (TMP)(0) Time (s) 6  vl  -4  VI  2  1  0 600 1530 2550 4530 8250  0.818 0.813 0.733 0.614 0.56 kobs = 9.0 x 1 0 - y  Table C.l.17. ['PrOH] = 0.0408 M in benzene-*. [KOH] = 2 x 10" M. ^ _ [Ru (TMP)(Q)2l = 4.0 x IO M. Temperature = 18.2 °C. Time (s) Mole Fraction of Ru (TMP)(0)j 5  v1  -4  vl  0 210 810 2910 3510 4410 koiibs  264  1  1 0.889 0.793 0.699 0.700 0.594 1.2 x 1 0 - V  \  Appendix C  Table C.1.18. ['PrOH] = 0.0816 M in benzene-^. [KOH] = 4 x 10" M. rRu " (TMP)(Q) ] = 4.0 x 10" M. Temperature = 18.2 °C. Time (s) Mole Fraction of R u ^ T M P X O ) : 6  v  1  4  2  0 900 2820 6600  1 0.90 0.75 0.60 k =l.lx1Q- s4  obs  Table C.1.19. ['PrOH] = 0.130 M in benzene-^. [KO'Bu] = 1.2 x 10 M. [Ru (TMP)(0)2l = 2 0 x 10" M. Temperature = 18.2 °C. Time (s) Mole Fraction of Ru (TMP)(0) -4  vl  4  VI  0 150 450 750  2  1 0.90 0.75 0.68 = 5.4 x 1Q- s-  ^  4  Table C.1.20. ['PrOH] = 0.130 M in benzene-fife [KO'Bu] = 1.6 x 10' M. [Ru (TMP)(0) ] = 4.0 x 10' M. Temperature = 18.2 °C. 3  vl  4  2  Time(s) _  Mole Fraction of Ru (TMP)(0) VI  ,  .  360 kob = s  265  0.133 5J3 x!0' s'' 3  2  Appendix C  Table C.1.21. ['PrOH] = 0.130 M in benzene-*. ['BuOH] = 0.177 M.  [Ru '(TMP)(0) 1 = 4.0 x IO M. Temperature = 18.2 °C. v  -4  2  Mole Fraction of Ru^(TMP)(0)  Time (s) 0 810 2850 5010  k  o b s  1 0.99 0.97 0.95 = 9.2xl0^s-  2  1  Table C.1.22. ['PrOH] = 0.130 M in benzene-*. ['BuOH] = 0.530 M. fRu VTMPVO)9l = 4.0 x IO M. Temperature = 18.2 °C. Mole Fraction of Ru (TMP)(0) Time (s) v  -4  v,  2  1 0.99 0.98 0.96  0 2520 4500 10000 ko  b s  = 3.6  x  io-y  Table C.l.23. [Benzyl alcohol] = 0.193 M in benzene-*. [Ru (TMP)(0) ] = 2.0 x 10" M. Temperature = 18.0 °C. Mole Fraction of Ru (TMP)(0) Time (s) 4  VI  2  vl  1 0.717 0.555 0.335 0.299 0.154 kobs = 5.06 x l Q - V  0 510 1290 2010 2610 3630  266  2  Appendix C  Table C.1.24. [Benzyl alcohol] = 0.129 M in benzene-fife. rRu (TMP)(0) ] = 3.0 x 10" M. Temperature = 18.0 °C. Mole Fraction of Ru (TMP)(0) Time (s) vl  4  2  vl  0 300 900 1800 2460 3000  k  2  1 0.852 0.719 0.509 0.432 0.359 = 3.57xl0- s-' 4  ohs  Table C.1.25. [Benzyl alcohol] =0.0966 M in benzene-fife. rRu (TMP)(0) ] = 3 0 x 10' M. Temperature = 18.2 °C. Mole Fraction of Ru '(TMP)(0) Time (s) 4  VI  2  N  2  1 0.856 0.726 0.609 0.575 0.434 ko = 2.28 x 1 0 - V  0 720 1320 2100 2700 3480  bs  Table C.1.26. [Benzyl alcohol] == 0.193 M in benzene-fife. rRu (TMP)(0) ] = 3.0 x 10" M. Temperature = 29.5 °C. Mole Fraction of R u ^ T M P X O ) : Time (s) 4  vl  2  0 300 600 900 1200  ^  267  1 0.613 0.451 0.275 0.15 = 1.47 x l O - V  Appendix C  Table C.l.27. [Benzyl alcohol] = 0.0966 M in benzene-*. rRu '(TMP)(Q) 1 = 3.0 x IO M. Temperature = 29.5 °C. Mole Fraction of Ru (TMP)(0) Time (s) v  -4  2  v,  1 0.768 0.616 0.401 0.425 0.274 1^ = 7.41 x 1  0 300 720 1200  1620 2100  2  0 - V  Table C.1.28. [Benzyl alcohol] =0.161 M in benzene-*. [Ru (TMP)(0) ] == 3 0 x IO M. Temperature = 34.5 °C. Mole Fraction of Ru"(TMP)(0) Time (s) -4  v,  2  2  1 0.486 0.277 0?164  0 270 615 900 ko  bs  = 2.26 x 1 0 V  Table C.l.29. [Benzyl alcohol] = 0.0966 M in benzene-*. [Ru (TMP)(0) ] = 3 0 x IO" M. Temperature = 34.5 °C. Mole Fraction of Ru (TMP)(0) Time (s) 4  %a  2  VI  1 0.545 0.427 0.410 0.286  0 360 720 990 1260  kobs = 1.37  268  x l 0 V  2  Appendix C  Table C.1.30. [Benzyl alcohol] = 0.0322 M in benzene-^. rRu (TMP)(Q)2l = 3.0 x 10" M. Temperature = 34.5 °C. ) Mole Fraction of R u ( T M P ) ( 0 ) %n  4  vl  T i m e ( s  0 300 600 900 1200  > 0  8  0  0  1  6  5  1  2  6  1  6  0k -7.52xlQ- s40  4  ntw  269  1  2  Appendix C  C.2  Data for the Catalytic Oxidation of Alcohols in Benzene at 50 °C under 1 Atm Air.  Table C2.1.  [Benzyl alcohol] = 0.121 M; [Ru^TMPXO^] = 2.56 x 10° M 30 pL 3.0 M aqueous KOH. Blank benzyl alcohol contains 0.174% benzaldehyde. Time (h) Amount of Benzaldehyde Amount of Benzyl alcohol (Arbitrary Units)" (Arbitrary Units)" 17.25 2466 128990 2146 84690 41.75  8935 5250  282790 113400  67,5  10358 10012  219070 179380  91.5  5580 6148  81365 84881  115.5  8372 12503  103440 154090  141  6663 5085  76489 58019  166  5423 6097  62989 65081  191.5  2340 2698  22020 26863  234.5  4674 4832  44081 44437  259  1894 2519  17512 25095  " Second set of values in correspond to data from a second GC run for the same sample.  270  Appendix C  Table C2.2.  [Benzyl alcohol] = 0.242 M; [Ru (TMP)(0) ] = 2.56 x 10' M 30 uL 3.0 M aqueous KOH. Blank benzyl alcohol contains 0.174% benzaldehyde. . Amount of Benzyl alcohol Amount of Benzaldehyde Time (h) (Arbitrary Units)" (Arbitrary Units)" 220470 5210 17.25 221710 5318 v,  5  2  41.75  10570 11035  275790 273770  67.75  22708 7206  424950 130280  91.75  12923 6204  188880 83797  116  29382 23962  392590 323130  141.5  11163 11865  129500 136620  166.25  15965 13078  166030 139400  191.5  6943 8241  65093 78154  234.5  2908 2453  24787 21542  ° See footnote a for Table C.l. 1.  271  Appendix C  Table C2.3.  [Benzyl alcohol] = 0.483 M, [Ru (TMP)(0) ] = 2.56 x 10' M 30 pL 3.0 M aqueous KOH. Blank benzyl alcohol contains 0.174% benzaldehyde. ' Amount of Benzyl alcohol Amount of Benzaldehyde Time (h) (Arbitrary Units)" (Arbitrary Units)" 468220 6356 17.75 605370 7991 VI  5  2  41.75  17669 16266  727430 693480  67.75  13809 16923  387560 500590  91.75  23066 24948  499500 568720  116.5  40029 16708  722480 311130  141.5  20428 21472  311660 332190  166.5  20531 5493  281680 77760  191.75  3120 2847  39047 35490  234.75  5127 5061  54642 54414  259.5  3589 4308  37622 47706  283.15  4032 2878  40980 27753  307.75  12039 10812  105910 96041  334  8293 7894  74321 67489  * See footnote a for Table C.2.1.  272  Appendix C  Table C2.4.  [Benzyl alcohol] = 0.878 M; [Ru (TMP)(0) ] = 2.56 x 10' M 30 uL 3.0 M aqueous KOH. Blank benzyl alcohol contains 0.174% benzaldehyde. . Amount of Benzyl alcohol Amount of Benzaldehyde Time (h) (Arbitrary Units)" (Arbitrary Units)" Y1  5  2  18  7986 6211  991370 869580  41.75  13053 15489  970480 1156000  67.75  11232 11727  582850 719600  91.75  22805 22861  1012100 1031700  116.75  17076 18004  652320 724730  141.75  26168 14971  842020 470820  166.5  5424 2499  150490 71781  192  3136 2056  76891 55694  235  3558 3171  77071 70126  259.75  4462 4819  88628 99322  283.5  2827 3038  53784 55869  308  12391 13183  214570 231900  334 " See footnote a for Table C.2.1.  10445  190150  273  Appendix C  C.3  Data for the Catalytic Oxidation of Alkanes in Benzene at 24 °C under 1 Atm Air.  Table C.3.1. [Ph CH] = 2.89 x 10' M; [Ru^TMPXO^I = 1.2 x W M Time (h) Percentage conversion of Ph CH to Ph COH (%) 0 0 1.51 20 2.07 45 3.33 93 3.98 118.5 4.30 142 5.12 166.5 5.22 191 6.29 215.5 6.68 244 6.96 262 6.87 287.5 7.88 360 8.80 410 9.86 505 13.93 1150 3  4  3  3  3  Table C.3.2.  [Adamantane] = 6.28 x 10" M; [Ru (TDCPP)(0) ] = 2.39 x 10" M Percentage conversion of adamantane to Time (h) 1-adamantanol (%) 0 0 0.44 19.5 1.13 43.5 2.11 67.25 3.42 93 4.30 117 4.38 145.5 4.96 166.5 5.37 189 6.20 213 6.48 262 8.82 312 10.21 407 3  vl  4  2  274  Appendix C  Table C.3.3.  [Ph CH] = 4.64 x lO" M, [Ru\TOCPP)(0) ] = 2.39 x 10" M 3  4  3  2  Percentage conversion of P h C H to P h C O H (%) 0 2.21 3.57 6.09 7.74 9.38 11.31 12.33 14.25 15.57 18.43 23.92 31.36 38.56 67.01  Time (h)  3  3  0 20 44 68 93 117 146 164 190 212.5 261 312 407.5 481.5 1150  275  Appendix D  Appendix  Table D . l . l .  Experimental Details. A.  Crystal Data  Empirical Formula  C62H06N4O2RU  Formula Weight  1000.30  Crystal Color, Habit  black, irregular  Crystal Dimensions  0.15x0.25 x0.32 mm  Crystal System  tetragonal  Lattice Type  I-centered  No. of Reflections Used for Unit Cell Determination (20 range)  25 (35.7- 53.8°)  Omega Scan Peak Width at Half-height  0.380  Space Group  a = 27.967(1) A c= 1.4.274(2) A V = 11164(1) A I4i/a (#88)  Z value  8  Lattice Parameters  3  1.190 gem'  3  Dcalc  4208  Fooo  26.13 cm"  1  u(CuKa)  B. Intensity Measurements Diffractometer  Rigaku AFC6S  Radiation  CuKa(X= 1.54178 A) graphite monochromated  Take-off Angle  6.0° 6.0 mm horizontal 6.0 min vertical  Detector Aperture Crystal to Detector Distance  285 mm  Temperature  21.0 °C  Scan Type  ©-26  277  Appendix D  Scan Rate  16.0°/min (in co) (up to 9 scans)  Scan Width  (0.89 + 0.20 tan 0)°  29 ax  155.5°  No. of Reflections Measured  Total 5676 Unique: 5448 (R*, = 0.020)  m  Lorentz-polarization Absorption (trans, factors: 0.779- 1.000) Secondary Extinction (coefficient: 3.2(4) x 10' )  Corrections  8  C  Structure Solution and Refinement  Structure Solution  Patterson Methods (DIRDIF92 PATTY)  Refinement  Full-matrix least-squares  Function Minimized  Ico(^ |-^)  Least Squares Weights  \/c\Fo) = 4Fo /o\F )  2  0  2  2  0  p-factor  0.000  Anomalous Dispersion  All non-hydrogen atoms  No. Observations (I > 3.00o(I))  3417  No. Variables  318  Reflection/Parameter Ratio  10.75  Residuals: R, R  0.043; 0.044  w  Goodness of Fit Indicator  2.34  Max Shift/Error in Final Cycle  0.001  Maximum peak in Final Diff. Map  0.42 e* A"  Minimum peak in Final Diff. Map  -0.32 e' A"  278  3  3  Appendix D  Table D.1.2. Atomic Coordinates and B . eq  atom Ru(l) 0(1) N(l) N(2) C(l) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(H) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28) C(29) C(29a) C(30) C(31)  B = eq  0.2500 0.2500 0.2814(1) 0.1975(1) 0.1987(1) 0.2059(1) 0.2096(1) 0.2604(1) 0.1999(2) 0.1827(2) 0.1562(2) 0.1562(2) 0.1295(2) 0.1636(2) 0.1559(1) 0.1951(1) 0.1399(1) 0.2113(1) 0.1650(1) 0.2416(1) 0,1486(1) 0.2583(2) 0.1827(2) 0.2868(2) 0.2214(1) 0.2885(2) 0.2634(2) 0.3148(2) 0.0900(1) 0.1980(2) 0.0519(2) 0.2266(2) 0.0063(2) 0.2153(2) -0.0023(2) 0.1774(2) 0.0356(2) 0.1498(2) 0.0824(2) 0.1590(2) 0.0595(2) 0,2699(2) -0.0526(2) 0.1662(2) 0.1225(2) 0.1274(2) 0.2679(2) 0.3419(2) 0.2531(2) 0.3895(3) 0.2558(3) 0.4117(3) 0.2710(3) 0.3895(4) 0.2850(2) 0.3433(4) 0.2837(2) 0.3186(3) 0.2345(3) 0.4152(2) 0.2732(3) 0.4153(4) 0.2988(3) 0.2672(3) 0.2763(4) 0.1679(4) 0.2972(9) 0.158(1) 0.3300(5) 0.1602(4) 0.2644(4) 0.1191(3)  0.2500 0.3064(3) 0.1968(2) 0.3663(2) 0.1111(3) 0.0999(4) 0.1765(4) 0.2375(3) 0.3245(3) 0.3831(3) 0.4722(3) 0.5084(3) 0.4424(3) 0.4530(3) 0.3557(3) 0.3280(3) 0.3581(3) 0.4170(4) 0.4442(3) 0.4140(3) 0.2669(4) 0.4491(4) . 0.4442(4) 0.5447(4) 0.5497(5 0.6377(6) 0.7152(6) 0.7088(5) 0.6227(5) 0.4670(6) 0.8103(6) 0.6198(5) 0.379(1) 0.309(2) 0.4065(9) 0.333(1)  Bleg3.80(1) 6.9(1) 4.17(8) 4.09(8) 5.0(1) 6.1(1) 58(1) 4.4(1) 4.3(1) 4.3(1) 4.8(1) 51(1) 45(1) 5.0(1) 4.3(1) 4.5(1) 5.0(1) 5.4(1) 5.6(1) 4.9(1) 60(1) 8.2(2) 7.2(2) 5.9(1) 7.5(2) 10.1(2) 116(3) 10.9(3) 8.2(2) 10.6(3) 18.6(4) 11.7(3) 11.6(4) 9.0(6) 25.0(6) 22.1(5)  OCC.  0.50  0.70 0.30  U (bb*) + U (cc*f + 2V aa*bb*cosy+ 2U&a*cc*cosB+ 2Unbb*cc*cosa]  8/37t [t7„(flo*) + 2  2  2  22  l2  3i  279  Appendix D  Table D.1.3. Bond Lengths (A).  fl  atom  atom  distance  atom  atom  distance  Ru(l)  0(1)  1.892(3)  Ru(l)  N(l)  2.038(3)  Ru(l)  N(2)  2.029(3)  0(1)  C(29)  1.34(1)  0(1)  C(29a)  1.18(3)  N(l)  C(l)  1.385(5)  N(l)  C(4)  1.366(5)  N(2)  C(6)  1.375(5)  N(2)  C(9)  1.380(5)  C(l)  C(2)  1.437(6)  C(l)  C(10)*  1.377(6)  C(2)  C(3)  1.341(6)  C(3)  C(4)  1.441(5)  C(4)  C(5)  1.396(5)  C(5)  C(6)  1.384(5)  C(5)  C(ll  1.511(5)  C(6)  C(7)  1.431(5)  C(7)  C(8)  1.346(6)  C(8)  C(9)  1.436(6)  C(9)  C(10)  1.394(6)  C(10)  C(20)  1.517(6)  C(il)  C(12)  1.389(5)  C(ll  C(16)  1.387(6)  C(12)  C(13)  1.384(5)  C(12)  C(17)  1.508(6)  C(13)  C(14)  1.373(6)  C(14)  C(15)  1.368(6)  C(14)  C(18)  1.511(6)  C(15)  C(16)  1.401(6)  C(16)  C(19)  1.493(6)  C(20)  C(21)  1.396(8)  C(20)  C(25)  1.364(8)  C(21)  C(22)  1.403(8)  C(21)  C(26)  1.476(9)  C(22)  C(23)  1.34(1)  C(23)  C(24)  1-35(1)  C(23)  C(27)  1 539(g)  C(24)  C(25)  1.410(8)  C(25)  C(28)  1 499(g)  C(29)  C(30)  156(1)  C(29)  C(31)  155(2)  C(29a)  C(30)  1.66(3)  C(29a)  C(31)  1.47(3)  "Here and elsewhere in D.l, * refers to symmetry operation: 1/2-x, 1/2-y, 1/2-z.  280  Appendix D Table D.1.4.  atom 0(1) 0(1) 0(1) N(l) N(2) Ru(l) Ru(l) Ru(l) C(6) N(l) C(l) N(l) C(3) C(4) N(2) C(5) C(7) N(2) C(l)* C(9) C(5) C(ll) C(13) C(13) C(15) C(ll) C(15) C(10) C(20) C(22) C(22) C(24) C(20) C(24) 0(1) 0(1) C(30)  B o n d Angles (°).  atom Ru(l) Ru(l) Ru(l) Ru(l) Ru(l) 0(1) N(l) N(2) N(2) C(l) C(2) C(4) C(4) C(5) C(6) C(6) C(8) C(9) C(10) C(10) C(ll) C(12) C(12) CO 4) C(14) C(16) C(16) C(20) C(21) C(21) C(23) C(23) C(25) C(25) C(29) C(29a) C(29a)  atom 0(1)* N(l)* N(2)* N(2) N(2)* C(29a) C(4) C(6) C(9) C(10)* C(3) C(3) C(5) C(ll) C(5) C(7) C(9) C(10) C(9) , C(20) C(16) C(13) C(17) C(15) C(18) C(15) C(19) C(25) C(22) C(26) C(24) C(27) C(24) C(28) C(31) C(30) C(31)  angle 180.0 89.0(1) 88.8(2) 90.0(1) 180.0 155(1) 126.4(3) 126.3(3) 107.2(3) 125.4(4) 107.6(4) 109.1(4) 124.9(4) 118.6(4) 126.2(4) 125.0(4) 107.5(4) 125.9(4) 125.7(4) 115.3(4) 120.8(4) 119.1(4) 119.5(4) 118.3(4) 121.2(5) 118.3(4) 120.2(5) 119.6(5) 117.0(7) 121.2(7) 118.7(8) 119(1) 119.1(7) 119.1(8) 103(1) 101(1) 100(1)  281  atom 0(1) 0(1) N(l) N(l) Ru(l) Ru(D  C(l) Ru(I) N(l) C(2) C(2) N(l) C(4) C(6) N(2) C(6) N(2) C(8) C(l)* C(5) G(12) C(ll) C(12) C(13) C(14) C(ll) C(10) C(21) C(20) C(21) C(22) C(23) C(20) 0(1) C(30) 0(1)  atom Ru(l) Ru(l) Ru(l) Ru(l) 0(1) N(l) N(l) N(2) C(l) C(l) C(3) C(4) C(5) C(5) C(6) C(7) C(9) C(9) C(10) C(ll) C(ll) C(12) C(13) C(14) C(15) C(16) C(20) C(20) C(21) C(22) C(23) C(24) C(25) C(29) C(29) C(29a)  atom N(l) N(2) N(l)* N(2)* C(29) C(l) C(4) C(9) C(2) C(10)* C(4) C(5) C(6) C(ll) C(7) C(8) C(8) C(10) C(20) C(12) C(16) C(17) C(14) C(18) C(16) C(19) C(21) C(25) • C(26) C(23) C(27) C(25) C(28) C(30) C(31) C(31)  angle 91.0(1) 91.2(2) 180.0 90.0(1) 139.7(5) 126.6(3) 107.0(3) 126.4(3) 108.7(4) 125.9(4) 107.6(4) 126.0(4) 125.0(4) 116.3(4) 108.8(4) 107.8(4) 108.6(4) 125.6(4) 119.0(4) 118.8(4) 120.3(4) 121.4(4) 121.9(4) 120.5(5) 122.1(5) 121.6(4) 119.7(6) 120.6(6) 121.8(6) 123.4(8) 121(1) 121.2(9) 121.7(6) 100(1) 101.0(8) 117(2)  Appendix  Table D.1.5. Least-Square Planes. Plane number 1 Atoms defining Distance plane -0.008(3) N(l) -0.005(3) N(2) 0.006(5) C(l) 0.007(5) C(2) 0.004(5) C(3) 0.002(4) C(4) -0.002(4) C(5) 0.001(4) C(6) 0.002(4) C(7) -0.001(5) C(8) -0.003(4) C(9) 0.014(5) C(10) Additional Distance Atoms 0.022 Ru(l) -1.867 0(1) 0.097 C(H) -0.021 C(20) Plane number 6 Atoms defining Distance plane -0.001(4) C(ll) 0.008(4) C(12) -0.011(4) C(13) 0.003(4) CO 4) 0.006(5) C(15) -0.006(4) C(16) Additional Distance Atoms 0.054 C(5) 0.053 C(17) -0.007 C(18) -0.029 C(19)  Plane number 3  Plane number 2 Atoms defining plane Distance N(l)" -0.003(3) C(l) 0.005(5) C(2) -0.002(5) C(3) -0.003(5) C(4) 0.004(4) Additional Atoms Distance Ru(l) 0.039 C(5) 0.005 C(10)* 0.005 Plane number 4 Atoms defining Distance plane -0.001(3) N(l) 0.000(3) N(2) 0.004(4) C(4) -0.003(4) C(5) 0.002(4) C(6) Additional Distance Atoms 0.034 Ru(l)  Plane number 5 Atoms defining plane Distance N(l)* 0.023(4) N(2) -0.002(3) C(l)* -0.002(3) C(9) 0.003(4) C(10) 0.000(5) Additional Atoms Distance Ru(l) -0.008  282  Atoms defining plane Distance N(2) -0.001(3) C(6) 0.002(4) C(7) -0.001(4) c(8)  0:000(5)  C(9) Additional Atoms Ru(l) C(5) C(10)  0.001(4) Distance 0.031 -0.004 0.022  Plane number 7 Atoms defining Distance plane 0.001(4) C(20) -0.004(5) C(21) 0.005(7) C(22) -0.001(8) C(23) -0.003(7) C(24) 0.001(6) C(25) Additional Distance atoms -0.084 C(10) -0.041 C(26) C(27) 0.004 -0.025 C(28)  Appendix D  Table D.1.5. Least-Square Planes (continued). Summary mean deviation 0.0046 0.0032 0.0010 0.0019 0.0019 0.0059 0.0025  plane 1 2 3 4 5 6 7  7 22.5 3.0 0.4 1.6 1.3 13.8 1.2 2  Dihedral angles between planes (°) plane 2 3 4 5 6 7  1 0.35 0.18 0.22 1 13 86 94 94 15  2  0.33 0.36 1.25 86.63 93 97  3  0.04 1.31 86.95 93.97  4  1.35 86.97 93.93  Table D.1.6. Non-bonded Contacts out to 3. distance ADC atom atom 3.511(6) 4 C(14) C(7) 3.515(6) 4 C(15) C(8) 2.89 4 H(2) C(7) 2.94 4 H(9) C(13) 2.87 4 H(5) C(14) 2.96 44411 H(3) C(15) 2.50 45507 H(34) H(l) 2.55 4 H(15) H(4)  283  86.74 95.22  81.61  atom C(7) C(13) C(13) C(14) C(l 5) C(16) H(2) H(6)  atom C(l 5) C(l 7) H(3) H(3) H(4) H(4) H(7) H(24)  distance •3.530(6) 3.552(7) 2.78 2.68 2.93 2.98 2.56 2.36  ADC 4 4 44411 44411 44411 44411 44411 45067  Appendix D  Appendix D  285  Appendix D Table D.2.1. Experimental Details. A.  Crystal Data  Empirical Formula  C62H02CI4O2N4RU  Formula Weight  1138.08  Crystal Color, Habit  dark-brown prism, prism  Crystal Dimensions  0.40 x 0.40 x 0.40 mm  Crystal System  tetragonal  Lattice Type  I-centered  No. of Reflections Used for Unit Cell Determination (29 range)  25 (20.1 -27.1°)  Omega Scan Peak Width at Half-height  0.39° a = 29.334(2) A c= 13.517(6) A V = 11630(4) A  Lattice Parameters  Space Group  I4,/a(#88)  Z value  8  D |c  1.300 gem'  3  3  M  4720.00  Fooo  4.98 cm"'  p(MoKa)  . Intensity Measurements Diffractometer  Rigaku AFC6S  Radiation  MoKa(X = 0.71069 A) graphite monochromated Take-off Angle 6.0°  Detector Aperture  6.0 mm horizontal 6.0 mm vertical  Crystal to Detector Distance  285 mm  Temperature  21.0 °C  Scan Type  ©-29  286  Appendix D Scan Rate  16.0° min (in ©) (up to 9 scans)  Scan Width  (1.37+ 0.35 tan G)°  -1  55.1°  20max  Total: 7249 Unique: 6984 (R*, = 0.034)  No. of Reflections Measured  Lorentz-polarization Absorption (trans, factors: 0.933 - 1.000)  Corrections  C.  Structure Solution and Refinement Patterson Methods (DIRDIF92 PATTY)  Structure Solution Refinement  Full-matrix least-squares  Function Minimized  Lco(|F | - |F |)  Least Squares Weights  Vc (Fo) = 4F /c\Fo )  0  2  C  2  2  2  0  p-factor  0.008  Anomalous Dispersion  All non-hydrogen atoms  No. Observations (I > 3.00a(I))  2421  No. Variables  376  Reflection/Parameter Ratio  6.44  Residuals: R, R«  0.051; 0.046  Goodness of Fit Indicator  2.62  Max Shift/Error in Final Cycle  0.03  Maximum peak in Final Diff. Map  0.75 e ' A  Minimum peak in Final Diff. Map  -0.41 e"A-  3  287  3  Appendix D  Table D.2.2. Atomic Coordinates and B*,. B  atom  tJ1  Cl(l) Cl(la) Cl(2) Cl(2a) 0(1) N(l) N(2) C(l) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) =0(26) C(27) C(28) C(29) C(29a) C(30) C(30a) C(31) C(31a)  5.02(2) 21.4(3) 20.0(7) 17.6(3) 21.3(8) 8.6(2) 54(1) 5.7(1) 60(2) 7.1(2) 7.1(2) 5.6(2) 5.6(2) 5.8(2) 7.4(2) 8.1(2) 6.1(2) 6.3(2) 5.3(2) 6.3(2) 66(2) 6.5(2) 6.4(2) 5.5(2) 9.1(3) 9.3(2) 7.9(2) 7.1(3) 8.3(3) 10.4(3) 10.7(4) 9.9(3) 9.5(3) 12.9(4) 16.3(4) 12.7(4) 13.8(10) 0.68 11(1) 0.32 30(1) 0.68 20(2) 0.32 25(1) 0.68 29(3) 0.32 f 2Uuaa*cc*'cos B+ 2U]2aa*bb*cosy 0.7500 0.6392(8) 0.703(1) 0.4757(6) 0.601(2) 0,6859(5) 0.6296(3) 0.8060(4) 0.5500(5) 0.4832(5) 0.5210(5) 0.6140(5) 0.6740(5) 0.7635(5) 0.8278(6) 0.9081(6) 0.8957(5) 0.9626(5) 0.6412(5) 0.5783(5) 0.5462(5) 0.5762(6) 0.6379(5) 0.6724(5) 0.5446(6) 0.5401(6) . 0.7382(6) 1.0588(7) 1.1419(7) 1.2306(7) 1.2347(9) 1.1540(10) 1.0622(8) 1.1396(7) 1.3306(8) 0.9746(9) 0.623(3) 0.689(3) 0.628(4) 0.638(5) 0.556(3) 0.496(7)  0.2500 0.2522(2) 0.2128(7) 0.1637(2) 0.1449(6) 0.2206(2) 0.2897(2) 0.2990(2) 0.2795(2) 0.3170(2) 0.3492(2) 0.3323(2) 0.3563(2) 0.3403(2) 0.3646(2) 0.3382(3) 0.2969(2) 0.2611(2) 0.4035(2) 0.4096(2) 0.4538(3) 0.4909(2) 0.4836(2) 0.4400(2) 0.3704(3) 0.5384(2) 0.4350(2) 0.2654(2) 0.2820(3) 0.2843(3) 0.2710(4) 0.2554(3) 0.2521(3) 0.2966(3) 0.2750(3) 0.2338(4) 0.222(1) 0.202(2) 0.2439(9) 0.201(3) 0.171(1) 0.216(2)  0.2500 0.4133(3) 0.4034(9) 0.3415(2) 0.3487(6) 0.2998(2) 0.2386(2) 0.2923(2) 0.2109(2) 0.2109(2) 0.2386(2) 0.2559(2) 0.2856(2) 0.3021(2) 0.3327(2) 0.3397(3) 0.3146(2) 0.3133(2) 0.2993(2) 0.3365(3) 0.3463(2) 0.3210(3) 0.2848(3) 0.2734(2) 0.3655(3) 0.3324(3) 0.2330(3) 0.3397(4) 0.3181(4) 0.3428(4) 0.3864(-D) 0.4080(3) 0.383 i-(4) 0.2689(4) 0.4151(4) 0.4085(3) 0.3269(9) 0.340(2) 0.366(1) 0.375(2) 0.318(1) 0.334(2)  Ru(D  Z/3n [Un(aa*f + U {bb*f + U {cc*Y + 2  B  eq  22  occ. 0.50 0.68 0.32 0.68 0.32  i3  2U 3bb*cc*cosa] 2  288  Appendix D  Table D.2.3. Bond Lengths (A). atom Ru(l) Ru(l) Cl(l) Cl(la) Cl(2) 0(1) N(l) N(2) C(l) C(2) C(4) C(5) C(7) C(9) C(ll) C(12) C(13) C(14) C(16) C(20) C(21) C(23) C(24) C(29a) C(29) C(29)  atom 0(1) N(2) C(30a) C(30a) C(31a) C(29a) C(l) C(6) C(2) C(3) C(5) C(ll) C(8) C(10) C(12) C(13) C(14) C(18) C(19) C(25) C(26) C(24) C(25) C(30) C(30) C(31).  atom Ru(l) Cl(l) Cl(la) Cl(2) Cl(2a) 0(1) N(l) N(2) C(l) C(3) C(5) C(6) C(8) C(10) C(ll) C(12) C(14) C(15) C(20) C(21) C(22) C(23) C(25) C(29a) C(29) C(29)  distance 1.905(6) 2.042(5) 1.87(8) 1.25(4)* 1.58(5) 1.29(5) 1.381(7) 1.373(7) 1.425(8) 1.346(8) 1.383(8) 1.509(8) 1.350(8) 1.387(8) 1.393(8) 1.397(8) 1.379(9) 1.513(9) 1.491(8) 1.35(1) 1.51(1) 1.34(1) 1.44(1) 1.66(5) 1.31(4) 1.77(5)  atom N(l) . C(30) C(30) C(31) C(30a) C(29) C(4) C(9) C(10)* C(4) C(6) C(7) C(9) C(20) C(16) C(17) C(15) C(16) C(21) C(22) C(23) C(27) C(28) C(30a) C(30a) C(31a)  Here and elsewhere in D.2, * Denotes symmetry operation: 1/2-x, 1/2-y, 3/2-z.  289  distance 2.029(4) 1.42(4) 1.75(5) 1.30(3) 1.89(7) 1.16(3) 1.365(7) 1.379(7) 1.394(8) 1.445(8) 1.384(8) 1.439(8) 1.427(8) 1.519(9) 1.378(8) 1.501(9) 1.366(9) 1.399(8) 1.38(1) 1.40(1) 1.34(1) 1.55(1) 1.49(1) 1.25(7) 157(4) 1.74(9)  Appendix D  Table D.2.4. Bond Angles (°). atom 0(1) 0(1) 0(1) N(l) N(2) Ru(l) Ru(l) Ru(l) C(6) N(l) C(l) N(l) C(3) C(4) N(2) C(5) C(7) N(2) C(l)* C(9) C(5) C(ll) C(13) C(13) CO 5) C(ll) C(15) C(10) C(20) C(22) C(22) C(24) C(20) C(24) 0(1) 0(1) C(30) Cl(l) Cl(l) Cl(la) Cl(2) Cl(2)  atom Ru(l) Ru(l) Ru(l) Ru(l) Ru(l) 0(1) N(l) N(2) N(2) C(l) C(2) C(4) C(4) C(5) C(6) C(6) C(S) C(9) C(10) C(10) C(ll) C(12) C(l 2) C(l 4) C(14) C(16) C(16) C(20) C(21) C(21) C(23) C(23) C(25) C(25) C(29) C(29) C(29) C(30) C(30a) C(30a) C(31) C(31a)  atom 0(1)* N(l)* N(2)* N(2) N(2)* C(29) C(4) C(6) C(9) C(10)* C(3) C(3) C(5) C(H) C(5) C(7) C(9) C(10) C(9) C(20) C(l 6) C(13) C(l 7) C(l 5) C(18) COS) CO 9) C(25) C(22) C(26) C(24) C(27) C(24) C(28) C(30) C(31) C(31) C(29) C(29a) C(29a) C(29) C(29)  angle 180.0 88.8(2) 88.8(2) 89.7(2) 180.0 146(1) 125.9(4) 126.4(4) 107.9(5) 125.4(6) 107.6(6) 108.5(6) 123.8(6) 117.7(6) 126.3(6) 125.3(6) 108.3(6) 126.4(6) 125.4(6) 118.7(6) 118.4(6) 118.0(7) 119.9(7) 118.2(7) 121.0(8) 118.4(6) 118.7(7) 119.5(9) 118.4(9) 119(1) 121(1) 116(1) 119(1) 117(1) 125(3) 104(2) 124(2) 160(3) 117(4) 98(5) 119(3) 106(4)  290  atom 0(1) 0(1) N(l) N(l) Ru(l) Ru(l) CO) Ru(l) N(l) C(2) C(2) N(l) C(4) C(6) N(2) C(6) N(2) C(8).  cor  C(5) C(12) C(ll) C(12) C(13) CO 4) C(ll) C(10) C(21) C(20) C(21) C(22) C(23) C(20) 0(1) 0(1) 0(1) Cl(l) Cl(la) Cl(l) Cl(la) Cl(2a)  atom Ru(l) Ru(l) Ru(l) Ru(l) 0(1) N(l) N(l) N(2) C(l) CO) C(3) C(4) C(5) C(5) C(6) C(7) C(9) C(9) C(10) C(H) C(ll) C(12) C(13) C(14) CO 5) C(16) C(20) C(20) C(21) C(22) C(23) C(24) C(25) C(29a) C(29) C(29) C(30) C(30) C(30a) C(30a) C(31)  atom angle 91.2(2) NO) 91.2(2) N(2) 180.0 N(l)* 90.3(2) N(2)* 150(2) C(29a) 126.7(4) CO) 107.4(5) C(4) 125.7(4) C(9) 109.0(6) C(2) 125.6(6) C(10)* 107.5(6) C(4) 127.7(6) C(5) 124.0(6) C(6) 118.3(6) C(H) 108.4(6) C(7) 107.2(6) C(8) C(8) 108.1(6) 125.4(6) C(10) C(20) 115.8(6) C(12) 120.4(6) C(16) 121.2(6) C(17) 122.0(7) 122.0(7) CO 4) CO 8) 120.8(8) 122.2(7) C(16) 122.9(6) C(19) 119.5(8) C(21) 121.0(9) - C(25) 121.6(8) C(26) C(23) .121(1) 122(1) C(27) 119(1) C(25) 123.0(10) C(28) 139(5) C(30a) 120(4) C(30a) 142(3) C(31a) 121(4) C(29a) 109(3) C(29) 102(4) C(29) 124(4) C(29) 98(3) C(29)  Appendix D  Table D.2.5. Least-Square Planes. Plane number 2  Plane number 1 Atoms defining plane Ru(l) N(l) N(2) C(l) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) Additional Atoms 0(1) C(29a) C(29) C(30) C(30a) C(31) C(31a) H(27)  Atoms defining plane N(l)  Distance 0.004 0.019 0.022 0.012 -0.022 -0.019 -0.003 0.005 0.013 0.011 -0.013 -0.008 -0.022 Distance 1.906 3.025 2.901 3.501 4.182 . 3.750 3.928 2.560  CO)  C(2) C(3) C(4) Additional Atoms Ru(l) C(5) C(10)  Distance 0.000(5) 0.003(7) -0.005(7) 0.005(7) -0.002(6) Distance -0.053 0.005 -0.113  Plane number 3 Atoms defining plane N(2) C(6) C(7) C(8) C(9) Additional Atoms Ru(l) C(5) C(10)  Distance 0.005(5) -0.009(6) 0.007(7) -0.002(8) -0.005(7) Distance -0.033 -0.035 -0-009  Plane number 4  Plane number 5  Plane number 6  Plane number 7  Atoms defining plane Ru(l)  Atoms defining plane Ru(l) N(l)* N(2)  Atoms defining plane  Atoms defining Distance plane C(20) -0.002(7) C(21) 0.004(8) C(22) -0.001(9) C(23) -0.01(1) C(24) 0.007(9) C(25) -0.002(8) Additional atoms Distance C(10) -0.043 C(26) -0.010 C(27) 0.048 C(28) -0.014  NO)  Distance -0.010 0.013 0.007 -0.007 -0.003 0.000  N(2) C(4) C(5) C(6) Additional Distance atoms -0.002 C(5) -0.048 C(10)  CO)*  Distance -0.007 -0.003 0.013 0.012 -0.007 -0.009  C(9) C(10) Additional Distance atoms -0.027 C(5) C(10) -0.009  291  C(ll)  Distance -0.003(6) 0.003(6) -0.004(7) 0.003(6) -0.004(6) 0.004(6)  C(12) C(13) C(14) C(15) C O 6) Additional Distance atoms -0.069 C(5) CO 7) 0.014 -0:006 C(18) -0.028 C(19)  Appendix D  Table D.2.5. Least-Square Planes (continued). Summary mean deviation  plane  0.0135 0.0029 0.0056 0.0067 0.0084 0.0034 0.0036  1 2 3 4 5 6 7  0.0 1.1 4.2 0.0 0.0 1.6 1.1  Dihedral angles between planes nlanp  L / l u l Iw  2 3 4 5 6 7  1 1.09 0.83 0.22 0.55 87.11 92.84  2 1.72 0.92 1.63 87.60 91.93  3  1.04 0.52 86.28 92.87  Table D.2.6. Non-bonded Contacts out to 3.60 A. atom atom distance ADC Cl(la) C(24) 3.44(2) 54616 C(3) C(14) 3.524(9) 45412 Cl(l) H(26) 2 96 45615 Cl(la) H(4) 3.24 54616 C(13) H(2) 2.99 3 C(14) H(6) 2.90 45412 C(15) H(2) 2.91 3 H(5) H(18) 2.55 55403 H(ll) H(18) 2.26 55403 H(21) H(22) 2.09 54716  292  4  0.76 87,30 92.75  86.72 93.19  atom atom C(2) C(2) C(3) C(3) Cl(l) Cl(l) Cl(2a) Cl(2a) C(14) n\A\ u C(15) C(15) C(27) C(27) H(6) H(6) H(20) worn  atom atom C(13) C(13) C(13) C(13) H(17) H(17) H(4) H(4) H(2) H n ^m, H(13) H(13) H(21) H(21) H(13) H(13) H(20) W2G\  W  83.87  distance ADC 3.592(9) 45412 3.581(9) 45412 -3.03 45615 3.15 54616 2.67 3 2.82 2.90 2.38 2 38  45412 45715 45412 55713  Appendix E  Appendix E. Oxidation of Alcohols, Alkenes and Alkanes by Ru(TDCPP-Cl ) 8  Species. E.l.  Oxidation of benzyl alcohol at 50 °C under 1 atm air.  Table E . l . Time (h) 0 24 47.5 74.25 92.5 116.5 140.5 244 289.5 360 412  [Ru (TDCPP-Cl )(0) ] = 3.5 x 10" M benzyl alcohol] = 0 580 M A alcohol] = 0.290 M Conversion to Time (h) Conversion to benzaldehyde (%) benzaldehyde (%) 0 0 0 0.627 24 1.06 1.74 47.5 2.28 2.60 74.25 3.95 3.33 92.5 4.31 3.71 116.5 5.85 4.34 140.5 6.08 4.90 166.5 7.36 4.72 188 7.90 5.20 216.5 8.65 5.66 294 9.74 5.74 263 6.29 313 6.90 384 vl  5  8  2  [422 nm species] = 1.9 x 10 M 0.12,1 M [benzyl alcohol] = 0.0242 M Conversion to Time (h) benzaldehyde (%) -5  0 24 49.5 101 119.75 144.25 168.75  0 2.7733 4.8985 6.7525 7.5445 8.377 7.9495  Time (h)  0 24.5 50 101.25 119.75 144.5 169 194 219 242.5 288.75 312 337 360.5  0 1.9161 2.81385 4.4155 5.1305 5.634 6.169  293  0.242 M 0483 M Conversion to benzaldehyde (%) 0 0.86 1.53 2.61 2.99 3.22 3.56 3.90 4.15 4.62 5.04 5.38 5.74 5.80  0 0.48 0.96 1.66 1.85 1.88 2.54 2.85 3.06 3.49 3.97 3.95 4.50 4.52  Appendix E  E.2.  Oxidation of Alkenes under 1 Atm 0 . 2  Table E.2.1.  Oxidation of cyclohexene at 35 °C [Ru (TDCPP-Cl )(C0)] = 3.1x10" M. D  8  Blank  cyclohexene*  23 h at 35 °C (arbitrary units 16098000  8  cyclohexene-oxide  2427  cyclohexene-2-ol  31695  cyclohexene-2-one  46473  cyclohexene-peroxides  638  dimers  4604  See S e c t i o n t.^t laier IUI  me m n i m i w u u , .  Ru (TDCPP-Cl )(CO) heated for 23 h (arbitrary units) u  Substance present"  200640 3755 47629 45773 1089  v  7414 . v..~  ,  " the 20% loss due to evaporation has NOT been taken into account in this reported value; i.e. the amount of cyclohexene is increased by 20% prior to the calculation of percentage conversion (see Chapter 5). Table E.2.2.  Oxidation of m-cyclooctene at 93 °C. [Ru (TDCPP-Cl«)(0)2] = 5.0 x 10' M. Values in parentheses are those for the blank cyclooctene system at 110 °C heated for 23 h. 55 32 26 TIME (h) {23} 26106 279330 185130 601640 Amount of {2517200, cyclooctene 1697400}° (Arbitary units) VI  5  Amount of epoxide  73218  112940 {232670; 166060}  226300  50896  Amount of other products*  14661  16954 {102897; 49390)  40074  13165  ,  Two sets of data are given, which correspond to 2 GC runs of the same sample. * See Section E.5 later for the identification of the other products by GCMS analysis. 8  294  Appendix E  E.3.  Oxidation of Alkanes.  Table E.3.1.  Oxidation of methylcyclohexane under 1 atm 0 . Ru (TDCPP-CU(CO) (1); Ru (TDCPP-Cl )(Q) (2) Blank [(l)] = 3.1xlO" M [(2)]=l.lxlO"'M Substance present 17.5 h at 93 °C 20 h at 93 °C 24 h at 100 °C 1324900 3206100 6460500 methylcyclohexane* 2  D  %a  g  2  s  6  v OH  v  OH  &  . OH  .OH  6 .  $  [(2)] - 3.1x10" M 22.5 h at 100 °C 347380  19985  88347  16673  17588  9044  21819  5428  2821  1643  15232  3257  2761  3000  36750  7010  7368  1353  14679  2945  2846  5900  12142  3357  5104  27272  8451  9441  C7H14O3  Mixture of ringopened acids and/or peroxides  r 1 • See Section E.6 later for the identification of the substances present by G C M S analysis. ' * The 20% loss due to evaporation has N O T been taken into account in this reported value; i.e. the amount of methylcyclohexane is increased by 20% prior to the calculation of percentage conversion (see Chapter 5).  Table E.3.2. Oxidation of Ph CH catalyzed by Ru (TDCPP-Cl )(0) at 24 °C under Y1  3  1 atm air in penzene. imi y i i ^ i Time (h) 0 26 45.5 75.5 96 148.5 484  8  2  Turnovers per mole of initial porphyrin 0 0.895 1.21 1.42 1.56 1.69 3.07  295  Appendix E  E.4.  GCMS Data for the Cyclohexene Oxidation.  3:51  Relative intensity  9:01  10:50 12:17  8:00  0:00  5:00  15:39  _  10:00  14:35 15:00  17:38 ! 18:06  21:16  20:00  Retention time (min) Figure E.4.1.. GC trace for the run in Table E.2.2 for the oxidation of cyclohexene.  Table E.4.1.  Retention times and identity of substances from the GCMS analysis. Substance Retention Substance Retention Time Time (min) (min) cyclohexene-peroxide 14:35 cyclohexene 3:51 Dimeric product 15:39 cyclohexene-oxide 8:00 DIMER 17:38 cyclohexene-2-ol 9:01 18:06 DIMER cyclohexene-2-one 10:50 21:16 DIMER cyclohexene-3-one 12:17  296  Appendix E  Figure E.4.2. Low Resolution Mass Spectra for the various products indicated in Figure E.4.1. 83  o:  Relative intensity 69  55  8:00  98 28 20  42  _au 40  u.  1  60  LUI  100  80  140  120  160  180  200  180  200  M/z  170  98  OH  83  Relative intensity 55  28 20  9:01  41 JLiiL.  40  60  100  80  120  "140  160  M/z  68  96  Relative intensity  10:50  55 24 20  39  81  +iiJi.  40  100  80  60  M/z  297  120  140  Appendix E Figure E.4.2. continued... 68  Relative intensity  96  12:17  81 28 20  55  39 40  60  80  100  120  140  M/z 68  114  OOH 55  Relative intensity  96 44 28 20  14:35  81 86  40  80  60  100  TJo  "  140"  M/z 81 -  Relative  28  53  41 40  i  ,  f„  6  60  105 lOO  1,1 1 80  115117 120  133  154 140  15:39 Dimeric Product ,162 160  • 180  ,  ._  200  220  M/z  298  24<>  260  55o~  Appendix E  Figure E.4.2. continued... 137 139 81  95  67  123  96  55  Relative intensity 20  Ii  Ii  109  JX  100  80  151  1+  120  _1_  140  17:38 Dimeric Product  160  180  260  240  220  200  280  M/z 139  137 81  68  95  96  55  Relative intensity 1) 2  123  109 60  ""'I',  "I  i l " " ' - '  80  100  ,1.1,1,  120  L  151 L  140  18:06 Dimeric Product  231 loO  220~  M/z  299  240  260  280  Appendix E  E.5.  GCMS Data for the Cyclooctene Oxidation.  1:38 7:26  Relative intensity  12:29 9:56  9:51 | 0:00  5:00  10:00  14:44 ll  ,  15:00  20:00  Retention time (min) Figure E.5.1. GC trace for the run in Table E.2.1 for the oxidation of cyclooctene.  Table E.5.1. Retention times and identity of substances from the GCMS analysis. Substance Retention Substance Retention Time Time (min) (min) unknown, possible 11:52 cyclooctene 1:38 dimer cis-112:29 cyclooctene-oxide 7:26 oxabicyclo[4,3,0]nonane unknown 14:44 unknown 9:51 unknown 9:56  300  Appendix E  Figure E.5.2. Mass spectra for the various products indicated in Figure E.5.1. 155  26  Relative intensity  100  120  140  160  180  M/z 98 Unknown; possible dimer 11:52  Relative intensity  181 i  140  301  1  i  160  180  197  Appendix E 83  P Relative intensity  12.29  126 70 93 28  108  55 41 !.,  20  40  131  .1 !  60  120  100 M/z  80  140  160  180  81  Unknown product 14:44  Relative intensity  124  68 28  53  95  39 j  20  40  60  80  L  106  100 M/z  302  120  140  160  180  Appendix E  55  O 41  Relative intensity  6?  03  2?  97 111 111  0  1111 11 i i  i  iii I  I'I i i  i  126 i  i i  I i  i  i  i  i '  ii ''i  10 2 0 3 0 40 50 60 70 80 90 100 110 120 1 3 0 1 4 0 M/z  83  o  Relative intensity  12b  41  67  97  93,. I, 11111111 M 11111111  0  20  40  60  80  I I  I' I * 11' I I 1  108 I II  I I I  100  » I  120  .M/z Figure E.5.3. Known fragmentation patterns for cyclooctene-oxide and m-7-oxabicyclo[4,3,0]-nonane.  3 0 3  I I I  I  I'I  r i i i | i ii i |  140  i  Appendix E E.6.  GCMS Data for the Methylcyclohexane Oxidation.  |3:30  18 4:47  16 14  Relative 12 intensity 10 8  7:02  6 7:51  4 2  11:04  °l— 0:00  2:00  4:00  6:00  8:00  10:00  12:05 , 14:00  12:00  16:00  18:00  Retention time (min) Figure E.6.1. GC trace for the run in Table E.3.1 for the oxidation of methylcyclohexane.  Retention Time (min) 4:47  7:02  Substance methylcyclohexane  1 -methylcyclohexanol  Retention Time (min) 7:47" 7:51 7:55" 10:30 11:04 11:11 12:05  Substance (2,3 and 4)methylcyclohexanone  l-ol-(2,3 and 4)-ones  Peroxide and/or acid (2,3 and 4)7:36" methylcyclohexanol 7:43" " These retention times were not shown on the above chromatogram due to the lack of space  304  Appendix E  Figure E.6.2. Low resolution mass spectra for the various products indicated in Figure E.6.1. 1  171  OH Relative intensity  7:02  99  43  fO  29 _L  40  114  81  58  60  100  80  Tio  1 4 0 1 6 0  180  M/z  68  81  96  57  Relative intensity  7:36 ii4  43 28 20  •II  i  40  60  80  100 M/z  305  120  140  160  180  Appendix E  Figure E.6.2. continued.. |96  71 81  OH  ^  -OH  7:43  Relative intensity 57  41 113  29 _JL  20  40  60  80  100 M/z  306  120  140  160  180  Appendix E  307  Appendix E  Figure E.5.2. continued. 184  55  OH  cr  Relative intensity  10:50  43 69  112  28  100  80  60  40  20  128  97  120  140  M/z  160  180  98  169  Relative intensity  55  11:04  42 128  80 29 20  40  60  80  100  -I  M/z  308  r-  120  140  160  180  Appendix E  Figure E.5.2. continued..  56  69  OH  Relative intensity  98 128  11:11 41 83 29  i  114 100  80  60  40  20  120  160  140  180  M/z  143  126  Relative intensity  C  58  1  2  98  73  20  H  111  144 145_  JJ  4TT  L  60  0  12:05 84  27  7  80  120  AW M/z  309  140  160  180  3  Appendix F Appendix F. Kinetics Data for the Oxidation of Phenol by Ru (TMP)(0) . v,  2  Table F . l .  Pseudo-first-order rate constants, kobs, for the oxidation of phenol by Ru (TMP)(0) (1) (5.0 x 10 M) in benzene under 1 atm air, unless indicated otherwise. Data acquired on stopped-flow instrument. vl  -6  2  283.4 K [phenol] (M)  288.2 K  293.2 K  303.6 K  k„ (s ) (errors < 5% from linear regression of semilog plots) 8.66xl0" 1.40xlQ1.45xl0" 2.58 x 10' 1  b5  0.0973  3  2  5.95 x  4.30 x 10'  0.257  2  IO  - 2  0.301  5.36 x 10"  7.70 x  IO'  0.467  1.07 x  1.56 x  IO  2  IO  - 1  2.98 x 10"' 0.989 " Solutions purged with N for 10 min. * [(l)] = 3.0x 10' M.  2  7.50 x  1.37 x 10"  1  IO  - 2  (7.25  x  IO" )"  (7.67  x  IO" )*  2  2  1.82 x 10'  9.40 x 10'  1  2  2  - 1  3.86x 10°  1  3.40 x 10'  5.12 x 10"  8.30 x 10'  1.93 x 10'  1  1  1  2  6  Table F.2.  Absorbance-time data for the oxidation of phenol by Ru (TMP)(0) (1) in benzene under 1 atm air at 293.2 K, unless indicated otherwise. Ill L/ Vi ii^VUV U„ I1IUlA Ml... _ W - _»v — " — • — 5 [(l)] ______= 5.2x 10^M [(l)] = 4.5x 10' M [(l)] = 5.2x 10' M [phenol] = 0.0292 M [phenol] = 0.0102 M [phenol] = 0.0292 M Time (s) Absorbance" Time (s) Absorbance" Time (s) Absorbance" " 1.408 20 0.139 20 1.195 30 1.360 140 0.120 140 1.070 750 260 1.286 0.103 260 0.932 1470 380 1.195 0.093 380 0.811 2190 500 1.108 0.084 500 0.721 2910 620 1.027 0.079 620 0.656 3630 740 0.959 0.074 740 0.609 4350 860 0.904 0.071 860 0.577 5070 980 0.862 0.069 980 0.554 5790 1100 0.828 0.067 1100 0.539 6510 1220 0.801 0,066 1220 0.527 7230 0 0 0.70 0.062 00 0.50 00 vl  2  6  7  kobs = 2.7 x 10-V 4.8 x 10 V " Absorbance at 422 nm, monitored for the loss of (1). kobs =  310  kobs =  2.0 x l O ' V  Appendix F  Table F.2. continued. [(l)] = 4.0x lO^M [phenol] = 0.0381 M Time (s) 20 80 140 200 260 320 380 440 oo  Absorbance" 1.099 1.006 0.920 0.844 0.777 0.719 0.670 0.629 0.42  [(1)] = 2.5 x lO^M [phenol] = 0.0381 M Time (s) 20 140 260 380 500 620 740 860 980 1100 1220 oo  ko  bs  = 2.85  x 10'  3  s" 1  [(!)] = 3.6x 10' M [phenol] = 0.0547 M 6  Time (s) 20 140 260 380 500 620 740 860 980 1100 oo  Absorbance" 0.909 0.668 0.537 0.468 0.435 0.418 0.411 0.408 0.406 0.406 0.40  Absorbance" 0.630 0.510 0.425 0.367 0.325 0.298 0.280 0.267 0.260 0.255 0.251 0.24 3.15 x  kobs  10"V  [(!)] == 3.8x lO^M [phenol] = 0.0381 M Time (s) 20 140 260 380 500 620 740 860 980 1100 1220 00  Absorbance" 0.980 0.693 0.531 0.450 0.410 0.390 0.380 0.376 0.374 0.374 0.373 0.37  6.0 x l O ' V ' Absorbance at 422 nm, monitored for the loss of (1). kobs = 6.03  x 10'  3  s°  kobs  —  311  [(1)] == l.Ox 10" M [phenol] = 0.0381 M (monitored at 518 nm) Absorbance Time (s) 0.236 20 0.220 140 0.209 260 0.201 380 0.197 500 0.193 620 0.191 740 0.190 860 0.189 980 0.189 1100 0.185 oo 5  kobs  3.43 x lO s' -3  1  [(1)] '= 4.7xT0"*M [phenol] = 0.0381 M Time (s) 10 100 190 280 370 460 550 640 730 oo  kobs =  Absorbance" 1.219 0.880 0.691 0.615 - 0.588 0.579 0.5760.576 0.577 0.575  1.19 x  10-V  Appendix F  Table F.2. continued [(1)] = 4x 10" M = 0.0943 M [phenol] Absorbance" Time 1.341 10 (s) 1.128 50 0.935 90 0.815 130 0.745 170 0.705 210 0.684 250 0.671 290 0.665 330 0.659 610 0.65 cc 6  [(l)] = 5x lO^M [phenol] = 0.0943 M 1 atm 0 Time (s) Absorbance" 1.404 10 1.230 58 1.034 106 0.913 154 0.846 202 0.812 250 0.795 298 0.787 346 0.783 394 0.781 442 0.780 490 0.78 oo 2  1.40 x 10'' s' " Absorbance at 422 nm, monitored for the loss of (1).  1  ko  b s  =  1.41  x  10"  1  s" 1  .  kobs  312  [(l)] = 5x lO^M [phenol] = 0.0943 M 1 atmN Time (s) Absorbance" 1.395 10 1.058 58 106 0.858 0.755 154 202 0.693 250 0.665 298 0.654 346 0.648 394 0.645 442 0.641 490 0.641 0.64 oo 2  kobs =  141  x  10"'  s'  1  Appendix G Appendix G. Oxidation of A^-dimethylaniline by R u ^ T M P H O h in benzene.  112:23  Relative intensity  4:15  0:00  1:00  2:00  3:00  4:00  5:00  6:00  8:00  7:00  9:00  Retention time (min) Figure G.l.  GC trace of a benzene solution containing Ru (TMP)(0) with N.JV-dimethylaniline added. The sample with analytes corresponding to the retention times of 2:23 and 4:15 minutes were subjected to MS analysis (Figures G.2 and 3). VI  2  313  Appendix G  120 NMej Relative intensity  77 51  42  91  63  28 20  105  40  L  k  60  100  8 0  L  J  120  140  160  180  M/z Figure G.2.  Mass spectrum of analyte at 2:23 in the GC trace in Figure G. 1.  106  Relative intensity  [M-2H] 135  +  77  28 38 40 20  51  66 'ill  60  181  94 .  100  80  liO  140  160  M/z Figure G.3.  Mass spectrum of analyte at 4.15 in the GC trace in Figure G. 1  314  180  

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