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The coordination chemistry of ruthenium porphyrin complexes Sishta, Chand 1990

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THE COORDINATION CHEMISTRY OF RUTHENIUM PORPHYRIN COMPLEXES by CHAND SISHTA B.Sc, The University of New Brunswick, 1984 M.Sc, The University of British Columbia, 1986  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES THE DEPARTMENT OF CHEMISTRY We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA February, 1990 © Chand Sishta, 1990  In  presenting  degree at the  this  thesis  in  University of  partial  fulfilment  of  of  department  this thesis for or  publication of  by  his  or  her  of  DE-6 (2/88)  an advanced  Library shall make it  It  is  granted  by the  understood  that  head of copying  my or  this thesis for financial gain shall not be allowed without my written  Chemistry  The University of British Columbia Vancouver, Canada  Date  representatives.  for  agree that permission for extensive  scholarly purposes may be  permission.  Department  requirements  British Columbia, I agree that the  freely available for reference and study. I further copying  the  March 14, 1990  Abstract  This thesis work reports developments in the coordination chemistry of ruthenium porphyrin complexes, both in terms of the synthesis and chemistry of new compounds, as well as the study of the solution chemistry of some previously reported complexes. The synthesis, characterization and chemistry of ten new Ru(porp) coordination complexes in the oxidation states Ru  111  containing halide (Br, CI) and other axial ligands (pyridine, CH CN, NH 3  3  and Ru  lv  and SbF ) are described 6  in this thesis. Some additional ten Ru(porp) complexes have been studied in situ. Measurement of the rate constants for forward and reverse reactions and the corresponding equilibrium constant by 'H NMR and UV/visible spectroscopy for the dissociation of PPh ligand 3  from Ru(OEP)L(PPh ) (OEP is the octaethylporphyrinato 3  dianion; L = CO, PPh ) in C D to 3  7  S  generate the previously reportedfive-coordinateRu(OEP)L complexes allowed for an estimation of the Ru-P bond strength (64 _+ 9 kJ mol") in these complexes. A study of PPh dissociation from 1  3  Ru(OEP)CO(PPh ) in C-jDg and in CDC1 indicates that solvation effects play a major role, with 3  3  CDC1 being more capable than C D 3  7  of solvating the Ru(OEP)CO complex. The presence of trace  8  H 0 in these systems was a major problem, and the coordination of H 0 to Ru(OEP)L complexes 2  2  to generate the in situ Ru(OEP)L(H20) complexes (L = CO, PPh ) is described. The formation of 3  Ru(OEP)L(H 0) and the observed difference in the solvation of Ru(OEP)CO by C H 2  7  8  and CHC1  3  indicate that truly Five-coordinate species may not exist in solution. The outer-sphere oxidation of Ru(OEP)PPh by 0 3  to give [Ru (OEP)OH] 0 was shown to occur only in the presence of rv  2  2  H 0. 2  Mechanistic  studies on the previously reported reaction of HCI with [Ru(OEP)] to generate 2  Ru^OEPJCl, (C. Sishta, M.Sc.Thesis, University of British Columbia, 1986) show that solvent plays a major role in directing this oxidation reaction. A reaction stoichiometry of 4:1 between HCI and [Ru(OEP)] in C D 2  6  6  or C D 7  g  showed that HCI itself was the oxidant and not trace Cl  2  in HCI, as thought previously. A range of HX acids having plC, values in the range 38 to less  ii  than -10 (HX = H , MeOH, H,0, H S, CH COOH, C H COOH, HF, CF COOH, HN0 , HBF , HCI. 2  2  3  6  5  3  3  4  HBr, and HSbFg) were tested for reactivity with [Ru(OEP)] in C D ; the data showed that a 2  6  6  strong acid (pK^ < ca. 0) was necessary to initiate reactivity. The complex Ru (OEP)(SbF ) was IV  6  2  generated in situ by reacting HSbF with [Ru(OEP)] . 6  2  In CH C1 , a 1:1 stoichiometric reaction between HCI and [Ru(OEP)] was observed, instantly 2  2  2  fanning a mixture of products, tentatively formulated as Ru (OEP)H and [Ru(OEP)] CHCl based ra  2  on spectroscopic  2  data. The species proved impossible to separate. These same products were  formed slowly by the reaction of [Ru(OEP)] with CH C1 2  2  2  in the absence of HCI, and kinetic  studies suggest that a direct reaction of [Ru(OEP)] with CH C1 2  2  is likely, rather than reaction  2  of [Ru(OEP)] with impurities in CH C1 . The product mixture generated Ru(OEP)Cl upon further 2  2  2  2  reaction with HCI, both in the absence and in the presence of air. The complex Ru (OEP)(BF )-> IV  4  was generated in situ by an analogous reaction of aqueous HBF  with the product mixture. The  4  required hydrogen-containing co-product from the reaction of HX (X = Br, CI) with [Ru(OEP)| in 2  C D or CH C1 was not detected, but was shown not to be H . 7  g  2  2  2  Oxidation of Ru(porp)(CH CN) and Ru(OEP)py (py = pyridine; porp = OEP, TMP (the dianion 3  2  2  of tetramesitylporphyrin)) by gaseous HX (X = Br, CI) in the absence of air yielded Ru (porp)X IV  complexes.  The  bis(acetonitrile)  new  compound  precursor,  and  Ru(TMP)Br  2  was  was  characterized  synthesized by  by  spectroscopy;  this the  method chloride  using  2  the  analogue  Ru(TMP)Cl was generated in situ. 2  The magnetic properties (susceptibility and moment) of Ru(OEP)Br from 6 to 300 K are unlike 2  those reported for ruthenium(IV) non-porphyrin complexes,  and reveal a significant contribution  from temperature-independent paramagnetism. The reaction of Ru(OEP)X, (X = Br, CI) with NH gave the complexes Ru (OEP)X(NH ), in  3  3  which upon acidification under an inert atmosphere yielded the Ru (OEP)X compounds. These m  Ru  111  complexes were characterized by spectroscopic techniques, and the solution chemistry of the  five-coordinate species Ru(OEP)X was developed: the Ru (OEP)X(CH CN) species were also m  3  iii  characterized. Solvation of the five-coordinate species Ru(OEP)X (X = Br, CI) was observed in coordinating solvents to form the six-coordinate species Ru(OEP)X(solvent) (solvent = py, CH CN 3  and MeOH). Ru(OEP)X  Estimates of the equilibrium constants  were  obtained  from  UV/visible  for the association of these ligands to  titration experiments  in  CH C1 . 2  Similarly,  2  the  equilibrium constant for the association of Br to Ru(OEP)Br to generate in situ (rc-Bu) N  +  4  [Ru (OEP)Br ]", was measured. Disappointingly, the complexes Ru(OEP)X were shown not to ra  2  catalyze the oxidation of organic substrates such as cyclohexene. Electrochemical and spectroelectrochemical studies of the complexes Ru(OEP)X and Ru(OEP)X 2  (X = Br, CI) showed that the Ru^/Ru  111  couple occurred at 480-460 mV and 950-870 mV vs. NHE,  respectively, and that the probable reductant for the reaction of Ru(OEP)X with NH was NH 2  itself.  A facile reduction of Ru(OEP)(SbF )  3  3  gave the complex Ru (OEP)SbF , by a probable IU  6 2  6  homolysis of the Ru-F bond. The outer-sphere oxidation of Ru(OEP)py  2  by air in the presence of HX acids gave the  isolated or in situ characterized complexes [Ru (OEP)py ] in  X" (X = CI, Br, F , B F ) . Similar  +  2  oxidation of Ru(OEP)(CH CN) 3  that 0  2  2  4  formed [Ru(OEP)(CH CN) ]  +  3  2  Br . Electrochenucal studies showed -  in acidic media was capable of oxidizing the Ru(OEP)(solvent) complexes (solvent = py, 2  CH CN) to the Ru complexes, presumably generating H 0 . UI  3  2  iv  Table of Contents Pace  Abstract.  ii  Contents.  v  List of Tables.  ix  List of Figures.  xi  List of Schemes.  xviii  Abbreviations.  xix  Numerical key to Ru(porp) complexes discussed in this thesis.  xxiv  Acknowledgements.  xxvi  Chapter 1. Introduction.  1  1.1. Coordination chemistry at ruthenium porphyrin centers.  1  1.1.a. Ruthenium(II) carbonyl complexes.  1  1. l.b. Dioxygen and dinitrogen ruthenium compounds from Ru (porp)(solvent) complexes.  3  n  2  1.1 .c. Ruthenium(II) phosphine complexes.  5  1.1 .d. Other ruthenium(II) complexes.  8  1.1 .e. Ruthenium(III) complexes.  8  1.1. f. Ruthenium(IV) complexes.  10  1.1. g. Ruthenium(VI) complexes.  11  1.2. Organoruthenium porphyrin complexes.  12  1.2. a. Compounds originating from [Ru(OEP)] .  12  2  1.2.b. Compounds originating from 2 K [Ru(porp)]~.  12  1.2.c. Compounds originating from Ru(porp)X .  13  +  2  2  1.3. Objectives of this dissertation.  13  Chapter 2. Experimental.  16  v  2.1. Reagents and solvents.  16  2.2. Instrumentation and techniques for synthesis.  17  2.3. Preparation of ruthenium complexes.  23  2.3.a. Spectroscopic parameters for compounds prepared from literature methods.  23  2.3.b. Synthesis and characterization of new Ru(porp) complexes.  27  2.4. General and specific reaction conditions used to study the solution chemistry of Ru(OEP) complexes  35  Chapter 3. The reactivity of thefive-coordinatecomplexes carbonyl(octaethylporphyrinato)ruthenium(II), (3a), and (octaethylporphyrinato)(triphenylphosphine)ruthenium(II), (5a).  38  3.1. Introduction.  38  3.2. Results and discussion.  39  3.2.a. Reaction of Ru(OEP)PPh (5a) with small molecules.  39  3.2.b. The Reaction of PPh with Ru(OEP)CO (3a) in C H .  45  3  3  7  8  3.2.c. The Reaction of PPh with Ru(OEP)CO (3a) in CHC1 .  59  3.2.d. The Reaction of Ru(OEP)PPh" (5a) and PPh in C H .  67  3  3  3  3  7  8  3.2.e. Discussion of die rate (k„ and k. ) and equilibrium n  (KJ constants for the reaction of PPh widi Ru(OEP)L 3  (L = CO and PPh ).  75  3  3.2.f. Summary and discussion of activation and thermodynamic data for the reversible dissociation of PPh from 3  Ru(OEP)L(PPh ) (L= CO, PPh ). 3  79  3  3.2.g. The decarbonylation of aldehydes using Ru(OEP)PPh (5a). 3  Chapter 4. Further studies on the oxidation of bis((octaethlyporphyriiiato)vi  84  ruthenium(II)) (7) by HX acids.  88  4.1. Introduction.  88  4.2. Results and discussion.  89  4.2.a. Oxidation of [Ru(OEP)] (7) by the mixture H 0/0 . 2  2  89  2  4.2.b. Measurement of the stoichiometry for the reaction between [Ru(OEP)] (7) and HCI.  92  2  4.2.c. The attempted isolation and purification of the intermediates obtained from the reaction of [Ru(OEP)] with CH C1 and HC1/CH C1 . 2  2  2  2  96  2  4.2.d. Further characterization of the mixture 13/14.  100  4.2.e. Measurement of the kinetics of the reaction of CH C1 2  2  with [Ru(OEP)] .  110  2  4.2.f. Chemical behavior of the in situ mixture.  127  4.2.g. The reaction of [Ru(OEP)] (7) with chlorinated 2  reagents.  133  4.2.h. The fate of H in HX upon oxidation of 7 by HX in C H 7  andC H . 6  8  137  6  4.2.i. The effect of the acid HX used.  141  4.2.j. Generation of Ru(porp)X (8) from Ru(II) sources.  143  2  Chapter 5. Further characterization of Ru(OEP)X complexes and synthesis, 2  characterization and chemistry of several new Ru (OEP) complexes.  149  5.1. Introduction.  149  5.2. Results and discussion.  150  ra  5.2.a. Electrochemical studies of Ru(OEP)X . 2  150  5.2.b. Further studies on the magnetic properties of Ru(OEP)Br .  154  2  vii  5.2.c. Attempted generation of other Ru (OEP)X' complexes by 2  metathesis reactions of Ru(OEP)X (X = Br, 8a; CI, 8b) 2  with AgX' salts (X' = BF , 8c; SbF , 8d, and PF ). 4  6  164  6  5.2.d. Synthesis, characterization and chemistry of Ru(OEP)X(L) (X = Br, L = vacant, 16a; X = Br, L = NH , 3  16c; X = Br, L = CH CN, 16e; X = CI, L = vacant, 16b; 3  X = CI, L = NH , 16d; X = CI, L = CH CN, 16f). 3  3  5.2.d.l. Synthesis of 16a-b.  165 165  5.2. d. 2. Characterization of 16a-f.  168  5.2.d.3. Chemistry of Ru(OEP)X (X = Br,16a; CI, 16b).  183  5.2.e. Synthesis, characterization and chemistry of [Ru (OEP)(py) ] X- (X = CI, Ha; X = BF , 17b).  200  5.2.e.l. Synthesis of 17a-b.  200  5.2.e.2. Spectroscopic characterization of 17a-b.  201  ni  +  2  4  5.2.e.3. Chemistry of [Ru(OEP)(py) ] X", (17a-b). +  2  5.2.f. Summary of electrochemical data for Ru(OEP) complexes.  211 213  Chapter 6. General conclusions and recommendations for future studies.  219  Chapter 7. References.  222  Appendix 1. Information needed for the use of the NMR simulation program DNMR3.  231  Appendix 2. Data obtained from the titration of Ru(OEP)CO by PPh in C D as 3  7  8  a function of temperature.  234  Appendix 3. Data obtained from the titration of Ru(OEP)CO by PPh in CDC1 as 3  3  a function of temperature.  236  Appendix 4. Data obtained from the titration of Ru(OEP)PPh by PPh in C D as 3  a function of temperature.  3  7  8  238 viii  Appendix 5. Kinetic data for the reaction of [Ru(OEP)] with CH C1 at 293 K. 2  ix  2  2  240  List of Tables Table 3.1  Page Spectroscopic data for Ru(porp) complexes containing carbonyl and phosphine axial ligands.  3.2  41  Data for the simulation of *H N M R spectra for the chemical exchange system Ru(OEP)CO(PPh ) ^ R u ( O E P ) C O + P P h 3  3>  in C D as a function of 7  8  temperature. 3.3  52  Data for the simulation of 'H N M R spectra for the chemical exchange system Ru(OEP)CO(PPh )-Ru(OEP)CO  + P P h in CDC1 as a function of  3  3  3  temperature. 3.4  63  Equilibrium constants ( K ' ) measured for Ru(OEP)CO(PPh ) ^ 2  3  Ru(OEP)CO + P P h as a function of temperature in CHC1 . 3  3.5  68  3  Data for the simulation of 'H N M R spectra for the chemical exchange system Ru(OEP)(PPh ) ^ Ru(OEP)PPh + P P h in C D as a function of 3  2  3  3  7  8  temperature. 3.6  70  Equilibrium constants ( K ' ) measured for Ru(OEP)(PPh ) H 3  3  2  Ru(OEP)PPh + P P h as a function of temperature in C H . 3  3.7  3  Rate constants ( k  obs  7  74  g  ) for the dissociation of a ligand L' from  Ru(porp)L(L') as in Ru(porp)L(L') -• Ru(porp)L + L' in C H . 7  3.8  76  8  Equilibrium ( K g ) data at 293 K for the dissociation of a ligand L' from Ru(porp)L(L') as in Ru(rx)ip)UL')«^Ru(porp)L + L'  3.9  78  Summary of the activation and thermodynamic data for the equilibria Ru(OEP)L(PPh ) Ru(OEP)L + P P h ( L = CO, PPh ) in C H and CHC1 . 3  4.1  3  3  7  8  3  Summary of 'H N M R spectroscopic data for compounds relevant to the characterization of the products from the reaction of [Ru(OEP)] with 2  80  CH C1 .  91  4.2  X P S binding energies for several Ru(OEP) complexes.  108  4.3  Raw data for the change in the position (6) of the resonances of  2  2  [Ru(OEP)] (2) with time upon reaction of 7 (4.9 mM) with C D C 1 as 2  2  2  measured from the *H N M R spectrum of the reaction mixture in CD C1 .  111  4.4  Summary of data for the reaction of [Ru(OEP)] with C H C 1 at 293 K.  120  4.5  Summary of spectroscopic data for Ru (porp) complexes.  132  4.6  'H N M R spectroscopic data for [Ru(OEP)] and products generated from the  2  2  2  2  2  IV  2  reaction of [Ru(OEP)] with various solvents.  135  4.7  Data for the Curie plot for Ru(TMP)Br, (8e).  147  5.1  Corrected magnetic susceptibility and moment data for Ru(OEP)Br .  158  5.2  Microanalysis and conductivity data for several R u ( O E P ) complexes.  169  5.3  Summary of UV/visible spectroscopic and magnetic moment data for  2  2  m  R u ( O E P ) complexes.  169  m  5.4  Summary of *H N M R spectroscopic properties of R u ( O E P ) complexes.  174  5.5  Data for the Curie plot of Ru(OEP)Br, (16a).  176  5.6  Data for the Curie plot for Ru(OEP)Br(NH ), Q6c).  187  5.7  Summary of 'H N M R spectroscopic data for R u  205  5.8  Data for the Curie plot for [Ru(OEP)(py) ]Cl (17a).  207  5.9  Summary of electrochemical data for Ru(OEP) complexes.  214  m  3  111  bis(solvent) complexes.  2  xi  List of Figures Figure 1.1.  Structural features of (a) Ru(OEP)L2, and (b) RutTMP)!^ complexes,  2.1  UV/visible spectroscopy sample cells incorporating a Teflon-valve to seal the sample solution under an inert atmosphere or under vacuum. Cell A has no reservoir, while cells B and C have plain and calibrated reservoirs, respectively.  2.2  N M R sample tubes for use in the study of air-stable (A) or air-sensitive (B) samples. The side-arm in B allows the introduction of reagents to the sample without causing decomposition of the latter. Tube (C) incorporates a septum-port screw-cap fitting for use in experiments involving titration of samples in N M R tubes.  2.3  Exploded view of the apparatus used for the detection of H by direct 2  sampling of the reaction vapor phase via a gas sampler of a mass spectrometer. 3.1  (a) UV/visible spectral changes observed upon addition of M e O H (2.47 M) to Ru(OEP)CO (2.24 x 10" M) in C H at 293 K. (b) Plot of log 6  7  8  [(A-A )/(Aj-A)] vs. log [MeOH] for the above titration, measured at 0  r  393 nm. 3.2  (a) U N M R spectra of a mixture of Ru(OEP)CO (5.1 mM) and P P h (3.3 mM) l  3  in C D measured at 10 K intervals, and (b) spectra simulated using 7  8  the parameters listed in Table 3.2 and Appendix 1. 3.3  Ey ring plot of In (k, IT) vs. 1/T (K" ) for the dissociation of P P h from 1  3  Ru(OEP)CO(PPh ) in C D . 3  3.4  7  8  Plot of In K[ vs. 1 IT (K" ) for the dissociation of P P h from 1  3  xii  Ru(OEP)CO(PPh ) in C D . 3  7  55  8  3.5  UV/visible spectrum of (a) Ru(OEP)CO, 3a and (b) Ru(OEP)(CO) in C H .  3.6  (a) UV/visible spectral changes observed upon addition of P P h  2  7  8  58  3  (0.0831 M) to Ru(OEP)CO (3.87 x 10" M) in C H at 293 K. (b) Plot of 6  7  8  log [(A-A )/(Aj-A)] vs. log [PPh ] for the above titration, measured D  3  f  at 393 nm. 3.7  60  (a) 'H N M R spectra of a mixture of Ru(OEP)CO (8.77 mM) and P P h  3  (4.52 mM) in C D C 1 measured at 10 K intervals, and (b) spectra 3  simulated using the parameters listed in Table 3.3. 3.8  62  Eyring plot of ln (k /T) vs. 1/T (K" ) for the dissociation of P P h from 1  2  3  Ru(OEP)CO(PPh ) in CDC1 . 3  3.9  64  3  Plot of ln K vs. 1/T (K" ) for the dissociation of P P h from 1  2  3  Ru(OEP)CO(PPh ) in CHC1 . 3  3.10  65  3  (a) UV/visible spectral changes observed upon addition of P P h (0.676 M) 3  to Ru(OEP)CO (6.75 x 10" M) in C H C 1 at 293 K. (b) Plot of log 6  3  [(A-A )/(Aj-A)] vs. log [PPh ] for the above titration, measured at 0  3  f  393 nm. 3.11  66  Plot of ln K ' vs. 1/T (K ) for the dissociation of P P h from _1  2  3  Ru(OEP)CO(PPh )inCHCl . 3  3.12  68  3  (a) 'H N M R spectra of a mixture of Ru(OEP)(PPh ) (3.88 mM) and P P h 3  2  3  (3.18 mM) in C D measured at 10 K intervals and, (b) spectra simulated 7  8  using the parameters listed in Table 3.5. 3.13  69  Eyring plot of ln (k /T) vs. 1/T (K" ) for the dissociation of P P h from 1  3  3  Ru(OEP)(PPh ) in C D . 3  3.14  2  7  71  8  Plot of ln K vs. 1/T (K ) for the dissociation of P P h from _1  3  3  Ru(OEP)(PPh ) in C H . 3  2  7  72  8  xiii  15  (a) UV/visible spectral changes observed upon addition of P P h (0.0422 M ) 3  to Ru(OEP)(PPh ) (2.78 x 10" M) in C H at 293 K. (b) Plot of log 6  3  2  7  8  [(A-A )/(A -A)] vs. log [PPh ] for the above titration, measured at 0  ;  3  f  395 nm. 16  Plot of In K ' vs. 1/T (IC ) for the dissociation of P P h from 1  3  3  Ru(OEP)(PPh ) in C H . 3  1  2  7  8  'H N M R spectra of [Ru(OEP)] in C D containing added (a) 0.1 2  6  6  H 0, 2  and (b) 500 A»L 0 . Spectra were measured at 293 K at 400 M H z (FT). 2  2  'H N M R spectrum of the products of the reaction of [Ru(OEP)] with 2  excess HCI in C D C 1 vacuo, at 292K, 300 MHz. 2  3  2  'H N M R spectra of (a) [ R u ( O E P ) ]  + 2  BF " in C D C 1 and, (b) Ru(OEP)Cl(NH ) 4  2  2  3  in C D . The spectra were measured at 292 K at 300 M H z (FT) under an N 6  6  2  atm. 4  !  H N M R spectra of the product eluted from the attempted purification of 13/14 using chromatography. Spectrum was measured at 293 K, 300 MHz.  5  Fast atom bombardment (FAB) mass spectra of (a) 13/14 and, (b) the deuterated analogue of 13/14.  6  IR spectrum of the mixture 13/14 as a Nujol mull with K B r plates.  7  X-ray photoelectron spectra of (a) Ru(OEP)py , (b) Ru(OEP)CH , (c) 2  3  Ru(OEP)Cl, (d) Ru(OEP)Br, (e) Ru(OEP)Cl and (f) 13/14. 2  8  First order plot of ln(P -P ) for the resonance C H t  f  2 a  vs. time (min) for  the reaction of [Ru(OEP)] with CD C1 . 2  9  2  2  Plot of the observed chemical shift (ppm) of the individual porphyrin signals of 7 vs. equivalents of added HCI ([Ru] = 3.1 mM, [HCI] = 91 mM).  10  *H N M R spectra measured as a function of temperature for the product mixture obtained from the incomplete reaction of [Ru(OEP)] with C D C 1 2  xiv  2  2  in C D C 1 (16 mg/mL). The spectra were measured at 300 M H z in vacuo. 2  4.11  115  2  (a) Typical changes from the initial UV/visible spectrum of [Ru(OEP)] (7) 2  to that of the mixture 13/14 with time at 293 K. [Ru ] = 0.39 mM, 2  [CH C1 ] = 15.6 M. (b) Plot of ln(A -A ) vs. time for the above reaction.  117  4.12  Dependence of k  o b s  on the concentration of [Ru(OEP)] at high [CH C1 ].  121  4.13  Dependence of k  o b s  on [CH C1 ] at 293 K, [Ru ] = 0.6 +. 0.1 mM.  124  4.14  'H N M R spectrum of the in situ reaction mixture of 13/14 (3 mg) and  2  2  t  f  2  2  2  2  2  2  pyridine (1 M L ) in C D C 1 (0.6 mL) sealed under vacuum, measured at 2  2  293 K, 300 MHz. 4.15  129  The 'H N M R spectrum of in situ Ru(OEP)(BF ) (8c) in C D C 1 at 293 K, 4  2  2  2  300 MHz. 4.16  1 9  131  F N M R spectra of (a) H B F  4 ( a q )  and, (b) Ru(OEP)(BF ) . The spectra 4  2  were measured at 293 K, at 282 MHz, and are referenced against («-Bu) N  +  4  BF " (0.00 ppm).  134  4  4.17  Gas chromatograms of (a) the vapor phase sample from 7/HX reaction mixture, and (b) the corresponding H control experiment.  138  2  4.18  MS Spectra obtained from the GC/MS of (a) the solvent from the reaction of 7 with HBr in C H , (b) the C H control and, (c) the hydrogenated/ 7  8  7  8  brominated C H obtained upon reaction of C H / H B r with the silicon 7  g  7  8  septum. 4.19  139  'H N M R Spectrum of R u ( O E P ) ( S b F ) formed in situ by die addition of IV  6  2  HSbF to 7 in C D under N . Obtained at 293 K, 300 MHz. 6  4.20  6  6  142  2  'H N M R Spectra of (a) R u ( T M P ) ( C H C N ) (6d) in C D and, (b) Ru(TMP)Br, 3  2  7  8  (8e) in C D . Obtained at 293 K, 300 M H z (FT) in vacuo. 6  145  6  4.21  Curie plot of the isotropic shift (ppm) vs. 1/T (K" ) for Ru(TMP)Br .  5.1  Cyclic voltammograms of (a) Ru(OEP)Br and (b) Ru(OEP)Cl . Data measured  1  2  2  2  xv  148  in 0.1 M ( n - B u ) N C10 " (TBAP) in C H C 1 under an N atmosphere, 293 K. +  4  5.2  4  2  Bulk coulometry of Ru(OEP)Br  2  2  151  (8a). Trace A shows the optical spectrum  2  of 8a before coulometry at -235 mV vs. F c / F c in 0.1 M T B A P in CH C1 . +  2  2  Trace B shows the generated optical spectrum, which corresponds to diat of Ru(OEP)Br given in Section 5.2.d. 5.3  153  (a) Changes observed in the optical spectrum of Ru(OEP)Br (8a) upon 2  bulk coulometric oxidation of 8a at 900 mV vs. F c / F c in 0.1 M T B A P in +  CH C1 . (b) ESR spectrum of the solution generated in part (a). 2  155  2  5.4  Plot of  5.5  Plot of x  /i  e  f  (corrected) and  f  m  x (corrected) vs. T for Ru (OEP)Br .  160  IV  m  2  (corrected) vs. T for several Ru(IV) complexes including  K R u F , K R u C l , ( N H ) R u C l , Rt^RuClg, K R u B r and 8a.  162  5.6  Plot of T  163  5.7  '-H N M R spectra of (a) Ru(OEP)Br  2  6  2  1/2  6  4  2  6  2  6  vs. Mefr(corrected) for Ru(OEP)Br . 2  2  (5.32'mM) in CDC1 , (b) the reaction 3  mixture 5 minutes after addition of N H  3  (five mole equivalents), (c)  after 215 minutes, and (d) after 1170 minutes. The experiment was conducted aerobically, at 293 K and die arrows indicate the fate of each signal as the reaction progresses.  167  5.8  FAB-MS of (a) Ru(OEP)Br (16a) and, (b) Ru(OEP)Cl (16b).  170  5.9  UV/visible spectra of (a) Ru(OEP)Br (26.4 / i M ) , (b) Ru(OEP)Br(NH ) 3  (28.8 /xM), and (c) Ru(OEP)Br(CH CN) (29.2 / i M ) in C H 3  7  8 >  cell pathlength  = 1.00cm. 5.10  171  300 MHz, 'H N M R spectra of Ru(OEP)Br (16a) in C D at 293 K. The 6  6  spectrum of Ru(OEP)Cl (16b) is very similar to that of the bromide analogue. 5.11  173  Curie plot for Ru(OEP)Br (16a). Solid lines represent die least-square fit of the data, with extrapolation to 1/T = 0.  xvi  177  5.12  (a) Cyclic voltammogram of Ru(OEP)Br (16a) and, (b) 16a and added excess (n-Bu) N 4  5.13  +  Br". X-axis scale is in Volts vs. the F c / F c couple. +  Changes observed in the optical spectrum of 16a upon bulk coulometric oxidation of the solution at (a) +400 mV vs. F c / F c both in the absence +  and presence (25 equivalents) of added (n-Bu) N Br", (b) coulometric +  4  oxidation at 900 mV vs. F c / F c in the absence of added (n-Bu) N Br". +  +  4  The experiments were conducted in C H C 1 with 0.1 M T B A P electrolyte. 2  5.14  2  Infrared spectrum of Ru(OEP)Br(NH ) in the 4000-2500 cm" region, as 1  3  a KBr pellet. The IR spectrum of Ru(OEP)Cl(NH ) is identical to that of 3  the bromide analogue. 5.15  Curie plot for Ru(OEP)Br(NH ), J6c. Solid lines represent the least3  squares fit of the data, with extrapolation to 1/T = 0. 5.16  Infrared spectrum of Ru(OEP)Br(CH CN) as a Nujol mull. The IR spectrum 3  of Ru(OEP)Cl(CH CN) is identical, except that the ^ 3  C 3 N  is observed at  2250 cm" . 1  5.17  300 MHz, 'H N M R spectrum of [ R u ( O E P ) ( p y ) ] Br", isolated from the ni  +  2  reaction of Ru(OEP)Br with pyridine (see Figure 5.23b). 5.18  (a) UV/visible spectral changes observed upon addition of («-Bu) N Br" +  4  (68 mM) to Ru(OEP)Br (2.95 x 10" M) in C H C 1 at 293 K. (b) Plot of log 6  3  [(A-A )/(Aj-A)] vs. log [Br"] for the above titration, measured at 0  f  397 nm. 5.19  J  H N M R spectrum of N H  + 4  [ R u ( O E P ) B r ] " generated in m  2  situ by the  association of Br" to Ru(OEP)Br in CDC1 at 293 K. 3  5.20  UV/visible spectrum of the reaction mixture of Ru(OEP)Br (16a) with excess mCPBA in C H C N . 3  5.21  Gas chromatograms of (a) the reaction mixture from the reaction of  Ru(OEP)Br with excess PhIO in the presence of excess cyclohexene and, (b) the corresponding cyclohexene blank. 5.22  (a) Optical spectra of [Ru(OEP)(py) ] CI" Q7a, [Ru] = 46.5 /iM) measured +  2  in  CHCI3  with a 1.0 cm pathlength cell, (b) FAB-MS of 17a. The  corresponding UV/visible and FAB-MS spectra of [Ru(OEP)(py) ] BF ~ (17b) +  2  4  were identical in pattern but not in intensity to those of the chloride analogue. 5.23  1  H N M R spectra of (a) Ru (OEP)(py) and (b) [ R u ( O E P ) ( p y ) ] BF ". n  m  +  2  2  4  Spectra were recorded in CDC1 under aerobic conditions at 2 9 3 K, 3 0 0 3  M H z (FT). 5.24  Curie plot for [Ru(OEP)(py) ] CI", J7a. Solid lines represent the least+  2  squares fit of the data with extrapolation to 1/T = 0 . 5.25  C V for (a) Ru"(OEP)(py) , (b) 17a and (c) 17b. Experiments were 2  conducted in 0.1 M T B A P in C H C N , die X-axis scale is in mV vs. F c / F c . +  3  5.26  Bulk coulometry of [Ru(OEP)(py) ] BF " in 0.1 M T B A P in C H C N to +  2  generate (a) Ru (OEP)(py) n  5.27  4  3  and, (b) [ R u ( O E P ) ( p y ) ] . n ,  2  +  + 2  2  Cyclic voltammogram of Ru(OEP)Br(PPh ) in 0.1 M T B A P in CH C1 . X-axis 3  2  scale is in mV vs. the F c / F c couple. +  xviii  2  List of Schemes Page  Scheme 2.1  Synthetic strategy used to prepare key Ru(OEP) complexes.  24  3.1  Reactivity of Ru(OEP)PPh .  40  3.2  Proposed mechanistic scheme for the reaction of Ru(OEP)PPh with 0 / H 0 .  43  3.3  Alternate mechanistic scheme for the reaction of Ru(OEP)PPh with 0 / H 0 .  43  4.1  Proposed mechanistic scheme for the reaction of HCI with [Ru(OEP)] .  97  5.1  Summary of the reactivity of Ru(OEP)Br (16a).  3  3  3  2  2  2  xix  2  2  184  Abbreviations A  absorbance  AIBN  2,2'-azobisisobutyronitrile  br  broad, used in UV/vis or N M R spectroscopy  CV  cyclic voltammetry  D or d  deuterium  d  doublet, used in N M R spectroscopy  6  chemical shift relative to T M S  A  heat  DMA  N,N-dimethylacetamide  DMF  N,N-dimethylforrnamide  e  electron  EI  electron impact ionization technique in mass spectroscopy  ESR  electron spin resonance  FAB  fast atom bombardment ionization technique in mass spectroscopy  Fc  ferrocene, dicyclopentadieneiron(II)  G  Gauss  GC  gas chromatograph  GC-MS  gas chromatograph-mass spectrometer  ° H°  standard enthalpy of reaction  AH)  enthalpy of activation  H  m  meto-proton of an aryl or pyridyl ring  H  m e s o  meso-proton of the O E P macrocycle  H  Q  ORTHO-PROTON  H  p  H  of an aryl or pyridyl ring  para-proton of an aryl or pyridyl ring ,  rr  pyrrole-proton of the T P P or T M P macrocycle  xx  h  hour  hf  irradiation with UV/visible light  IR  infrared  K  degree Kelvin  Kp  equilibrium constant kinetic rate constant  k  observed kinetic rate constant  o b s  L  ligand  M  metal, or molarity unit  m  multiplet, used in N M R  mCPBA  meto-chloroperbenzoic acid  mJe  mass-to-charge ratio  NMR  nuclear magnetic resonance  OEP  octaethylporphyrinato dianion  spectroscopy  (OEP )  octaethylporphyrinato pi-cation radical anion  PhCN  benzonitrile  +  PPh  triphenylphosphine  3  P(n-Bu) PhIO  3  tri-n-butylphosphine iodosylbenzene  porp  porphyrinato dianion  ppm  chemical shift in parts per million relative to a reference  pyrr  pyrrole  q  quartet, used in N M R  R  aryl or alkyl  RT  room temperature  S  ground spin state  spectroscopy  xxi  s  second, or singlet when used in N M R spectroscopy  A S°  standard entropy of reaction  A St  entropy of activation  sh  shoulder  T  temperature  t  triplet, used in N M R spectroscopy  TBAP  tetra-n-butylarnmonium perchlorate  TEMPO  tetramethyl-l-piperidinyloxy  THF  tetrahydrofuran  TMP  tetramesitylporphyrinato dianion  TPP  tetraphenylporphyrinato  TTP  tetra-p-tolylporphyrinato dianion  UV/visible  ultraviolet-visible  v  infrared frequency  B.M.  Bohr magneton  M  effective magnetic moment  efr  e X V  dianion  molar extinction coefficient m  magnetic susceptibility Volts  xxii  Structure of porphyrinato dianions:  Ri  R2  Ri  porp  R[  R  OEP  Ethyl ( C J H J )  TPP  H .  Phenyl ( C H )  TMP  H  Mesityl ( 2 , 4 , 6 - { C H 3 ) C H )  TTP  H  para-Tolyl  2  H  6  5  3  xxiii  6  (0-CH )C H ) 3  6  4  2  Numerical key to Ruthenium complexes discussed in this Thesis Number  ComDlex  1  Ru^l-j^O  2  (Ru°) (CO)  3a  Ru (OEP)CO  3b  Ru (OEP)CO(MeOH)  4a  Ru (OEP)(PPh )  4b  Ru (TPP)(PPh )  5a  Ru"(OEP)PPh  3  5b  Ru (TPP)PPh  3  5c  Ru (OEP)PPh (H 0)  5d  Ru (TMP)P(«-Bu)  6a  Ru (OEP)py  6b  Ru (OEP)(CH CN)  6c  Ru"(TMP)py  6d  Ru (TMP)(CH CN)  7  [Ru (OEP)]  8a  Ru (OEP)Br  2  8b  Ru (OEP)Cl  2  8c  Ru (OEP)(BF )  8d  Ru (OEP)(SbF )  8e  Ru (TMP)Br  9  [Ru (OEP)OH] 0  10  Ru (OEP)Br(PPh )  ii  Ru (OEP)CO(PPh )  12  Ru (TPP)PPh (P(n-Bu) )  3  12  u  n  n  3  2  n  3  2  H  n  3  2  n  3  n  2  n  3  2  2  n  3  2  n  2  IV  IV  lv  4  2  lv  6  2  IV  2  rv  2  II!  3  n  3  n  3  3  xxiv  il  [Ru(OEP)] CHCl  ii  Ru (OEP)H  11  Ru (OEP)SbF  16a  Ru (OEP)Br  16b  Ru (OEP)Cl  16c  Ru (OEP)Br(NH )  16d  Ru (OEP)Cl(NH )  16e  Ru (OEP)Br(CH CN)  16f  Ru (OEP)Cl(CH CN)  Ha  [Ru (OEP)(py) ] C r  17b  [Ru (OEP)(py) ]  iZc  [ R u ( O E P ) ( p y - d ) ] Cl-  17d  [Ru (OEP)(py),] Br"  I7e  [ R u ( O E P ) ( p y ) ] F"  121  [ R u ( O E P ) ( C H C N ) ] Br'  2  2  m  m  6  m  m  ffl  3  m  3  in  3  m  3  ni  +  2  ,n  BF "  +  2  4  ni  +  5  ni  2  +  ni  +  2  ni  +  3  2  XXV  Acknowledgements. I  thank  Dr. Brian  throughout my  James  and  Dr. David  Dolphin for their  assistantship stipend from graduate  and  encouragement  tenure here at the University of British Columbia as a graduate student. Further,  I thank Mr. Carl Jacobson for measuring the ESR  fellow  support  the Department  students for valuable  spectra discussed in this thesis. A  of Chemistry is gratefully acknowledged. discussions,  and  the support  without whose help the work described in this thesis could not be completed.  xxvi  staff  teaching  I thank  my  of the department,  Chapter 1. Introduction. The study  of ruthenium porphyrin complexes originated with models for natural protein and  systems such as hemoglobin and cytochromes P-450. The active site  enzyme  systems was identified as an iron porphyrin center, designed  to mimic the observed  of studies reflect  and early studies of iron complexes were  1  primarily  at low-valent porphyrin centers,  the organometallic/high-oxidation state nature  The presumed similar reactivity of ruthenium to iron, coupled nithenium  natural  reactivity of these systems. Studies of die globins, for example,  examined the coordination chemistry group  in both  complexes, made die latter an obvious  2  while a second  of die P-450 enzymes.  3  with the greater stability of the  choice for modelling  both  the enzymatic  and  protein-free iron porphyrins. 1.1. Coordination coordination  chemistry  chemistry  at ruthenium  of nithenium  porphyrin  porphyrin  centers. Because several reviews  complexes  have  recently been  ol the  reported,  45  the  scope of this Introduction will be to introduce to the reader only the areas of research that arc of immediate relevance to the work conducted for this thesis. Coordination chemistry, mediated by  or centered  at metalloporphyrin  complexes, normally  involves chemistry  axial positions of an octahedral geometry because the porphyrin macrocycle equatorial  sites  macrocycle  of an  octahedron  is an essentially  planar  centered  about  a  metal  (see Figure  chelating ligand, offering  presence of delocalized jr-aroniaticity. The review  is presented  rich  into  sections  representing  the four  general  1.1). The  porphyrin  because  in sections indexed  classes of Ru(II)  to the two  coordinates the four  chemistry  the oxidation state of ruthenium; the discussion of the divalent nithenium divided  limited  of the  according to  complexes is further porphyrin  coordination  compounds. 1.1.a. Ruthenium(II) carbonyl complexes.  An early aim was to model the 0^ and CO  binding  capabilities of hemoglobin, which has an imidazole group (part of a histidine residue) coordinated at one of the axial coordination sites available at the Fe. Almost all reactions of the parent 6  1  Figure 1.1:  Structural features of a six-coordinate (a) Ru(OEP)L2, and (b) Ru(TMP)L, complex showing  that  when  a porphyrin  free base coordinates  to a  ruthenium, the four  equatorial sites of an octahedral arrangement about the metal are occupied, leaving the two axial sites for coordination of ligands, L. See the abbreviations section for crude representations of other porphyrin structures  (a)  L  L  ( b )  2  porphyrin bases with Ru precursors yield Ru (porp)CO as the major product. n  a  major hurdle  to early workers i n this  field  because of the strong  7  This proved to be  Ru-CO  bond  and  the  consequent difficulty in decarbonylating these complexes. Hence, much of the early work involved the coordination chemistry trans to the carbonyl group:  Ru(porp)CO + L  While  these  works  demonstrated  -  8  Ru(porp)(CO)L  the thermal  (1.1)  stability  of the Ru(porp)CO  fragment,  little  information on the strength of the Ru-L bond trans to C O was reported. Further, the carbonyl ligand,  being  a strong  jr-acid,  inhibits  binding  of 0  2  i n a trans six-coordinate geometry.  Therefore, methods had to be developed for the removal of C O from these complexes so that the 0  2  binding question could be addressed.  1.1.b. Dioxygen and dinitrogen ruthenium compounds from Ru (porp)(solvent) n  early  method  dissociation complexes:  developed  of C O  from  for decarbonylating these  complexes  Ru(porp)CO(L) complexes i n coordinating  2  complexes. One  was the photo-assisted  solvents, resulting  in bis(solvent)  9  hi/, A r Ru(porp)CO + solvent  -» Ru(porp)(solvent) + C O  (1.2)  2  solvent: pyridine, acetonitrile, tetrahydrofuran Some of these complexes were found to bind 0  2  reversibly, presumably after dissociation of one  axial ligand, but long reaction times resulted i n oxidized, substitution-inert binuclear complexes:  oxo-bridged  10  0 , solvent ^ vacuum 2  Ru(OEP)(CH CN) 3  2  Ru(OEP)(0 )(solvent) 2  RT, slow -  [Ru(OEP)(OH)] 0  (1.3)  2  solvent = pyrrole, D M F , D M A A similar problem was encountered i n the reaction of iron porphyrin complexes with 0 3  2  in which  the oxo- and peroxo-bridged  dinuclear species were commonly  complexes containing bound 0 steric  obstacles  to  2  focused  "dimerization";  substituents at the periphery  formed. Strategies for obtaining  on the synthesis of metalloporphyrin complexes  typically,  this  of the macrocycle.  113  involved  appending  Indeed, the iron  bulky  having  hydrocarbon  "picket fence"  porphyrin  complex (in which several hydrocarbon chains are appended to the porphyrin ring, forming a kind of protective fence) remains the best synthetic model for the binding of 0 to myoglobin: 2  0 (0 )Fe(PFP)(im) 2  0  2  «-  Fe(PFP)(im)  2  *»  (im)(PFP)Fe-0-Fe(PFP)(im)  (1.4)  PFP = "picket fence" porphyrin, im = an imidazole  Similarly, ruthenium complexes of sterically encumbered porphyrins have recently been shown 10 bind 0  2  0 . 2  n b  Although  substantial effort was expended on the development of these  complexes, the analogy  model  ruthenium  and iron  to the natural globins is limited porphyrin  by the non-protein  compounds. Further, while  the ruthenium  protcin-frcc  nature  of the  complexes arc  always of the low-spin state, iron complexes are capable of both low- and high-spin states (for example, the iron(II) high-spin in hemoglobin becomes iron(II) low-spin upon ligation of 0 CO).  ?  or  12  Some of these R u bis(solvent) complexes also bind N 11  Ru(porp)(L) + N 2  2  2  reversibly:  - Ru(porp)(L)N  13,14  2  + L  porp = OEP, L = THF, DMF; porp = TMP, L = THF,  While  the availability  of these  bis(solvent) complexes showed  that rich  (1.5) Et 0 2  chemistry  mediated by  ruthenium porphyrin complexes was possible, with two exceptions (see Sections 1.1.d and l.l.e), no  further developments originating from these  4 and 5 describe the chemistry  derived from  solvent-bound  complexes were reported. Chapters  the oxidation of these latter complexes to yield  4  Ru  and R u  m  l.l.c.  I V  species.  Rutheniumfn)  Ru(porp)CO  species  complexes: " 15  phosphine  complexes.  involved  the  A  addition  second of  method  excess  for displacing CO  phosphine,  yielding  from  the  Ru(porp)(PR ) 3  2  17  C H 7  Ru(porp)CO + excess PR  8  Ru(porp)(PR )  3  3  + CO  2  (1.6)  Ar R = Ph, n-Bu; porp = OEP, TPP,  These bis(phosphine)  complexes show chemical  TMP  behavior similar to that of die precursor  carbonyl  complexes, suggesting that the strong Ru-CO bond has been replaced by a strong Ru-PR The the  bis(phosphine) complexes are more substitution-inert and also inert to oxidation by 0  bis(solvent) complexes.  reported Ru(porp)(solvent) of die reported  2  For  example, with  the  exception  of  Ru(porp)(py)  2  2  than  complexes, all  compounds are unstable in solution under aerobic conditions, while all  Ru(porp)(PR ) 3  other reagents such as C O ^  species are air-stable in solution. ' 15  2  or H B r ^  to Ru(porp)(solvent)  species  2  18  Secondly, the addition of  to the bis(phosphine) complexes usually results in a mixed  coordination complex of the type Ru(porp)(L)PR reagents  bond.  3  (where L  3  =  CO,  usually yields products  Br).  1 6 a  In contrast, addition of  where both  solvent ligands have  been substituted (see, for example Chapters 4 and 5). In spite of the obvious disadvantages porphyrins,  some unexpected and  phosphine complexes yield  16e~,  of using  potentially  phosphines to displace CO  useful reactivity  has  from  been observed. Six-coordinate  five-coordinate mono-phosphine species when subjected  forcing conditions as pyrolysis under vacuum:  ruthenium  to such  168  1 x 10~ torr -> Ru(porp)(PR ) + PR 493 K, 2h 5  Ru(porp)(PR ) 3  2  3  porp = OEP, R = Ph; porp = TMP, R =  These  five-coordinate complexes  were  the  first 5  Ru(porp)PR  (1.7)  3  n-Bu  3  species  reported,  although  some  dinuclear  ruthenium  monomeric  porphyrin  five-coordinate  mono-phosphine  complexes,  because  species of  have  their  been  reported  coordinatively  recently.  The  unsaturated nature, were  found to bind ligands trans to the phosphine, as do the Ru(porp)CO complexes. Measurement of die equilibrium  constant for the dissociation of die phosphine from  coordinate complexes  some of die generated six-  as a function of temperature allows for the assessment  of the Ru-P  bond  strength (see Chapter 3). Another complexes  interesting was  type of reaction  chemistry noted  the observation that Ru(TPP)(PPh ) , 3  earlier  involving  diese Ru(porp)(PR ) 3  n  in the presence of a slight excess of P(n-  2  Bu) , could catalytically decarbonylate a wide range of aldehydes, for example, phenylacetaldehyde 3  (>  10000 turnovers/h) and  involved  dissolving  followed by optical  was  formation  Ru(TPP)(PPh ) 3  a brief purge of CO  spectrum  reaction  benzaldehyde  of  has  a  2  (about 2  2  3  two  other porphyrin species with 420  2  onset of catalysis was  adding  indicating  initiated  3  nm  in toluene. " 19  The  21  procedure  100-1000 equivalents of aldehyde  gas through the reaction mixture; this gave a solution whose  then  Ru(TPP)(P(7z-Bu) ) ) and  tumovers/h)  in CH C1 /CH CN, adding  Soret absorbance by  10  P(«-Bu)  3  the presence  (about ten equivalents), which Soret absorption bands  (of an unknown species). A  encountered, and  of Ru(TPP)(CO)(PPh ). 3  The  resulted  in the  at 437  nm  (due  variable initiation period  for the  the formation of this unknown species with a 420  Soret band absorbance always resulted in the onset of catalysis. No in the absence of this species, which was  suggested to be  decarbonylation was  Ru(TPP)PPh ,  nm  observed  thought to be  3  to  formed  by the equilibrium shown in Equation 1.8. The  mono-phosphine complex Ru(TPP)PPh  decarbonylation carbonyl  and/or  complexes Ru(TPP)PPh  of  aldehyde,  phosphine  to yield  ligand  Ru(TPP)(PPh )P(n-Bu) 3  3  3  3  was  Ru(TPP)(PPh )CO  (Equation  3  of die latter by and  postulated to associate CO,  P(«-Bu)  3  Ru(TPP)(P(n-Bu) ) 3  2  would  generated by the  1.9).  Displacement  give  the mixed  (Equations  1.10  and  complex, which is known to have an absorption maximum at 420 nm,  as the species most likely to be responsible for the observed catalysis.  6  19  of the phosphine  1.11).  The  was proposed  Ru(TPP)(PPh ) 3  Ru(TPP)PPh  2  + CO  3  £  Ru(TPP)PPh  + PPh  ^  Ru(TPP)CO(PPh )  3  (1.8)  3  (1.9)  3  Ru(TPP)CO(P(n-Bu) ) + P P h 3  Ru(TPP)CO(PPh ) + P(/i-Bu) 3  3  (1.10)  3  W Ru(TPP)(PPh )(P(n-Bu) ) + C O 3  Ru(TPP)CO(P(«-Bu) ) + P(n-Bu) 3  3  2  3  Ru(TPP)(P(/i-Bu) ) + CO 3  (1.11)  2  When phenylacetaldehyde was used as substrate, some biphenyl was produced, strongly suggesting that radical processes were occurring. The ESR spectrum of an cyclic voltammetry  data, revealed the presence of R u  111  in situ reaction mixture, and some  species. Formation of the R u  was attributed tentatively to the abstraction of a hydrogen atom from R C H O :  Ru(TPP)PPh  The  3  + RCHO -  acyl radical dius formed  from the R u  111  decarbonylation  hydride by  products  19  H-Ru (TPP) + C ( 0 ) R  (1.12)  m  could then dissociate to generate CO  R would complete a catalytic cycle.  of aldehydes mediated  111  by Fe(TPP)(P(n-Bu) ) , 3  2  24  23  and R; reabstraction of H  In a recent report of catalytic an alternative proposal for this  catalysis was made, based on the formation of oxidized iron porphyrin products observed at the end Fe , m  of the catalysis. In this case, the presence of trace 0 giving  C(0)R. product these  0 , which then abstracts a hydrogen _  2  2  was suggested to oxidize Fe  11  to  atom from the aldehyde, forming H 0 " and 2  Unfortunately, in both the Ru and Fe systems, the reactions, especially  the rates of  formation, were  difficult.  Consequently,  Further  studies  catalytic  not reproducible,  decarbonylation processes  making remain  mechanistic studies poorly  understood.  were  undertaken, as described in Chapter 3 of this thesis, to assess the role of five-coordinate monophosphine complexes  such as Ru(OEP)PPh  3  in catalytic aldehyde decarbonylation reactions, and to  determine  what  conditions  are conducive for the reproducible  initiation  of the decarbonylation  reaction. 1.1.d. Other rutheniumfJJ) complexes. Pyrolysis of the Ru(porp)(py) complexes 2  results  in loss  bonded dimers.  of the axial  pyridine  ligands,  forming coordinatively  under  vacuum  unsaturated metal-metal  These dimers react widi a range of added ligands 'L' to form six-coordinate  25  complexes; some examples include organic sulfides and nitroso derivatives as ligands, as shown in Equation 1.13: ' 26  27  2 Ru(OEP)(py)  A, vacuum -  2  [Ru(OEP)]  4 L -  2  2 Ru(OEP)(L)  2  (1.13)  L = S R (R = methyl, decyl), PhNO 2  In contrast, pyrolysis of R u ( T M P ) ( C H C N ) 3  bulk  of the macrocycle preventing  ligands:  2  under vacuum yields the monomer Ru(TMP), the steric  dimerization.  The monomer  also  binds a wide  range of  14  Ru(TMP)(CH CN) 3  A, vacuum 2 L Ru(TMP) -  2  Ru(TMP)(L)  for example, L = OEt , DMF, THF, N 2  2  l . l . e . Ruthenium(III) complexes. Oxidation of Ru (porp)(PR ) (n = n  3  electron chemical oxidants yields the mixed phosphine halide Ru  111  (1.14)  2  n  1, 2) compounds by single-  compounds: ' 163  Ru"(porp)(PR ) + HX/air - R u ( p o r p ) X ( P R ) + 0 = P R  28  m  3  2  3  3  (1.15)  porp = OEP, R = Ph, n-Bu, X = Br, CI; porp = TPP, R = Ph, X = Br porp = TMP, R = n-Bu, X = Br, CI  Ru (porp)(PR ) + 1/2X - R u ( p o r p ) X ( P R ) + P R n  m  3  2  2  3  3  (1.16)  porp = OEP, R = Ph, n-Bu, X = Br, CI; porp = TPP, R = Ph, X = Br  Ru (porp)PR n  + HX/air - R u ( p o r p ) X ( P R ) m  3  3  porp = OEP, R = Ph, X = Br; porp = TMP, R = n-Bu, X = CI  8  (1.17)  Chemical or electrochemical oxidation of Ru(OEP)CO complexes yields products first sight the ruthenium has a formal oxidation state of +3. been shown to be of the formulation [ R u ( O E P ) C O ( L ) ]  +  ring-centered  of  n  oxidation.  [Ru (OEP)(P(/i-Bu) ) ] ra  3  2  +  In  17,29  Br":  contrast,  Ru (OEP)(P(7j-Bu) ) n  2  bis-phosphine  + 1/2 B r  n  2  complexes  radical species [ R u ( O E P ) C O ( L ) ] u  +  31  2  Br, py, vacant), the products of a  Ru(OEP)(P(n-Bu) ) 3  2  by  Br  + e  +  m  3  also be  by  Br"  +  2  prepared  py, Br, vacant; R  by  =  chemical  (1.19)  adding  n-Bu,  and by the electrochemical oxidation of [Ru(porp)] :  Ph).  PR 17  3  to the  Other Ru  111  -  2  porp = OEP,  2  [Ru (porp)] n  K  +  organometallic  and  (1.20)  2  TPP  2  -  dimeric were  products  are  presented.  No  derivatives) of  Ru  m  32  (1.21)  2  [Ru(porp)] 4  data  30  32  [Ru(porp)(CN) ]- + CO  2 X" + 2 e  +2 2  porp = OEP, TPP; X = BF , SbCl , P F  conductivity  porphyrin  oxidation of R u ( p o r p ) C 0  Ru(TPP)(THF), + air + E t O H / C H C l - Ru(TPP)(OEt)(EtOH) (1:1 v/v)  last-mentioned  n -cation  2  Ru(porp)CO + A i r o r B r + K C N  The  yields  2  (1.18)  [Ru (OEP)(P(n-Bu) ) ]  can  (L =  +  -  +  complexes not containing phosphines were generated Ru(TPP)(THF) ,  (L =  [Ru (OEP )CO(L)]  n  Ruthenium(III)  oxidation  These compounds, however, have  17  17  Ru (OEP)CO 3  +  in which at  6  considered other  porphyrins  6  electrolytes  coordination  have been  9  in  solution,  compounds  reported, prior  Ru(OEP)X ( X = Br, CI, SbF ) described in Chapters 4 and 5 of this diesis. 6  (1.22)  33  to  although  (i.e. the  no  excluding  synthesis  of  l.l.f.  Ruthenium (TV)  complexes.  The  first  Ru  porphyrin  [Ru(OEP)OH] 0,  was incorrectly  was  characterized by X-ray crystallography.  2  subsequently  have been reported since:  coordination  characterized as the methoxide congener 34  Several other  complex  reported,  in solution, ' 31  34  but  /x-oxo dinuclear species  31  0 /H 0 [Ru(porp)OH] 0 2  [Ru(porp)]  2  2  2  HX -> [Ru(porp)X] 0  (1.23)  2  porp = OEP, TPP, TTP; X = OMe, Br, CI  This  net four-electron oxidation is thought to require the presence of trace 0  although  experimental  [Ru(OEP)]  in Chapters  species [Ru(porp)] give R u  products:  l v  of the oxidation reaction on 0  3 and 4. In anodier  was oxidized by H X  2  35  is lacking. Attempts made with the complexes Ru(OEP)PPh  to ascertain the dependence  2  described  evidence  and H-,0,  2  2  and on  3  and  H,0 arc  net four-electron oxidation reaction, the dimcric  acids in organic solvents in the absence of oxygen to  36  [Ru(porp)] + 4 H X -  (1.24)  2 Ru(porp)X + '4 H'  2  2  porp = OEP, X = Br, CI, F; porp = TPP, X = Br  As  dihydrogen  oxidant. ' 36  37  could  Further  not be detected,  trace X  studies were initiated  2  in H X  in the present  was consequently work  to identify  thought  to be the  the actual  oxidant  and the co-product in this reaction, and to ascertain the mechanism (see Chapter 4). The dibromide complex can also be prepared, although less effectively, via reaction 1.25: ' 36  [Ru(OEP)] + 2 B r 2  Synthesis  of  the  Ru (TTP )(CO)Br n  +  TTP  analogue  of  2  - 2 Ru(OEP)Br  Ru (OEP)Br rv  2  (1.25)  2  by  i n moderate yields was recently reported. 10  37  die 38  thermal  decomposition  These monomeric  Ru  , v  of  dihalidc  products  have  complexes  been  used  I V  in the investigation  (vide infra). The halide  reported  complexes and, being of intermediate-spin (S = l, d ), exhibit interesting  magnetic  chemistry  complexes  were  4  behavior. Why these compounds are paramagnetic, diamagnetic,  porphyrin  of organoruthenium the first  and their  monomelic R u  as precursors  is not well  understood;  while the aryl and alkyl R u  therefore, measurements  analogues are  I V  of the magnetic  moments  of  Ru(OEP)Br as a function of temperature were made, as discussed in Chapter 5. 2  Other  monomelic  Ru^Oporp)  Ru(TMP)(OC H OH) , 6  4  39b  2  Ru (OEP)Br(PPh )  and  with  m  3  iodosylbenzene (PhIO)):  complexes  an  oxene  reported  ill-characterized reagents  previously  species  by  generated  (e.g. meto-chloroperbenzoic  [ 0 = R u ( O E P ) ] Br" + 0 = P P h +  3  the  acid  39a  and  reaction  of  (mCPBA)  or  (1.26)  +  This oxo O E P complex (formally R u ) was formulated as a R u v  3  porphyrin w-cation radical, and  I V  as die catalyst responsible for oxidation of saturated and unsaturated hydrocarbon  proposed  substrates  Ru(TMP)0  40  Ru(OEP)Br(PPh ) + [0] -  was  include  to  epoxides,  alcohols  and  Ru(OEP)Br(PPh ) and excess PhIO in C H 3  6  epoxides, alcohols and ketones; c tochromes P-450  as a  40  ketones.  Catalytic  oxidation  of  by  resulted in a distribution of oxidized products such as  6  similar oxidized products were observed  catalyst  cyclohexene  for the oxidation  of organic  in systems involving  substrates.  3  Thus,  the  Ru(OEP)Br(PPh )/PhIO catalyst mimics to some extent the natural enzymes; however, a 'better' 3  c tochromes P-450 mimic is Fe(TMP)Cl, which gives higher overall yields. 1.1.g. RutheniumCVT) complexes. The dioxo R u TMP, date  and O C P  V I  41  porphyrin complexes, Ru(porp)(0)? (porp = OEP,  (octachloroporphyrinato dianion)) are the only  Ru  v l  porphyrins  reported  to  .14b,39b,42,43  0 Ru(TMP) -> 2  These  Ru(porp)dioxo  Ru(TMP)(0)  2  species are essentially  /-BuOOH <Ru(TMP)CO  models 11  for the dioxygenases,  (1.27)  and  not  for  the  cytochromes / M 5 0 . 1.2. Organoruthenium appeared  recently  porphyrin complexes. Again, because several comprehensive reviews have  in the literature, ' 45  this  46  section of the introduction will  be brief and  intends to show how ruthenium porphyrin coordination compounds have been utilized to generate organoruthenium porphyrin complexes. 1.2.a. Compounds originating from  [Ru(OEP)] . This complex has been instrumental is  the  2  development of both coordination chemistry and organometallic synthesis; for example:  47  Ru(OEP)(CH =CH ) 2  C H 2  [Ru(OEP)]  2  '/  4  (1.28)  2  HRCC1  2  \ Ru(OEP)(=CHR)  R = methyl, trimethylsilylmediyl The  synthesis of the R u ( O E P ) ( C H = C H ) complex by the addition of ethylene to Ru(OEP)(THF)  was  reported previously; however, the proposed product was not well-characterized at that time.  2  Reduction monomer:  2  2  13  of the dimer by Na/K amalgam results i n the formation of a dianionic Ru° 'naked' 47  [Ru(porp)] + Na/K amalgam -. 2 K 2  1.2.b. Compounds originating from 2 K iodides, giving R u  l v  di-alkyl derivatives:  [Ru(porp)]"  (1.29)  2  [Ru(porp)]" . These Ru° monomers oxidatively add alkyl  +  2  48  2 K . [Ru°(porp)]- + 2 R-I +  +  2  Ru (porp)(R) IV  2  + 2 KI  (1.30)  porp = OEP, TTP; R = methyl, ethyl  While this method proved useful for the generation of alkyl products, formation of the di-aryl analogues has not been reported. Several R u of  the  Ru°  dianions  widi  carbene  n  carbene complexes were also generated, by reaction precursors  12  such  as  1,1-dichloroethane  and  (dichloromethyl)trimethylsilane. 1.2. c. Compounds originating from Ru(porp)X . The first reported route to R u ™ aryl derivatives 2  was  via metathesis of the R u ™ di-halide complexes, a process that is applicable also for the di-  alkyl species:  36,58  Ru(porp)X  + R L i or R M g X -» Ru(porp)(R)  2  2  + LiXorMgX  (1.31)  2  for example, porp = OEP; R = methyl, phenyl, tolyl, p-fluorophenyl  These  alkyl  and aryl  products  organoruthenium(III) products:  homolytically cleave  a Ru-C bond  upon  thermolysis, giving  49  A . Ru(OEP)(R)  -  2  Ru(OEP)R + organic products  (1.32)  R = methyl and phenyl Where  R  =  ethyl,  the Ru(IV)  precursor  decomposes  at  room  temperature  Ru (OEP)(C(H)CH ) and R u ( O E P ) E t via a series of steps involving both n  a- and  m  3  abstraction from an ethyl ligand of Ru(OEP)Et , by attack of a ethyl r a d i c a l .  to  give  p-H atom  48,50  2  1.3.  Objectives  of this  coordination chemistry While  dissertation.  thesis describes  of ruthenium porphyrin  the initial aim of this  substrates  This  (i.e. as mimics  work  continuing  efforts  complexes explored partly  in an earlier thesis.  was to synthesize catalysts capable  of cytochromes  PASO),  the observed  to develop the  of oxidizing  inability  37  organic  of the ruthenium  porphyrin halide complexes to oxidize organic substrates, with high turnovers in the presence of suitable  oxygen  donors,  suggested  that ruthenium  porphyrin  complexes,  in general, are poor  mimics of cytochromes P-450. Hence, the aim of this work became broader such  basic  issues as (a) Are four- and five-coordinate ruthenium  coordinatively unsaturated  in scope, addressing  porphyrin  complexes  in solution? (b) What factors influence substitution chemistry  really  at these  centers (e.g. axial ligand bond strengths, stability)? (c) Why are these compounds not good models  13  the c tochromes P-450?  for  It was  hoped  that  while  the coordination  chemistry  of these  complexes was being developed, some answers to these issues and others mentioned earlier in this introduction would be found. Because this work is a continuation of the earlier Master's thesis work, a description of the new versus the old results is provided  to ensure diat die new data arc  properly highlighted. The  section (Chapter 2 ) describes the synthesis of the new complexes described  experimental  in this thesis. The main body of the thesis work is presented in the three Results and Discussion chapters.  of these chapters (Chapter 3 ) describes  The first  \€>e~ complexes Ru(OEP)(L) (L = compounds were described  measurements  Only the synthesis and characterization of these  PPI13).  in the Master's thesis.  molecules CO, 0 , H 0 , 2  CO,  the reactivities of the monomelic,  37  The reaction of Ru(OEP)PPh  3  with the small  N , and H , and with PPh , is discussed here. These data include two  2  2  2  of the Ru-P  3  solution bond  strength.  The possible  role  of the five-coordinate  phosphine complex in the reported catalytic decarbonylation of aldehydes was tested. Chapter [Ru (OEP)]  4  describes by H X  n  2  suggested as trace X  efforts  to yield in H X  2  to determine Ru (OEP)X ." IV  2  (X = Br, C I ) .  37  the oxidant  responsible  In the earlier Master's work, the oxidant This suggestion  itself. The mechanism of the HX/[Ru(OEP)]  of  for the reaction to be successful, were  prediction  acid  required  of possible  reactivity  between  [Ru(OEP)]  2  was  is shown to be incorrect and the  oxidant is identified as H X the H X  for the "oxidation of  and other  HX  2  reaction, and the nature  studied, allowing acids.  Other  for  the  routes to  R u ( p o r p ) X species from Ru (porp)(L) are described (porp = OEP, TMP; L = C H C N , py). rv  n  2  The  last  2  Results  and Discussion  3  chapter  describes  dihalide complexes described in the Master's thesis. Ru  I V  and  37  the further characterization of the R u  l v  The initial findings of the inability of these  complexes to act as catalysts for the oxidation of cyclohexene were further substantiated, new studies were conducted to help ascertain the reasons. The poorly  understood change in  ground spin state with change in axial ligand from halide (S = l) to aryl and alkyl (S=0) within the Ru  I V  oxidation  state  was  studied  further. Facile reduction  14  of these  monomeric  Ru  I V  halide  complexes leads to novel R u characterization  and reactivity  m  compounds of the formulation Ru(OEP)X (X = are documented. Oxidation  of Ru (OEP)(solvent)  Br, CI), whose  n  2  generate [Ru (OEP)(solvent) ] X" species (solvent = py; X = CI, B F ) is also described. m  +  2  4  15  compounds to  Chapter 2: Experimental  2.1. Reagents and solvents. A l l solvents (CH C1 , C H , C H , pentanes, hexanes, and T H F ) were 2  2  6  6  7  8  distilled from the appropriate drying agents and stored under argon until needed. these solvents (excluding THF, but including all deuterated were stored over a bed of activated molecular  over  sodium  benzophenone ketyl  instead  solvents required for N M R  by grease. T H F was also stored under vacuo  of molecular  sieves. These  anaerobic,  solvents were prepared for use by three successive freeze-pump-thaw cycles at l x l O " manipulated solvents  using  were  standard  obtained  vacuum-transfer  from  purchased from either M S D  Fisher  Isotopes  studies)  sieves (Davidson type 4A) in flasks sealed by  Teflon valves under vacuum to avoid contamination but  Aliquots of  51  techniques  Scientific,  BDH,  when  needed.  or Aldrich.  52  The  Deuterated  anhydrous 3  torr, and  non-dcuteratcd solvents  ( C D , C D , C D C 1 , CDC1 , C D O D ) or Stohler 6  6  7  8  2  2  3  3  were Isotope  Chemicals ( C D C N and C D N ) and used as purchased. 3  5  5  A l l gases (Ar, N , 0 , CO, and anhydrous H X (X=F, 2  synthesis  were used  Prepurified N and  2  2  as obtained  from  either Linde  CI, Br)) used for routine applications or  (Union  Carbide  Inc.)  or Matheson Ltd.  for use in the inert atmosphere chamber (glove-box) was also supplied by Lindc  used directly. When argon or N  2  were required to be oxygen- and moisture-free, these cases  were passed dirough a Ridox column (2.5 x 50 cm column, a Cu based catalyst used for removal of 0  2  from a gas, purchased from Fisher) and then through an activated molecular  (2.5 x 50 cm, type 4A) to remove moisture. Dry 0 Aquasorb column (1 x 10 cm of P 0 2  5  sieve column  was obtained by passing the gas through an  2  on Vermiculite), purchased from Mallinckrodt. A l l gases  required for use i n gas chromatography (He, Air, H ) were of the zero-gas grade from 2  indicating the removal of hydrocarbons to the <  Lindc,  0.5 ppm level, and were further purified by  passing through activated charcoal columns (2.5 x 10 cm). Triphenylphosphine  and tri-n-butylphosphine were obtained 16  from Aldrich. The latter was stored  under argon  after distillation under reduced  H N 0 , HCOOCF3, 3  Cyclohexene formation) Aldrich),  perchlorate  were purchased  Aqueous acids (HBr, HCI, HF, HSbF ,  51  6  from B D H  or Fisher Scientific and used directly.  (passed dirough an activity I alumina column every six months to prevent peroxide and  53a  HCOOCH3)  pressure.  benzaldehyde  were  supplied  tetramethyl-l-piperidinyloxy (TBAP, Eastman K o d a k )  17b  by  Fisher.  (TEMPO,  2,2'-Azobisisobutyronitrile  Aldrich)  were purified  and  53b  following  (AIBN,  tetra-n-butylammonium  literature methods.  RuCl .3H 0 3  2  (about 4 0 % Ru) was loaned from Johnson, Matthey Ltd., and OEP was kindly supplied by Dr. T. Wijesekera of this laboratory. 2.2. Instrumentation and techniques for synthesis. UV/visible spectra were recorded using either an HP  8452A, a Perkin-Elmer 552A or a Cary  17D spectrophotometer  using either standard or  specially developed quartz and pyrex cells of 0.01, 0.10 and 1.00 cm pathlength (see Figure 2.1). Infrared  spectra (as Nujol mulls  spectrophotometer.  on C s l plates) were obtained  using  a Nicolet  5DX  FT-IR  Alternatively, a Pye Unicam SP1100 IR spectrometer was used when the sample  to be studied was either a solution (0.1 mm pathlength cells) or a K B r pellet. NMR  data were compiled using either a Varian (XL-300, 300 M H z  HXS-270 or WP-80; 400, 270 and 80 M H z  F T respectively) spectrometer utilizing standard 5  (outer diameter) sample tubes, as well as specially developed inert  atmosphere or for N M R  FT) or a Bniker (WH-400,  spectroscopic titration  mm  sample tubes for work requiring an  experiments  (see Figure 2.2). A l l N M R  spectra were referenced using an external standard: solvent:  C D  reference:  7.15  reference:  All  3 1  P{ H} NMR ,  6  128.0  6  Ph-CD  3  2.08 20.4  CDC1  CD C1  3  2  7.25  2  5.32 ppm (for H N M R spectra) !  77.0  53.8 ppm  (for C N M R spectra) 13  data were referenced to the external standard P P h  3  (6.05 ppm upfield relative  to 8 5 % phosphoric acid). The data are presented using die diamagnetic convention where signals upfield of the reference are negative in sign.  17  Figure 2.1: UV/visible spectroscopy sample cells incorporating a Teflon-valve to seal the sample solution under an inert atmosphere or under vacuum. Cell A has no reservoir, while cells B and C have plain and calibrated reservoirs, respectively.  18  Figure 2.2:  NMR  sample tubes for use in the study of air-stable (A) or air-sensitive (B) samples.  The side-arm in B allows for the introduction of reagents to the sample without causing decomposition of the latter. Tube (C) incorporates a septum-port fitting for use in experiments involvingtitrationof samples in NMR tubes.  19  screw-cap  Mass spectra were obtained  using  a Kratos-AEI MS902 mass spectrometer operating  in  the  electron impact (EI, 70 eV) direct insertion mode at 473-573 K source temperatures. Fast atom bombardment (FAB)  mass spectra were measured using a updated MS-9 mass spectrometer. GC/MS  studies were conducted using a Nermag R-l0-10 spectrometer. Electrochemical programmer standard  studies  were  and a model  three-electrode  performed  with  the use of a E G & G  173 galvanostat/potentiostat  electrochemical  17b  from  Princeton  and spectroelectrochemical  54  model Applied  cells  175 universal Research. The  required  for use  with die above equipment have been described previously. The electrodes used were a Ag/AgCl electrode for the reference, a Pt disk electrode for die working and a Pt wire for the counter electrode. The  typical cyclic voltammetry  (CV) experiment involved measuring the voltammogram of a  sample solution (ca. 0.1 mM) in C H C 1 2  solvent) containing 0.1 M  2  or C H C N (depending on solubility of the sample in each 3  tetra-n-butylammonium perchlorate (TBAP) under argon. After the C V  of the sample was successfully obtained, ferrocene (Fc) was added to the cell and the C V of the solution measured again. The data were then reported with respect to the Fc /Fc couple (632 mV +  vs. NHE). In all cases, no change in the reduction potential of die redox couples of the sample were observed upon (a) changing the scan rate, or (b) the initial scan direction, or (c) upon addition of Fc. The  typical  spectroelectrochemistry  experiment  involved  pre-electrolyzing  the  solvent/  electrolyte mixture at the potential of interest, followed by addition of the sample. A purge of A r through the solution was used to stir, as well as to remove oxygen, from the solution during the experiment. The concentration was  electrolyzed, the bulk  observing progresses.  the changes  of the sample solution was then measured, and the sample itself coulometric  in the optical  Upon completion  experiment spectrum  being  followed  of the sample  with  respect  to time by  solution as the experiment  of die experiment, as judged by the lack of change in the optical  spectrum of the electrolyzed solution, the potential was adjusted  20  to test for reversibility of the  bulk coulometry. Equivalent conductivity measurements were made in either C H C 1 , C H C 1 2  cell (cell constant = Company. using  55  and a conductivity bridge (model R C M  -1  Measurements  Evans'  reference.  1.0 cm )  method  of  the  with  a  magnetic Varian  susceptibility  XL-300  MHz  of FT  (13X)  detection of H column and  by GC  2  a thermal  injector temperature, and were 0.90,  2.25,  and  was  Thomas  paramagnetic  samples  spectrometer  and  a 333  5.20  K  detector temperature. The  die flask, die mixture gas-tight syringe, 500 vapor  was  with a 12' x 1/8"  allowed  being  trapped  from  oven  and  and  N  O^ flask  2  with a  67 /xmol) in the glove box and the flask  dien refrozen using a liquid N-,  solution at  die results obtained  77  K.  from GC  Because  of  the  bath. With a  the residual  the  studies were further corroborated  by  2  importance  HX  of  — 2. To address die possibility of leakage of H  which allowed  K  retention times for H,,  injecting vapor samples from the reaction flask into a gas probe of a MS analyzed for mle  and  37  the  of a HX/solvent solution was added by vacuum transfer to  to react, and  in  as  molecular sieve  fiL vapor samples were withdrawn and injected into the GC,  implications of diis study,  devised  f-butanol  minutes, respectively. In a typical experiment, a 10 mL  sealed with a Teflon valve; then, 5 mL  was  were affected  conductivity detector, 30 mL/minute column flow, 303  2  solvent  15B1) from the A.H.  3  56  done using a HP5890 GC  side-arm septum port was loaded widi [Ru(OEP)] (85 mg,  and  using a  3  Diamagnetic corrections were made using data reported earlier for OEP,  totalling the contributions from each atom using Pascal's constants. The  or C H C N  2  and  the vapor then  from the syringe, an apparatus  the attachment of the reaction flask directly to the MS  2.3). This allowed the reaction flask to be evacuated to approximately  10'  7  torr and,  (see  Figure  by  simply  opening the Teflon valve, sample could be introduced to the gas probe of the MS. Samples of the thawed reaction liquid were also withdrawn from the flask and possible hydrogenation (25 m  x 0.5  minutes, 423  mm).  of the solvent by injecting 0.5  The  temperature program used was  uL  aliquots onto a OV101  tested for the  capillary column  323 K for one minute, 10 K/minute for 10  K for one minute, 25 K/minute for four minutes and lastly 523 K for one minute.  21  Figure 2.3: Exploded view of the apparatus used for the detection of  by direct  sampling of the reaction vapor phase via a gas sampler of a mass spectrometer.  B-14 ball/socket joint with stopper  5 mm Teflon valve  metal o—rln to to  1 I  I  §  c  r rubber o-rlng  6 mm nut  gas probe of mass spectrometer reaction vessel (10 mL volume)  22 mm  The injector and flame ionization detector (FID) temperatures were 523 and  623 K, respectively.  These same samples were also tested for hydrogenation of solvent with a Nermag GC/MS. 2.3. Preparation of ruthenium complexes. Scheme 2.1 describes the syndietic strategy used to prepare the key complexes Ru(OEP)(PPh ) (5a), Ru(OEP)X 3  Ru(TMP)(CH CN) 3  Ru C0 , 3  2  Ru(OEP)CO(MeOH)  5 8  1 2  Ru(OEP)PPh ,  Ru(OEP)(py)  16a  3  [Ru(OEP)]  (6c) using reported  2  (7),  Ru(OEP)Br  25  methods. Thus, H T M P ,  (6a),  Ru(OEP)(PPh )  17  3  applicable) UV/visible, IR and N M R  (4a),  2  Ru(TMP)CO(MeOH),  9  (8a) and  2  and the ruthenium complexes  57  2  (3b),  2  (X = Br, 8a; CI, 8b), and  2  Ru(OEP)Cl  (8b)  2  36  15  Ru(TPP)(PPh ) 3  Ru(TMP)(CH CN) 3  were  (4b),  2  (6c), ' 37  2  characterized  by  15  14a  (where  spectroscopy and the data compared with the spectroscopic  properties reported for each compound; die data obtained were in excellent agreement with those reported. Because die synthesis and characterization of the precursor OEP presented in the Master's thesis, TMP  compounds are provided  only  37  complexes have been  die characterization details for the precursor  in Section  2.3.a. The  synthesis details for all new  TPP  and  Ru(porp)  complexes are provided in Section 2.3.b.  2.3.a. Spectroscopic parameters for compounds prepared from literature methods. Bis(triphenylphosphine)(tetraphenylporphyrinato)ruthenium(II) (4b).  15  90 % yield.  Anal, calcd. for C H N P R u : C,77.59; H.4.72; N.4.52. Found: C, 77.37; H, 4.84; N, 4.37. 8 0  •H N M R 8H, m-H  phenyl  5 8  4  2  spectrum (6,  CDC1 , aerobic): 8.06 (s, 8H, H 3  ); 7.51 (m, 8H,  ppm (br, 12H, o-H  o-H  phenyl  ). P{'H} N M R 31  phos  UV/visible spectrum (CH C1 , A 2  2  m a x  pyrr  ) ; 6.71 (t, 6H, p - H  ) ; 7.55 (m, 4H, p - H  phos  phenvl  ) ; 6.47 (t, 12H, m-H  ) ; 7.53 (ni,  phos  ) and 4.22  spectrum (CDC1 , 13 mM): 6.87 (s). 3  nm): 433 (Soret), 515, 555.  Tetramesitylporphyrin (H TMP): 6 % yield. 57  2  !  H NMR  spectrum ( 5 , CDC1 , aerobic): 8.60 (s, 8H, H 3  pyrr  ) ; 7.25 (s, 8H, m-H); 2.61 (s, 12H, p-  C H ) and 1.84 (s, 24H, o-CH ). 3  3  UV/visible spectnim (CH C1 , A 2  2  m a x  nm): 409 (Soret), 511, 544, 589.  23  60 atm  C 0  (g)»  Ru CI .H 0 2  1  2  3  C7H5  K  •  n,  3  4  Ru C0 3  MeOH  r 6 f l u x  »  A r  •  12  J2  Ru"(porp)CO  H (porp)  3^  2  porp = OEP, TPP, TMP  to  4^  10 PR , CyHg reflux, Ar  1 x 10 ^torr, 473 K, 2h  3  Ru"(porp)(PR ), 3  CO t  porp = OEP, R = Ph 4a  Ru (porp)PR + P R n  3  3  porp = OEP; R = Ph 5a  porp = TPP, R = Ph 4b  Scheme 2.1: Synthetic strategy used to prepare key Ru(porp) complexes.  -5  hv, Ar  Ru (porp)CO  >  ll  Ru'WpXS),  1 x 10  torr, 493 K, 2h  _3_  [Ru (porp)] l!  porp = OEP 7 ex cess S  COf  porp - OEP; S - py (6a), CH-jCN (6b)  2 S  P P = o r  0 E F > :  S  "  P V  porp = TMP; S = py (6c), CH CN (6d) 3  [Ru»(porp)]  HX/_s, anaerobic conditions ™ •  Ru (porp)X lv  2  + '2 H'  porp = OEP, X = Br 8a porp = OEP. X « CI 8b  Scheme 2.1 continued.  Carbonyl(methanol)(tetramesitylpo  This complex was synthesized via a  modified procedure of an method reported for the OEP analogue. ' " 178 14  A solution of H TMP (2.1g, 3.4 mmol) in mesitylene (300 mL) was stirred under a CO 2  atmosphere for two hours to presaturate the solution with CO^y  Ru CO 3  p  (2.0g, 3.1 mmol) was  added to the porphyrin/CO solution, and the reaction mixture refluxed under a CO atmosphere until the fluorescence due to the presence of H TMP disappeared (several days). The reaction 2  mixture was cooled to room temperature, and three-quarters of the solvent was removed under reduced pressure. This concentrated solution (ca. 80 mL) was then added to an alumina column (activity I, neutral grade, 50 x 4 cm), and the column was eluted with CH C1 . A purplish-red solution eluted 2  9  first which was a mixture of H TMP and Ru(TMP)CO. Upon further elution with CH,C1 , an 2  7  orange colored solution (containing just Ru(TMP)CO) was collected. Then, the first eluate was concentrated under reduced pressure and rechromatographed on the same type of column, further separating  the H TMP 2  and Ru(TMP)CO.  The combined eluates of Ru(TMP)CO  were then  concentrated, and chromatographed a diird time to remove any last traces of H,TMP. The Ru(TMP)CO solution was collected as it eluted from the column, the solvent removed under reduced pressure, and the residue collected by scraping the solid from the walls of the flask. This red solid was dien recrystallized from CH Cl /MeOH/pentanes and dried under vacuum at room 2  2  temperature. Yield, 1.6g (62 %). !  H NMR spectrum (S, C D aerobic): 8.86 (s, 8H, H 6  6  pvrr  ); 7.24 (s, 8H, m-H); 2.56 (s, 12H. p-  CH ); and 2.25 ppm (s, 24H, o-CH ). 3  3  UV/visible spectrum (CH C1 , A 2  2  m a x  nm): 414 (Soret), 532.  Bis(acetonitrile)(tetramesitylporphyrinato)ruthenium (6c). This compound was prepared using the method described for the OEP analogue,  37  but using a 1:1 CH CN:C H mixture in place of neat 3  6  6  CH CN as is required for the synthesis of Ru(OEP)(CH CN) . The spectroscopic data were close 3  3  26  2  to those reported in Reference 14a. 'H NMR spectrum (6, C D 6  6  vacuo): 8.67 (s, 8H, H  pyrr  ); 7.27 (s, 8H, m-H); 2.56 (s, 12H, p-  CH ); 2.23 (s, 24H, o-CH ); -1.30 (s, 6H, CH^CN). 3  3  UV/visible spectrum (CH CN, A 3  mn): 402 (sh), 420 (Soret), and 510.  m a x  2.3.b. Synthesis and characterization of new Ru(porp) complexes. Dichloromethylbis((octaethylporphyrinato)ruthenium(II,III)) (13) and hydrido(octaethylDorphyrinato)ruthenium(III) (14):  This mixture of compounds, which have not been unambiguously identified, can be prepared via two routes: Route A: 3/2 [Ru(OEP)], + CH C1 2  2  2  [Ru(OEP)] CHCl + Ru(OEP)H 13 14 2  (2.1)  2  [Ru(OEP)] (30 mg, 24 /xmol) was placed in a Teflon-valve equipped flask and CH C1 (10 mL) was 2  2  2  transferred onto the solid under vacuum. The resulting greenish solution was then heated to reflux under vacuum for 30 minutes, the solution color changing from green to red. The solvent was removed under vacuum, and the solid residue dried overnight under vacuum at ambient temperature. The reaction flask was then taken into the glove box, and the product was scraped off the walls of the flask, collected and stored in the glovebox. The deuterated analogues of J_3 and 14 were prepared using diis method with CD C1 used in place of CH C1 . 2  2  2  2  Route B: 3/2 [Ru(OEP)] + HC1/CH C1 7 2  2  2  -  [Ru(OEP)] CHCl + Ru(OEP)H 13 14 2  2  (2.2)  [Ru(OEP)] (30 mg, 24 /xmol) was placed in a Teflon-valve equipped flask and an HC1/CH C1 2  2  2  solution (10 mL, made by bubbling H C l ^ into CH C1 for 30 seconds) was transferred onto the 2  2  solid under vacuum. An immediate reaction took place upon dissolution of the green solid as 27  by  evidenced  the instantaneous change in color  from  green  to red. The subsequent  isolation  procedure was the same as that described for route A. Anal, calcd for a 1:1 mixture of 13 and 14 formed from the reaction of 1_ with HCI: C, 65.86; H, 6.75; N, 8.46; CI, 3.52. Found: C, 64.39; H, 6.66; N, 8.30; CI, 4.46. Analysis found for the mixture generated from 7 and CH C1 : C, 64.57; H, 6.56; N, 8.43. 2  2  U N M R spectrum (6, C D C 1 , 293 K, in vacuo): 13.06 (s, 4H, H  l  2  2  m e s o  ) ; 10.07 (m, 8H, C H ) ; 5.78 2  (m, 8H, C H ) ; 4.20 (m, 8H, CH '); 2.28 (t, 24H, C H ) ; -3.45 (br, 12H, CH '); -8.20 (br, 2H, 2  H  meso  2  3  3  ' ) ; see Section 4.2.b.  Conductivity (10 mg sample in 5 mL C H C 1 , 293 K): 1 fimhos/cm. 2  2  UV/visible spectrum (2 mg sample in 5 ml C H C 1 , A 2  2  m a x  nm): 400 (sh), 486 (Soret), 504, 542,  574. FAB-MS: 1282 mle ( [ R u ( O E P ) ] C H ) , 1268 ([Ru(OEP)] ) , 634 (Ru(OEP)) . +  2  +  2  +  2  Solution molecular weight (3 mg sample of I3/J4, Ru(OEP)Cl->  used as the reference sample):  920 +_ 100 g/mole. M r (corrected, 2.2 mg sample in CD C1 , at 293 K): 2.0 B.M. ef  2  2  Hexafluoroantimonate(octaethylporphyrinato)ruthenium(III) (15):  [Ru(OEP)] + excess H S b F 7 2  [Ru(OEP)] sample  2  this  -  'Ru (OEP)(SbF ) ' - R u ( O E P ) S b F 8d 15 IV  tube  under  a N  stage  atmosphere.  2  3  (2.3)  m  6  (7 mg, 5.5 /xmol) and H S b F  dissolved by adding C D C 1 at  6  6 ( a q )  A  2  6  (1 /iL) were reacted in C D 6  dark  red solid  precipitated  6  (0.5 mL) in an N M R  immediately, which  was  to the sample tube under aerobic conditions. The product in solution  was identified  as 'Ru (OEP)(SbF ) ' IV  6  2  (8d, see Section  spectroscopy. This reddish colored solution was removed from die N M R mL) was added to afford a brownish-red colored solid, which  28  4.2.i) by  'H N M R  tube, and n-pentanc (10  was collected  by filtration and  reprecipitated  from  CH Cl /n-pentane 2  (1  2  mL/10  mL).  The  resulting  suspension  was  filtered  to  collect the product, which was then air-dried. Yield, 5 mg (70%). The  microanalysis and  for R u ( O E P ) S b F ( T H F )  'H  NMR  spectroscopic data for 15 are consistent with those  with the exception that the THF  37  6  reported  ligand in the latter complex is absent  in 15. Anal, calcd. for C H N R u S b F : C, 49.66; H, 5.06; N, 6.44. Found: C, 49.12; H, 5.18; N, 3 6  !  H  NMR  4 4  4  spectrum (5, CDC1 , 293 K, aerobic): 18.22 3  (br, 8H, CH ), 1.71 (br, 24H,  3  stopcock was  (100 mg,  0.1  2  mmol) was  and  (2.4)  3  loaded into a reaction flask equipped with a Teflon  this solution was  transferred onto  the  solid  solution being bright orange in color. The approximately  five mL  cooled to 253  product was  K  ) , 3.11  m e s o  (8e):  6  solution was  was  (br, 4H, H  in die glove-box. In another flask, also equipped with a Teflon stopcock, C H  saturated with H B r ^  HBr  9.45  Ru(TMP)Br -I- 2 C H C N + '2 H' 8e  excess HBr + R u ( T M P ) ( C H C N ) 6c  2  2  3  Dibromo(tetramesitylporphyrinato)ruthenium(IV)  3  (br, 8H, CH ),  CH ).  2  Ru(TMP)(CH CN)  5.86.  6  degassed by 3  2  under  volume of this solution was was  vacuum, the  brownish solid was  mL)  resulting  reduced under vacuum to  added under vacuum. The  to yield a brownish colored suspension, which was  collected by filtration. The  (20  diree freeze-pump-thaw cycles. This  Ru(TMP)(CH CN)  and then n-pentane (15 mL)  6  reaction mixture  exposed to air and  then dried under vacuo at 353  the  K for  12h. Yield, 100 mg, 93 %. Anal, calcd. for C H N B r R u : C, 64.68; H, 5.00; N, 5.39; Br, 15.21. Found: C, 64.58; H, 5 6  5 2  4  2  5.21;  N, 5.57; Br, 15.08. l  U  spectrum (6,  NMR  C D 6  6  vacuo, 292 K): 13.76 (br, 8H, m-H);  12H, p-CH ); -44.37 ppm (br, 8H, H 3  T  t  measurement (4 mM,  pyrr  4.49 (br, 24H, o-CH ); 4.01 (br, 3  ).  293 K, C D 6  6  vacuo):  H 29  D  = 9 ms, H  m  = 121 ms, H  p  = 417 ms, that for  the H  p y r r  could not be measured accurately because the relaxation time was too short.  UV/visible spectrum (CH C1 , A 2  2  nm): 416 (Soret), 518.  m a x  vale ( R u ( T M P ) B r ) , 881 ( R u ( T M P ) ) , 80/82  Mass spectrum (EI, 523 K source temperature): 960  +  +  (HBr) . +  M  e f f  (corrected, 5 % *-butanol in C H , at 293 K): 2.73 B.M. 7  8  (Ammine)bromo(octaethyIporphyrinato)ruthenium(III) (16c):  Ru(OEP)Br + 1 a t m N H 8a 2  A brownish-red suspension of Ru(OEP)Br with  NH  3 ( g )  -  3 ( g )  2  Ru(OEP)Br(NH ) + '1/2N H ' + 'HBr' 16c 3  2  (50 mg, 0.06 mmol) in C H 7  and this reaction mixture was heated  to 323 K  g  4  (2.5)  (50 mL) was saturated  and sonicated for five  minutes,  resulting in the formation of a clear deep red solution. This reaction mixture was cooled to room temperature, extracted with water (6 x 20 mL) and die aqueous phase was back-extracted with C H 7  g  (3 x 20 mL). The combined organic phase was then dried over M g S 0  4  for ten minutes,  filtered and die filtrate added to a column (neutral alumina, activity III, 10 x 1 cm). Elution of the column widi C H C N yields a deep red solution, from which the solvent was removed under 3  reduced pressure to yield a reddish residue. The reddish product was dissolved in C H 7  precipitated  out of solution  by  adding  reprecipitated from a C H /n-pentane 7  g  n-pentane  (15 mL), collected  by  g  (5 mL),  filtration,  and  (5/15 mL) mix. The product was collected and dried under  vacuum at 373 K for 6h. Yield, 36 mg 8 3 % . Anal, calcd. for C H N B r R u . H 0 : C, 57.75; H, 6.55; N, 9.35; Br, 10.56. Found: C, 57.43; H, 36  47  5  2  6.34; N, 8.89; Br, 10.13. The compound decomposes at 403 K without evolving H 0 , as evidenced 2  by the thermal gravimetric analysis of a 3 mg sample. J  H N M R spectrum ( 5 , CDC1 , 293 K, aerobic): 11.43 (br, 8H, C H ) , 6.10 (br, 8H, C H ) , -2.28 3  (br, 24H, C H ) , -5.29 (br, 4H, H 3  m e s o  2  ).  UV/visible spectrum ( C H , 28.8 u-M, A 7  g  2  m a x  (log e) nm): 385 (4.41), 420 (4.52), 512 (3.79), 550 30  (sh). Mass spectrum (FAB-MS): 713 rale (Ru(OEP)Br) , 634 (RuOEP)) . +  Infrared spectrum (KBr pellet): v . N  M  eff  +  = 3100 cm" (broad), J> 1  H  = 3700-3300 cm" . 1  oh  (corrected, 5 % f-butanol in C H , at 292 K): 1.92 B.M. 6  6  (Ammine)Aloro(octoeUiylporphyrinato)ruthenium(ni) (16d): This complex was prepared using the method discussed for the bromide analogue, but using R u ( O E P ) C l in place of Ru(OEP)Br . 2  2  Yield, 36 mg (86%).  Ru(OEP)Cl + 1 a t m N H 8b 2  3 ( g )  -» Ru(OEP)Cl(NH ) + '1/2 N H ' + 'HCI* 16d 3  2  4  (2.6)  Anal, calcd. for C H N C l R u . H 0 : C, 61.10; H, 6.93; N, 9.90. Found: C, 61.51; H, 7.00; N, 3 6  4 7  5  2  9.62. 'H N M R spectrum (5, CDC1 , 293 K, aerobic): 11.24 (br, 8H, C H ) , 6.19 (br, 8H, C H ) , -2.31 3  (br, 24H, C H ) , -5.07 (br, 4H, H 3  m e s o  2  2  ).  UV/visible spectrum (CHC1 ): identical to that of die bromide analogue within +_ 1 nm and _+ 3  0.01 units of log e. Mass spectrum (FAB-MS): 669 m/e (Ru(OEP)Cl) , 634 ( R u O E P ) ) . +  +  Infrared spectrum (KBr pellet): i / . = 3105 cm" (broad), J/_ = 3700-3300 cm" . 1  N  H  1  0  h  Bromo(octaethyIporphyrinato)ruthenium(III) (16a):  Ru(OEP)Br(NH ) + H F 16c 3  HF  ( a q )  ( a q )  -» Ru(OEP)Br + ' N H 16a  + 4  F"'  (2.7)  (0.5 mL) was added to a reddish colored solution of Ru(OEP)Br(NH ) (20 mg, 0.03  mmol) i n C H C 1  3  3  (50 mL), and die two-phase mixture was stirred vigorously for 10 minutes at  ambient temperature under a N  2  atmosphere. This reaction mixture was concentrated  31  to 5 mL  under reduced pressure, and then added to an alumina column (activity III, 3 x 2 cm). The column was eluted with CHC1 to 3 mL  until a reddish eluate was obtained, which was collected and concentrated  3  under reduced pressure. The product was precipitated out of solution by adding  n-  pentane (15 mL), the precipitate collected by fdtration, and reprecipitated from a C H /«-pcntanc 7  8  (5/15 mL) mix. The product was collected and dried under vacuum at 373 K for 6h. Yield, 21 mg (95%). Anal, calcd. for C H N B r R u : C, 60.59; H, 6.17; N, 7.85; Br, 11.08. Found: C, 60.83; H, 6.27; 3 6  4 4  4  N, 8.03; Br, 10.81. ]  spectrum (6,  H NMR  CDC1 , 293 K, aerobic): 14.15 (br, 8H, C H ) , -0.20 (br, 8H, C H ) , -0.90 3  (br, 24H, C H ) , -2.20 (br, 4H, H 3  m e s o  2  ).  UV/visible spectrum ( C H , 26.4 M M , A 7  2  g  m a x  ( l o g e)nm): 396 (4.61), 500 (3.77), 538 (3.75).  Mass spectrum (FAB-MS): 713 rale (Ru(OEP)Br) , 634 ( R u O E P ) . +  +  Conductivity ( C H C N , 4.12 mM, 293 K): 5 cm" ohm" 1  1  3  M"  1  /* (corrected, 5 % r-butanol in C H , 293 K): 1.78 B.M. eff  7  8  Chloro(octaethylporphyrinato)njthenium(IIT) method  discussed  for the  bromide  (16b):  analogue,  but  This  complex  using  was  prepared  Ru(OEP)Cl(NH ) 3  in  using the place  of  Ru(OEP)Br(NH ). Yield, 20 mg (95%). 3  Ru(OEP)Cl(NH ) + H F 16d 3  ( a q )  -  Ru(OEP)Cl + N H 16b  + 4  F"  (2.8)  Anal, calcd. for C H N C l R u : C, 64.57; H, 6.58; N, 8.37; CI, 5.23. Found: C, 64.32; H, 6.51; N , 3 6  4 4  4  8.30; CI, 5.25. spectrum {8,  'H N M R  CDC1 , 293 K, aerobic): 14.13 (br, 8H, C H ) , -0.16 (br, 8H, C H ) , -0.93  (br, 24H, C H ) , -1.11 (br, 4H, H 3  3  m e s o  2  ). 32  2  UV/visible spectrum (CHC1 ): identical to that of the bromide analogue. 3  Mass spectrum (FAB-MS): 669 m/e ( R u ( O E P ) C l ) , 634 ( R u O E P ) . +  +  Conductivity ( C H C N , 1.34 mM, 293 K): 7 cm ohm" M" 1  1  3  M  E F R  (corrected, 5 % f-butanol in C H , 293 K): 2.03 B.M. 7  8  (Acetonitrile)bromo(octaethylporphyrinato)ruthenium(III) (16e): This complex  was syntlicsized  following the method for the synthesis of 16a, except that the solvent used was C H C N .  Also,  after  under  3  the chromatographic purification  of the product, die C H C N  solvent  3  was removed  reduced pressure, and the residue precipitated out of solution using a C H /n-pentanes mixture. 7  Ru(OEP)Br(NH ) + H F 16c 3  ( a q )  -  g  Ru(OEP)Br(CH CN) + N H 16a 3  + 4  F"  (2.9)  Anal, calcd. for C H N B r R u : C, 57.51; H, 6.35; N, 9.07; Br, 10.23 Found: C, 57.37; H, 6.16; 3 8  .  4 7  5  N, 9.31; Br, 9.87. 'H N M R  spectrum (<5, C D C N , 293 K, aerobic): 9.02 (br, 8H, C H ) , 5.80 (br, 8H, C H ) , -2.57 3  (br, 24H, C H ) , -5.77 (br, 4H, H 3  2  m e s o  2  ).  UV/visible spectrum ( C H C N , 29.2 /xM, A 3  (log e) nm): 381 (sh), 396 (4.58), 519 (4.00), 538  m a x  (sh). Mass spectrum (FAB-MS): 713 mle (Ru(OEP)Br) , 634 (RuOEP)) +  Infrared spectrum (Nujol mull, K B r windows): I ^  +  - 2257 cm . -1  C e N  (Acetonitrile)chloro(octaethylporphyrinato)ruthenium(III) (16f): This analogue was synthesized from Ru(OEP)Cl(NH ) using the method described for the bromide analogue 16e. 3  Anal, calcd. for C H N C l R u . H 0 : C, 62.64; H, 6.73; N, 9.62; CI, 4.81. Found: C, 62.86; H, 3 8  4 7  5  2  6.68; N, 9.90; CI, 5.21. J  H NMR  spectrum (6,  C D C N , 293 K, aerobic): 9.20 (br, 8H, CH,), 5.78 (br, 8H, CH,), -2.70 3  33  (br, 24H, C H ) , -5.85 (br, 4H, H 3  m e s o  ).  UV/visible spectrum (CH CN): identical to that of the bromide analogue. 3  Mass spectrum (FAB-MS): 669 mle  (Ru(OEP)Cl) , 634 (RuOEP)) . +  Infrared spectrum (Nujol mull, K B r windows):  +  i /  C  E  = 2250 cm  N  -1  (broad), v0_H  =  3700-  3300 cm" . 1  Bis(pyridine)(octaethylpoiphyrinato)nithenium(in)  Ru(OEP)(py) + H C l 6a 2  7  8  (10 mL)  was  / a i r - [Ru(OEP)(py),] CI" 17a  (2.10)  +  (aq)  A red-yellow solution of Ru(OEP)(py) mmol) in C H  chloride (17a):  2  (50 mg, 0.06 mmol) and concentrated H C l  (50 y.L,  ( a q )  sonicated for five minutes at room temperature or until a salmon  colored suspension was generated. This suspension was filtered to collect the product, which purified  by  two  0.6  successive reprecipitation  steps from  collected from die second reprecipitation step was  CH Cl /n-pentanes 2  (5/15  2  mL).  dien dried under vacuum at 333  The K  was solid  for 12h.  Yield 49 mg, 94%. The  [Ru(OEP)(py-d ) ] CI" analogue (17c) to J_7a was prepared by adding py-d +  5  2  5  (3 mL) to  [Ru(OEP)] (10 nig, 8 Mmol) under vacuum, tliis generating Ru(OEP)(py-d ) in situ. The py-d 2  5  2  then removed under vacuum, and the residual solid redissolved in CDC1 . Some HCI ., 3  (  to this solution in air to generate die required Ru(III) product, which was  q)  5  was  was added  isolated using the  procedure described for 17a. Anal, calcd. for C H N C l R u : C, 66.75; H, 6.53; N, 10.16; CI, 4.23. Found: C, 66.43; H, 6.52; 4 6  5 4  6  N, 10.05; CI, 4.15. >H N M R  spectrum («, CDC1 aerobic, 293 K): 22.96 (br, 4H, m-H ); 17.21 (br, 16H, CH ); 3.21 3  py  (br, 2H,p-H ); -0.20 (br, 24H, CH ); -1.26 (br, 4H, H pv  3  /x f (corrected, 5 % C H in CHC1 , 292 K): 1.99 ef  6  6  3  m e s o  ) ; -6.97 (br, 4H, o-H ).  B.M. 34  2  pv  Conductivity ( C H C N , 2.34 mM,  293 K): 125 M"  3  UV/visible spectrum (CHC1 , 46.5 3  1  A»M,  ohm"  1  cm" . 1  (log e) nm): 390 (5.09); 454 (sh); 503 (4.01); 529  (4.08); 628(2.97); 719(3.25). Mass spectrum for 17a (FAB-MS): 792 rale- (Ru(OEP)(py) ) ; 712 (Ru(OEP)py) ; 634 (Ru(OEP)) . +  +  +  2  FAB-MS of 17c: 802 rale- (Ru(OEP)(py-d ) ) ; 717 (Ru(OEP)(py-d )) ; 634 (Ru(OEP)) . +  5  +  2  +  5  Bis(pyridine)(octaethylporphyrinato)ruthenlum(III)  tetrafluoroborate (17b). This complex  prepared following the method discussed for the chloride analogue, but using H B F  was of  in place  4 ( a q )  aqueous HCI. Yield, 50 mg (91 % ) .  Ru(OEP)(py) + H B F 6a 2  4(aq)  /air  Anal, calcd. for C H N B F R u . 2 H 0 : 46  54  6  4  2  [Ru(OEP)(py),] BF " 17b  (2.11)  +  4  C, 60.33; H, 6.34; N, 9.18. Found: C, 60.37; H, 6.11;  N,  9.13. !  H  spectrum (6,  NMR  C D C 1 aerobic, 293 K): 24.19 (br, 4H, m-H ); 18.05 (br, 16H, CH ); 3  py  (br, 2H, /;-H ); -0.33 (br, 24H, CH ); -1.88 (br, 4H, H py  /x  eff  3  (corrected, 5 % C H in CHC1 , 292 K): 2.44 6  6  3  293 K): 120 M"  1  UV/visible spectrum ( C H C N , 13.9 fiM, A 3  3.43  ) ; -7.60 (br, 4H, o-H ). pv  B.M.  3  Conductivity ( C H C N , 1.11 mM,  m e s o  2  m a x  ohm"  1  cm.  (log £) nm): 390 (4.62); 454 (sh); 503 (3.59); 530  (3.65); 634 (2.52); 719(2.82). Mass spectrum (FAB-MS): 793 rale- (Ru(OEP)(py) ) ; 713 (Ru(OEP)py) ; 634 ( R u ( O E P ) . +  +  +  2  2.4.  General  and  complexes. The  specific reaction conditions used to study the solution chemistry of Ru(porp)  intense v  -» rr* transition (labelled the Soret band) observed  for metalloporphyrin  complexes in the 380-420 nm  region, and other bands typically observed in the 500-600 nm  make UV/visible spectroscopy  an extremely  region,  useful tool for the smdy of the solution chemistry  35  of  diamagnetic Ru(porp) complexes. Solutions of Ru(porp) complexes of the concentration range 10" 6  10"  M  5  were  used  to measure the equilibrium  of PPh  constants for die dissociation  3  from  Ru(OEP)L(PPh3) ( L = CO, PPh , see Sections 3.2.b to 3.2.d), as well as for identifying species in 3  solution whose UV/visible spectra are well known. UV/visible spectroscopy is generally less useful where paramagnetic Ru(porp) complexes are studied, because the Soret and odier bands observed in the UV/visible spectra of these species are generally of much lower intensity, and vary to a lesser extent in position (for example, the Soret band positions range over 300-400 nm) than the corresponding  bands observed for diamagnetic complexes. Nevertheless,  the use of UV/visible  spectroscopy to study kinetic processes involving paramagnetic Ru(porp) complexes is possible, as exemplified by the study of die reaction of [Ru(OEP)] (0.1 to 4 mM) with C H C 1 2  2  2  (see Section  4.2.e). ]  H  NMR  spectroscopy  is an ideal  technique  for studying  the solution  chemistry  of  paramagnetic Ru(porp) complexes because die 'H resonances of these paramagnetic complexes are well separated from each other, appearing in the range -55 to 70 ppm relative to TMS. Typically, samples analyzed by 'H N M R spectroscopy were prepared by dissolving 2-3 mg of the Ru(porp) concentration solutions. If the  complex in 0.5-0.6 mL of an appropriate solvent, giving 1-5 m M sample  to be studied  was air-sensitive, the solution was sealed under an inert atmosphere or  under vacuum in N M R sample nibes such as those shown hi Figure 2.2. Where the conditions of NMR  experiments differed  from  those described  above,  specific  details  are  provided in the  relevant accompanying text. In studies involving the reaction of H 0 2  widi Ru(porp) (see Sections 3.2.a, 4.2.a, 4.2.f, and  5.2.d.3), 1 t i L of H 0 was added to a solution of the appropriate Ru(porp) complex, and where O, 2  was  the reagent, a 0.5 mL sample  was added  to the N M R  sample tube; in all cases, the  subsequent reaction solutions were sealed under vacuum. Unless stated odierwise, gaseous reagents such as H  2  and C O (or other gases mentioned in the text) were introduced  solution by bubbling die gas through die solution under ambient pressure.  36  into the reaction  Studies of the possible stoichiometric decarbonylation of benzaldehyde or phenylacetaldchydc by Ru(OEP)PPh , Ru(TPP)(PPh ) or P P h 3  3  2  3  (Section 3.2.g) were conducted using 4-5 mM  of Ru(porp) complex and aldehyde (25-30 mM). (1  uL)  The reagents 0  (0.5 mL), H 0  2  2  solutions  (1 //L) or P(n-Bu)  3  were added separately to the reaction mixture of Ru(porp) complex and aldehyde using a  syringe, and each reaction solution was then sealed under vacuum (total reaction solution  volume  was 0.5 +_ 0.1 mL in each case). In general, 1-2 uL  samples of pyridine or H B F  were used in the reaction of these reagents  4  with [Ru(OEP)] (see Section 4.2.f). Samples of [Ru(OEP)] (10-20 mg) were reacted with C H B r 2  (3 mL), CC1 mixture  4  2  (5 mL) or C H C H C 1 6  obtained  by  5  2  (5 mL) under vacuum; the isolated solid from each reaction  2  the removal of die solvent  under  vacuum  spectroscopy (Section 4.2.g). Solutions of [Ru(OEP)] (1-5 mM)  was  analyzed  by  'H  were also reacted with  2  NMR 1-5 fiL  volumes of C H C O O H and aqueous C H C O O H , C F C O O H , HF, H N 0 , H B F , HCI, HBr, and HSbF 6  or  5  3  one atm of gaseous HF  in N M R  2  3  3  4  6  sample tubes under an N, atmosphere, and each resulting  solution was subsequently analyzed by *H N M R  spectroscopy (Section 4.2.i).  The attempted oxidation of cyclohexene (70 /xmol) by PhIO or mCPBA (70 //mol) catalyzed by Ru(OEP)X  (X =  Br, CI; 1.4 //mol) was studied in C H , C H C 1 6  5.2.d.3).  37  6  2  2  or C H C N (2 mL, 3  sec Section  Chapter 3. The reactivity of thefive-coordinatecomplexes  carbonvKoctaethylporphyrinato)-  rutheniumfJTJ). (3a). and (octaethylporphvrinato)(triphenylphosphine)rutheniiim(II), (5a). 3.1. Introduction. A  number  dissociate involved  of six-coordinate  a phosphine ligand in catalytic  Ru(TPP)(PPh ) 3  in solution  systems  yielding  (see Chapter  (4b) and Ru(OEP)CO(PPh )  2  Ru(OEP)CO  i ) .  1  6  b  phosphine complexes  five-coordinate intermediates . 9 1  2  The  1  complexes  (IT) have been found  3  extent in solution, yielding and  ruthenium(II) porphyrin  15,17  This  chapter  describes  which  may 3  3  to some  (5a), Ru(TPP)PPh  3  be  Ru(OEP)(PPh )i (4a),  to dissociate P P h  the five-coordinate complexes Ru(OEP)PPh  (3a), respectively.  are reported to  some  solution  3  (5b)  coordination  chemistry originating from 3a and 5a and the possible role of 5a in the catalytic decarbonylation of aldehydes. " • 16  The measurement containing the  of the dissociation rate of a ligand ' L ' from Ru and Fe porphyrin complexes  phosphines and nitrogenous ligands such as imidazoles, isocyanates and nitriles, and  subsequent association  rates  of CO  M ( p o r p ) L have been documented: ' ' 13  21  «-  2  +CO,k M(porp)L  -fL,k^L  «-  species  M(porp)(L)CO  (3.1)  ~CO,k_QQ  3  for only  intermediate  + c o  The dissociation of a phosphine ligand from Ru(OEP)(PR ) 3.1) has been studied  five-coordinate  59-62  -LJC.L M(porp)(L)  to the proposed  one system to date (R  2  complexes (i.e. k.  L  =  n-Bu).  step in Equation  The measurement  62  of the  dissociative rate constant (k ) and overall equilibrium (K,,) constant, as well as the corresponding n  activation  and thermodynamic  parameters for the dissociation  of P P h  3  from  the two species  Ru(OEP)L(PPh ) ( L = CO, PPh ), are presented in Sections 3.2.b to 3.2.f: 3  3  -PPh k 3>  Ru(OEP)L(PPh ) 3  n  £ Ru(OEP)L + PPh + PPh ,k 3  n  L = PPh , CO ('n' will be defined in the following Sections) 3  38  3  (3.2)  The  complex  Ru(TPP)(PPh ) 3  (4b] has been  2  reported  aldehydes in a variety of solvents, and it was suggested intermediate Ru(TPP)PPh  3  (5b) generated  for the catalysis to be observed. was  19  to catalyze  die decarbonylation of  that the formation of a five-coordinate  by the dissociation of a phosphine from 4b was cnicial  When attempts to synthesize the T P P species 5b f a i l e d ,  5a  16a  tested instead as a possible catalyst for the decarbonylation reaction. Due to the repotted  ^reproducibility of the decarbonylation reaction catalyzed by 4b using the described conditions, " 19  experimental  no attempts were made to repeat the previous work. Instead, the effects of trace  21  impurities such as 0  2  and H 0  on the decarbonylation reaction were studied and are documented  2  in Section 3.2.g. 3.2. Results and Discussion. The  syndiesis of Ru(OEP)(PPh ) (5a) utilizing a vacuum pyrolysis technique has been described 3  previously. ' 163  37  This  monomeric,  16e", five-coordinate complex  is capable  of reacting  with  several ligands to yield coordinatively saturated compounds as diagrammed in Scheme 3.1. 3.2.a. Reaction of Ru(OEP)PPh  3  (5a) with small molecules. Solutions of 5a in C D 6  or C D C 1  6  2  react with air at ambient temperatures to yield die M-OXO dinuclear species [Ru(OEP)OH] 0 2  2  (9)  and 0 = P P h within minutes as observed by 'H N M R spectroscopy, and therefore 5a is stored as a 3  solid  in an inert atmosphere glove-box until required. A n attempt was made to elucidate the  mechanism of diis aerobic oxidation by adding either H 0 or dry 0 2  2  to C D 7  g  solutions of 5a. In  the latter case, an aquo complex, Ru(OEP)(PPh )(H 0) (5c) is observed by H N M R  spectroscopy  ]  3  (see Table  3.1),  die species undergoing  2  rapid exchange with  (water signal observed at -0.54 ppm, 50 Hz full-width  free water at room  temperature  at half-height, 400 M H z (FT)). This result  agrees well with other data widiin ruthenium porphyrins where exchange of bound and free water is observed. and  the H l  27  The mixture containing 5a and dry 0 NMR  signals of the porphyrin  2  showed no reactivity at either 293 or 213 K  and phosphine ligands remained  sharp  temperature range. A similar behavior was observed for Ru(TMP)(P(n-Bu) ) (5d) in C D 3  0  2  7  over 8  this  with dry  over die same temperature range, suggesting diat the more basic trialkylphosphine axial ligand  39  Scheme 3.1: Reactivity of Ru(OEP)PPh , 5a. 3  40  Table 3.1:  Spectroscopic data for Ru(porp)  complexes containing carbonyl and phosphine  axial  ligands. (a) H (300 and 400 M H z ) and P{'H} (121 M H z ) N M R spectroscopic data, measured ]  31  at 293 K. *H N M R macrocycle  resonances phosphine phenylS p-H 6 m-H S o-U  2  complex  solvent  6  H  meso  8  C  H  2  1.95  -  9.92  4.03  1.92  -  8.99  3.67  1.81  Ru(OEP)CO, 3a  CDC1  Ru(OEP)(PPh ) , 4a  C D  Ru(TPP)(PPh ) , 4b  CDC1  Ru(OEP)PPh , 5a  C D 7  8  9.53  Ru(OEP)PPh (H 0), 5c  C D  8  9.36 3.75 (br)  3  2  3  V  2  3  3  7  2  3  8  3  H  4.00  C D  8  C  10.15  Ru(OEP)CO, 3a  7  6  3.81  ~  6.46  6.25  4.25  8.27 (s)  6.71  6.47  4.22  6.87 (s)  1.87  6.47  6.28  4.22  58.89 (s)  1.86  6.64  6.28  4.21  c  3  i_31E  -0.54 (br)4 e  Ru(TMP)(P(n-Bu) ), 5d  C D 7  8  [Ru(OEP)OH] 0, 9  C D 6  6  Ru(TPP)(P(n-Bu) )  C D  6  3  2  3  2  6  Ru(OEP)CO(PPh ), 11  CDC1  3  f  9.43 4.40,4.04^ 1.89  3  53.09 (s)  -  -9.39 (OH)  h  i  -2.01  9.50 3.96 (br) 1 .74  k  11.23 (br)  - Unless stated otherwise, the multiplicity of each signal of the macrocycle is as follows: H  = singlet (s), C H = quartet (q), C H = triplet (t), br = broad.  m e s o  2  3  - Unless stated otherwise, the multiplicity of each signal of the phosphine phenyl ring is as follows: p-H (doublet, d), m-H (t), o-H (t). £ TPP resonances: 8.06 ( H  p y r r  , s), 7.55 (p-H, multiplet, m), 7.53 (m-H, m), 7.51 (o-H, m).  - Trace free H 0 appears at 0.34 ppm in C D as a sharp singlet. 2  5 T M P resonances: 8.31 ( H  7  p y r r  8  , s), 7.21 and 7.05 (m-H, s), 2.57 (p-CH , s), 2.44 and 1.62 3  (o-CH , s). 3  f Axial ligand resonances: 0.43 (-CH CH , br), -0.74 (P-CH -CH -, br), -1.59 (P-CH -, br). 2  3  2  41  2  2  Table 3.1: Continued. 2  These signals appear as two sets of multiplets.  * T P P resonances: 8.60 ( H  p y r r  , s), 8.36 (m-H, m), 7.57-7.48 (p- and o-H, m).  i Axial ligand resonances: 0.55 (-CH^CH^, br), -0.92 (P-CH -CH -, br), -1.95 (P-CH -, br). 2  2  - Spectrum measured in the presence of a large excess of PPh . 3  (b) UV/visible spectroscopic data for Ru(porp) complexes. complex  solvent  Ru(OEP)CO, 3a  C H  Ru(OEP)CO, 3a  CHC1  Ru(OEP)CO(MeOH), 3b  7  C  A  max> ( ?  Onm  lo  393 (Soret, 5.40), 518 (4.41), 549 (4.65)  g  3  7 8" H  393 (Soret, 5.62), 515 (4.43), 547 (4.74) 392 (Soret), 517, 547  Ru(OEP)(PPh ) , 4a  C H 7  g  422 (Soret), 518, 532  Ru(OEP)PPh , 5a  C H  g  395 (Soret), 520  3  2  3  Ru(OEP)(CO)  2  Ru(OEP)CO(PPh ), J l 3  7  C  7 8~  395 (Soret, 5.32), 512 (4.34), 546 (4.65)  C  7 8  407 (Soret), 525, 555  H  H  £  2 Measured by adding excess M e O H to Ru(OEP)CO in C H . 7  g  - Measured under a CO atmosphere. - Measured in the presence of 100 equivalents of P P h to Ru. 3  42  2  in  5d does not enhance the binding  solvent  polarity  of 0 ; ^-acceptor/donor capacity 2  are both known to affect 0  binding  2  of the axial  to Ru and Fe porphyrin  Although it was apparent that there is no association of 0  ligand and  complexes.  to 5a or 5d, a (porp)Ru(0 ) adduct  2  2  must exist to yield eventually 9, which forms upon addition of 0  2  to the first mixture (5a and  H 0 ) or the addition of H 0 to the second mixture (5a and 0 ) . These results confirm 2  2  2  oxygen and moisture are required  for the aerobic  710  that both  oxidation of 5a to the M-OXO species  9, as  observed for other Ru(OEP) complexes where there are either weakly bound (THF, C H C N ) or no 3  axial l i g a n d s . H 0 2  9,10  '  47  A  similar reactivity was observed for the T M P  to a solution of Ru(TMP)(P(/z-Bu) ) (5d) and added 0 3  2  case, where the addition of  led to the oxidation of 5d; however,  the oxidized Ru(TMP) product was not identified. Two mechanisms can be considered based on a mechanism reported oxidation of 5a by 0  for the oxidation of 5a to 9 by O, and H 0 . The first, 7  for the oxidation of P P h  to yield 0 = P P h  2  3  by Ru(OEP)(PPh )->,  and 0=Ru(OEP), the latter porphyrin  3  reacting further widi anodier molecule of 5a to form [Ru(OEP)] 0 = P P h . The [Ru(OEP)] 3  and  0  2  (Scheme  3.2).  2  35  16b  3  involves the complex  then  (7) and another equivalent of  2  then decomposes to the M-OXO dinuclear species upon reaction with The second  mechanism  is based  on the H  +  catalyzed  H 0  outer-sphere  oxidation of 5a by 0 , leading to [Ru(OEP)PPh ] and 0 ~. +  2  3  Ru(OEP)PPh + 0 3  2  2  -> 0 = R u ( O E P ) + 0 = P P h  0 = R u ( O E P ) + Ru(OEP)PPh - [Ru(OEP)] + 0 = P P h 3  [Ru(OEP)] + 0 2  2  2  + H 0 -» [Ru(OEP)OH] 0 2  (3.3)  3  3  (3.4) (3.5)  2  Scheme 3.2  Ru(OEP)PPh + 0 <- [ R u ( O E P ) P P h ] + +  3  0 " + H  2  +  2  2 H0  2  3  - H0  2  - H 0  2  2  43  0' 2  (3.6) (3.7)  + 0  2  2  (3.8)  H 0 2  2  + 2 [Ru(OEP)PPh ]  - 2 0 = P P h + [Ru(OEP)] + 2 H  +  3  [Ru(OEP)] + 0 2  2  3  (3.9)  +  2  (3.10)  + H 0 - [Ru(OEP)OH] 0 2  2  Scheme 3.3  In Scheme 3.2, the expected slow-step would be the formation of 0=Ru(OEP). Because species ol' die  type  0 = R u ( O E P ) have been shown to be very  reactive, *' 39  generated i n step 3.4 is known to be very reactive toward a i r , ' ' 2 5  assumed to be fast. Because 7 does not react with dry 0 concentration  of 7 i n the reaction  mixture  should  and because  40  3 7  even  in the reaction  of 5a widi  J  steps 3.4 and 3.5 can be  4 7  (see Chapter 4) to generate 9, the  2  increase in the absence  According to Scheme 3.2, die loss of the intensity of the 'H N M R observable  the dimer  dry 0 ; this 2  of added H-,0.  signals of 5a should be  is contrary to the findings and,  therefore, Scheme 3.2 is not the best model for the observed reactivity. In  contrast, die outer-sphere oxidation of 5a by 0  2  would be the slow-step for Scheme 3.3,  and because the 0 " generated is diought to be stabilized by trace H , +  2  need for the presence of H 0 2  [Ru(OEP)PPh ] 3  +  in the oxidation of 5a to 9 by 0  2  2 8  Scheme 3.3 reflects the  and H-,0. The detection of  would have enhanced the case for die latter mechanism, but no such species was  observed, suggesting that the equilibrium depicted by Equation 3.6 favors reactants over products (as expected). Mixtures of 5a and H As The  noted  2  or N  2  in C D 6  6  were unreactive as attested  by *H N M R spectroscopy.  in the introduction, 5a reacts widi H B r ^ / a i r , resulting in Ru(OEP)Br(PPh ) (10).  reaction of 5a with CO  16,1  3  immediately  generates Ru(OEP)CO(PPh ) (11), which  under these  3  conditions (see below) establishes an equilibrium involving dissociation of a phosphine:  k  -l  44  Ru(OEP)CO + P P h 3a  3  (3.11)  The  species  3a instantly associates  a further molecule of C O  under diese  conditions  to give  Ru(OEP)(CO) (this latter equilibrium will be discussed in further detail later in this Chapter). 2  3.2.b. The reaction of P P h  3  with R u ( O E P ) C O (3a) in C H . 7  g  Initial attempts in this laboratory to  measure the rate constants (kj and k.]) detailed i n Equation 3.11 following synthesis of JJ. by a literature method initiated using  17  failed due to the inability  impure  63  Kinetic  1_1 suggested that this system (1 l/3a/PPh ) was ideal for study 3  technique of dynamic N M R of P P h  to prepare 1_1 analytically pure.  spectroscopic  analysis,  63  studies by the  and so an alternate route involving reaction  with Ru(OEP)CO(MeOH) (3b) was devised, the system yielding the same overall K, (K, =  3  k,/k.j). It is known that the dissociation of ethanol from Ru(OEP)CO(EtOH) is almost complete in  CH C1 2  EtOH:  2  solution  at /xmolar concentrations  at room  temperature, yielding  Ru(OEP)CO and  17  Ru(OEP)CO(EtOH) £  Because die 'H N M R  Ru(OEP)CO + EtOH, K  = 1.8 x IO" M  (3.12)  3  e q  exchange mechanism is suggested to involve  the association  Ru(OEP)CO (3a) to give Ru(OEP)CO(PPh ) (JD, the extent of dissociation of MeOH 3  give 3a was measured by titrating a 2.24 / i M solution of 3b with a M e O H : C H 7  in C H 7  by following the changes in die UV/visible  g  g  of PPh  3  to  from 3b to  solution (10:90 v/v)  spectrum of the solution upon addition of  MeOH. The analysis of die data was done according to:  Ru(OEP)CO(MeOH) ^ 3b  Ru(OEP)CO + M e O H 3a  (3.13)  K ^ = [Ru(OEP)CO][MeOH]/[Ru(OEP)CO(MeOH)] hence  -log K  and  log [(A-A )/(A A)] = log {[Ru(OEP)CO(MeOH)]/[Ru(OEP)CO]}  where  e q  = log {[Ru(OEP)CO(MeOH)]/[Ru(OEP)CO]} - log [MeOH] 0  A  0  (3.14) (3.15)  f  (3.16)  r  is the absorbance of the solution  before  the addition  of any MeOH,  A  is  the  absorbance of die solution after die addition of an aliquot of MeOH, and A; is the absorbance of  45  the solution i n the presence of a large excess of MeOH. [MeOH] MeOH  refers to the concentration oi"  f  in solution after each addition, after correcting for the amount coordinated  to ruthenium  using: [MeOHlf = [MeOH], - [ ( A - A ) / ( A A ) ] [ R u ] 0  where  [MeOH], is the total  amount  r  0  of M e O H  (3.17)  lolal  added  to the reaction cell,  coordinated to the ruthenium. Thus, a plot of log [(A-A )/(A;-A)] vs. log [MeOH] 0  straight line with slope equal to one and the y-intercept will changes observed  f  should give a  give K g . Figure 3.1 shows the q  in the UV/visible spectrum of the solution upon addition of M e O H to a dilute  solution of 3b, and the corresponding  log plot to obtain K g . The data used to determine K q  were measured at 393 nm and 293 K* a sample treatment of die data to give K  A(393 nm): 0.564 log[(A-A )/ (A;-A)]:  including that  0.601 0.628  0.665  0.697  0.723  e q  is shown below:  0.761 0.786 0.814  0.874  0.995  0.41  --  0  --  -1.03 -0.76 -0.51 -0.35 -0.23 -0.07  Volume MeOH: 0.0 (in fiL) log[MeOH] : f  -  0.5  1.0  1.5  2.0  3.0  4.0  0.03 5.0  0.14 10.0  20.0 220  -3.62 -3.32 -3.14 -3.02 -2.84 -2.72 -2.62 -2.32 -2.02  The stock [MeOH] was 2.47 M, and the correction to [MeOH], (as in Equation 3.17) was minimal (<  1%) and, therefore, was ignored. From the log plot, K  +_ 0.1. This 10"  6  M  = 2.5 x 10" M and the slope was 0.9 3  e q  value for the dissociation of M e O H from Ru(OEP)CO(MeOH) (3b) shows that at  concentrations, 3b is >  9 5 % dissociated to Ru(OEP)CO  (3a) and MeOH. This result  compares well with that for the extent of dissociation of EtOH from Ru(OEP)CO(EtOH) at similar concentrations (>97 % dissociated).  17  However, at N M R sample concentrations (1-5 mM), calculations show that the MeOH should be ca. 5 0 % dissociated from 3b. The N M R spectrum of Ru(OEP)CO(MeOH) (3b) at 5.1 mM  46  in C D 7  8  Figure 3.1:  (a) UV/visible  spectral changes observed  Ru(OEP)CO (2.24 x 1CT M ) i n C H 6  7  8  upon  addition  of M e O H  (2.47 M ) to  at 293 K. The total added M e O H present in  solution after each addition corresponds to 0, 107 , 214, 321, 428, 642 , 876, 1071, 2142, 4284 and ca. 45000 equivalents. The limiting spectrum is not shown because of significant dilution of the solution, (b) Plot of log [(A-A )/(A A)] vs. log [MeOH] D  r  f  for the above titration, measured at 393 nm.  Ca)  <b) o  <  .  ^ao 1  1  < CD  2  -081  ,  -a6  1  1  1  -Z8 log D4eQH3  u z < pp  1  -2.0 f  0.5  a  PQ  0.0 350  400 WAVELENGTH 47  450 nm  containing  added P P h  (3.3 mM,  3  see Figure  3.2a), only  shows H  m e s o  signals for two Ru(OEP)  complexes at 10.145 and 9.776 ppm at 223 K corresponding to Ru(OEP)CO and RuOEP)CO(PPii ), 3  respectively, and no third signal corresponding to that for 3b. This result shows that the MeOH is fully dissociated at N M R on  sample concentrations,  i n apparent contradiction to the result based  the measured equilibrium constant for the dissociation of M e O H from 3b, and suggested that a  more careful assessment of the reaction conditions in each type of experiment should be made. The  UV/visible  spectroscopic  because at this concentration the concentration  titration  experiment  the trace [H 0] 2  / J M concentrations  involves  in dried C H 7  8  of 3b and,  could be higher {ca. 10-100 fiM) than  of 3b, association of H 0 to Ru(OEP)CO is likely, forming Ru(OEP)CO(H 0). 2  2  Thus, the analysis used to treat the titration data for die dissociation of M e O H from 3b probably needs to be modified to include the [ H 0 ] , an unknown but constant parameter for the system. 2  Indeed, the addition of trace H 0 (14 mM) to a solution of Ru(OEP)CO(MeOH) (3b) (5 /xM in 2  C H ) prior to the addition of any excess M e O H caused no change in the UV/visible spectrum of 7  8  3b. This result shows that the generated species in solution upon dissolving 3b in C H 7  certainly  Ru(OEP)CO(H 0), and not Ru(OEP)CO  (3a).  2  Ru(OEP)CO(EtOH)/EtOH/CH Cl 2  titration  2  system,  A  is almost  similar result was observed  suggesting that the EtOH  17b  8  in  the  system also needs  to be reassessed. In  die N M R  spectroscopy  experiment, the [ H 0 ] is less than the concentration 2  judged by the relative intensity of the *H N M R  2  2  dissociation of M e O H  from  as  signals of 3b and H 0 ; therefore, the formation  of Ru(OEP)CO(H 0) would be limited at these concentrations. the  of 3b,  The actual equilibrium constant for  3b must be larger than the number measured  by UV/visiblc  spectroscopy. Indeed, the room temperature H N M R spectrum of neat 3b shows dissociated MeOH ]  at die expected position for free M e O H in C H 7  show that, at N M R and  sample concentrations  8  (5 3.30 (CH3OH), 4.78 (CH OH)), and the data 3  in dry C D , 3b fully dissociates to give 7  8  MeOH. The implications of these findings will be discussed  later in this Chapter, after other  evidence for this disparity in data between those obtained from UV/visible  48  Ru(OEP)CO  spectroscopic  titration  Figure 3.2: (a) H NMR spectra of a mixture of Ru(OEP)CO (5.1 mM) and PPh (3.3 mM) In CyDg measured 1  3  ot 10 K Intervals, and (b) spectra simulated usfng the parameters listed In Table 3.2 and Appendix 1. The temperature and the rate constant, k^, are listed for each spectrum. (a)  T (K)  VO  T  10.10  k  1  (b)  Cs") 1  333  3600  323  2000  313  950  303  450  293  200  283  60  273  40.0  263  7.0  253  2.0  243  0.7  233  0.1  223  0.04  ppm 9.90  ppm 10.10  9.90  and those from N M R spectroscopic experiments have been presented. Discussions on the theoretical aspects of the phenomenon of dynamic numerous, yield  64  processes are  and the use of this technique to study the lineshape of an observed N M R  signal can  data such as rate constants and activation parameters. The phenomena described by this  process indicate  that two or more separate sharp N M R  exchange rate region; the resonances would and  NMR  then finally  first broaden  collapse into a single sharp resonance  resonances  would  exist  in the slow  in the medium exchange rate region, witii  increasing  temperature  when fast  exchange is realized. The conditions under which this analysis apply to diamagnetic complexes arc that, in die absence  of chemical exchange,  (1) the lineshapes must  be Lorentzian,  linewidths at half-height arise from die homogeneous and inhomogeneous effects which the  normal broadening of N M R  signals; for the present study, the T  2  (2) the result in  relaxation time measured  from the solvent signal linewidth at half-height at low temperature (i.e. 223-233 K) was used as an  approximation of the normal  line-broadening that  would  be observed  interest, and (3) diat the separation between die two non-exchanging the  for the signals of  signals (in Hz) must exceed  natural linewidths of these same signals so diat the effects of chemical exchange can be  easily observed. Additional factors diat simplify die measurements are that the ratio of the two exchanging species be as near as possible to 1:1 and that the observed exchange occurs between two resonances of singlet multiplicity. These additional factors are non-essential, but helpful. The 'H N M R spectra of a C D 7  8  solution of Ru(OEP)CO(MeOH) (3b) (5.1 mM) and P P h  3  (3.3  mM) sealed under vacuum were measured as a function of temperature, with an emphasis made to study the H spectra  m e s o  (Figure  resonances of each porphyrin species, 3a and Ru(OEP)CO(PPh ) (11). From these 3  3.2a),  the chemical  shifts  of the non-exchanging  H  resonances  m e s o  temperature were measured. The measurement of the position of each of the H and  J l (formed  temperature  using an excess of added PPh ) as individual  extremes  3  (223 and 333 K) showed  that  samples  the absolute position  signals of 3a  m e s o  in C D 7  at low  g  at the  of each  two  resonance  relative to the solvent standard increased with temperature by about 0.03 ppm overall, due to  50  some  temperature  samples  dependence;  however,  the relative  difference  against the internal solvent standard was found  measured at low temperature from the 'H N M R  in position  between  the two  to be negligible. Thus, the positions  spectrum of the mixture were used as assignments  for 3a and 11 over the entire temperature range of the study. The individual population of each complex (A = 3a, B = 11_, where A + B = 1.0) involved in the exchange  mechanism at each temperature was measured several ways: (1) at temperatures below  the coalescence temperature (for example, below 293 K in Figure 3.2), the population of each species was obtained from above  the ratio of integration for these two signals; (2) at temperatures  die coalescence temperature, the population  of each  species  was calculated  from the  position of the coalesced signal, relative to the difference in position of the two signals in the absence of chemical exchange; (3) in the intermediate region (for example, between 283 and 303 K),  the individual  population  of each  signal  was obtained by interpolation  of a graph of  population A (or B) vs. temperature, using die previously determined populations in the two other temperature regions. The estimated error in the population of each species is +_ 5 %. The  populations and assigned positions  temperature (Table 3.2) were utilized  of the H  in the program  resonances  m e s o  DNMR3  6 5  of 3a and N. at each  (details of this program arc  provided in Appendix 1) to simulate spectra as a function of a single rate constant, k,:  k, Ru(OEP)CO(PPh ) 3  By  Ru(OEP)CO + P P h  (3.18)  3  varying the value for k j , spectra which matched those measured at each temperature were  obtained (Figure 3.2b). The error limit for each value of kj is estimated to be +_ 5%, as suggested by  the range  of values that yield  a simulated spectrum  which  had a reasonable fit to the  measured spectrum. This method gives reliable values for the first order rate constant k,, and the data were treated by the Eyring plot analysis to obtain die activation parameters A H i and AS t (as in Equation 3.19).  66  51  Table 3.2: Data for the simulation of 'H NMR  spectra for the chemical exchange system  Ru(OEP)CO(PPh ) -• Ru(OEP)CO + PPh , in C D as a function of temperature.£ 3  Temp.k-  3  7  8  Population of 3a-  K,,(xl0  223  0.360  0.04  -  233  0.360  0.10  -  243  0.369  0.7/  0.51  -  253  0.378  2.0/  1.23  7.8  263  0.386  7.0/  2.87  10.6  273  0.395  40.0/  6.35  14.0  283  0.404  60.0/  12.71  17.7  293  0.413  200 / 29.90  21.6  303  0.422  450 / 50.24  25.7  313  0.431  950 / 90.50  30.2  323  0.440  2000 /156.50  34.9  333  0.449  3600 /265.00  39.9  - The T  2  value used (0.1 s) was obtained from die linewidth of the  solvent signal at 223 K, die low temperature extreme in diis solvent. - +_ 1 K uncertainty in temperature. £  5  H  meso =  1 0  -  1 4 5  PP  m  f o r  3a and 9.776 ppm for 11.  - +. 5 % uncertainty in k j . Data provided after the '/' mark were taken from Reference 63 and represent the kj values obtained for this same system using an impure sample of Ru(OEP)CO(PPh ) (11). 3  - Calculated from the ratio of populations of 3a and JJ., and from the initial concentrations of 3a and PPh , see Text; _+ 2 0 % uncertainty in K,. 3  52  ;  In (k„/T) = In (k /h) - AE /RT + A S } /R b  where *  5  (3.19)  a  is the Boltzman constant (1.38 x 10"  23  J K" ), h is Planck's constant (6.63 x 10" 1  34  J s)  and R is the gas constant (8.31 J K" mol" ). A plot of In (kj/T) vs. 1/T will yield A E from the 1  1  a  slope and A S } from the intercept by calculation (Figure 3.3). For a solution reaction, A E and A H } a  are related by the expression given in Equation 3.20. AH}  66  = A E - RT  (3.20)  a  The A H } (62 _+ 6 kJ mol" ) and A S } (18 + 4 J K" mol" ) values for this reaction and their 1  1  1  implications will be discussed in detail later in this chapter. The [PPh ] 3  0  calculation of  at any one temperature can be accomplished  with a knowledge of  and [3a] (the initial concentrations of phosphine and 3a, respectively), and of the ratio c  of the populations of 3a and 11 (denoted as 'n' here): k, Ru(OEP)CO(PPh ) ^ 11 kj  Ru(OEP)CO + P P h 3a  3  (3.21)  3  K, = k,/k , = [Ru(OEP)CO][PPh ]/[Ru(OEP)CO(PPh )] 3  (3.22)  3  K j = ([3a] - X ) ( [ P P h ] - X) / X 0  3  (3.23)  G  where X is the f i l l at equilibrium. Therefore, at equilibrium:  n = [3j] /[ll] e q  e q  = ([3a] -X)/X  (3.24)  0  X = [3a] / (1 + n)  (3.25)  0  This gives K j with an estimated +_ 2 0 % error at one temperature (see Table 3.2). Applying this analysis to the other temperatures where 'n' is known allows K j to be determined as a function of temperature.  These values of K j as a function of temperature were applied to the van't Hoff  equation to obtain die A H ° (16 ± 6 kJ mol" ) and AS° (-16 ± 8 J K" mol" ) values (Figure 3.4), 1  1  53  1  Figure 3.3:  Eyring plot of ln (kj/T) vs. 1/T (K" ) for the dissociation of P P h 1  3  from  Ru(OEP)CO(PPh ) in C D . 3  7  8  4.0 — 5  0.0  H  " c  •4.0  •8.0  H  0.0038  0.0030  0.0046 -1  1 / T, K  54  Figure 3.4:  Plot of ln K j vs. 1/T (K" ) for the dissociation of P P h 1  C D . 7  8  3  from Ru(OEP)CO(PPh ) in 3  which will be discussed later in Section 3.2.f of this Chapter:  ln K,, = -AH°/RT + AS°/R  (3.26)  experiment, K,' (used to  As an independent check of the K, values obtained from the N M R  differentiate these values from those determined by N M R spectroscopy) was measured titration of 3a by P P h  in C H  3  7  by a  at several temperatures followed by UV/visible spectroscopy.  g  15  Equations 3.27-3.30 describe the analysis used to determine Kj':  Ru(OEP)CO(PPh ) ^  Ru(OEP)CO + P P h  3  (3.27)  K j ' = [Ru(OEP)CO][PPh ]/[Ru(OEP)CO(PPh )]  (3.28)  3  3  -log  3  = log {[Ru(OEP)CO(PPh )] / [Ru(OEP)CO]} - log [PPh ] 3  3  (3.29)  f  and log (A-A /Aj-A) = log [PPh ] - log K,' 0  where A  is the measured  absorbance of the solution  3  (3.30)  f  absorbance of the solution at any given in die  absence of added  PPh , 3  [PPh ] , A 3  f  is the initial  and A- is the absorbance of the t  solution at the end of the titration. A plot of log ( A - A / A A ) vs. log [PPh ] 0  Q  r  3  f  should give a  straight line with a slope of one and the intercept of log K j ' . Although 3a does not decompose appreciably  as a concentrated solution  [Ru(OEP)OH] 0 2  conducted  under  (9) within three hours under aerobic conditions in C H ; thus, the titrations were 7  an inert  atmosphere  study: The addition of too much P P h Ru(OEP)(PPh ) 3  2  in air, dilute solutions were found to oxidize fully to  ( N ) . Several 2  3  8  were encountered during  complexities  to a solution of 3a in C H 7  g  this  results in the formation of  (4a) as judged by the increase in the intensity of the Soret absorbance of 4a at  422 nm via the further equilibria:  Ru(OEP)CO(PPh ) ii 3  <-  Ru(OEP)PPh 5a 56  3  + CO  (3.31)  Ru(OEP)PPh + P P h 5a 3  <-  3  Ru(OEP)(PPh ) 4a 3  (3.32)  2  The  contribution from the competing equilibria (Equations 3.31 and 3.32) was minimized  two  methods: (i) the titration was attempted  by using  under an atmosphere of C O because this would help  prevent the formation of 5a by loss of C O from 1_1, and (ii)  the absence of CO, by analyzing  m  only at the wavelength for the loss of 3a (393 nm) instead of at both 393 nm and at 407 nm (the latter wavelength representing the formation of i i ) . fiM)  The UV/visible bands of 3a in C H (14.6 7  8  at 518 and 549 nm shifted to 512 and 546 nm, respectively, when the solution was saturated  with CO(g  )(  and die Soret band shifted from 393 to 395 nm (Figure 3.5). Under these conditions,  an equilibrium between 3a and Ru(OEP)(CO) is present as shown in Equation 3.33:  67  2  Ru(OEP)(CO) Quite surprisingly, die former  2  - CO ^  (3.33)  Ru(OEP)CO  method (method i) results in the increase in the intensity of the  Soret band at 393 nm upon addition of two equivalents of PPh . Further addition of P P h 3  3  then  leads to the loss of intensity at 393 nm, and an increase in the intensity at 407 nm, the Soret band position for Ru(OEP)CO(PPh ). Analysis of die overall data as described earlier gives K, = 5 3  x 10* M widi the slope of the log plot line equal to 0.9 +.0.1 at 293 K. The equilibrium depicted 5  in Equation 3.33 cannot account for the increase in die amount of 3a upon addition of PPh , and 3  as such, we are unable to explain these initial spectral changes under CO. Consequently,  method  (ii) was emphasized, die data being analyzed at only one wavelength (393 nm). Another problem encountered  was the reactivity of the C H 7  8  solvent with the silicon septum  used to seal the cuvette under an inert atmosphere. This problem was averted by using Teflonfaced  septa  experienced  so diat was that  presumably  no leaching  i f the cell  wavelength of light passing through  was left  of plasticizer  occurred.  i n die cell-holder  Yet another  of the instrument  die anaerobic solution, either in the presence  problem when the  or absence of  PPh , was below that of the Soret band of 3a ( < 393 nm), loss of 0.1 absorbance units in five 3  57  Figure 3.5:  UV/visible spectrum of (A) Ru(OEP)CO, 3a and (B) Ru(OEP)(CO) Ru(OEP)(CO)  2  was made in situ by bubbling C O ^ into a C H 7  a N atmosphere. 2  1.0  WAVELENGTH  8  2  in C H . The 7  8  solution of 3a under  minutes for the Soret band was observed,  and is attributed to die photolytic decarbonylation of  68  of light well above that of  3a/l 1. This last complication was avoided by keeping the wavelength  the Soret band ( > 600 nm) when (a) not recording the spectrum, (b) while adding titrant and (c) while waiting for the solution to equilibrate. Figure 3.6 shows the changes i n the optical spectrum of the system with the addition of PPh  3  to 3a, and the corresponding plot of log [(A-A )/(A;-A)] vs. log [PPh ] . The data give straight0  3  f  line plots widi slope near one (0.8 +_ 0.1, see Appendix 2). The K,' values obtained, which arc presented below, show that the equilibrium constants are essentially temperature  independent, and  because of this, no van'T Hoff plot was attempted: Temperatures  K x 10 . M-  K ' x 10 . M  293  2.16  1.42 j f 0.10  303  2.57  1.25 _+ 0.15  313  3.02  1.39  323  3.49  1.54 + 0.05  4  4  t  t  ±0.01  - _+ 0.2 K, data tabulated in Appendix 2. - These values of  were taken from Table 3.2.  Discussion of these equilibrium constants (K,') will be presented later in this Chapter. 3.2.c. The reaction of P P h  3  with R u ( O E P ) C O (3a) i n CHC1 . The H 3  m e s o  observed to vary in position depending on the solvent used (10.145 ppm in C D 7  N M R signal of 3a is 8  and 9.918 ppm in  CDC1 ). In contrast, the 'H N M R signals of six-coordinate complexes such as Ru(OEP)(py),, which 3  are known not to dissociate a axial ligand in solution, are essentially invariant in chemical shift in various solvents (6 H  m e s o  = 9.3 _+ 0.1 ppm in C D , C D C 1 or C D ) . The solution IR v  of 3a also varies with solvent ( v  6  6  3  8  c  o  band  = 1926 cm" in CHC1 , 1927 cm" in C H C 1 , 1929 cm" in 1  c o  7  1  3  1  2  2  C H C N , 1940 cm" in E t 0 , and 1945 cm" in C H ) . These data suggest that significant solvation 1  3  1  2  7  59  8  Figure  3.6:  (a) UV/visible  spectral changes observed  Ru(OEP)CO (3.87 x 10" M) 6  solution  after each addition  in C H 7  upon  addition  of P P h  (0.0831  at 293 K. The total added P P h  8  corresponds  to 0, 5.2,  16, 53,  equivalents, (b) Plot of log [(A-A )/(A A)] vs. log [ P P h ] 0  3  r  3  f  3  M)  to  present in  160, 291  and  420  for the above titration,  measured at 393 nm.  ° )  Ld O Z < CD  0.6  QL O 00 CD <  0.0 350  400  WAVELENGTH 60  450  nm  effects  are present  i n reaction systems where  the possibility  species in situ exists. Therefore, the reaction of P P h  3  of generating "five-coordinate"  with 3a was studied in C D C 1  3  to detect if  a solvent dependence was present, both by *H N M R spectroscopy to measure the first order rate constant k , and the equilibrium constant K , and by UV/visible spectroscopy to obtain K '. The 2  2  7  analysis of the data obtained from these studies was done analogously to that for k j , K  1 ;  and K,'  in the previous section:  Ru(OEP)CO(PPh ) 11  3  (3.34)  = [Ru(OEP)CO][PPh ] / [Ru(OEP)CO(PPh )]  (3.35)  Ru(OEP)CO + P P h 3a  3  K  2  3  3  The measured and simulated H N M R spectra for a mixture of Ru(OEP)CO (8.77 mM) and PPh J  (4.52  mM) are presented  3.3. From the  i n Figure 3.7 and the data are tabulated i n Table  experimental data, it is apparent that the k  2  3  value varies to a lesser extent in C D C 1  3  than the k,  value in C D , although die coalescence temperatures are similar. From the Eyring plot for the 7  k  2  g  data in C D C 1  (see Figure 3.8), the A S * value obtained (-63 _+ 13 J K" mol" ) is more 1  3  negative dian diat in C D 7  than that in C D 7  (18 J K" mol" ). The A H i value (37 _+ 4 k j mol" ) in CDC1 1  8  1  1  (62 k j mol" ). The calculated K 1  8  1  2  3  is less  from the N M R data are presented in Table  3.3, and the A H ° (21 ± 8 k j mol" ) and AS° (21 ± 11 J K" mol" ) values were determined from a 1  1  1  plot of hi K vs. 1/T (Figure 3.9). 2  The  measurement  spectroscopy  of K ', the equilibrium constant  as outlined  2  i n the previous  section.  sensitive, and so die titration of 3a with P P h  3  i n CHC1 , 3  The C H C 1  3  was done  by UV/visible  solutions of 3a were not air-  was done aerobically, by following the loss of the  Soret band at 393 nm (corresponding to the loss of 3a), and die same data were obtained within experimental  error when the titration was done under a N  2  atmosphere. Figure 3.10 shows a  sample titration experiment and the corresponding log plot of relative absorbance vs. added PPh . 3  61  Figure 3.7« <a> *H NMR s p e c t r a of Q mixture o f RuCDWCO <8.77 mM) and P P h  3  (4.52  mM)  In CDCI3 measured at 10 K Intervals, and <b) s p e c t r a simulated using the parameters listed In Table 3.3. The temperature  and the r a t e constant, kg,  are listed f o r each spectrum.  (°)  ^  .  ( K )  T  CN  -A -A 9.90  323 313 303 293 283 273 263 - A _ 253 JL_ 2 4243 3 233 - X . 233 2  5  9.50 ppm  3  , - u  (b)  k (s-1) - 2  980 670 480 330 170 60 25 12 ? 7 4 1  2  _  J  \  9.90  '  9.50ppm  Table 3.3: Data for the simulation of 'H N M R spectra for the chemical exchange system  Ru(OEP)CO(PPh )  Ru(OEP)CO + P P h in C D C 1 as a function of temperature.3  3  Temp>  3  3  K , (x 10'  Population of 3a-  2  233  0.484  4  -  243  0.484  7  -  253  0.514  12  2.7  263  0.544  25  6.2  273  0.574  60  10.6  283  0.604  170  16.0  293  0.639  330  24.0  303  0.664  480  31.1  313  0.694  670  41.6  323  0.724  980  55.1  - The T value used (0.45 s) was obtained from the linewidth of the 2  solvent signal at 233 K, the low temperature extreme in diis solvent. - + I K uncertainty in temperature. -  6  H  meso = 9  9 1 8  PP  3a and 9.501 ppm for 11.  m f o r  - +_ 5 % uncertainty in k . 2  - Calculated from the ratio of populations of 3a and i i , and from die initial concentrations of 3a and PPh ; _+ 2 0 % uncertainty in K . 3  2  63  Figure 3.8:  Eyring plot of ln (k /T) vs. 1/T (K" ) for the dissociation of P P h 1  2  3  from  Ru(OEP)CO(PPh ) in CDC1 . 3  3  1  j—  0.0032 1  /  64  T,  r— 0.0040 K  Figure 3 . 9 :  Plot of ln K CHCI3.  vs. 1/T ( K ) for the dissociation of P P h 1  2  3  from Ru(OEP)CO(PPh ) in 3  Figure 3.10:  (a) UV/visible  spectral changes observed  Ru(OEP)CO (6.75 x IO" M) in CHC1  upon  addition  of P P h  3  (0.676 M ) to  at 293 K. The total added P P h  6  3  3  present in  solution after each addition corresponds to 0, 39, 160, 597, 1090, 1578 and 2917 equivalents, (b) Plot of log [(A-A )/(A A)] vs. log [PPh ]f for the above titration, 0  r  3  measured at 393 nm.  a  °-t 350  !  1  400  450  WAVELENGTH 66  nm  The  raw data are tabulated in Appendix 3 and the calculated K ' data are presented in Table 3.4. 2  A plot of In K ' vs. 1/T allowed the determination of the thermodynamic parameters A H ° (10 _+ 1 2  kJ mol" ) and AS° (-18 +_ 4 J K" mol" , see Figure 3.11). 1  1  1  3.2.d. The reaction of R u ( O E P ) P P h fiM  3  (5a) and P P h  concentrations yields Ru(OEP)(PPh ) 3  amount of P P h at 293 K) H  3  m e s o  3  i n C H . The addition of excess P P h 7  g  3  (4a) while the addition of less than a stoichiometric  2  yields a solution whose *H N M R spectrum has a very broad ( > 150 Hz linewidth signal (Figure 3.12), signifying another system undergoing chemical exchange (as  described by Equation 3.36). Using the method described earlier for the Ru(OEP)CO/PPh in C D 7  to 5a at  reaction  3  and CDC1 , the individual rate constants (k ) and equilibrium constants ( K and K-.')  g  3  3  3  were calculated.  Ru(OEP)(PPh ) 4a 3  The  ^ k.  2  mixture of 5a (3.88 mM) and P P h  Ru(OEP)PPh + P P h 5a 3  3  (3.18 mM) in C D  3  7  3  exhibited 'H N M R  8  similar in behavior to those of the Ru(OEP)CO/PPh system in C D 7  (3.36)  3  8  spectra quite  (Figure 5.12). The AH f (66  ±  1 kJ mol" ) and A S } (49 _+ 10 J K" mol" ) values were obtained from the Eyring plot of (k /T) 1  1  1  3  vs. 1/T (Table 3.5 and Figure 3.13). The A H ° (18 +_ 5 kJ mol" ) and A S (-10 +_ 5 J K" mol" ) 1  0  1  1  values were obtained from the Van't Hoff plot of In K vs. 1/T (Table 3.5 and Figure 3.14). 3  The  measurement of the K ' by UV/visible spectroscopy 3  dilute (10" M ) solutions of Ru(OEP)(PPh ) 6  3  following  die loss in intensity  increase in the intensity observed  competing  2  as described earlier,  by titrating  with PPh , was done under inert conditions, by 3  of the Soret band of Ru(OEP)(PPh ) (5a) at 395 nm and 3  of the 422 nm  the  Soret band of Ru(OEP)(PPh )-, (4a). There were no 3  equilibria, and the analyses of the data were straightforward. Figure 3.15  shows a sample titration experiment  and the corresponding plot of relative absorbance vs. added  PPh . The raw data are tabulated in Appendix 4 and die calculated K ' data are presented in 3  3  Table 3.6. The thermodynamic parameters A H  0  (27 +_ 3 kJ mol" ) and AS° (-4 +_ 1 J K" mol" ) 1  were subsequently obtained from a plot of In K ' vs. 1/T (Figure 3.16). 3  67  1  1  Table 3.4: Equilibrium constants CK,') measured for Ru(OEP)COfPPh ) ^ 1  3  Ru(OEP)CO  + PPh  3  as a function of temperature in CHC1 . 3  Temperature^  K x 10 . M-  K ' x 10 . M  293  2.40  2.00 ±0.10  303  3.11  2.27 ±0.10  313  4.16  2.52±0.01  323  5.51  2.91 + 0.02  3  3  2  2  - ± 0.2 K, data tabulated in Appendix 3. - These data were taken from Table 3.3.  Figure 3.11:  Plot of ln K ' vs. 1/T (K" ) for the dissociation of P P h 1  2  3  from Ru(OEP)CO(PPh ) in 3  CHC1 . 3  -5.8  -  0.0032  0.00340 1 /  68  T . K"  1  Ffgure 3.12: (a) H NMR spectra of a mixture of Ru(OEP)PPh (3.88 mM) and P P h 1  3  3  (3.18 mM) in CyDg measured at 10  K intervals, and (b) spectra simulated using the parameters listed In Table 3.5. The temperature and the rate constant, k , are listed for each spectrum. 3  (a)  <3\  vO  T (K) kk, T_(K) (s~ ) 3 ( s z H 1  7V  323 313  18000 12000 7000  303  3000  293  1400  283  300  273  90  263 253 243  22 6.0 2.0  233  0.7  333  (b)  -A.  A A  Table 3.5:  Data for the simulation of 'H N M R spectra for the chemical exchange system  k Ru(OEP)(PPh ) 3  Temp.-  2  3  -  Ru(OEP)PPh + P P h in C D as a function of temperature. 3  3  7  8  K,. (x 10  Population of 5a-  :  -  233  0.180  0.7  243  0.198  2  -  253  0.216  6  3.8  263  0.234  22  6.4  273  0.252  90  9.4  283  0.270  300  12.9  293  0.288  1400  15.5  303  0.306  3000  21.5  313  0.324  7000  26.8  323  0.342  12000  32.6  333  0.360  18000  39.2  a The T value used (0.1 s) was obtained from die linewidth of die 2  solvent signal at 233 K, the low temperature extreme in diis solvent. - + 1 K uncertainty in temperature. £ 6  H  meso = 9  5 4 1  PP  & ^  mf o r  8  -  9 9 3  PP  mf o r  ^  - +_ 5 % uncertainty in k . 3  - Calculated from the ratio of populations of 5a and 4a, and from die initial concentrations of 5a and PPh ; ± 2 0 % uncertainty in K . 3  3  70  2  Figure 3.13:  Eyring  plot  of In (k /T) 3  vs.  1/T (K" ) 1  for the dissociation  of P P h  Ru(OEP)(PPh ) in C D . 3  6.0  2  7  8  -I  0.0030  0.0034 1 / 71  0.0038 T, K  0.0042  3  from  Figure 3.14:  Plot of ln K C H . 7  g  3  vs. 1/T  (K" ) for the dissociation of P P h 1  3  from  Ru(OEP)(PPh ) 3  2  Figure  3.15:  (a) UV/visible Ru(OEP)(PPh ) 3  spectral changes observed (2.78 x 10" M) in C H 6  2  7  8  upon addition of P P h  3  (0.0422 M ) to  at 293 K. The total added P P h  3  present in  solution after each addition corresponds to 0, 3.8, 7.5, 11, 15, and 150 equivalents, (b) Plot of log [(A-A )/(A A)] vs. log [ P P h ] for the above titration, measured at c  r  3  f  395 nm.  (a)  0.75  -  0.25  1  UJ  o <  CD  DC  O (/) GO  <  350  400 WAVELENGTH 73  450  nm  Table 3.6: Equilibrium constants (K ') measured for Ru(OEP)a Pb )o ^ Ru(0EP1PPh + P P h >  3  3  3  3  as a function oftemperature in C H . 7  K x 10  Temperatures  g  K j ' x 10 , M  4  5  3  293  1.55  0.86±0.10  303  2.15  1.22+0.07  313  2.68  1.69 ± 0 . 0 7  323  3.26  2.43 + 0.10  - +_ 0.2 K, data tabulated in Appendix 4. - These data were taken from Table 3.5.  Figure 3.16:  Plot of In K ' vs. 1/T (K" ) for the dissociation of P P h 1  3  3  from Ru(OEP)(PPh )  C H . 7  g  -10.8 -  *  -11.2  -11.6  -  0.0034  0.0030 1 /  74  T , K  -1  3  2  in  3.2.e. Discussion of the rate (k^ and k. ) and equilibrium ( K and K ') constants for the reaction n  of P P h  with R u ( O E P ) L ( L =  3  CO  n  n  and PPh ). Table 3.7 summarizes the rate constants ( k ) 3  obs  measured in this present work and provides a listing of comparable rates for other ruthenium and iron porphyrin complexes containing pyridine, nitrile and phosphine axial ligands. Comparison of k shows  that  PPh  obtained i n this study for die dissociation of P P h  o b s  dissociates  3  Ru(OEP)CO(PPh ) Q I ) in C D 3  7  8  seven  times  faster  at 293 K. Also, P P h  3  from  Ru(OEP)(PPh ) 3  that P P h  g  dissociates  3  >  10  5  times faster from Ru(OEP)(PPh ) 3  2  those reported  62  The  k  o b s  7  g  3  the previous work, from  63  from 3  do from  69  3  value for the dissociation of P P h  reasonably well widi that reported  60  3  earlier shows  than other L ligands  Ru(OEP)(L) in C H at 303 K (L = C H C N , P(«-Bu) ) and 298 K (L = PhCN). > 2  (4a) than  2  dissociates 1.7 times faster from J i in CHC1  than in C D . Comparison of the data obtained in this study with 7  from Ru(OEP)(L)PPh  3  from J i measured in this study (200 s" ) compares 1  3  earlier for die same system (107 s" ) at 293 K. 1  63  However, in  one error apparent in the method used for calculation of the rate constants  the data involved  the estimation  of k  from the linewidth  o b s  signals of i i and 3a. These data for use in a N M R  Mc  H  n u ; s o  spectral simulation program based on measured  linewidths of a signal should be expressed in units of 2ir angular momentum nature of w.  (w) of the observed  radians instead of Hz, reflecting the  Thus, in the previous work, k  more correctly calculated  o b s  should be 672 s" . The data from this previous study are therefore justifiably suspect. 1  Direct  comparison of the dissociation rate constant (k ) for the dissociation of P P h n  from  3  Ru(OEP)CO(PPh ) with other M(porp)CO(PPh ) systems is possible for one case only, that being 3  the previously  3  mentioned work involving Ru(OEP)CO/Ru(OEP)CO(PPh )/C H . 3  7  g  63  The other entries  in Table 3.7 for the dissociation of a ligand L' from M(porp)L(L') and two other non-porphyrin systems are provided to show die range of values that have been reported. The  rate  of association  knowledge, been  reported  of a P R for only  Ru(OEP)CO in C H , studied using 7  g  ligand  to a ruthenium  one case  to date; that  3  porphyrin  of the association  impure samples of Ru(OEP)CO(PPh ). 3  75  complex  63  has, to our of PPh  3  to  The association rate  Table 3.7: Rate constants (k ) for the dissociation of a ligand L' from Ru(porp)L(L')S as in o5s  •obs  Ru(porp)L(L') Ru(norD)L  Ru(porp)L + L' L'  reference  TemD. K  Ru(OEP)CO  PPh  3  293  200  tw  Ru(OEP)CC£  PPh  3  293  107  63  Ru(OEP)CO^  PPh  3  293  330  tw 61  6.2 x IO"  4-(f-Bu)py  298  Fe(PPIX-DME)CC£  Melm  298  1500  59  Fe(PPIX-DME)C02  P(«-Bu)  298  20  59  PPh  293  1400  tw  3  304  2.11 x 10"  62  Ru(OEP)CH CN  CH CN  303  2.41 x 10"  62  Ru(OEP)(PhCN)  PhCN  298  2.56 x 10'  60  PhCN  298  5.87 x 10"  69  PPh  3  323  2.60 x IO"  70  PPh  3  323  1.40 x IO"  Ru(TPP)CO^  Ru(OEP)PPh  3  3  Ru(OEP)P(n-Bu)  P(n-Bu)  3  3  3  Ru(OEP)(PhCN)-  f  RuCl(C(0)C H )(CO) PPh 7  9  2  3  RuCl(C(0)C H )(CO) PPh £ 7  3  9  2  3  2  3  3  3  3  5  - Measured in C H , unless noted otherwise; the last two entries are non7  g  porphyrin systems; tw = diis work. - Considered less reliable than data from the present work (see Text). £ Measured in CHC1 . 3  - Measured in 1,1,2,2-tetrachloroediane. - PPIX-DME refers to the dianion of protoporphyrin(IX) dimethyl ester, M e l m refers to methylimidazole. - Measured in PhCN. £ Measured in N,N-dimethylacetamide. 76  5  70  constant k.j (obtained from k j / K j , see Table 3.2) for the association of P P h C H 7  (9.3 x 10 M" 5  8  (4.3 x 10 M" 5  x  10  5  M"  1  1  1  and is ca. 7 times larger than the corresponding value (k_ ) in C D C 1 (1.4  63  2  s" , see Table 1  3  3.3). Also, the rate constant k.j for die association  Ru(OEP)CO is ca. 10 times smaller than that for association to Ru(OEP)PPh 1  to Ru(OEP)CO in  s" ) compares well with that reported earlier for the same system at 293 K  1  s" );  1  3  of P P h  to  3  (k. = 9.0 x 10 M' 6  3  3  s , Table 3.5) in C H at 293 K. 1  7  8  The K^ values calculated at 293 K from the N M R PPh  3  data (see Table 3.8) for the dissociation of  from Ru(OEP)L(PPh ) (L = CO, PPh , see Sections 3.2.b to 3.2.e) agree quite closely to 3  3  those (K,,') obtained from UV/visible spectroscopic titration experiments at 293 K where L = CO. but not for L = PPh . The agreement is fortuitous because the thermodynamic parameters for the 3  K  n  and K„' systems are quite different: thus, as seen, the equilibrium constants measured by  NMR  spectroscopy  spectroscopy  varied  with  temperature  to a greater extent  (Table 3.8), giving rise to different A H  0  and A S  0  than  those  from  values for the same  equilibrium. These differences almost certainly arise from the effects of trace H 0  involving die probable association of H-,0 to five-  coordinate Ru(OEP)CO in the Ru(OEP)CO/MeOH/C H 7  studied  by N M R  spectroscopy  differs  from  'apparent'  in the system.  2  In light of the previously mentioned problem  UV/visible  8  titration experiment, the equilibrium being  that measured  by UV/visible spectroscopy  in the  following manner:  UV/visible spectroscopic studies: Ru(OEP)L(PPh ) + H 0 1 Ru(OEP)L(H,0) + P P h 3  N M R spectroscopic studies:  2  Ru(OEP)L(PPh ) ^ 3  Ru(OEP)L + P P h  (3.37)  3  (3.38)  3  (L = CO, PPh ) 3  Thus, the equilibrium constants measured by UV/visible spectroscopy directly  to those measured from  NMR  spectroscopy  (K^). The near  K j ' measured by UV/visible spectroscopy for die dissociation of P P h  77  3  (K„') cannot  be compared  temperature-independence from JJ. in C H (see 7  g  of  Table 3.8: Equilibrium ( K ^ ) data at 293 K for the dissociation of a ligand L' from Keq  Ru(porp)L(L') as inRu(porp)L(L')  V  Ru(porp)L  ^  Ru(porp)L + L'.  solvent  reference  K„, M —eq' 2.16x IO"  Ru(OEP)CO  PPh  3  C H 7  8  Ru(OEP)CO  PPh  3  C H 7  8  Ru(OEP)CO  PPh  3  C H  8  Ru(OEP)CO  PPh  3  CHC1  Ru(OEP)CO  PPh  3  CHC1  Ru(OEP)CO  PPh  3  CH C1 2  Ru(OEP)CO  PPh  3  CH C1  Ru(OEP)CO  PPh  3  CH CN  7.1 x IO"  71  Ru(OEP)CO  PPh  3  Et 0  2.6 x IO"  71  Ru(TPP)CO  PPh  3  C H 7  8  2 x IO"  15  Ru(OEP)CO  MeOH  C H 7  8  2.5 x 10"  Ru(OEP)CO  EtOH  C H 7  8  1.8 x IO"  7  tw  4  1.42 x IO"  twt  2.44 x IO"  63  3  2.40 x IO"  tw2  3  2.00 x IO"  tw^  2  3 x IO"  71  2  3 x IO"  17t£  4  4  2  2  3  3  5  6  3  4  4  2  6  t\v!2  3  17b^  3  Ru(OEP)PPh  3  PPh  3  C H 7  8  1.55 x IO"  tw2  Ru(OEP)PPh  3  PPh  3  C H 7  8  8.6 x IO"  twi!  Ru(OEP)PPh  3  PPh  3  C H 7  8  1.2 x IO"  15  P(«-Bu)  C H 7  8  < IO"  15  PPh  C H  8  1.35 x IO"  Ru(OEP)P(n-Bu) Ru(TPP)PPh  3  3  3  3  7  4  6  5  8  4  - tw = this work. Calculated from data obtained from N M R spectroscopic studies. - Obtained from UV/visible spectroscopic titration studies.  78  15  Section 3.2.b) suggests that P P h  and H 0 bind to the Ru(II), trans to a CO, with similar bond  3  2  strength. A similar temperature-invariance 11  in CH C1 2  diat  i n K,, was observed for the dissociation of P P h q  measured using an analogous method to that described i n this Chapter,  2  the dissociation product  in both  71  from  3  showing  Trace H 0 from the  systems exhibits similar chemistry.  2  solvent as suggested by the present study, or M e O H from the precursor (Ru(OEP)CO(MeOH) was compete with die solvent or PPh for  also used in the work reported i n Reference 71) probably the remaining for  axial coordination site of 3a. That H 0 or M e O H competes effectively with PPh 2  die last coordination site of 3a could  ligand;  72  3  the C O and P P h  3  could  2  aid dieir binding trans to CO. The reasons for the large  die K,,' for the dissociation of P P h  UV/visible spectroscopy  in C H C 1 2  (3 x 10" M, 5  2  presently unknown. The K,,' values UV/visible spectroscopy  trans influence of the CO  the strong  will compete for available TT-electron density, while the weak TT -donor  properties of H 0 and M e O H differences between  result from  3  71  3  from  3 x 10" M ) 6  Ru(OEP)CO(PPh )  measured by  3  1 7 b  and C H C 1  (2 x 10" M) arc 3  3  measured for the same equilibrium in different solvents by  show die expected trend in decreased binding of P P h  3  to Ru(OEP)CO in  coordinating solvents such as C H C N or E t 0 . 3  The  equilibrium constant  from Ru(OEP)(PPh ) 3  (JJ_) in C H 7  influences.  8  2  2  measured by N M R spectroscopic studies for the dissociation of PPh  (4a) is die same as that for the dissociation of P P h  at 293 K, suggesting  that in these systems, C O and P P h  Comparisons, noted 'in previous  binding of PPh  3  studies,  17b  3  also observed  from Ru(OEP)CO(PPh ) 3  3  have similar strong trans here  to Ru(TPP)L than to Ru(OEP)L complexes ( L = C O , P P l i ) ,  binding of P(/z-Bu)  3  3  to Ru(OEP)P(n-Bu)  3  than P P h  3  to R u ( O E P ) P P h  15 3  3  the stronger  include 1 5 , 1 7 b  and the stronger  because of the increased  basicity and generally smaller steric bulk of the alkylphosphines compared to the arylphosphines. 3.2.f. Summary and discussion of activation and thermodynamic data for the reversible dissociation of P P h  3  from R u ( O E P ) L ( P P h ) ( L = C O , PPh ). While the data were introduced  discussed in the preceding  3  3  and cursorily  three sections, a summary (see Table 3.9) is required to emphasize the  findings and dieir implications. The activation entropy  79  for a reaction that generates two products  Table 3.9: Summary of the activation and thermodynamic data for the equilibria  K Ru(OEP)UPPh ) ^ ?  Ru(OEP)L + PPh, (L = CO. PPh ) in C H and CHCU. ?  7  8  (a) Activation parameters obtained from k by N M R spectroscopic studies. n  L. solvent  A H t. k j mol'  CO, C H  62 ± 6  18 ± 4  57 ± 1 4  37 ± 4  -63 ± 13  55 ± 1 3  66 ± 7  49 ± 10  52 ± 12  7  8  CO, C H C 1 PPI13, C H 7  3  8  1  A S t , J K' mol'' 1  2  AGi.kJmor's  (b) Thermodynamic parameters obtained from K,, by N M R spectroscopic studies.  L. solvent CO, C H 7  AH°. kJ mol' ^ 1  21 ± 8  PPh , C H  18±5  7  0  8  A G , k j mol'  1  16 ± 6  8  CO, C H C I 3  3  A S . J K' mol''a  0  -16 ± 8  12  21 ± 1 3  21 ± 1 1  15  -10± 5  ±10  21±7  (c) Activation parameters obtained for k. from K„ and k . n  L. solvent CO, C H 7  AHt. kJ mol'  16 ± 8  PPh ,C H  48 ± 15  7  1  A S i , J K' mo!'' 1  46 ± 18  8  CO, C H C I 3  3  n  8  34 ± 18 -84 ± 4 7  59 ± 3 2  80  2  A G t , kJ mol' 36 ± 2 4 40  ±28  31 ± 13  12  Table 3.9 continued.  (d) Thermodynamic parameters obtained from K„' by UV/visible spectroscopic studies.  L, solvent  AH°. kJ m o r  CO, C H  ca. 0  ca. -9(£  ca. -27  10 ± 1  -18 ± 4  15 ± 4  -4 ± 1  28 ± 8  7  8  CO, C H C 1  3  PPh , C H  8  3  7  1  Aj^lK^jnoJ-  27 _+ 3  1 2  AG°, kJ mol''a  a Calculated at 293 K. ^ Estimated error in A H from N M R studies is +. 30%, that for AS° is +. 50%. 0  - Calculated assuming A H is ca. zero. 0  81  solvation effects, qualitatively should be  from one reactant (i.e. a dissociative process), ignoring positive: k,n Ru(OEP)L(PPh ) L = CO, 11; PPh ,4a  Ru(OEP)L + P P h  3  (3.39)  3  3  The  variation in ASi.  the  above reactions,  values obtained by N M R spectroscopy in C H 7  significant solvation  of the activated  and CHC1  8  3  from JJ. in CHC1  negative (-63 J K" mol" ) in comparison to that for dissociation of P P h K"  solvates  1  3  7  and  8  in C H C 1  (37 kJ mol" ), indicating  7  are also different in C H 7  diat solvation  1  3  3  (18 J  g  complex to a greater extent than docs  die activated  C H . The activation enthalpies for the same reaction  is quite  3  from U in C H  1  mol" ), suggesting diat CHC1  1  suggest that, for  complex relative to the reactants may  be present. For example, the A S J value for the dissociation of P P h 1  3  (62 kJ mol" ) 1  8  more to the  energies are contributing  observed activation enthalpy values in the latter case. For  Reaction 3.39, the activated  complexes is pictured a  'reactant-like'  complex.  as involving  activated  Based 3  this  somewhere between a slightly stretched  complex,  and an almost  on the activation  Ru(OEP)CO(PPh ) in C H of  complex for die dissociation of P P h  7  'five-coordinate'  8  parameters  dissociated  obtained  3  from  Ru(OEP)L(PPli ) 3  Ru-P bond, generating  'five-coordinate  for the dissociation  like' of  activated  PPh  3  from  and CHC1 , die latter type of activated complex seems likely, solvation 3  like  activated  complex  accounting  for the observed  differences  activation parameters in different solvents for the same reaction:  Yeactan-t-Uke'  'five-coordinate 82  like'  in  Based on the assumption that C H 7  does not solvate significantly die 'five-coordinate' like  8  activated complex, and that the activated complex resembles closely die five-coordinate product, the Ru-P bond dissociation energy may be approximated as 64 ± 9 kJ mol" ; this is for a bond 1  trans to a CO or PPh , ligands of strong trans effect.  72  3  A  similar solvent  dependence  has  been  observed  for  die  dissociation  of  PPh  3  from  RuCl(C(0)C H9)(CO) (PPh ) to form a five-coordinate kinetic intermediate, diis reaction being a 7  2  3 2  rare case where activation parameters have been measured in more than one solvent:  70  RuCl(C(0)C H )(CO) (PPh ) - RuCl(C(0)C H )(CO) (PPh ) + PPh 7  9  2  3 2  7  9  2  3  (3.40)  3  Solvent = C H , N,N-dimethylacetamide (DMA) 7  8  The activation parameters for Reaction 3.40 are presented below:  70  solvent C H 7  AH}, kJ mol"  AS}. J K" mol"'2  1  1  128 ± 12  8  DMA  62 ± 6  69 + 7  -126 + 13  *• Calculated at 293 K. The negative entropy of activation (-126 J K" mol") obtained when Reaction 3.40 was conducted 1  1  in DMA was ascribed to the increased solvation by DMA compared to C H 7  of the anticipated  8  "five-coordinate like" activated complex formed from the partial dissociation of PPh to  a PPh  3  ligand trans  in RuCl(C(0)C H )(CO) (PPh ) , because the activation entropy was found to be  3  7  9  2  3 2  positive (62 J K" mol") when the same reaction was done in C H . The activation enthalpy 1  1  7  (AH} ) obtained in C H 7  8  8  was, therefore, suggested to represent the upper limit of the Ru-P bond  strength. One other estimation of die M-P bond strength may be obtained from the dissociation of PPh from rrans-RuCl (CO)(PPh ) in chlorobenzene (AH} 3  2  8 J K" mol" ). 1  1  3 3  738  83  = 129 ± 2 kJ mol" and AS} 1  = 33 ±  Axial ligands in 'octahedral' metalloporphyrin complexes show quite generally increased lability compared to related non-porphyrin  macrocycle  systems and other six-coordinate complexes.  7311  The  lower AHt values noted in the Ru(porp) systems (64 kJ) compared to die carbonyl phosphine nonporphyrin systems (128 kJ) are consistent with this generalization. The  positive AH° values obtained for the dissociation of P P h  mol" ) and 4a in C H  (27 +_ 3 kJ mol" ) by UV/visible spectroscopy  1  7  from U in C H C 1  3  1  8  3  (10 _+ 1 kJ  are consistent with a  process involving breaking a Ru-P bond (bond dissociation energy of about 64 kJ mol" ) and 1  formation  of an  aquated  dissociation of P P h titration are ca.  product.  from  3  Indeed,  the enthalpies  Ru(OEP)CO(PPh ) in C H 3  7  10-15 kJ mol" more exothermic 1  of reaction  and CHC1  8  3  determined  for  the  by UV/visible spectroscopic  than diose measured by N M R  spectroscopic  studies. These differences may be due to die association of H 0 to Ru(QEP)CO generated by the 2  dissociation of P P h  from Ru(OEP)CO(PPh ) at UV/visible spectroscopy concentrations (/iM). The  3  3  close to zero AS° values for the 3a/PPh /CHCl 3  Ru(OEP)PPh  5a/PPh /C H  3  3  7  8  system  3  system  (-4 _+ 1 J K"  1  (-18 ±  4 J K"  1  mol" ) and for the 1  mol" ), are considered consistent with the 1  replacement of one coordinated ligand by another, as in Equation 3.37. The enthalpy of activation for the association of P P h mol" ), calculated from 1  from  that in C H C 1  K,, and k  (data obtained from  n  to 3a in C H 7  7  the N M R  8  (46 +_ 18 kJ  experiment), is quite different  (16 _+ 8 k j mol" ), showing again that solvation of reactants and/or the plays a major role in these systems.  activation for the association of P P h 3  to 'Ru(OEP)CO' in C H  1  3  activated complex probably  association of P P h  3  3  to 'Ru(OEP)CO' (3a) in C H 7  The enthalpy and entropy of g  are similar to those for the  to 5a (Table 3.9). These data indicate diat the association of P P h  3  to 5a and  are equally favorable, suggesting that in these Ru(OEP) complexes, CO and PPIi  8  have similar trans effects. The entropies of activation for the association of P P h (-84 + 47 J K" mol" ) and in C H 1  1  7  to 3a in CHC1  3  (34 _+ 18 J K" mol" ) also reflect the difference in solvation 1  8  3  3  1  by C H C 1 and C H of Ru(OEP)CO compared to the activated complex. 3  7  8  3.2.g. The decarbonylation of aldehydes using Ru(OEP)PPh  3  84  (5a). Five-coordinate intermediates  such as 5a have been suggested to play perhaps a role in the catalytic decarbonylation of aldehydes by binding some free CO generated upon decarbonylation of the aldehyde. " When 19  Ru(TPP)(P(n-Bu) )  (ca. mM concentration)  3 2  phenylacetaldehyde (PhCH CHO) in CH C1 2  detected by GC analysis.  2  21  2>  was  reacted  with  a stoichiometric  21  amount of  the formation of a stoichiometric amount of C H 7  8  was  At lower [Ru], the formation of some Ru(TPP)CO(P(n-Bu) ) was noted 3  from UV/visible spectroscopic studies:  21  *-obs  Ru(TPP)(P(/i-Bu) ) + PhCH CHO 3 2  2  Ru(TPP)CO(P(n-Bu) ) + PhCH + P( -Bu) 3  3  n  (3.41)  3  This reaction was found to be only 70% complete because die starting bis(phosphine) complex was slowly oxidized in a side reaction by impurities from die aldehyde to Ru UV/visible spectroscopy  and cyclic voltammetric measurements.  21  111  products, as judged by  While the decarbonylation of  PhCH CHO (3.4 x 10" M) by Ru(TPP)(P(n-Bu) ) ((1.7-5.1) x 10" M) gave straight-line first2  5  2  3 2  order plots for die loss of die bis(phosphine) reproducible. The addition of trace 0  species, the k  values obtained were not  obs  to die reaction mixture did not affect the k  2  obtained nor its range of irreproducibility; however, the rigorous removal of 0  2  obs  value  by argon purge  led to die complete inhibition of the stoichiometric decarbonylation of PhCH CHO. The role of 2  the 0  2  in this  stoichiometric decarbonylation was tentatively suggested to be the abstraction of  a hydrogen atom from the aldehyde, giving C(0)R. The addition of a radical inhibitor (2,6-di-/butyl-p-cresol)  also  led  to  die  inhibition  stoichiometric decarbonylation of PhCH CHO 2  of  the  decarbonylation  by Ru(OEP)(CH CN) 3  2  reaction.  A similar  21  was noted; however, this  system was found to be unapplicable for the catalytic decarbonylation of PhCH CH0.  21  2  These results were used to devise a catalytic decarbonylation system using Ru(TPP)(PPh )  3 2  (4b), CH CN, CH C1 , P(«-Bu) 3  2  2  3  and aldehyde. The use of 4b was dictated by the lack of  significant dissociation of a phosphine from Ru(TPP)(P(/i-Bu) ) in solution, and because of the 3 2  noted side-reaction involving this complex. Complex 4b is known to dissociate PPh in solution, 3  giving Ru(TPP)PPh  3  (see Table 3.8).  The catalytic system devised involved bubbling 'a small 85  amount' of C O ^ into a C H C 1 : C H C N (1:60 v/v) solution of 4b (2 /imol) and P h C H C H O (2 2  2  3  2  mmol) to generate Ru(TPP)CO(PPh ), as judged by UV/visible  spectroscopy. The addition of P(«-  3  Bu)  3  (20-40 nmol  in total) to the reaction mixture then initiated the decarbonylation  different complexes presumed to be generated i n solution at this point include Bu) ), Ru(TPP)(PPh )(P(n-Bu) ) (12) and Ru(TPP)(P(n-Bu) ) 3  3  3  3  reaction. The  Ru(TPP)CO(P(n-  via the equilibria discussed  2  in Section  1.2.c. The role of C H C N as the solvent for this catalytic system was to enhance the stability of 3  any  five-coordinate  Ru(TPP)L(CH CN)), 3  species  generated  thereby  in situ by occupying  preventing  decomposition  the sixth coordination  of these  five-coordinate  'soup' was stirred at ambient temperatures, yielding decarbonylated  eventually  brown-green  colored  inactive  solution.  The irreproducibility  stoichiometric decarbonylation reaction was observed in this catalytic system. ' 19  Thus, because the presence of five-coordinate  aldehyde  by 5a was attempted,  stoichiometric  decarbonylation  concentrations, studied  16a  3  widi  reaction  amount of toluene was detected  of Ru(TPP)PPh ,  in the  observed  21  in its  the stoichiometric decarbonylation  of an  understood.  die catalytic Further,  from the reaction of Ru(TPP)(P(n-Bu) ) 3  the stoichiometric reaction of Ru(OEP)PPh  aldehyde and  torr and 473 K resulted only  5  the aim of studying was well  This  was deemed necessary for the catalytic  species  system, and because die vacuum pyrolysis of 4b at l x l O " sublimation- and not in the formation  in  (as  species.  orange-colored a  site  3  systems  because 2  once  the  a stoichiometric  with P h C H C H O at m M 2  (5a) with P h C H C H O 2  and PhCHO was  by 'H N M R spectroscopy, to ascertain which Ru(OEP) complexes were present in this  reaction, and to determine if any spectroscopically observable intermediates existed. Solutions of 5a and benzaldehyde in C D 6  6  (see Section 2.4 for further experimental details)  under vacuum were found to remain unchanged even after heating at 373 K for 24h. Because the previous stoichiometric system was not always reproducible, ' 19  21  the presence of trace impurities  such as air, moisture or free phosphine was thought perhaps to be responsible for the initiation of with  the stoichiometric reaction. To address these possibilities, 5a and benzaldehyde were mixed added  H 0 or dry 0 2  2  in sealed  rube N M R  86  experiments. Again, no decarbonylation  of  aldehyde was observed, even  when the solutions were heated at 373 K  for  22h. When the  contents of each sealed tube were exposed to air, the it-oxo dinuclear species [Ru(OEP)OH] 0 (9) 2  was formed,  without any decarbonylation of the added aldehyde. In a further experiment, a  mixture of P P h the  added  and benzaldehyde i n the absence of 5a was also tested for decarbonylation of  3  aldehyde  i n the same deuterated solvent, with  similar  negative results.  The same  reactivity was observed for the reaction of 5a with P h C H C H O i n C D , even when trace 0 or 2  6  6  2  H 0 were added. 2  Several  important conclusions can be drawn from  these experiments: (1) the role  of five-  coordinate species such as 5a i n die stoichiometric reaction may not be critical, (2) the presence of trace moisture or trace oxygen alone is not enough to initiate decarbonylation, and (3) in the absence of trace 0 , H 0 , or other added reagents, no stoichiometric decarbonylation of aldehyde 2  2  is expected. A system involving Ru(TPP)(PPh ) 3  of P P h  3  from Ru(OEP)(PPh ) 3  2  2  (4b) (which has the same K  to yield Ru(OEP)PPh  3  (5b) and P P h  3  as that for the dissociation  e q  in solution (see Table 3.8)),  was studied using the reaction conditions devised for the attempted stoichiometric decarbonylation of benzaldehyde by 5a, to assess whether die conditions described earlier involving 5a would lead to decarbonylation of benzaldehyde by a mixture of 4b/5b. A solution of 4b and benzaldehyde or phenylacetaldehyde in C D 6  6  was found, to be unchanged even after being heated at 373 K for 20h  in vacuo. The addition of dry 0  or H 0  2  2  or P(n-Bu)  3  to 4b and benzaldehyde  (conducted in  sealed  tube experiments) induced no reactivity. Indeed, in the reaction mixture containing P(n-  Bu) ,  a bis-phosphine complex  3  Ru(TPP)(PPh ) 3  2  Ru(TPP)(P(n-Bu) ) 3  2  can be observed  in a 70:30  (see Table 3.1). This suggests that in a 10:1 ratio of P(n-Bu) 20  3  2  3  87  with  to 4b, as in the  3  original paper, - Ru(TPP)(P(«-Bu) ) (4c) is certainly present as well as Ru(TPP)(PPh ) . 19  ratio  2  Chapter 4. Further studies on the oxidation of bis(octaethvlporphyrinato)ruthenium(II)) (7) by H X acids. 4.1. Introduction. The of  oxidative addition of H X to coordinatively unsaturated non-porphyrin  M°) to generate products  of the type  ancillary  ligand) has been reported  observed.  74  M (H)(X)(L) n  previously with  and M ( X ) ( L )  metal complexes (e.g.  n  n  both  2  n  (where L  cis- and rrans-isomer  is some  products  being  Within metalloporphyrin complexes, examples of the oxidative addition reaction include  die reaction of K [Ru°(OEP)] with C H I to give Ru (OEP)Me2 (double oxidative-addition), IV  2  the protonation of [M^OEP)]" generating The  the hydride complexes M ( O E P ) H  reaction of excess H X with [Ru(OEP)]  8a; X  m  2  (M =  Rli, I r ) . ' 7 5  (7) in aromatic solvents generates R u ( O E P ) X  2  7 6  ( X = Br,  = CI, 8b), possibly via a similar oxidative addition route, but the oxidant responsible for  the oxidation of R u in H X  and  48  3  to R u  11  I V  had not been identified definitively. ' 36  was tentatively postulated as the probable  The presence of trace X  37  oxidant based on two results: (1) no H  2  2  was  observed to be formed during the reaction, and (2) B r instead of H B r could be used to oxidize 7, 2  again yielding 8a. ' 36  Subsequently, more detailed studies were carried out in this present  37  work  to identify both the oxidant and the mechanism for the generation of 8 from 7. The stoichiometry between HCI and 7 was measured by a titration of HCI vs. 7 which proved unambiguously that H was  the oxidant in aromatic  solvents (Section 4.2.b). Consequently, tests for the formation of H  were repeated and others devised to detect H ; however, all of diese tests indicated that H 2  2  +  2  was  not generated during this reaction. These results are discussed in Sections 4.2.h. Varying  the H X  acids used (HX =  H , MeOH, H 0 , H S, C H C O O H , C H C O O H , HF, 2  2  2  3  6  5  C F C O O H , H N 0 , H B F , HCI, HBr, and HSbF ) allows for an estimation of the strength of acid 3  3  4  6  (i.e. p K J required for die reaction of 7 with H X to proceed. Knowing the p K reaction in aromatic  a  required for this  solvents then allows for die prediction of the possible products utilizing this  reaction with other acids. In C H C 1 , two intermediates Q3 and 14) are generated rapidly when excess HCI is added to 2  2  88  7, both of which yield 8b upon further oxidation with HCI. A much slower formation of these intermediates was found, in fact, to not require HCI, and needed only the solvent; the reactivity of  7  with  other  characterization  chlorinated  (both  solvents  spectroscopic  confirms  this  and chemical)  solvent  dependence.  The isolation  and  and their  further  other than 7 is also presented  in this  of these  intermediates,  reaction with H X to yield 8b are presented. The  generation  of R u ™ products  from R u  11  sources  py, 6a; C H C N , 6b) by H X (X = Br, CI) was  chapter. Anaerobic oxidation of Ru(OEP)(S) (S = 2  3  these reactions  found to give 8a or 8b in quantitative yields and the conditions under which proceed  are documented. Similarly, the HX/7 ( X =  application  to other  porphyrin  Br, CI) reaction can be generalized in  (TMP, TPP) complexes,  58  and details  for the synthesis and  spectroscopic characterization of Ru(TMP)Br are provided. 2  4.2. Results and Discussion. 4.2.a. Oxidation of 7 by the mixture H 0 / 0 . The aerobic oxidation of 7 was postulated to need 2  the presence of both 0  2  and moisture  2  to yield [Ru(OEP)OH] 0 ( 9 ) , ' 31  2  never been proven. A solution of 7 in C D 6  6  conditions) did not react with added N -flushed 2  4.1). dry  35  but this hypothesis has  (see Section 2.4 for specific details of the reaction H 0 as studied by 'H N M R spectroscopy (Figure 2  The 'H N M R spectrum of a solution of similar concentration of 7 in C D 6  0  2  6  containing added  indicated that ca. 5 0 % of /x-oxo dinuclear species (9) had formed, but the remaining  porphyrin residue was essentially 7. Some change in the position of the C H  2  resonance of 7 at S  25-27 ppm was detected in each spectrum (7 and H 0 , or 7 and 0 ) relative to that observed for 2  the same set of protons in 7 in C D 6  6  2  in the absence of H 0 and 0 2  2  (ca. 26 ppm, Table 4.1), and  these shifts i n position are considered to be due to the effects of the added reagents on the bulk solution. When either reaction mixture reagent  (7 with H 0 , or 7 with 0 ) was exposed to the other 2  ( 0 or H 0 , respectively), 9 was fully 2  postulation. ' 31  2  35  Thus, 7 was stored in a  2  generated  instantly, confirming  the proposed  glove-box as a solid and, when needed in solution, the  subsequent reaction conditions are rigorously anaerobic  89  but not necessarily anhydrous. The source  Figure 4.1:  »H N M R spectra of [Ru(OEP)] in C D wntaining added (a) 0.1 ftL H 0 , and 2  6  6  2  (b) 500 M L 0 . Spectra were measured at 293 K at 400 M H z (FT), = C H . 2  s  90  6  6  Table 4.1: Summary of 'H N M R spectroscopic data for compounds relevant to the characterization of the products (13/14) from the reaction of R u O E P ) l with r  2  CH CJ .5 2  2  complex  solvent  i-£H  C D 6  6  26.25  11.20  10.18  3.49  7 + H 0  C D 6  6  27.45  11.09  10.20  3.53  2+ 0  C D 6  6  25.37  10.98  10.13  3.59  C D  6  9.45  1.98  [RuOEP)]  7  2>  2  2  [Ru(OEP)OH)] 0, 9 2  13b  6  2a  ACH  i-Hmeso  2 b  4.45 (m) 4.08 (m)  I  CH  9.99  5.79  13.00  2.27  2  10.07  5.78  13.06  2.28  CD C1 2  2  10.05  5.73  13.01  2.22  [Ru(OEP)] BF 5  CD C1 2  2  9.92  5.65  12.91  2.15  Ru(OEP)H, 1 4 ^  CD C1  2  CD C1 2  2  CD C1 2  [Ru(OEP)] BF ^ 2  2  Ru(OEP)Cl-  4  4  f  2  C D 6  Ru(OEP)Cl(NH )-  f  3  The diird component, X£  14.13  6  CD C1 2  -0.20  11.24  CDCI3  -8.20 (br)  4.20 (br)  6.19  -3.45 (br)  -2.20  -0.90  -5.07  -2.31  3.90  2  9.73  3  1.82  - Measured at 300 or 400 M H z at 293 K. Unless stated otherwise, the multiplicity each signal of die macrocycle is as follows: C H CH  3  (quartet, q), H  2  m e s o  (singlet, s),  (triplet, t), br = broad, m = multiplet.  ^ Generated from the reaction of [Ru(OEP)] with CH C1 . 2  2  2  £ Generated from the reaction of [Ru(OEP)] with HCI in CH C1 . 2  2  2  - Generated from the reaction of [Ru(OEP)] with H B F in C H C 1 , see Section 4.2.f. 2  4  2  2  - From Reference 32. - From Chapter 5 of this thesis; all signals appear broad. £ Refers to a minor component of the mixture formed by the reaction of CH,Clo HC1/CH C1 with [Ru(OEP)] ; see Text, Section 4.2.b. 2  2  2  91  of the water in the dry 0  2  reaction is clearly the C D 6  6  solvent, despite rigorous attempts to dry  die solvent (see Chapter 2). 4.2.b. Measurement of the stolchiometry for the reaction between [Ru(OEP)] Gaseous HCI dissolved at one atm in C D 7  293  K)  intensity  7 7  (7)  and HCI.  corrected for the solvent vapor pressure at  was added in single equivalents to the dimer 7 in C D , and the instantaneous 7  quantitative yield  solvents),  (8a-b are known  solubilized by the addition of CDC1 , and the 'H N M R  data confirmed the  3  reported for this reaction. 7  8  6  to, be  suggesting a 4:1 stoichiometry between HCI and 7. The  37  manner at 243 K in C H , and in C H  loss in  of 8b was observed. Complete  upon addition of four equivalents of HCI to 7,  sparingly soluble in aromatic 8b was  8  signals of 7 due to the formation  of the 'H N M R  precipitation occurred  product  (83 m M  8  2  6  37  The same stoichiometry was measured in the same  at room temperature, indicating that (1) the reaction is  instantaneous even at 243 K, (2) no spectroscopically observable intermediates exist and, (3) the same reactivity occurs in toluene and benzene. The  titration of a C H 7  analogously  solution of H C l ^  vs. 7 in C D C 1 2  was done in partial equivalents  2  solvents, but complete rapid loss of the ' H  to diat for the same titration in aromatic  signals of 7 now corresponded to a 1:1 stoichiometry between HCI and 7 at either 243 or  NMR 293  8  K; further, the addition of excess H C l ^  generated  product  approximately  was a mixture  of three  to 7 in C D C 1 2  porphyrin  yielded the same products. The  2  species, two of which  are present in  equal proportions and comprise ca. 9 0 % of die mass balance based on the relative  integration ratios of the two sets of *H N M R  signals (see Figure 4.2). These intermediates were  stable in solution for weeks under inert conditions (under N  2  or vacuo in CH C1 ), and the two 2  major intermediates are tentatively assigned the formulations [Ru(OEP)],CHCl  9  2  (13) and Ru(OEP)H  (ii). The  *H N M R  spectrum of the mixture  in C D C 1 2  2  (see Figure 4.2) suggests that two of the  components of the mixture are paramagnetic because the resonances for O E P are not usual range of positions for diamagnetic  Ru(OEP) complexes. ' ' 9  92  16  17  within the  One component (J_3) has a  Figure 4.2:  'H NMR  spectrum of the products of the reaction of [Ru(OEP)]  C D C I vacuo, at 292 K, 300 2  2  MHz.  2  with excess HCI in  (13) has a *H N M R (X =  spectrum very similar to those reported by Collman et al. for [ R u ( O E P ) ]  SbCl , PF , B F ) , 6  6  3 2  with the same coupling constant ( J . H  4  protons of the ethyl group of OEP  ppm)  paramagnetic dinuclear  78  The  ruthenium  structure.  observation of the J . H  porphyrin complexes,  No  paramagnetic  3  (5  X" 2.28  (compare the signals for 13 in Figure 4.2 with Figure  4.3a), and two resonances at 10.07 and 5.78 ppm (see Table 4.1).  = 7.4 Hz) for die C H  H  + 2  for the anisochronous methylene protons of H  H  is significant because  where the coupling  ruthenium  discussed in Chapter 5, has observable J .  coupling in 13  is always  porphyrin monomer,  coupling in its H  NMR  J  H  OEP  the only  observed, have a  including  those  to  be  spectrum. These results  indicate that 13 has the probable formulation of a dinuclear species; for example, [Ru(OEP)] X. 2  The other component (14) is suggested to have a formulation similar to R u ( O E P ) X ( L ) (16a-f. UI  X  = Br, CI; L = vacant, NH ,  C H C N , see Chapter 5) because the positions of die H  3  -8.20), C H  3  (6  -3.45) and C H  3  (6  2  4.20) resonances of the OEP  pattern to those for the corresponding protons in 16a-f. The  CH  m e s o  (S  macrocycle in 14 are similar in resonance of 14 at S  2  4.20  integrates to the same number of protons (16H) as that for the single methylene resonance of J_3 at 5.78 ppm,  consistent with the proposed generation of JJ3 and 14 in equal proportions during the  reaction. However, \A separated having  has only one broad methylene OEP  (approx. 5 ppm)  the smallest  resonance, instead of the two widely  resonances observed for Ru(OEP)Cl(NH ), 3  difference between die positions of die two  the Ru  methylene  halide complex  111  resonances of the  macrocycle (compare the signals for 14 in Figure 4.2 with Figure 4.3b). Of interest, the 'H spectnim of K  [Ru(OEP)H]~ also has only one methylene resonance, indicating that the hydride  +  ligand does not significantly  alter the mirror plane of symmetry offered by  The  for J4  formulation  type of N M R  NMR  Ru (OEP)H m  is tentatively suggested based on  spectrum observed, and because the methylene  'H  NMR  the macrocycle.  the Ru  111  45b  'paramagnetic'  shift appears as a broad  signal at 293 or 193 K. Because  of the paramagnetic  resonances for the C H C 1  2  and  nature of J3 H  and  14, the normally observable proton  fragments were not detected in L3 and  94  NMR  14, respectively, (nor  Figure 4.3:  *H NMR  spectra of (a) rRu(OEP)]  BF " in CD C1 ; the spectrum reported by  +  2  4  2  2  Collman et al. for the same complex does not have the impurities, labelled V , present, and (b) Ru(OEP)Cl(NH ) in C D . The spectra were measured at 292 K at 3  6  6  300 MHz (FT) under an N atm. 2  r l''H[tiii|iiti[iiH|iHi|iiii|tivTpTTM"' |iMi|"H ;rtn|TiH[titT-[i"i|iiii|mTj-n n i  12  111111111111111  12  i  n  ii11111nTTrm11111; 4 £  10  A  8  0  i;11111111111!111111111111111111111111;  i  4  95  6  - 4  11111;11111111  -2  -4  n 1111!  11111'  -fe PPM  P P M  were those for Ru-CDC1 example, NMR  or for Ru-D by H N M R  spectroscopy). In diamagnetic complexes, for  2  2  the resonances for the CH C1 fragment i n R h ( T P P ) ( C H C l ) 2  spectroscopy at -2.81 and -2.82 ppm (JR^H = 2.9 H z ) ,  [Ru(TPP)H]" was observed at -59 ppm.  79  and the hydride resonance for K  However, that for the C H  48  was not observed because of the paramagnetic nature of the R u NMR  can be observed by 'H  m  2  spectrum of 13/14 in C D C 1 2  2  (16 mg/mL)  111  +  resonance in R u ( O E P ) C H n,  3  complex.  The 75 MHz,  49  13  3  C  showed only broad resonances between -100 and  300 ppm relative to TMS, all of which were too broad to assign; consequently, the resonance for the  CHC1  could not be assigned. Further chemical characterization data for \3 and 14 will be  2  presented later in tliis Chapter. The diird component (labelled 'x' in Figure 4.2) of the mixture is diamagnetic and, because it has  only  one mediylene  resonance  (6  3.90 ppm, quartet), is consistent  formulation, although it is hard to envision what 'L' would be. Subsequent  with  a Ru(OEP)L2  characterization of the  mixture will concentrate on the identification of the two major paramagnetic species L3 and 14. The intermediates YS and j 4 were found to react slowly with further HCI in the absence of air to yield 8b only (requiring about two hours for completion), but instantly in the presence of both air and HCI. The analogous reaction of excess H B r with 7 under anaerobic conditions in CH C1 2  2  gave die dibromide analogue 8a directly. During die titration experiments, it was observed  that while 7 was indefinitely stable in C D 6  slow reaction of 7 with C H C 1 2  the  2  6  or C D 7  g  under inert conditions at 293 or 373 K, a  was found to occur (vide infra). This result was startling in that  products generated by this slow reaction were spectroscopically identical to those of the in  situ species generated by the reaction of excess HCI with 7 in CH C1 . The data unambiguously 2  suggest a dual pathway  2  to die generation of 8b from 7 and HCI, dependent on the type of  solvent used, as shown in Scheme 4.1. 4.2.c. The attempted isolation and purification of the intermediates obtained from the reaction of [Ru(OEP)]  2  with  solution of C H C 1 2  CH C1 2  2  2  and HC1/CH C1 . 2  2  The intermediates were isolated  saturated widi H C l ^ ) or neat C H C 1 2  96  2  by transferring a  onto 7 (see Section 2.3.b) under  CI  13  Scheme 4.1:  Proposed mechanistic  scheme for the  reaction  of HCI with [Ru(OEP)] .  vacuum; this instantly formed a reddish solution when HC1/CH C1 2  2  was used, and a subsequent  freeze-drying step yielded a brownish-red  powder. This solid was then collected and stored in an  inert-atmosphere  of isolated intermediates dissolved in C D C 1  glove-box.  This mixture  2  2  had  the  same H N M R spectroscopic characteristics as the mixture, formed in situ from the reaction of 7 !  with HC1/CH C1 . Many attempts 2  2  were made to separate the intermediates  formed, all of which  failed. conditions, but a large portion (ca.  Chromatography was attempted under rigorously anaerobic 60%)  of the reaction mixture  alumina,  1 x 10 cm, C H C 1 2  2  adhered irreversibly  to the chromatographic support  (activity IV  eluent). The only porphyrin residue collected from the column was  found to be a mixture (Figure 4.4), a component of which had H N M R spectroscopic J  characteristics similar to those of Ru(OEP)X(L); for example, the C H found at -2.2 ppm and  -4.6 ppm, respectively (see Table  3  and H  m e s o  resonances arc  4.1 and Section 5.2.d.2), and  spectrum  was different from diat of the one component J 4 of the in situ mixture.  attempts  were  made  to separate  the components of the mixture  using  other  the  Although  chromatographic  supports (silica gel or Florisil) and other solvent systems, all gave similar or worse results. Precipitation  techniques  were attempted also. The slow  addition of n-pentane to a C H C I 2  2  solution of the mixture led to complete precipitation of the porphyrin mixture present, instead of the preferential precipitation of one species. Similar results were obtained solvent  mixtures  (CH Cl /hexanes, THF/n-pentane or OEt /n-pentane) used 2  2  2  using other  common  for precipitation of  porphyrin complexes. The attempted dissolution of a solid sample of die mixture in C D 6  6  led to  the formation of a reddish solution with a suspended precipitate. The H N M R spectrum of the J  reddish filtrate showed  it to contain a  major ruthenium porphyrin  Ru (OEP)X-lilce m  species (see Section 5.2.d.2) as  the  species of a mixture, and this major species was the same as the  product eluted in low yields during the attempted separation of the mixture using chromatography (Figure 4.4). The precipitate from die C D 6  solution was collected by filtration and dissolved in  6  C D C 1 . The U N M R spectrum of the C D C 1 l  2  2  2  2  solution suggested a mixture also, with Ru(OEP)Cl  98  2  Figure 4.4:  'H  NMR  spectrum of the product eluted from the attempted purification  using chromatography. Spectrum was measured at 293 K, 300  MHz.  of  13/14  as the major fraction. Neither the C D 6  6  nor the C D C 1 2  2  solutions gave 'H N M R spectra similar  to those obtained for the in situ species shown i n Figure 4.2, showing that chromatography or selective precipitation techniques do not work in this case. 4.2.d. Further characterization of the mixture 13/14. Because of the difficulty in separating the components of the mixture, die  mixture  subsequent chemical  and spectroscopic characterization was done on  in attempts to identify each of the species, which tentatively have been assigned the  formulations [ R u ( O E P ) ] C H C l Q3) and Ru(OEP)H (14). 2  2  Microanalysis data obtained for the proposed 13/14 mixture (see Section 2.3.b) formed by the reaction of 7 with HCI do not fit the analysis calculated for a 1:1 mixture of j_3:J4, ignoring the contribution from the diird component of die mixture.  However, die microanalysis obtained for  the mixture synthesized from die reaction of 7 with HCI in C H C 1 2  for the products from the reaction of 7 with C H C 1 2  2  2  was similar to that obtained  or C D C 1 , showing that the same products 2  2  are formed in all three cases, and diat diese products contain chloride. The  highest-mass peak observed  in the FAB-MS  spectra of the mixture  and its deuterated  analogue (made by reacting 7 with CD C1 ) was at 1282 vale' (Figure 4.5), suggesting a complex 2  of dimeric structure [Ru(OEP)] 1,2)  vale') having a single carbon hydrocarbon ligand (CH ,  (1268  2  2  n  n=  is present ( ( [ R u ( O E P ) ] C H ) , 1282 mle~). The slight differences in intensity of the signals +  2  2  observed in the spectrum of each sample may be due to differences in sample sizes rather than differences in the samples themselves. Due to the large uncertainty of die peak position (+_ 3 m/e~) at this extreme high-end region of the FAB-MS spectral range, no deuterium incorporation could be discerned. Also, the same mass spectrum showed a signal for [Ru(OEP)] no parent peak for [Ru(OEP)Cl]  +  +  (634 m/e"), bin  (669 mle~). A n authentic sample of Ru(OEP)Cl, when  studied  separately by FAB-MS (see Section 5.2.d), always showed the parent mass peak in the FAB-MS. Thus, the mass spectral data also rule out the formulation Ru(OEP)Cl for 14, and are consistent with the presence of [Ru(OEP)] CHCl 2  mixture shows peaks for [ R u ( O E P ) ]  + 2  2  (13) in the mixture. The low resolution EI-MS of the (1268 rale'), [Ru(OEP)]  100  +  13/J4  (634 vale'), and HCI (36/38 m/e).  Figure 4.5:  Fast atom bombardment (FAB) mass spectra of (A) the mixture including 13/14 and (B) the proposed deuterated analogue of the mixture. 12  m/e~  —+  12 6 8 B  101  68  No signal due to ( C H C 1 )  (83/85 mle) was observed. Of note, the EI-MS of CH,C1  +  2  signals for HCI (36/38 mle'). Thus, the observed  also show  2  signal for HCI in the EI-MS of the mixture  could be due to the presence or generation of CH C1 . The measured solution, molecular weight in 2  CH C1 2  2  using the Signer method  80  2  gave a value of 920 _+  100 g/mole for the mixture, in  agreement with the expected value of 993 g/mole for a 1:1 mixture of Ru(OEP)H (635 g/mole) and [Ru(OEP)] CHCl 2  2  (1351 g/mole).  The infrared spectra of the mixture as a Nujol mull (Figure 4.6) or a C H C 1 2  bands  assignable to either  a  terminal hydride  Further, the ring oxidation marker band near radical in metalloporphyrin complexes,  82  ( R -H) v  o r  terminal chloride  a  U  1500 cm" , 1  solution had no  2  commonly  observed  (u ,_ ). R l  3 7 : 8 1  C ]  for the n -cation  was missing indicating that a metal-centered rather than  a porphyrin-centered ( O E P ) oxidation had occurred in forming 13 and 14. The matrix bands for +  Nujol or C H C i , 2  CHC1 2  c  by IR spectroscopy. The IR spectrum  2  CD C1  and die porphyrin ring bands prevented the direct observation of u .  2  2  should have a v . c  band between 2300 and 2000 cm"  3050 and 2800 cm" ) for die proposed CDC1 1  possible reasons why  die t > _ c  in a sample having ca.  of the mixture of products obtained from 1  D  D  2  for Ru-  H  analogue of 1 3 ;  1_ and  ( u _ is normally observed between c  81b  H  however, none was detected. Two  band was not detected are that (1) only one C-D  bond is present  60 carbon atoms, and (2) die region of interest usually has significant  interference from the presence of moisture in the sample and the sample cavity. The  UV/visible  spectrum  of die mixture of products in C H C 1 2  oxidation marker typified by a broad absorption centered at 580 nm.  17  is also missing the ring  2  The possible  mixed-valence  nature of J_3 (Ru /Ru ) suggests diat a metal-to-metal charge transfer ( M M C T ) band may ni  as observed  n  in odier mixed-valence  13/14 in the 700-1600 nm mixture in C H C 1 2  2  dinuclear complexes;  83  exist  however, no bands were observed for  region. The near-zero specific conductivity  measured  for the 13/14  (see Section 2.3.b) shows that 13/14 are non-electrolytes, consistent with the  suggested formulations. Attempts to measure the redox potentials for 13/14 by cyclic voltammetry  102  in C H C 1 2  2  with  Figure 4.6:  IR spectrum of tlic mixture 13/14 of u  the  Ru-Ci  mixture m  m  c  13/14  measured  as a Nujol mull with KBr plates. The IR spectrum using Csl plates showed  no assignable  band for the  500-250 cm" region. 1  1  -f-  3BOO. O  3200. O  -f-  2BDO. D  -f-  -4-  »DOO- O  17DD. O  1400. O  WAVENUMBERS <CM-J>  1 lOO. O BOO. OO  SOO. OO  0.1  M  tetra-n-butylammonium perchlorate (TBAP) as electrolyte in order to compare the data with  those obtained, for example, for [ R u ( O E P ) ] reaction of 13/14  (X  =  BF , 4  PF , 6  SbCl )  failed due  3 2  6  to the  with the solvent/electrolyte matrix, resulting in irreversible voltanimetric waves  (peak-to-peak separations of > solvent system  X"  + 2  200-400 mV).  The reaction of the mixture of products with the  84  ( 5 % f-butanol in C H C 1 ) precluded the measurement of the solution 2  2  magnetic  susceptibility using this system; however, that measured using a sample of 13/14 in neat C D C 1 2  and a formula weight of 920  +_ 100 g/mol gave n  (corrected) of 2.0 B.M.,  e{T  2  consistent with the  observation that the product mixture has unpaired spin present (a spin-only value of 1.83 B.M.  is  expected for a R u , d , low-spin configuration, S = 1/2). m  The  5  mixture of 13/14 was studied by X-ray photoelectron spectroscopy because it was hoped 85  that direct, unambiguous identification for the axial ligand in 13 (CHC1 ) could be obtained. The 2  XPS  spectra of die well-characterized complexes  5), Ru(OEP)Cl (16b). Ru(OEP)CH  3  Ru(OEP)Cl  and Ru(OEP)py  2  2  (8_b), Ru(OEP)Br  (16a. see Chapter  (6a) were used as a database because, to our  knowledge, no other studies involving ruthenium porphyrin complexes have been reported. From the XPS  spectrum of each sample (see Figure 4.7), the signals due to the ionization of  an electron from the Ru  4p, 3 d , 3 p 5/2  3/2  and 3p , die carbon Is, and the N 1/2  Is orbitals were  identified. Where possible, die signal from the chlorine 2p orbital and that from the bromine  3p  and 3d orbitals were also identified. These assignments were made by comparison of the observed data to those of a general database of non-porphyrin complexes, and are presented in Table 4.2. Because  86  of the high ratio of carbon to ruthenium, nitrogen and halide in these complexes, the  signal corresponding to the carbon Is orbital was always the highest intensity signal, and always obscured the signal due to the ionization of an electron from the Ru 3 d Because the signal for die C signal  due  2  orbital.  Is orbital was so intense, it was not possible to detect a specific  to the carbon atom of the axial ligand  proposed C H C 1  3/2  attached to R u ( O E P ) C H  3  or that for the  ligand in 13. The CI 2p signal was studied as an alternative because the kinetic  energy of the electrons removed from this orbital varies when a chlorine is attached to carbon  104  Figure 4.7: X-ray photoelectron spectra of (a) Ru(OEP)py , (b) Ru(OEP)CH , (c) Ru(OEP)Cl, 2  3  (d) Ru(OEP)Br, (e) Ru(OEP)Cl and (f) 13/14. The spectra were externally referenced 2  against the carbon Is signal of polystyrene (284.6 eV), x = trace 0 contaminant. 2  •  C l l  (a)Ru(OEPXpy) ,6a. 2  ?  1600 • •Ru3p3/2  z  .013  80 0-  \  •Bu3p1/2  500  4  BINDING  00  300  ENERGY,eV  • C  (b) Ru(OEPX:H3 ••160 0  •Ru3p3/2  a o  to  Z ui  800 •  T  T  5 00  4  BINDING  105  00  ENERGY,eV  300  LS  (c) Ru(OEP)Cl, lft. I  120  +Cls  j  *nu3p3/2  M  w  >  -i  1  1  4 00 BINDING  1—  2 00  E N E R G Y , eV  (d) Ru(OEP)Br, J6a. • ClB  a.2 0  u  *3u3p3/2 • 018  _  to  12  \  •  •flu3p  NIB  1/2  4 4  •Br3p  4 00 BINDING 106  —I  200  ENERGY,eV  • Br3d  r  (e) Ru(0EP)Cl2, Sb.  (f) the mixture of products ircluding 13/14.  BINDING ENERGY,eV  107  Table 4.2: X P S binding energies for several Ru(OEP) complexes. binding energies, eVcomplex-  C Is  5  N Is  Ru 3 p  Ru 3 d n  3/2  Ru 3 p  ] / 2  halogen-  Ru-py , 6a  286.2  275.8  400.3  462.7  487.0  -  R11-CH3  285.0  275.8  399.7  464.1  486.8  -  Ru-Cl, 16b  283.9  275.7  404.4  472.4  489.7  197.3 (CI 2p)  Ru-Br, 16a  285.3  275.4  398.6  463.5  485.2  181.2 (Br 3p)  2  70.4 (Br 3d) Ru-Cl , 8b  284.1  271.1  399.7  464.7  486.8  197.1 (C12p)  13/14  284.8  272.3  401.5  467.9  489.7  197.0 (CI 2p)  2  - Excitation energy 1486.6 eV, 3-6 scans per sample, energy steps of 400 meV, errors in binding energies are _+ 0.1 eV. ^ Ru denotes Ru(OEP). - Represents the signal from the appropriate halogen atom and the origin of the electron.  108  (observed at approximately 200-201 eV) or to a metal (197-199 e V ) . at  The CI 2p signal was found  86  197.1 eV for 8b, 197.3 eV for 16b, and 197.0 eV for 13/14. These data suggest that the  chlorine is attached to ruthenium from the N M R  and M S  rather than carbon, in contrast with the conclusions reached  data presented previously. No other significant trends in the data can be  observed; for example, the Ru 3 d from  Ru (OEP)CH  (275.8  m  Ru (OEP)Br m  expected occurs.  3  signal from  5/2  eV), and is similar  (275.4 eV). The Ru 3 d  2  (275.8 eV) is the same as that  to that from  signal for R u ( O E P ) C l  of the lack  complexes needed for comparison  n  IV  5 / 2  to be detected at higher binding energy Unfortunately, because  Ru (OEP)py  2  Ru (OEP)Cl  H  86  2  larger  eV) or  (271.1 eV) would have been  than that for R u ( O E P ) p y ,  of a  (275.7  m  database  but the reverse  for nithenium  porphyrin  with the data obtained in this present study, the XPS results  offer no insight into the structures of the components of die mixture. In  summary, die spectroscopic data show diat diree products are generated by the reaction of  7 with HCI in C H C 1 2  2  or with C H C 1 2  2  itself; two of which (13,14) are formed in equal proportions  and comprise 9 0 % of the product mixture (observed by 'H N M R  spectroscopy). Further, these two  products Q3 and 14) are paramagnetic, with 13 likely having a dinuclear structure (from 'H and  FAB-MS data) and a R u / R u n  m  mixed-valance  state. The FAB-MS data suggest that a 'CH ' n  fragment is attached perhaps to 13. The other paramagnetic Ru  m  NMR  species (14) is likely  species not containing chloride (as assessed by FAB-MS and 'H N M R  solution magnetic susceptibility confirms die presence of paramagnetic  a monomelic  spectroscopy). The  species. The component J_3  contains chloride, judged by die microanalysis and 'XPS data to be either coordinated to the metal or  within an axial ligand, because the product mixture dissolved in C H C 1 2  2  does not generate  ionic chloride. These data, taken together, are consistent widi die tentative formulations of for  13 and Ru(OEP)H  for _14. The third  evidence for the coordinated C H C 1 !  H  NMR  spectroscopy  or from  2  component  remains unidentified.  [Ru(OEP)] CHCl 2  2  Unfortunately, no  in 13 or the hydride ligand in 14 was obtained from IR and  X P S studies, preventing the unambiguous identification  109  of the  components of the product mixture. Therefore, the chemistry of the product mixture was studied to characterize further the components of the mixture (see Sections 4.2.e and 4.2.f). 4.2.e. Measurement of the kinetics of the reaction of C H C I 2  data are best obtained for systems in which  2  2  2  2  2  66  system, kinetic studies might establish  2  mixture, and to clarify  reactants. The reaction of 7 with C D C 1  with [Ru(OEP)] . Although kinetic  the reactants and products are fully characterized,  it was thought that, in the present [Ru(OEP)] /HCl/CH Cl better the nature of the product  2  the roles of C H C 1 2  was first observed  at *H N M R  and/or HCI as  2  sample concentrations  (1-5 mM) and was noted to be slow (approximately one day for complete reaction):  3/2 [Ru(OEP)] 7  Of  interest, the  H  2  NMR  k.obs  + CH C1, 2  [Ru(OEP)] CHCl 13 2  resonances  + Ru(OEP)H 14  2  (4.1)  due to 7 did not diminish in intensity  as the reaction  progressed, but instead broadened and moved with time. For example, the chemical shift for one of the C H  2  the C H  resonances  2  signals of 7 was found to change from 26.05 ppm to 9.99 ppm (the position of one of of 13). Concomitantly, the intensity of die signals of J 4 increases as the  reaction proceeds, and the ratio of the formation of 13:14 from  7 is always  1:1. First order  analysis of die change in position of one of the signals of 7 (In P -Pf, where P t  of the signal at any time 't' and P k  is the position  is die final position of this same signal) versus time gave  of 4.3 x 10" s" at 293 K (see Table 4.3 and Figure 4.8). A similar shift in the resonances 5  o b s  f  t  1  of 7 was observed for the titration of 7 with HCI in CD C1 , followed by H  NMR  i  2  2  (see Figure 4.9 for details of die experiment); the spectral changes toward  spectroscopy  formation of 13/14  were now instantaneous. Figure 4.9 shows the change in the equilibrium position of each signal of 7 as partial equivalents of HCI were added to 7. These results indicate that as 7 is converted to the mixture by reacting with C D C 1 2  2  or HC1/CD C1 , the remaining amount of 7 is involved in a 2  2  chemical exchange mechanism widi 13 as in Equation 4.2; surprisingly, complex J4 does not appear to be involved in this exchange. The exhange of Ru(OEP)H (14) with [Ru(OEP)]  110  2  (7) would  Table 4.3:  Raw data for the change in the position (5) of the resonances of [Ru(OEP)] time upon reaction of 7 (4.9 mM) with C D C 1 2  2  as measured from the *H  spectrum of the reaction mixture in C D C 1 at 293 K. 2  2  £CH  2 b  i_CH  0  26.05  11.06  3.39  10.77  75  22.01  9.78  3.10  11.32  90  21.30  9.47  3.30  11.45  105  20.74  9.32  3.00  11.51  120  20.50  9.18  2.97  11.57  150  19.66  8.89  2.93  11.66  180  19.07  8.72  2.88  210  18.49  8.55  2.84  11.85  240  17.98  8.36  2.80  11.93  270  17.45  8.20  2.77  12.01  300  17.00  8.04  2.74  12.07  330  16.47  7.89  2.71  12.14  360  16.03  7.74  2.68  12.20  390  15.59  7.61  2.65  12.26  420  15.32  7.49  2.62  12.32  450  14.63  7.35  2.60  12.38  480  14.54  7.24  2.57  12.43  510  14.01  7.12  2.55  12.48  540  13.46  6.83  2.49  12.61  570  13.10  6.83  2.49  12.61  750  11.41  6.28  2.37  12.78  2160  9.99  5.79  2.27  13.00  2 a  111  £CH  £H eso  time, min  m  3  .  11.78  2  (7) with  NMR  Figure 4.8: First order plot of ln(P -P ) for the resonance C H t  f  of [Ru(OEP)] with CD C1 . 2  2  2  2 a  vs. time (min) for the  reaction  Figure 4.9:  Plot of the observed *H N M R of 7 vs.  equivalents of added HCI ([7] = 3.1 mM,  conducted under an N  £  o. a  chemical shift (ppm) of the individual porphyrin signals  2  [HCI] = 91 mM). The titration was  atmosphere at 292 K, 300 M H z (FT).  LEGEND  25  X  o Ld X  15  O  CH2  o  CH  '  CH  *  Hmeso  a  2 b  3  -  u  e—o  -e  u  > u CO  m •  5  -  0.6  0.2  1.0  E Q U I V A L E N T S DF HCI ADDED v s . CRuCDEP)]  * R e p r e s e n t s chemical s h i f t s of * * R e p r e s e n t s chemical s h i f t s of  113  CRuC0EP)]g. CRu<0EP)] CHCl . 2  g  [Ru(OEP)] CHCl 2  2  + [*Ru(OEP)]  11  ^  2  1  [Ru(OEP)] + [*Ru(OEP)] CHCl 2  2  (4.2)  2  11  1  require the cleavage of the metal-metal double bond i n 7 and the Ru-H bond in 14,  perhaps  making the process unfavorable. Taking advantage of the noted long reaction time between 7 and CD,C1 , one can cool a half-reacted solution of 7 in C D C 1 2  the  reaction) and observe  (Figure  (16 mg/mL, effectively  quenching  spectra as a function of  temperature  2  4.10).  Because  the changes i n the *H N M R  the two species involved  2  in die chemical  mechanism arc  exchange  paramagnetic, a full analysis of the data by dynamic N M R analysis techniques (as several systems described in Chapter 3) becomes very difficult; however,  there  is  was  little  done doubt  for that  a chemical exchange mechanism between 7 and 13 is present. For example, the resonance due to a methylene  proton of 7 is observed at ca. 40 ppm at 193 K (see Figure 4.10), but this  disappears as the temperature is raised instead of shifting upfield, as expected of at  [Ru(OEP)] . 2  25  for  a  of bodi of these signals, one observes a broad resonance at about 15  is partially overlapped with the H 303  sample  Similarly, the resonance due to one of die methylene protons of j_3 is observed  approximately 12 ppm at 193 K, and diis signal also disappears as the temperature  place  neat  signal  resonance of 13. The C H  m e s o  3  p p m at  is  In  raised.  303 K,  which  resonance of 14 at -3 ppm at  K essentially varied linearly with temperature over the same range, showing  that  j_4  is  not  involved in the chemical exchange mechanism. In principle, the loss of the C H C 1 with  2  fragment from 13 will give 7, and a reaction o f CHC1  either 7 or the solvent (i.e. exchange with the solvent as in Equation 4.5)  followed  by  reaction with 7, will yield 13:  2 [Ru(OEP)] CHCl 2  2  2 [Ru(OEP)] + 2 C H C 1 2  114o  2  (4.3)  2  a  Figure 4.10: 'H  NMR  spectra measured as a function of temperature for die product mixture  obtained from the incomplete reaction of [Ru(OEP)] mg/mL). The spectra were measured at 300 M H z  2  with C D C 1 2  in C D C 1  2  2  2  in vacuo; arrows define the fate of  each signal specified.  T E M P.,K 3 0 3  2 8 3  2 6 8  2 5 3  2  43  2 3 3  2 2 3  213  203  193 I  I I I  40  I  I | I I I I  1  I  30  i I  I  I  I  I I  I  I  I  |  20  I  I I I  I  10  115  I  I I  (16  i i;ii  i  i  i  i  i  |  I  |  I  I !  -10 PPM  C H C 1 + [*Ru(OEP)] 2  2  C H C 1 + *CH C1 2  2  2  *CHC1 + [*Ru(OEP)] 2  2  2  [*Ru(OEP)] CHCl  2  C H C 1 + -*CHC1  ^  [*Ru(OEP)] *CHCl  2  2  2  2  Net Reaction:  2  2  (4.5)  2  2  2 [ R u ( O E P ) ] C H C l + *CH C1 + 2 [*Ru(OEP)] 2  2  (4.4)  2  (4.6)  2  ^  2 [*Ru(OEP)] CHCl + C H C 1 + 2 [Ru(OEP)] 2  Because of the large excess of C D C 1 2  2  2  2  present relative to 7 (approximately  2  (4.7)  2  10 equivalents), the 6  exchange with solvent as described in Equation 4.5 cannot be observed directly. If an exchange of CHC1  2  with  the solvent  is present,  a solution of [ R u ( O E P ) ] C D C l 2  in C H C 1  2  2  deuterated analogue of 13/14) should give an observable deuterium signal for C D C 1 2  by  45 M H z  detected  2  H  NMR  spectroscopy;  and not one equivalent  however, only  of C D C 1 2  2  natural abundance C D C 1 2  based on a blank  2  (using the  2  when studied  2  in C H C 1 2  of CH C1 /CD C1 . 2  2  2  2  2  was  Thus, no  exchange with solvent seems to be occurring and, on neglecting a contribution from reaction 4.5, Equation  4.7 is simplified to Equation  4.2. The possibility of exchange of the axial ligand by a  radical cage mechanism where J_3 generates [Ru(OEP)] C H C 1 seems plausible. 2  The  2  and  CHC1  as a loose radical pair in  2  23  2  added complication of observing  of reaction of 7 with CD C1? by H N M R !  7  a chemical  exchange mechanism while studying the rate  spectroscopy was avoided by studying the same reaction  by UV/visible spectroscopy, because die exchange of 7 with 13 would be too slow to be observed by diis technique. * 64  A  1  typical experiment involved making up a solution of 7 in C H C 1 2  2  (0.17 - 4.4 mM)  in a  UV/visible cell in die glovebox, sealing the cell under an atmosphere of N , and then transferring 2  the cell from the glovebox to the spectrophotometer. Because the amount of 7 being weighed out in the glove-box was 0.5 .+ 0.1 mg, the uncertainty in the concentration of 7 is >  2 0 % . The  temperature differential between the glovebox and the cell holder of the spectrophotometer was _+ 2 K, and the experiments were conducted at 293 K. Figure 4.11a shows the changes in the 116  Figure 4.11: (a) Typical changes from the initial UV/visible spectrum of (Ru(OEP)I (7) to that of 2  the mixture 13/14 with time at 293 K. [Ru ] = 0.39 mM, 2  [CH C1 ] = 2  2  15.6 M (neat  solvent), time between scans was 84 seconds, (b) Plot of ln(A,-A ) vs. time for the f  above reaction; the data were measured at 540 nm  and 293 K and are presented in  Appendix 5.  1.0  -i  Ld CJ <Z  •  0,5 -  pq  0.0 480  540 WAVELENGTH  600  nm  TIME, s 118  UV/visible spectrum  of 7  in C H C 1 2  2  with time and  the associated first-order plot of relative  absorbance vs. time; the changes in absorbance at 516  and  540  nm  were used for the kinetic  analysis of the data. Because of the extreme air-sensitivity of 7 in solution, some of the kinetic runs were aborted when the color of the reaction mixture turned in minutes from red; (A  the spectral changes differed from m a x  =  565 nm)  the type shown in Figure 4.11a, and  corresponded to that of the /*-oxo dinuclear species 9.  the final  spectrum  Interestingly, if C H C 1  31  solutions of 7 were handled was  green to green-purple instead of  2  appeared to be unaffected by trace  H 0/0 2  conducted  2  room light. These results show that the oxidation  is light-dependent  (Section 4.2.a). While  die reaction  under die best possible anaerobic atmosphere, the presence  avoided. Thus, some conversion of 7 or spectrum  13/14  to 9  of the reaction mixture. Where there was  reaction solution at 565 nm  to 9  in the dark, the qualitative rate of conversion of 7 or 13/14  considerably slower (hours instead of minutes), while that of formation of 13/14  was  always  of  7  with  from  7  of 7 to 9  by  CH C1  was  2  2  of trace air could not observed  2  be  in the UV/visible  a significant increase in the absorbance of the  (where 9 has a absorbance maximum)  compared to that at 540  31  these data were also discarded; data passing these criteria are presented in Appendix 5. A  nm, first-  order analysis of die data gave straight line plots of ln(A,-A ) vs. time (see Figure 4.11b), where f  A, is the absorbance of the solution at eitiier 516  or 540  nm  at any  time Y  absorbance of die solution at die end  of die reaction. Surprisingly, the k  decreased as [ 7 ] increased from 0.17  to 4.4  4.4,  mM  while the [CH C1 ] was 2  see Figure 4.12), showing that the reaction cannot  because k  o b s  Kinetic  a  first  order  concentration have been reported before. kinetics within each experiment, but k that the data only approximate  rate constant 87  o b s  In one decreased  case,  r  is the  for die reaction  kept constant (Table  (k 87a  66  obs  )  decreased  with  increasing  dimcr  the data analyzed well for first-order  with increasing dimer concentration, showing  an overall first-order behavior. A  119  A  be a simple overall first-order process  should be independent of [ 7 ] for a first-order reaction. studies where  2  o b s  and  dimer/monomer equilibrium  was  4.4. Summary of data - for the reaction of [Ru(OEP)] with C H C 1 at 293 +_ 1 K. 8  2  2  rCH Cl 1. M  2  entry  f R u l x 10 , M  1  1.7  15.6  40  2  1.7  15.6  47b  3  1.9  15.6  46  4  1.9  15.6  4lk  5  2.8  15.6  21  6  3.7  15.6  7  3.9  15.6  12  8  4.6  15.6  14  9  4.6  15.6  13k  10  5.7  15.6  7.0  11  9.1  15.6  8.0  12  9.2  15.6  7.0  13  9.2  15.6  7.4*-  4  2  2  2  ko  * 10 , s4  bs  1  9.1  14  13  15.6  3.5  15  44  15.6  1.2  16  6.1  8.9  2.7  17  7.3  2.0  2.0  18  7.3  2.0  1.9*-  19  12  0.9  0.5/1. C£  20  12  0.9  0.3/0.6^  - Data measured at 540 nm used for analysis, +_ 30 % uncertainty in k  obs  .  - Data measured at 516 nm used for analysis, _+ 3 0 % uncertainty in k  obs  .  - Data after the '/' mark are adjusted using the data from the above Table to reflect a k  o b s  when [Ru ] = 0.6 mM, see Text. 2  120  ure4.12:  Dependence of k  o b s  on the concentration of [Ru(OEP)]  M) at 293 K.  121  2  (7) at high [ C H C i ] 2  2  (15.6  suggested  for this reaction. In the other system,  was observed also to decrease with  7 b  increasing metal concentration, and an analysis of the data was proposed for the reaction of a monomer generated from the disproportionation of a dimeric species with added reagent. While both  the reactants and the products of the reactions were identified  systems, lending system,  credibility  for these two analogous  to the quantitative kinetic analysis of the data suggested for each  the products of the reaction  being  examined  in the present study  have  not been  identified. Thus, only a tentative analysis of the data can be provided here. At high [ 7 ], k  o b s  appears to be independent of [ 7 ], indicating a first-order dependence of  the rate on 7. However, at low [ 7 ], a less than first-order dependence of the rate on 7 is apparent (Figure 12). These results were quite similar to those derived from kinetic studies of the reactions described in Equations 4.8 and 4.9:  87a  k, [HRuCl(PPh ),] 3  2  £  2 HRuCl(PPh ),  HRuCl(PPh ) + PPh 3  At low [PPh ], the k 3  2  2  (4.8)  3  -> H R u C l ( P P h )  3  3  3  .  (4.9)  was found to be the rate-determining step; therefore die rate expression  was shown to be: rate = k [PPh ][HRuCl(PPh ) ] 2  3  3  (4.10)  2  k, / {k.,k [PPh ][Ru],} 2  3  rate =  (4.11) 2[HRuCl(PPh ) ] + kj/k.j 3  2  where {2[HRuCl(PPh ) ] + k,/k ,} 3  [Ru] = [ R u ] t  lotal  = [HRuCl(PPh ) ] x 3  2  (4.12)  2  (k,/k.i)  122  Thus, for increasing monomer concentration (increasing [HRuCl(PPh ) ]), the k 3  2  for this system  o 5 s  will decrease because the former term in the denominator of rate expression (Equation 4.11)  will  be dominant. If a similar equilibrium involving the monomer [Ru(OEP)] and 7 (Equation 4.13) is present for the system being studied, a similar rate expression will apply here, and a decrease in k t> 0  s  a s  [ 2 ] increases would be expected:  [Ru(OEP)]  No discernable change (in either A  ^ 2[Ru(OEP)]  2  (4.13)  or extinction coefficient, O in the UV/visible spectmm of  m a x  7 was observed over the concentration range  10" -10" 3  M  5  in C H , indicating diat Equilibrium 6  5  4.13 lies well to the left, favoring dimerization. The  dependence of the rate of the reaction on [CH C1 ] could not be measured quantitatively 2  because  stock solutions of 7 in C H 6  leading to variation in experiment,  a  6  were unstable even  2  dependence  of the reaction  determined. However, comparison of the observed k similar but [CH C1 ] varied shows that k 2  [ 7 ] ca. 0.6 mM 10"  4  when stored in the glovebox, thus  [ 7 ]. Thus, because both [ 7 ] and [CH C1 ] are varying in each  quantitative  2  2  o b s  o b s  rate  on  2  [CH C1 ] 2  alone  2  obtained for reactions where [ 2 1  decreased with decreasing [CH C1 ]. 2  (entries 10 and 16 in Table 4.4), k  1  1  2  (entries 14, 19, and 20), k  decreased from 3.5 x 10" s" to ca. 4 x 10 4  o b s  1  decreased from 15.6 to 0.9 M, respectively. If the measured k [ 2 ] (0-6 +_ 0.1 mM) dependence of k  o b s  2  2  o b s  -5  1.2  mM  s" as [CH CI 1 1  2  2  values are 'scaled' to a constant  using the previously determined dependence of k  o b s  on [ 2 L  a  linear  on the [CH C1 ] is obtained as a crude estimate (see Figure 4.13).  The increasing k 7 with C H C 1  w a s  decreased from 7 x 10" s" to 2.7 x  s" as [CH C1 ] decreased from 15.6 to 8.9 M, respectively. Also, for [ 7 ] ca. 2  be  For example, for  2  4  o b s  cannot  2  o b s  2  with increasing [CH C1 ] could in principle be due to either a reaction of 2  2  or an impurity in CH C1 . For C H C 1 , and for all the halogenated solvents used 2  2  2  2  for synthesis and discussed later in this Chapter except C H B r 2  123  2  (which was used as obtained), the  Figure 4.13: Dependence of k  8  o b s  on [CH C1 ] at 293 K, [Ru ] = 0.6 ± 0.1 2  2  2  A  [CH CI ], 2  124  2  M  mM.  procedure for purification involved first elution from a column (alumina, activity I, 3 x 50 cm) to remove acidic impurities, followed by distillation from C a H  under N  2  2  into an flask equipped with  a Teflon valve and containing CaH . The solution was then degassed by three successive 2  freeze-  pump-thaw cycles and stored under vacuo. The presence of impurities was tested for by G C and none was found (HP-1 column (15 m), T C D detector). In light of the quantitative nature of the reaction of 7 with C H C 1 , the presence of a stoichiometric amount of impurity being responsible 2  for  the observed  discounted. of  2  reactivity  at the 10" M 3  level  after this  Indeed, when the reaction of 7 with undried C H C 1 2  the same  ratio  of products was observed, showing  that  solvent  purification  treatment  is  was studied, the slow formation  2  trace  H 0 does 2  not affect  the  formation or stability of 13/14. Furthermore, the addition of more 7 to the solution at the end of a kinetic run re-initiates the same reaction to generate 13/14 in the same These findings suggest that die reaction of 7 with C H C 1 2  1:1 ratio as before.  is not caused by the presence of a  2  in the solvent; catalysis by an unknown trace impurity is  stoichiometric amount of an impurity not ruled out by this experiment.  One possible route toward the synthesis of 13/14 from 7 is that cleavage of the C-Cl bond in C H C 1  are formed from the homolytic This  route  strengths:  takes  2  into consideration  and the  H C I  2  (Equations  CHCIT  radical  4.14 and 4.15).  the C-H (412 k J mol" ) vs. C-Cl (338 kJ mol" ) bond 1  1  88  CH C1 2  CI + C H C 1 2  ^  2  (4.14)  CH C1 + CI 2  (4.15)  - C H C 1 + HCI  2  2  the subsequent reaction of HCI with the 14e" species [Ru (OEP)] yields R u ( O E P ) H and C I , and n  m  die reaction of the C H C 1 radical with 7 gives [Ru(OEP)] CHCl : 2  2  2  (4.16)  HCI + [Ru(OEP)] - Ru(OEP)H 4- CI C H C 1 + [Ru(OEP)] 2  2  [Ru(OEP)] CHCl 2  125  2  (4.17)  The  effect of added HCI  may  While the addition of HCI  be to promote the formation of Ru(OEP)H (and therefore, CHC1 ). 2  to 7 in C H C 1 2  2  does give the mixture 13/14  rapidly, the HCI  is not a  catalyst in the traditional sense because addition of less than a stoichiometric amount of HCI 7 does not generate the fully formed mixture mixture  13/14  to  13/14. Instead, only partial conversion of 7 to the  is observed. This result shows that the above mechanism is not correct because  HCI  is formed as part of the proposed mechanism (step 4.15). Another  possible  route  involves  the  direct  reaction of  [Ru(OEP)]  with  CH C1 2  to  2  give  Ru(OEP)H and CHC1 : 2  C H C 1 + [Ru(OEP)] - Ru(OEP)H + C H C 1 2  Aldiough  2  this mechanism requires the cleavage  (4.18)  2  of the stronger C-H  bond instead of the  bond in C H C 1 , the driving force for die reaction could be die formation of a Ru-H 2  stronger by  combination  (2  controlled. The  Rh  m  reaction 4.17  is a diradical species, S  bond in C H  =  l)  would be expected to be diffusion-  2 5  m  and  R h ( T M P ) C H . The UI  3  diamagnetic  complexes allows for the identification of the axial ligands present  be  system, the activation of C H  2  903  forming  nature  die latter system. Similarly, [Rh(OEP)]  2  the [Rh(TMP)] system is quite different from  has been reported to abstract an 6  4  H  from 3  Other examples of metalloporphyrin reactivity with C H C 1 2  2  The  the  by the previous system does provide some precedent for  4  2  2  these  in each complex.  ((CH )C H R) 3  at elevated temperatures to give Rh(OEP)(CH (C H R)) and Rh(OEP)H (R = H, p-CH , m-CH ).  with C H C 1  of  the  macrocycle in [Rh(TMP)] prevents dimerization; dierefore, the monomer  studied in solution readily. Although  [Ru(OEP)]  Further, the radical  89  by [Rh(TMP)] has been recently reported,  4  known complexes R h ( T M P ) H  steric bulk of the T M P can  60-100 kJ/mol than M-alkyl bonds.  M-H  53  cleavage of a C-H  previously  bond;  2  bonds are known to be  C-Cl  2  6  4  90b  3  include the reaction of  [Rh(TPP)]-,  to yield Rh(TPP)(CH Cl), which is thought to proceed via a dissociation of the dimer 2  126  to the monomer [Rh(TPP)], Ru(OEP)(THF) Several  and  2  79  and  the reaction of 2 K  [Ru(OEP)]"  +  with C H C 1  2  2  in THF  2  R u ( O E P ) ( H C = C H ) , via a presumed alkylidene ( O E P ) R u = C H 2  2  other non-porphyrin systems have been reported  to abstract a CI  2  to give  intermediate.  atom from chlorinated  solvents to give complexes containing products generated from the cleavage of a C-Cl die chlorinated solvent. ' 91  the  reaction  with  7  This present kinetic study suggests that C H C 1  92  2  and  not  some impurity  that was  initially  48  bond of  itself is involved in  2  present or  generated  in situ;  indirectly, these results support the proposed formulations of 13 and 14. 4.2.f. Chemical behavior of the in situ mixture. reactions involving 13/14 was  CH CI 2  2  were conducted under a N  (see Section 2.4  was  followed by  'H  NMR  3  atm  2  to give initially a mixture with Ru(OEP)Cl  It was  hoped  days; 8b  that the  products which could  be  decomposed products had  the solvent used  dissolved in, and  itself  is indefinitely  decomposition of  detected  by  'H  NMR  in CDC1  13/14  ca. fifty signals in the 0-10  ppm  reacted  3  3  in  ring, as monitored by  stable in CDC1 , showing  that  which lead to the decomposition  in CDC1  spectroscopy,  13/14  (8b) as the major fraction; this  2  die complete destruction of 8b, as well as die porphyrin  spectroscopy over two  8b.  or under vacuum, and  mixture of products 13/14  radicals are generated in situ upon dissolution of 13/14 of  all of the following  for details of the reaction conditions). Under these conditions,  are indefinitely stable in solution. The minutes with, C D C 1  Unless stated otherwise,  but  would  3  generate  CH Cl -like 2  2  because the spectrum of the  region, no  readily discernable product  signals were observed. The when 0 was  addition of trace H 0  purged with N  2  2  and  H 0 7  *H  NMR  unreactive to added gaseous H , 2  n  as  the  chlorinated  spectroscopy. dry 0 , 2  2  solvents  ]  H  NMR to  give  Solutions of 13/14  C H , and 2  major product, along  products as studied by in  in C D C 1  2  caused no  reaction; however,  were added together to the mixture, formation of the n-oxo dinuclear species 9  noted in minutes by  Ru (OEP)CO  to 13/14  2  4  with  spectroscopy.  The  Ru(OEP)CO  has  127  N,  2  were found to be  2  but rapidly reacted with CO  2  some 8b  and  ability of CO been  in C D C 1  noted  to form  unidentified minor paramagnetic to reduce R u ( O E P ) C l IV  before,  although  the  2  rapidly  mechanism  involved is unknown. The H N M R  spectrum of the reaction mixture formed upon adding pyridine to a solution of  l  13/14 in C D C 1 2  under N  2  (Figure 4.14), shows that some Ru"(OEP)(py)  2  (6a), R u ( O E P ) X and m  2  [ R u ( O E P ) ( p y ) ] X" species are formed: m  +  2  [(OEP)Ru -Ru (OEP)]CHCl n  + R u ( O E P ) H + py -•  m  m  2  Ru (OEP)(py) n  + [ R u ( O E P ) ( p y ) ] C l + Ru (OEP)Cl(py) + 'others' m  2  (4.19)  ra  2  These three products were identified chemical shifts with those reported  in the in situ spectrum for Ru(OEP)(py)  2  (6a).  by comparison [Ru(OEP)(py) ]  37  2  +  of the observed CI" (see  Section  5.2.e), and Ru(OEP)Cl(L) (X = CI; L = vacant, N H , C H C N , py, MeOH, see Section 5.2.d). No 3  Ru  3  paramagnetic products are formed as judged by the absence of a signal at ca. 60 ppm. If  I V  one assumes that pyridine does not oxidize or reduce the precursors it reacts with, but instead " only binds to the metal either via substitution of coordinated ligands or coordination to a vacant axial coordination site, then die products obtained from die reaction of 13/14  with pyridine show  that the oxidation states of the ruthenium porphyrin species of the mixture including 13/14 must include R u  11  and Ru . Unfortunately, the signals of die 'liberated' axial ligands of .13 and J_4 111  cannot be discerned among the myriad of peaks in the 0-12 ppm range. The  mixture 13/14 reacted with HCI to give Ru(OEP)Cl  UV/visible  spectroscopy; however, the reaction  2  two hours, as judged by  within  was instantaneous when  HCl/air  was  used  to  oxidize the mixture to 8b. The addition of H B F / C H C 1 4  NMR  2  2  to 7 under argon gives [ R u ( O E P ) ]  + 2  BF ~ (observed both by 'H 4  (see Figure 4.3a) and UV/visible spectroscopy, with the data in complete agreement with  those reported by Collman et a l . ) .  32  This route to synthesize [ R u ( O E P ) ]  + 2  BF " is superior to that 4  devised by Collman et al. because there is no need to control the stoichiometry of addition of HBF  4  to 7. Collman's method requires the stoichiometric addition of A g B F  128  4  to 7; further addition  Figure 4.14:  In situ 'H NMR  spectrum of the reaction mixture of 13/14 (3 mg) and pyridine  ( l /*L) in C D C 1 (0.6 mL) scaled under vacuum, measured at 293 K, 300 2  MHz.  2  6  A  2  0  -  2  -  4  PPM  of  AgBF  results in the formation of [Ru(OEP)]  4  [Ru(OEP)]  + 2  B F " in C D C 1 4  2  H  meso  Hmeso  4  containing excess H B F  2  'H N M R spectrum similar to that of Ru(OEP)Cl NMR  2 BF ". Exposure to air of a solution of  2  2  4  generates a new in situ species (8c) with a  (8b) (Figure 4.15, Table 4.5). The in situ 'H  spectrum of this species (8c) shows the O E P methyl (6.95 ppm), methylene (59.10) and the (10.42 ppm) resonances are similar to those for Ru(OEP)Cl (8b 6 C H = 6.34, C H 2  8.20). '  =  36  3  This new species is tentatively assigned the formulation  37  2  = 59.75,  Ru (OEP)(BF ), IV  4  (8c): excess H B F -» ' [Ru(OEP)] CH C1 4  [Ru(OEP)], 7 "  The reaction of H B F  2  4  + 2  BF " 4  air, H B F -  4  2 Ru(OEP)(BF ) 8c 4  2  2  (4.20)  widi in situ 13/14 under anaerobic conditions (complete within 2h) or in air  (instantaneous) yields the same single product; this product has an H N M R spectrum identical to l  that of 8c:  CH,C1, + [Ru(OEP)], - 13/14  excess H B F -  4  Ru(OEP)(BF ) 8c 4  Just as HCI reacts with 13/14, die reaction of aqueous H B F Of  note, the only Ru(OEP) complexes  9  (4.21)  widi 13/14 appears to give some 8c.  4  (in any oxidation state) which have a single  methylene  resonance at 60 ppm in their H N M R spectrum are complexes of the type 8a-b. Further, the in !  situ spectrum of 8c is very similar to that for Ru(OEP)(SbF ) 6  Complex  (see Section 4.2.i and Table 4.5).  2  8c was isolated as a solid from the H B F / C H C l / 7 aerobic reaction mixture by 4  2  2  the  addition of «-pentane; the precipitated reddish solid was collected by filtration, which was then reprecipitated  again  from  CH Cl /n-pentane, 2  2  collected  by filtration  and air-dried  at room  temperature. The *H N M R spectrum of the isolated solid indicated that it was impure. The optical spectrum of 8c is dissimilar to diat for 8b and the molar conductance measured for 8c shows it to be a non-electrolyte (see Table 4.5). Unfortunately, die i/ _ B  130  F  bands normally observed at 900-  Figure 4.15: The 'H N M R  spectrum of in situ Ru(OEP)(BF ) 4  2  (8c) in C D C 1 2  2  at 293 K, 300 MHz.  The other peaks in the Figure are suggested to arise from other Ru(OEP) complexes, as well as impurities from H B F  4(aq)  .  H Q 2  ' W i i i I i i i i | i i i i I i i i i | i i i i I i i i i | i i i i I i i i i | i i 8 10 6 4  I i  I i i  i  i | i i 2  i  i | i i i i |  PPM  0  Table 4.5: Summary of spectroscopic data for Ru^tporp) complexes. H N M R spectrum, C D C 1  l  complex  CH  6  2  CH  6  3  UV/visible spectrum, nm-  i-Hmeso  3  Ru(OEP)Br , 8a  60.12  7.10  3.50  365 (sh), 398 (Soret), 505, 535  Ru(OEP)Cl , 8b  59.75  6.34  8.20  364 (sh), 398 (Soret), 505, 535  Ru(OEP)(BF ) , 8c>  59.10  6.95  10.42  346 (sh), 384 (Soret), 408, 510  Ru(OEP)(SbF ) , 8d  57.25  6.45  10.03  -  2  2  4  2  6  2  c  Ru(TMP)Br , 8e 2  d  R u ( T M P ) C l , 8f 2  ~  -  —  —  416 (Soret), 518 -  2 In C H C 1 or CH C1 . 3  £ 6  1 9  2  2  F (8c) = 4.54 ppm vs. («-Bu) N BF " (0.00 ppm); B { H } = 4.28 vs. («-Bu) N +  11  4  1  4  4  (0.00 ppm). Molar conductance = 4.6 cm" M" ohm" , 5 mM solution in C H C 1 at 293 K. 1  1  1  2  - SU = m  13.76, S o - C H  3  ^ <5H = 11.21, So - C H m  3  = 4.4, c5p-CH = 4.01, 5 H 3  p y r r  = 3.83 5p-CH = 3.52, S H 3  132  2  = -44.37 (see Section 4.2.j). = -52.22 (see Section 4.2.j).  1000  cm" ,  are eclipsed by  la  the bands from the porphyrin macrocycle (see Figure 4.6  for a  typical example of an IR spectrum of a Ru(OEP) compound). The 282 M H z  1 9  F  NMR  spectrum of the in situ species Ru(OEP)(BF ) 4  dissimilar to that for (/i-Bu) N  BF " or H B F  +  4  4  4(aq  8c could be coordinated to the Ru. The 96 M H z also confirm this result; the  BF  4  ligands  in 8c  coordinated to the Ru™ species [ R u ( O E P ) ] m  magnetic would data  + 2 2  94  ^ in C D C 1 , 2  "B^H}  (8c) (Figure 4.16) is  2  showing that the BF " ligands in  93  2  4  spectra of 8c, H B F  (and  presumably  the S b F  ligands  6  in Ru(OEP)(SbF ) 6  (X") . 2  32  Further, based on the MO  the paramagnetic  (7), [ R u ( O E P ) ]  2  Ru (OEP)X  instead  IV  2  formulation or die 1:2 electrolyte [Ru^OEP)]" " 1  Aerobic oxidation of 13/14  in C D C 1 2  2  2  and  + 2  [Ru (OEP)] U I  + 2 2  of the diamagnetic  , ' 2 5  both 8c and  3 2  8d  oxidation state. The  I V  {[Ru (OEP)]->  (X"),}  IV  containing five equivalents of («-Et) N  +  4  spectrum (-3.6 (br), C H  resonance could not be assigned easily because  +2  CI" does not  (24H); -7.8 ppm (br),  3  of the presence of many  range, see Chapter 5), showing the need for the presence of HCI  8b from 13/14. The role of the H  to form  in the aerobic oxidation of 13/14 in the presence of HCI could  +  be attributed to the stabilization of the 0 " 2  of 13/14 by 0 .  (8d)) are not  2  2  m  ppm  4  (X") formulation for the complexes 8c and 8d.  yield 8b but a species having a R u - l i k e 'H N M R  peaks in the 0-10  BF "  diagrams used to explain the observed  be diamagnetic i f they are dimeric in structure, in spite of die R u  2  +  4  centre, the ensuing compound would tend to dimerize, as for the dimeric  n  Hmeso (4H); the C H  and ( n - B u ) N  while the spectra are not shown, the data are provided in Table 4.5. If  properties of [ R u ( O E P ) ]  favor  4  (as H 0 ) 2  formed  during the outer-sphere oxidation  2 8  2  4.2.g. The reaction of [Ru(OEP)] unambiguously attempts  2  (7) with chlorinated reagents. The  to determine  the nature of the axial ligation of the compounds comprising the mixture led to  to prepare  other complexes  of  similar  character by  chlorinated solvents. Table 4.6 lists die macrocycle 'H N M R The  inability  difference between the two methylene  reacting  7  with  a  variety  resonances of 7 in various solvents.  resonances ( C H - C H ) calculated from Table 4.6 2a  of  2b  can  be used to perhaps judge die 'degree of association' of solvent ligands to 7 at the vacant axial  133  Figure 4.16:  , 9  F  NMR  spectra  of (a) H B F  4 ( a q )  measured at 293 K, at 282 MHz,  and,  (b) Ru(OEP)(BF ) . 4  2  The  spectra  and are referenced against ( n - B u ) N 4  +  BF " 4  were (0.00  ppm)  HBF.  HBF  4  8c  i  I I I ' 1 i I I 1 | I I I 1 | i I I 111 I I I|IiII | I I I 11 1 11 11 I 1 I i|I I I I|I 1 I 11 I I I I | I I I I | I I 1 I | I I I 11I 11 I| I i ( I | I I I I | 1 I I 11 I i  7  6  5  4  3  2  134  1  0  -1  PPM  Table 4.6: *H N M R spectroscopic data for rRu(OEP)l and products generated from the 2  reaction of [Ru(OEP)1 with various solvents.  5  2  solvent CD C1 2  C D 6  6  C D  8  7  * CH 2  THF-d 8  MeOH-d  4  11-  3  2 b  Uimeso  8 CH  26.05  11.06  10.77  3.39  26.25  11.20  10.18  3.49  26.25  11.21  9.80  3.59  25.72  11.20  9.80  3.36  22.13  9.59  10.76  4.90  9.99  5.79  13.00  2.27  -8.20 (br)  4.20 (br)  14£  CDC1 £  6 CH  2 a  3  -3.45 (br)  10.07  5.78  13.06  2.28  10.23  5.96  13.15  2.40  10.1 (br)  2.1 (br)  7 + CCl/  4.2 (br)  - Measured at 300 M H z at 293 K. Unless stated otherwise, the multiplicity for each signal of die macrocycle is as follows: C H  2  (quartet, q), H  m e s o  (singlet, s), C H  (triplet, t), br = broad. - From Reference 45b. £ From die reaction of [Ru(OEP)] with CH C1 . 2  2  2  - From the reaction of [Ru(OEP)] widi HCI in CH C1 . J4 was also syndiesized 2  2  2  from this reaction, but the data are not shown. £ From the reaction of [Ru(OEP)] widi CHC1 . 2  3  - From the reaction of [Ru(OEP)] widi CC1 . Product is diamagnetic. 2  4  135  3  coordination sites because upon such ligand coordination, the metal is known to move more into the porphyrin plane. " Although the differences in position ( A <5) of die two mediylene resonances 5  ( C H - C H ) i n C D C 1 , C D , or C D 2a  2b  2  those for THF-d  8  2  6  6  7  are similar (14.99, 15.05, and 15.04 ppm respectively),  8  (14.52 ppm) and MeOH-d (12.54 ppm) suggest stronger association of these two 4  solvents. In contrast, the resonances for the protons of the O E P macrocycle for Ru(OEP)(py) , a 2  six-coordinate complex  which is known not to dissociate a pyridine ligand in solution, vary only  0.1 ppm i n the solvents C D , C D , C D C 1 6  suggest that THF-d  8  6  7  8  2  and C D C 1  2  3  (see Section 3.2.c). While these results  or MeOH-d coordinate to 7, the possibility that C D C 1 , C D 4  also be coordinated, albeit  2  2  7  weakly, cannot be discounted. For example,  reaction was observed between 7 and CU Cl(^  6  CDC1 , an instantaneous reaction occurred (as judged 3  6  a  95  6  by die difference  3  in CDC1  6  in C D , but when 7 was dissolved in  3  reddish solution formed  or C D may  dichloromethane as  coordinated ligand in a silver/palladium heterobinuclear complex has recently been reported. No  8  in color  between  the  and the greenish color of 7 in aromatic solvents) to give a  mixture of species, the major fraction of which had a H N M R spectrum similar to that of J_3 ]  (see Table 4.6); of interest, no 14 was detected. The reaction of 7 with C H B r 2  to be instantaneous; however, the 'H N M R spectrum reaction in C D 6  6  of an isolated  2  also was observed  crude product from  this  had signals from five different compounds as judged by the number of H  m c s o  and C H resonances present in the 9-10 and 2 ppm regions, respectively. When 7 was dissolved in 3  CC1 , an instantaneous reaction ensued, but the product solution did not give a 'H N M R spectrum 4  similar to that of 13/14 (Table 4.6). A l l these in situ products (except those from the 7 / C H C l 2  2  system) were not stable widi time, die 'H N M R spectrum for each system showing ca. twenty signals between 0-10 ppm after a few days. A possible explanation for the complex observed between 7 and CHC1 , C H B r 3  2  2  or C C 1  4  reactions  is that radicals are generated in situ which  attack the macrocycle, thus reducing the overall symmetry of die OEP ring. An  instantaneous reaction occurred when 7 was dissolved in C H C H C 1 6  5  2  at room temperature,  and the isolated product, when dissolved in C D , had an H N M R spectnim which showed that 1  6  6  136  the product was a mixture of four diamagnetic products. The same products were detected when two equivalents of C H C H C 1 were added to 7 i n C D , the reaction being much slower in this 6  5  2  6  6  latter case. The four porphyrin species were dissimilar to 13/14. and because of the complicated nature of this mixture, the isolation of these products was not pursued further.  4.2.h. The fate of the H in HX upon oxidation of 7 by HX in toluene and benzene. It was initially thought that H  2  would be generated during the oxidation of 7 by H X in aromatic solvents, but  diis possibility was ruled out when initial attempts to detect H of GC  2  by G C failed.  37  However, because  the later established 4:1 stoichiometry between HCI and 7 (Section 4.2.b), and because better equipment  was available,  96  these initial  experiments  to detect H  experimental details presented in Chapter 2); however, no H  2  2  were repeated  7  Again, no dihydrogen could be observed  8  the  was detected by G C (see Figure  4.17). Because of the key nature of this negative result, vapor samples taken from flask containing 7 and H B r in C H  (see  the reaction  were injected into a mass spectrometer to analyze for H . 2  was detected in the reaction mixture aldiough blanks indicated  easily at the expected levels. To address die possible loss of H  2  that H  2  from the  syringe used to inject the vapor samples from the reaction flask into the gas probe of the MS, a direct sampling apparatus was designed (see Figure 2.1). The use of this apparatus showed again that dihydrogen was not present in the reaction vapor phase. Samples of the filtrate of the reaction mixture from detection of H , and the H B r / C H 2  7  8  solution without 7, were injected into both a G C and a  GC/MS in attempts to detect the loss of H reacted  with  H B r in C H 7  8  the above study involving the possible  2  due to possible solvent hydrogenation. When 7 was  (two attempts), C D 6  6  (once)  or C H 6  6  (one attempt)  under the  conditions previously described in die experimental Chapter, all die resulting solutions except one of  the C H 7  8  reaction mixtures tested negative for hydrogenated  4.18a/b). In the one exception, the solvent was both hydrogenated  toluene or benzene (see Figure and brominated (Figure 4.18c);  however, this appears to have occurred as the solution (with and without 7 present) reacted with die  silicone septum used to seal the flask. A similar reaction of Ru(OEP)CO in C H 7  137  8  with the  Figure 4.17:  Gas chromatograms of (a) the vapor phase sample from the 7 (85 mg, 67 //mol) and HBr/C H 7  (5 mL)  g  H /HBr/C H 2  7  conducted  8  reaction mixture, and (b) the corresponding H  mixture (500 / i L sample, 12 /imol). A n  was  that  involving  addition  of H  completion of the synthesis reaction. The GC  2  control from a  2  additional control experiment  to the 7/HBr/C H 7  8  solution after  trace from this last control experiment  was identical to that shown in trace (b) below. The reaction of 7 with HBr should generate 134 /imol of H . 2  A  to  in  CO  CM CM  B  CM  138  Figure 4.18: Mass spectra obtained from the GC/MS of (A) a 0.5 uL sample of the solvent from the  reaction  of 7  with  HBr in C H , 7  hydrogenated/brominated C H 7  8  (B) the C H  8  7  control,  8  and (C) the  obtained upon reaction of C H / H B r with the silicon 7  8  septum.  •M-1 M r C H 7  i» .  B  i  |'»'i  i ' i  1  i  •M-1 >»  _  B«  _  76  _  IB  _  SB  _  ie  _  38  _  IB  _  II  _  LwJl 'I ' " j '  f  Iff  I'" I" i '  i—i—i—pr  us  in  C »f  M+1+Br  •f 71  tl  M+1  it IB 3B  2t If  f  13  -r-"*i—|—r  Iff  139  in  171  8  septum was documented i n Section 3.2.b. The three other attempts were done in a Teflon valvesealed  flask, and no hydrogenation  or bromination  method of testing for the possible hydrogenation concentrated sample of 7 i n C D 6  6  repeated  than those  using  DC1  solutions was observed. A  (10 mM) with H B r i n a sealed tube, and to study the in situ spectroscopy. Even after 60,000 scans (FT), no  for the solvent and excess H B r were detected.  and C H , 6  6  second  of solvent by the HX/7 mixture was to react a  system (which contained a suspension) by 'H N M R signals other  of these  and the resulting  "suspension"  This  experiment was  was analyzed  by H 2  NMR  spectroscopy, yielding the same conclusion in that only the signal for DC1 was seen (only 5,000 scans were accumulated, however). The  reaction of 7 with excess H B r in the presence of two mole equivalents of cyclohexene or  1 atm of C H 2  shown  in C D  4  7  by the H ]  8  gave Ru(OEP)Br  NMR  2  spectra of these  exception, no hydrogenation  (8a) without any hydrogenation solutions. A l l these  of the added olefin as  results suggest that, with one  of the solvent or an added olefin occurred during the reaction of 7  with HBr. When HCI was added to a mixture of 7 and 100 equivalents of T E M P O (TEMPO is tetramethyl-l-piperidinyloxy, a free radical t r a p ) product  was not Ru(OEP)Cl  UV/visible spectrum ( A pyrrole  ring  2  =  m a x  had occurred.  characteristic sharp,  in C D  53b  6  6  at N M R  sample concentrations, the  (8b), but instead the reaction gave a ° greenish  solution whose  680 nm) suggested that reduction of a double bond of an OEP These  ring-reduced  compounds  strong absorbance at 680 nm  are termed  'chlorins'  in their visible spectrum.  and have a  This  97  result does  imply, however, that the HX/7 reaction in aromatic solvents occurs via a radical pathway, as does the reaction of 7 and HCI or CH C1 . 2  In light of the complicated hydrogen atoms presumed  2  radical-based reactivity of the 7/HX or 7/HX/CH Cl 2  to be formed during  the reaction of H X  2  with 7 could  systems, the be trapped  possibly by the solvent and other species formed in situ, diluting die amount of any one product to an undetectable  level. Although  this explanation is weak, with the experiments performed to  date, the fate of the required 'hydrogen' co-product remains unsolved.  140  4.2.i. The effect of the acid HX used. Although B r reacts with 7 (in a 2:1 stoichiometry) to give 2  8a,  37  this  synthesis route  is inferior  to the H X  method  stoichiometric amount of B r to 7 results in the bromination 2  aqueous acids, HX( ^, also react with  7 under anaerobic  aq  because addition of more of O E P macrocycle. conditions to yield  than a  As expected,  37  monomeric R n  ! V  complexes analogous to 8. When X = Br or CI, 8a or 8b respectively were generated, and when X =  SbF , the new compound R u ( O E P ) ( S b F ) IV  6  6  Figure 4.19)  2  (8d) was obtained. The 'H N M R spectrum of 8d (sec  is similar to those of 8a-c. This new product rapidly decomposes in air, yielding  R u ( O E P ) ( S b F ) (15) upon attempts to purify 8d by precipitation techniques  (see Section 2.3.b);  m  6  the H N M R J  spectrum of 15 is consistent with that reported for Ru(OEP)(SbF )THF.  37  6  complex was prepared  by reacting A g S b F  6  This latter  with 8b in T H F under anaerobic, dark conditions;  37  presumably 8d is generated first, which then undergoes Ru-F bond homolysis to generate L5. The  acids attempted to date and their pK^'s in aqueous phase (unless stated otherwise) arc  presented below: ' 98  99  HX: pK,:  H 38 -  MeOH 15  HX: pK,:  HF 3  CF3COOH 0.2  2  s  H 0 15 2  H S 7  CH COOH C H COOH 4 4  2  3  HNO3 -2  HBF -3  4  6  HCI -7  5  HBr -9  HSbF <-10  6  - Measured in the gas phase.  It was found that excess H F ^ or HF ^ does not react with 7 in C D (aq  6  while excess C F C O O H  6  3  does and, presumably in the p K j range 3 to 0.2, reactivity of 7 toward H X is first observed. Ii should  be emphasized  solution, ' 98  99  that  the p K j scale used  while the studies presented  here  An  98  estimated  values  in aqueous  here were conducted in C D . However, in general, the 6  scale appears to work well for predicting which H X example, HI (pK,, < -10)  represents  reagents  6  are likely  to react with  7.  For  would be expected to react with 7.  exception to this rule is the reaction of H S with 7, which resulted in a green residue 2  that was sparingly soluble in C H C 1 2  2  and whose 'H N M R spectrum (6 C H 141  3  = 1.92 (t); C H  2  = 4.05,  Figure 4.19:  'H N M R in C D 6  Spectra of Ru (OEP)(SbF ) IV  6  6  2  formed in situ by the addition of H S b F  under N . Obtained at 293 K, 300 MHz. 2  6  to 7  The other signals observed in the  spectrum arc suggested to arise from impurities from the HSbF ( ^ or from other 6  aq  Ru(OEP) complexes formed in low yields.  i i i •[ l i i i I i i M I i i T r p 14  12  i i i I i i i i | i i TT-rrr i i | i i i i i i i n 10  8  6  | i i i r-rrri i | i i i i i i i i i | i i i i i i i i i | i i i i i i i i i|  4  i  6  -2  3.97 (m); H  m e s o  = 10.37 (s); UV/visible spectrum in C H C 1 2  2  = 370 (sh), 392 (Soret), 516, 548 nm;  compare these data with those provided i n Table 4.1) was very similar in pattern (but not in position) to that of the bridging  U-OXO  dinuclear species [Ru(OEP)OH] 0 (9). A possible product 2  which would generate the observed spectrum is (HS-)(OEP)Ru-S-Ru(OEP)(-SH). the  reaction of aqueous C F C O O H , H B F 3  4  or H N 0  3  with 7 in C D 6  6  The products from  were in each case found to be  a mixture of compounds and, as such, were not identified. The synthesis of 'Ru(OEP)F ' from 7 2  and  H F ^ (the route analogous to that used for 8a-b) was reported during the Master's thesis  work,  36  but could not be reproduced. From the results of the reaction of 7 with various aqueous  acids, it is apparent that Ru(OEP)F gaseous  cannot be generated by die reaction of 7 with H F (either  2  or aqueous) in C D ; thus, some other unknown oxidant must be responsible for the 6  6  observed formation of Ru(OEP)F  2  from 7. Thus the data show diat a H X acid with a p K  than 0.2 will react with 7, and those that have a pIC,  a  less  of -7 or lower will react with 7 to form  complexes of the type R u ( O E P ) X . The data show diat 7 is a weak base, requiring strong H X IV  2  acids to initiate reactivity.  4.2.j. Generation of Ru(porp)X (8) from Ru(II) sources. While 8a and 8b can be easily prepared 2  from the dimer 7, the H X (X = Br, CI) oxidation of monomeric Ru(OEP)(L) yield 8a-b. Solutions of Ru(OEP)(py)  2  (6a) in C D 6  6  very  =  2  = 12.10, 10.22;  Ru(OEP)(CH CN) 3  2  when this  to air. The two step formation of 8b from 6a via the generation of the  solid samples of this complex  6  = -1.75; C H  similar to that of Ru(OEP)Cl(py). Further reaction to give 8b occurs rapidly  intermediate can be avoided by removing  6  3  -3-98, all resonances appear as broad signals; refer to Table 5.4, Section 5.2.d.2) looks  mixture is exposed  C D ;  complexes can also  react rapidly with gaseous HCI under inert  conditions to give an intermediate whose 'H N M R spectrum (6 C H Hmeso  2  the coordinated pyridine of Ru(OEP)(py)  at high temperatures under high vacuum to yield 7.  2  25  by heating In contrast,  (6b) directly yields 8b within six hours upon anaerobic oxidation by HCI in  however, the synthesis of 6b from  unreacted Ru(OEP)CO(MeOH) contaminant,  37  Ru(OEP)CO(MeOH) always  results in some trace,  and the use of 6b as a precursor is not the best  143  route to synthesize species such as 8a, 8b. An interesting discovery made during these studies of the oxidation of 6a by HCI was that aerobic oxidation of 6a in the presence of H X yields novel species formulated as [ R u ( O E P ) ( p y ) ] m  X" (X = CI, 17a; B F , 17b, see Section 5.2.e) instead of  +  2  4  8b or 8c, respectively. Other Ru (porp) complexes, as exemplified by the anaerobic  oxidation of Ru(TMP)(CH CN)-,  IV  (6d) by H B r to generate Ru(TMP)Br observed in the 'H N M R  2  (8e), can also be synthesized. Figure 4.20 shows the changes  spectrum of R u ( T M P ) ( C H C N ) 3  under anaerobic conditions; R u ( T M P ) C l method  (but only  3  2  2  upon bubbling H B r ^ into the solution  (8f) can be generated analogously using HCI via the same  the bromide analogue was isolated  Surprisingly, the reaction of Ru(TMP)(py)  2  and fully  characterized, see Table 4.5).  (6cJ with HCI does not yield 8f, in contrast to the  findings for O E P system. The T M P complexes 8e and 8f can be also generated by the reaction of HX  f e )  (X = Br, CI) with Ru(TMP) or R u ( T M P ) ( N ) 2  Ru(TMP) and R u ( T M P ) ( N ) 2  2  2  in aromatic solvents. However, because both  are more unstable than R u ( T M P ) ( C H C N ) 3  towards oxidation by trace  2  H 0 / 0 , die easiest route experimentally into Ru(IV)TMP compounds is via the Ru(TMP)(CH CN), 2  2  3  route. The  formulation for 8e was based on similarity of the synthesis procedure for 8e to that used  for the R u ( O E P ) X  2  (X =  Br, CI) complexes, and from  the microanalysis data. The infrared  spectrum of 8e as a Nujol mull using Csl windows offers no details of the bonding of ligands in the axial positions (no w  Ru-Br band was observed), while die EI-MS of 8e shows the peaks tor  Ru(TMP) (881 vale') and Ru(TMP)Br (960 vale'). The  assignments of the 'H N M R  resonances of 8e were made by correlating the observed  linewidth of each resonance with the distance of the proton from the metal (see Section 2.3.b), and  64  by integration. The trend in the change in position of the proton signals of T M P from their  position in diamagnetic R u ( T M P ) complexes, IV  complexes to those in 8e and 8f is similar to those reported for other 39  as well as that observed  additional resonances for die ortho- and para-mediyl 144  for Ru(TPP)Br ,  5a  2  protons  are present  with  the exception  that  for 8e instead of the  Figure 4.20: H NMR  Spectra of (a) Ru(TMP)(CH CN)2 <6d) in 0,D  !  3  and, (b) Ru(TMP)Br (8e) in  t  2  C D . Obtained at 293 K, 300 MHz (FT) in vacuo. 6  6  CHgCN  u  Ru  —t  pyrr  CH CN  o-CH.  3  CH CN 3  pyrr  > 7 8 C  H  l l | I I l I | I l I I | I I I I [ I I I I | I I  8 "  6  I I | I I I I | M I I | I I I I | I I l l | l I I I | I II  4  2  0  PPM  o-CH, H, pyrr pyrr  I I I | I I I I | I II I | I I I I | I  -44  -45  P-CH.  IM | -46  m  C  6 6 H  .•J  j M  -,4  I I | M  M  I I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I  12  10  8 145  6  4  PPM  ortho- and para-protons of Ru(TPP)Br . The presence of only one 'H N M R  signal for  2  methyl  groups  of  the  mesityl  group  of  TMP  indicates  that  the  complex  o-  the  is symmetrically  substituted in the axial positions. From  Figure 4.20b, it is apparent  paramagnetic, and  that  8e  and  Ru(TMP)Cl  the corresponding plot of isotropic shift vs. 1/T  185 to 373 K for 8e in C D 7  d,  56  are  4.5)  for the data measured  55  from  magnetic susceptibility for  at 293 K) is consistent with a spin-only value of 2.83 B.M.  intermediate spin-state).  4  Table  indicates that only one spin state is occupied over this temperature  8  range (see Table 4.7 and Figure 4.21). The solution Evans' method (2.73 B.M.  (8f) (see  2  for a S =  Thus, these data are consistent with the suggested  8e  1 system ( R u , lv  formulation  of  R u ( T M P ) B r for 8e. IV  2  This compound differs from aerobic oxidation, yielding spectroscopy. The  OEP  the OEP  Ru(TMP)(0)  analogues  14b 2  analogues '  (8a and  42  8b) in that it is unstable toward  (8a and  within a day  in C H , as judged 7  g  by  8b) were air-stable for weeks in solution.  difference is the thermal stability of 8e in solution. Complex 8e can be heated in C D ) under 7  8  vacuo  at 373  K  for days  UV/visible  3  3  (or  an  after only a few hours. Lastly, 8e-f  are  quite soluble in aromatic solvents, unlike the OEP analogues 8a and 8b.  146  CDC1  decompose to  widiout decomposition, while 8a-b  insoluble green product when heated to reflux in CDC1  Another  Table 4.7: Data for the plot of isotropic shift (ppm) vs. 1/T (K' ) for Ru(TMP)Br (Se)A 1  2  T(K)  1/T(K)  185  5.41xl0-  204  «H (obs/iso^  «o-CH (obs/iso)^ 5p-CH (obs/iso)^ c5H „ (obs/iso)^  m  3  3  r  rr  17.14/9.88  5.72/3.51  5.28/2.74  -68.18/-76.83  4.90  16.20/8.94  5.37/3.16  4.93/2.39  -63.29/-71.94  224  4.46  15.38/8.12  5.09/2.89  4.83/2.30  -58.66/-67.31  243  4.12  14.69/7.43  4.84/2.64  4.40/1.87  -54.22/-62.87  264  3.79  14.09/6.84  4.62/2.42  4.13/1.59  -50.18/-58.83  284  3.52  13.56/6.22  4.43/2.22  4.00/1.46  -46.41/-55.06  303  3.30  13.15/5.88  4.27/2.07  3.88/1.35  -43.24/-52.89  323  3.10  12.77/5.51  4.15/1,94  3.75/1.21  -40.22/-48.87  353  2.83  12.48/5.21  4.04/1.84  3.66/1.12  -37.69A46.34  373  2.67  12.21/4.94  3.94/1.74  3.57/1.03  -35.52/-44.16  3  °- Obtained for a 5 mM solution of 8e in C D in vacuo, _+ 1 K at 300 M H z (FT). 7  8  - (Observed/isotropic) chemical shift in ppm, diamagnetic correction made from data for R u ( T M P ) ( C H C N ) : d5H = 7.26 ppm, 6 o-CH = 2.21 ppm, 6 p-CH = 2.54 ppm, 5 H 3  2  m  3  ppm.  147  3  p v r r  =  9.26  Figure 4.21:  Plot  of the isotropic  shift  (ppm)  vs. 1/T  ( K ) for Ru(TMP)Br . -1  represent the least-square fit of the data with extrapolation to 1/T = 0.  148  2  Solid  lines  Chapter 5. Further characterization of Ru(OEP)X complexes and synthesis, characterization and 2  and chemistry of several new Ru (OEP) complexes. m  5.1. Introduction.  In the earlier Masters work, the inability to oxidize chemically RuOEP)X (X = Br, 8a; CI, 37  2  8b) either the metal to the Ru oxidation state or the macrocycle to a »r -cation radical in 8a-b v  to generate higher oxidation compounds of ruthenium porphyrins was noted, as was die facile reduction of 8a and 8b to generate R u complexes. These results suggested at the time that the m  reduction potentials for the  Ru^/Ru™ and Ru (OEP )/Ru (OEP) couples were both relatively rv  +  IV  high. Consequently, studies were initiated to measure these reduction potentials, and these results are discussed in Section 5.2.a. Also of interest is the observation diat while the dihalogeno derivatives of Ru (OEP) are IV  paramagnetic with S = 1 (die first examples widiin monomeric Ru (porp) complexes), the diaryl rv  and dialkyl derivatives are diamagnetic (S = 0). The measurement of the magnetic properties of 8a over the temperature range 6-300 K was thus undertaken in order to understand more fully the differences  in the electronic ground states for these Ru  IV  complexes.  These data, which are  presented in Section 5.2.b, suggest that 8a has magnetic properties unlike those measured for other  Ru  IV  noii-porphyrin  complexes,  in  having  contributions  from  effects  other  than  temperature-independent paramagnetism. As discussed in the introduction (Chapter 1) of tiiis thesis, die number of Ru coordination 111  complexes of porphyrins are synthesize a variety of R u  f m  e w  .  1 6 a  >  1 7  '  2 8  >  3 0  ~  3 2  Sections 5.2.d and 5.2.e outline attempts made to  complexes of OEP from 8a-d, utilizing the knowledge of the  reduction potential for die Ru^/Ru  111  couple. Attempts to generalize the synthetic route first  encountered in the reaction of 8a-b with AgX' salts (X' = SbF , PF and BF ) 6  6  4  37  showed that this  route was inferior to that developed using amines as reducing agents. Section 5.2.d documents the synthesis, spectroscopic characterization and chemistry of the new complexes Ru (OEP)X (X = Ill  Br,  16a; CI, 16b). which were synthesized by reducing 8a-b with amines. Because these five-  149  coordinate, I5e' complexes have been sought as possible catalysts for the oxidation of organic substrates, analogous to the reported behavior of Fe (TMP)Cl, m  particular emphasis was made to  41  study the oxidation chemistry of 16a-b. Section 5.2.e describes the aerobic oxidation of Ru(OEP)(py) in the presence of HX acids to 2  generate products of the formulation [Ru(OEP)(py) ] X (X = CI, 17a; X = BF , 17b). These +  -  2  complexes  are  six-coordinate,  1:1  electrolytes.  4  The  electrochemical data measured for Ru™ and R u  m  last  section  (5.2.0  summarizes  the  complexes discussed in this chapter, with an  emphasis toward explaining their lack of activity as catalysts for the oxidation of cyclohexene by oxygen atom sources. 5.2. Results and Discussion. 5.2.a. Electrochemical studies of Ru(OEP)X, (X = Br, 8a; CI, 8b). The reaction of 8a± with oxidants such as  or PhIO resulted in die complete destruction of the macrocycle, as  JWCPBA  evidenced by the bleaching of the colored solutions of 8a-b.  37  The decomposition of 8a-b upon  chemical oxidation by PhIO or mCPBA was surprising and, therefore, cyclic voltammetric studies of these complexes in CH C1 2  voltammogram  shows  two  Ru (OEP )/Ru (OEP) IV  +  (see Figure 5.1) were pursued to perhaps understand why. Each  2  reversible  waves  assigned  (see  below)  to  the  couples at roughly -160 and 740 mV, respectively,  IV  Ru /Ru ,v  vs.  in  and  the internal  ferrocene standard: reduction potentials* redox couple  X = Br  X = CI  -154  -170  782  694  Ru (OEP)X /[Ru (OEP)X ]IV  m  2  2  [Ru (OEP )X ] /Ru (OEP)X IV  +  +  IV  2  2  * _+ 10 mV vs. Fc /Fc in CH C1 in 0.1 M («-Bu) N C10 " at 293 K; the +  +  2  2  4  4  Fc /Fc couple in CH C1 is at 632 mV vs. NHE. +  2  2  The peak-to-peak separation for each wave is approximately 70 mV, indicating that each redox  150  Figure 5.1: Cyclic voltammograms of (a) Ru(OEP)Br («-Bu) N 4  +  C10 " (TBAP) in C H C 1 4  2  2  2  and (b) Ru(OEP)Cl . Data measured in 0.1 M  under an N  in Volts relative to the F c / F c couple. +  151  2  2  atmosphere, 293 K. X-axis scale is  couple is a reversible, one-electron process. The  4  only other redox datum available for a R u ™  dinuclear species [Ru(OEP)OMe] 0 (9'), which was 2  wave at approximately  -1  V  vs. Ag/AgCl.  porphyrin complex is diat for the /x-oxo  found to have only one  the  ligand  Ru^/Ru  couple  111  systems; and  in complexes with  tetraazacycloalkyl- " 100  much of these data fall  within the -85  comparable to the values found for 8a-b. The  IV  +  H  +  was  reported as 665  reduction potential also involves protonation of the Fe true  estimate  of  the  Fe /Fe I V  Bu) )] /Os (porp)Br(P(w-Bu) ) +  mV  3  for die TPP  couples  will  be  106  analogue. discussed  108  The  after  vs. F c / F c +  pyridyl- " 1 0 3  mV  based  1 0 5  range vs. Fc /Fc, +  The  107  implication  mV  couple. The  IU  Os^/Os  ,v  therefore may  couples  111  for  a  system and 3 6 5  potentials for the complexes  111  be  IV  +  several Ru  not  [Os (porp)Br(P(/?-  vs. F c / F c for the OEP  from  but this  +  of the measured  electrochemical data  Fe /Fe'" couple  vs. F c / F c at 2 3 3 K,  species, and  111  were reported as -135 mV  m  3  couple. -  m  mV  that the porphyrin perhaps plays a  IV  m  and  102  to -135  the reduction potential of the R u / R u  for F e ( T M P ) 0 / F e ( T M P ) O H  to -135  non-  absence of a delocalized aromatic ring system such  as a porphyrin within the tetraazacycloalkyl systems suggests minor role in determining  reduction  However, there are many measurements on  31  porphyrin ruthenium complexes, with reduction potentials ranging from 555 for  unassigned  Ru^/Ru  111  have been  presented. A  further  confirmation  of  the  assignment  of  the  Ru /Ru I V  coulometric reduction of 8a by one-electron equivalent at -235 (see Chapter 2  for the details needed to perform  mV  couple  m  (see Figure 5.2). This process was  oxidation at 265 present.  This  experiment experiments.  mV  vs. F c / F c , while the C V +  seeming  involved  contradiction can  between  die  CV  be scan  that  controlled  vs. F c / F c yields Ru(OEP)Br +  the coulometry  experiment and  Chapter for details of the spectroscopic properties of Ru(OEP)Br) as monitored chemistry  is  found to be irreversible on  later in this  by spectroelectro-  attempting  coulometric  data show diat a reversible one-electron process is explained  by  the  (seconds) and  the  difference in timescale bulk  coulometry  If there is appreciable dissociation of a halide from die generated  152  of  the  ( 3 0 minutes) [Ru (OEP)Br ]" m  2  Figure 5.2:  Bulk coulometry of Ru(OEP)Br before coulometry at -235 mV  2  (8a). Trace A shows the optical spectrum of 8a  vs. F c / F c in 0.1 M +  T B A P in C H C I . Trace B shows 2  2  the generated optical spectrum, which corresponds to that of Ru(OEP)Br given in Section 5.2.d.  wavelength  to give  Ru(OEP)Br  (as in the  coulometric  experiment),  then the  reduction  potential for this  product will be different from that for [Ru(OEP)Br ]\ 2  The  reduction potentials at 800-700 mV  process. The  vs. F c / F c for 8a-b  bulk electrolysis of Ru(OEP)Br  T B A P electrolyte was  are assigned to a ring oxidation  +  (8a) at 900  2  mV  vs. F c / F c in C H C 1 +  2  followed using a spectroelectrochemical cell. Bulk  2  with 0.1  M  electrochemical oxidation  of the solution with time results in the loss of the intensity of the absorbance of the solution in the wavelength range 300-700 nm  (see Figure 5.3a), but the solution retains a greenish  color after this oxidation, showing that the porphyrin ring remains intact. The this in situ product measured at 77 K (Figure 5.3b)  showed a signal at g = 2.01  from the position of the signal to a TT-cation r a d i c a l . ' "  linewidth), assigned  29  109  of the difference in potential for the first ring oxidation ( ( O E P ) / O E P ) and (OEP/(OEP')) couple for a range of Ru(OEP) complexes shows important ring-oxidation occurs  A  mV  and  vs. Fc /Fc,  565  mV  5.1)  is tentatively assigned this  8a-b is approximately 2100  Also, a study  111  trends:  (1) the first  112  +  -1335  mV  vs. F c / F c , not shown in +  to the first macrocycle reduction potential for 8a-b,  first-reduction  potential to  that for the  first-oxidation  Br, 8a; CI, 8b; BF , 4  2  are  paramagnetic (S  d  4  =  potential of  complexes (X  IV  2  Ru(OEP)R  because  mV.  5.2.b. Further studies on the magnetic properties of R u ( O E P ) B r . The R u ( O E P ) X =  G  and (3) this difference in potentials is invariably 2000-2400 raV.  +  difference between  (3200 G, 20  vs. F c / F c , (2) the first ring-reduction couple  reversible potential near the solvent discharge range (ca.  Figure the  between 965  spectrum of  first ring-reduction  +  occurs near -1435  ESR  brown  8c and  systems,  SbF , 8d) and 6  but  the  latter  are  2  their organoruthenium(IV) porphyrin derivatives diamagnetic  while  the  former  1). Three ground-state d-orbital occupancy types for these d  4  (8a-d)  are  complexes are  possible: (a)  The  _(L2  — W  (b)  _d 2.y2 _ cL2 x  (c)  _  d ^ _d 2 z  x/y plane for the above diagrams is defined by that which includes the four Ru-N 154  bonds. The  Figure 5.3:  (a) Changes  observed  in the optical  coulometric oxidation of 8a at 900 mV  spectrum  of Ru(OEP)Br  vs. F c / F c in 0.1 M +  2  (8a) upon  T B A P in C H C I . Time 2  between scans was 6 minutes, (b) ESR spectrum of the solution generated in part (a).  4 0 0  6 0 0  WAVELENGTH  .nm  bulk  2  Figure 5.3b: 9.03 GHz, 10 mW  microwave power, 100 G sweepwidth. The spectrum was measured  at 77 K as a frozen C H C 1 glass sample. 2  2  Ru  organometallic complexes are diamagnetic  and so type (c) occupancy is present. Because X-  ray crystallographic data for ruthenium porphyrin complexes containing a variety of axial ligands generally for  show that tetragonal elongation distortion is present,  the paramagnetic  complexes  8a-d; however, the other  discounted. The magnetic moment of Ru(OEP)Br  occupancy  53  type  type  (b) is favored  of occupancy  (a) cannot be  (8a) measured as a solid sample at 300 K (2.65  2  B.M., see Table 5.1) agreed well with that from the solution Evans' method measurement (2.55 B.M.) made earlier for the same complex at 293 K.  37  However, from the plot of x  (corrected) vs. T, (see Figure 5.4) it is apparent that 'non-ideal' behavior present because the corrected magnetic moment l/x  (M ff e  c o n  )  a n m  d M rr c  for a paramagnet is  decreases as the temperature drops, and  (which can be inferred from Figure 5.4) appears to deviate from a linear relationship with  m  temperature as predicted by the Curie law:  X  In the earlier Masters work, CDC1  3  37  m  = C/T  (5.1)  the reported Curie plot of isotropic shift vs. 1/T for 8a-b in  for the temperature range 223-323 K showed that significant deviation of the data from  ideal Curie behavior  was present. Normally,  this deviation from die expected theoretical  behavior  is explained by invoking anti-ferromagnetic coupling between two or more paramagnetic centers, leading  to a decrease in the magnetic moment for die complex. Antiferromagnetic  common but  i n polymers where there is significant  in porphyrins  molecules  of which  two- and three-dimensional  this effect is usually observed are closely  conditions do not apply  separated  in both  the solid  coupling is  structure  in coordinatively unsaturated  56  present,  56  complexes, the  state and in solution.  113  These  to 8a because it is coordinatively sadirated, and the steric bulk of the  macrocycle prevents two or more molecules from getting close together. An d , xz  alternative to die anti-ferromagnetic  coupling  explanation  is that  the t  2 g  orbitals ( d ,  and d ) of the ruthenium in 8a are closely spaced in energy and that a thermal xy  157  x z  population  Table 5.1: Corrected magnetic susceptibility and moment data for RufOEP^BrT.-  T_1K£.  y . x 10 c.g.s. units£ 3  m  it . cff  BMA  6.00  16.85  0.90  7.00  15.36  0.93  8.00  14.19  0.95  10.00  12.49  1.00  12.00  11.37  1.04  15.00  10.21  1.11  20.00  9.00  1.20  25.00  8.32  1.29  30.00  7.85  1.37  35.00  7.51  1.45  40.00  7.26  1.52  45.00  7.03  1.59  50.01  6.91  1.66  55.27  6.77  1.73  60.35  6.65  1.79  65.00  6.54  1.84  69.98  6.42  1.90  75.30  6.15  1.92  80.40  6.11  1.98  90.00  6.05  2.09  99.90  5.84  2.16  110.70  5.62  2.23  120.68  5.41  2.28  158  Table 5.1 continued. x. m  x 10 C.E.S. units^ 3  iicff. B.M.4  130.30  5.23  2.33  140.68  5.04  2.38  161.48  4.65  2.45  180.00  4.64  2.58  200.00  4.02  2.53  219.90  3.84  2.60  239.93  3.51  2.60  259.90  3.31  2.62  279.87  3.10  2.63  299.82  2.92  2.65  - Data measured by Dr. C.A. Reed, University of Southern California, Los Angeles. ^ +_ 0.01 K uncertainty in temperature. - +_ 0.01 x 10" c.g.s. units uncertainty in die magnetic susceptibility. 3  ^ _+ 0.01 B.M. uncertainty in the magnetic moment.  159  Figure 5.4: Plot of M fr (corrected) and x e  (corrected) vs. T for R u ( O E P ) B r (8a). IV  m  2  0.02 o  o  o  . o  CO  eff CD •  o  W  o o  • •  o  0.01  o  9  o  •  CD  o  E  1  m  T  0.00  r  100  200  T, K  160  300  of  these orbitals exists such that the population represented by types a and b decreases with  temperature and the population represented by type c occupancy  increases. This would  lead to a  decrease of the magnetic moment as the temperature is lowered. There are many examples of this type of behavior i n porphyrin and other macrocyclic systems  of i r o n .  1 1 4  '  The presence of  1 1 5  spin-orbit coupling in 8a will alter these d-orbital levels such diat die newly-generated 'J' levels are  separated in energy by the amount indicated by the spin-orbit coupling constant.  this value is large (700 cm"  1  for R u ™ ) ,  116  Because  the possibility of a spin-state thermal equilibrium in  116  8a can be ruled out. The  reported magnetic susceptibility of the R u ™ complexes K R u C l , ( N H ) R u C l , 2  K RuBr 2  6  and K R u F 2  x  with  m  susceptibility  temperature (300-80  a significant  contribution  K) for the non-porphyrin compounds,  from  /i  e  f  f  vs. T  1/2  (as in  /x  e f f  Rb RuCl ,  6  2  6  1 at 300 K."  7  measurements indicated that there was little variance  temperature-independent  I V  = 2.83(x  m  x T)  1 / 2  117  whereas x  m  for 8a  non-porphyrin complexes  paramagnetism  contribution from TIP must be smaller than that for die non-porphyrin R u plot of  2  show that they are of the intermediate spin state (d ), S =  varies greatly with temperature (see Figure 5.5), showing that the R u have  4  4  6  Variable temperature magnetic of  6  l v  (TIP).  In 8a, the  complexes. Indeed, a  , see Figure 5.6) shows a linear dependence  except for die high-temperature region, where there is evidence that a contribution from TIP is present, the extent of which  cannot be easily  estimated because  of a lack  of data generally  within ruthenium(IV) systems. Thus, while the magnetic behavior for 8a remains unexplained, the contributions from thermal spin  equilibria  or temperature-independent  paramagnetism  have been  largely  discounted. Further  discussion of the data will have to await the availability of a larger database for Ru systems. An the  additional factor that could effect the relative energy levels of die ruthenium d-orbitals is  extent of the 7r-charge transfer from  the axial ligands to the metal, because  increase the energy of the d ^ and d ^ orbitals of the t of  the non-bonding  d  x v  2 g  this  would  set without affecting the energy level  orbital. The diamagnetic nature of the organoruthenium(IV) analogues  161  Figure 5.5:  Plot of  x  (corrected) vs.  m  T for  several Ru(IV) complexes including K RuF , 2  K RuCl (NH ) RuCl , Rt^RuClg, K RuBr and Ru(OEP)Br (8a). 2  6>  4  2  6  2  6  2  6 LEGEND  OT *C  o  KgRuF^  D  K RuCt g  6  Z  2 <NH ) RuCl  A  KgRuBr  x  Ru<DEP>Br  5  OT  4  6  6  0  o ro O  4  H x o  A  A  •  O A  A  3  X  4  150  250  TEMPERATURE, K  162  •  350  6  Figure 5.6:  Plot of T  m  vs. *» (corrected) for Ru(OEP)Br . eff  2  163  suggests that less »r-charge density is transferred to the metal from the aryl and alky] ligands (an expected result, considering the er-only (alkyl) and weak  rr -acceptor (aryl) nature of these  ligands when they are bound to Ru) compared with that transferred from the halide axial ligands to ruthenium. Normally, from the 'H N M R spectrum of each type of rudienium porphyrin complex, one case,  can qualitatively assess the extent of porphyrin-to-ruthenium charge transfer; the fact  that  the organometallic complexes  are diamagnetic  whereas  but in this  118  die coordination  complexes are paramagnetic makes even a qualitative estimate impossible. 5.2.c. Attempted generation of other R u ^ O E P J X ' j complexes (X' = B F , 8c; S b F , 8d, and P F ) 4  by metathesis reactions of R u ( O E P ) X  6  (X = B r , 8a; CI, 8b) with A g X ' salts. Because of the  2  changes i n the magnetic properties of these ruthenium porphyrin complexes axial  ligand  6  coordination, the generation of R u ™ complexes  with changes in the  other than 8a-b was attempted to  ascertain i f there was an explainable trend in magnetic behavior. One route previously attempted was to exchange die axial ligand of 8a-b by metadiesis with AgX' (X' = SbF , P F and B F ) ; 6  the other was to generate Ru(OEP)X'  2  species from the dimer [Ru(OEP)]  2  6  37  4  (7). In Chapter 4, the  synthesis of some of these R u ( O E P ) complexes from 7 was accounted. Here, the details of the IV  reactions of 8a-b with AgX' salts are presented, h i die Masters study, of 8a;b with A g S b F  in  6  I V  to R u  111  occurred either via the oxidation of A g  homolysis of die Ru-F bond within Ru-SbF 6  2  the attempted metathesis  in T H F was shown to give Ru (OEP)(SbF )THF, and it was suggested that  6  this reduction of R u  Ru(OEP)(SbF )  37  to give Ru(OEP)SbF  the reduction of R u ™ to R u of Ag . In testing 1  111  6  6  11  or via the  (15) was documented in Chapter 4; therefore the route for  is considered to be via bond homolysis and not via the oxidation  the generality  of this AgX' metathesis reaction, it is observed  that two major products were formed  6  6  6  with 8a in CDC1 , it was apparent  in a 2:1 ratio. The H N M R  (4H); 18.4, C H  ]  2  that facile  = P F and SbF ). From analysis of the 'H N M R  spectrum of the reaction mixture of two equivalents of A g P F  m e s o  to A g  by some undetermined manner. The auto-reduction of  reduction occurs in two of three cases (with X  mixture (24.5 ppm, H  1  (16H); 0.0, C H  164  3  3  spectrum of this reaction  (24H); and 32.7, H  m e s o  (4H); 10.1, C H  2  (8H); 5.6, C H later  3  in this  (24H); -7.0, C H Chapter).  The  (8H)) suggests the formation of R u  2  components  of  this  mixture  chlorinated solvents but not in aromatic solvents), and  had  species (see data presented  m  similar  could not be  techniques; nor could they be separated by chromatography due  solubilities  (soluble in  separated by  precipitation  to decomposition of the mixture  on die column (alumina, activity I, neutral, 1 x 10 cm, C H C 1 eluent). 2  2  In the reaction of 8a with A g B F , R u ( O E P ) ( B F )  (8c) was generated as evidenced by the 'H  rv  4  NMR HBF  spectrum  The  2  of the reaction mixture; this spectrum  to the 13/14  4 ( a q )  4  was  identical to that generated by  mixture formed by the reaction of [Ru(OEP)]  widi C H C 1  2  2  2  adding  (Chapter 4).  latter route is preferable for die synthesis of 8c because the difficult task of separating the  Ag products from the reaction mixture of 8a-b with A g B F can be avoided. 4  Thus, the best route to syndiesize R u ( O E P ) X ' IV  oxidation of 7 with HX'  2  (X' =  SbF , B F 6  and presumably  4  P F ) is via 6  acids in aromatic solvents, and not by the reaction of 8a-b with  AgX'  salts. 5.2.d. Synthesis, characterization and chemistry of Ru(OEP)X(L) (X = Br, L = vacant, 16a; X = Br, L = NH , 3  16c; X = Br, L = C H C N , 16e; X = CI, L = vacant, 16b; X = CI, L = N H , 16d; X = CI, 3  3  L = C H C N , 16f). 3  5.2.d.l. Synthesis of 16a-b. dihydroxy  analogue  Attempts  Ru(OEP)(OH)  like diose of Ru(OEP)R (R  =  2  Me,  gave instead new Ph). '  Ru(OEP)X(NH ) (X  =  couple in basic pH  solutions (-0.10 V  3  to react 8a-b  5a  49  with N H O H " +  4  in order to prepare the  products having spectroscopic characteristics  Subsequently, these new  products were identified as  Br, 16c; CI, 16d). Comparison of the known potential of the N H / N H 2  vs. S C E )  1 1 9  with those of die R u / R u  (ca. 0.35 V vs. SCE) indicates that 8a-b could be reduced to R u  Ru(OEP)X + 2 N H 2  3  -  IV  m  products by N H  3  165  2  4  + 4  couple in 8a-b  or N H O H : 4  Ru(OEP)X(NH ) + 1/2 'N H ' + 'HX' 3  HI  4  (5.2)  Figure 5.7 shows the changes i n the *H N M R about a five-fold excess of a solution of N H  3  spectrum of Ru(OEP)Br  i n CDC1  Although the larger-scale syntheses were conducted NMR  3  (19.3 m M  in C H 6  6  NH  2  (8a) upon addition of  in C H C 1  3  or C H , C D C 1 7  8  study because both reactants and products are soluble i n C D C 1  at 293 K ) . 1 2 0  3  was used  3  for the  while die reactant 8a is  3  sparingly soluble i n C D . The chemical shifts of 8a are observed at approximately 60 (CH ), 7 6  (CH ) and 4 ( H 3  m e s o  6  2  ) ppm in CDC1  3  (Figure 5.7a). As the reaction progresses at 293 K, the loss of  the intensity of these signals occurs with a concomitant increase in the intensity of the product signals at S 11.4 ( C H ) , 6.1 ( C H ) , -2.2 ( C H ) and -5.4 ( H 2a  2b  3  m e s o  ) ppm (Figure 5.7d). The presence  of roughly an equal mixture of reactant and product is observed after approximately 215 minutes at 293 K (Figure 5.7c), suggesting that the reaction would be complete within 1100 minutes at 293 K, as is clearly observed (Figure 5.7d). If the ratio used for a reaction of N H  with 8a was less  3  than 2:1, incomplete conversion of 8a to Ru(OEP)Br(NH ) (16c) occurred; for example, when a 1:1 3  ratio of N H  3  to 8a was used, 5 0 % conversion of 8a to 16c occurred. The products of the reaction  of 8a widi N E t . ) H (3  n  n  (n = 0, 1, 2) had  NMR  spectra similar to those from the reaction of 8a  with N H O H or N H ; however, these alkylamine reactions were not pursued in favor of using NH-, 4  3  as the reductant. The Ru(OEP)Cl(NH ) complex (16d) was synthesized in the same manner as 3  Ru(OEP)Br(NH ) by reacting N H 3  NH  3  is required to reduce  3  widi Ru(OEP)Cl  Ru(OEP)Br  2  (8b). The data suggest that one equivalent of  2  to give Ru(OEP)Br (presumably  the slow  step for this  reaction), which immediately coordinates the N H present in solution, to give Ru(OEP)Br(NH ): 3  Ru(OEP)Br 8a  The  co-product from  2  slow NH 3  Ru(OEP)Br 16a  3  fast NH  Ru(OEP)Br(NH ) 16c  (5.3)  3  3  this reaction was not identified, but may be N H 2  4  or N H 2  + 5  B r , both of  which could be the one-electron oxidation products of N H . 3  The five-coordinate species Ru(OEP)X (X = Br, 16a) was generated from 16c by protonation of the N H  3  ligand of J6c with HF  (aq  ^ under anaerobic conditions in CHC1 , with the generation of 3  166  Figure 5.7:  'H N M R  spectra of (a) Ru(OEP)Br  minutes after addition of N H after  1170  minutes. The  3  2  (5.32 mM)  in C D C 1  (b) die reaction mixture 5  3>  (five mole equivalents), (c) after 215 minutes, and (d)  experiment was  conducted aerobically, at 293  K  and the  arrows indicate the fate of each signal as the reaction progresses.  (a)  0 m in  i  CH. i a  H0 2  i  m  (b)  5  1  min  T  JUL  JL  (O 215  I  1  11  i  min  w  (d)  1170  iiimni|i)ii|iiii|iiii|iiii|iiii|iiii|iiii|iiii|  64  58  min  |iiii[iiii|iiii[iiii|iiii|iiii|iiii|iiii|iiiijiiii|iiii|iiii|iiii|iiii|''!'jiii:|iiiijnii|iiiniin  10  5 167  6  ~  5  N H F . The  corresponding reaction of J6c with H F  4  complex was also observed in the 'H N M R  in air also gave 16a, but some Ru  spectrum of the reaction mixture in CDC1 . This R u  I V  3  complex was not Ru(OEP)Br , and may indeed be Ru(OEP)F (6 2  10.3 ppm,  (OEP)  1  CH  2  see Section 4.2.h). The chloride analogue Ru(OEP)Cl  = 53.3; C H  2  3  = 6.7; H  m e s o  =  (16b) was syndiesized in the same  manner from Ru(OEP)Cl(NH ) (16d) by reacting 16d with aqueous H F under anaerobic conditions. 3  5.2.d.2. Characterization of 16a-f. The microanalyses (C, H, N, and halogen) for the compounds 16a-f (halogen analysis was not done for 16d) are presented in Table 5.2, and are consistent with the proposed  formulations for each  complex. In the case of Ru(OEP)X(NH ) and 3  Ru(OEP)Cl  ( C H C N ) , these products were found to have a broad IR band between 3700-3400 cm"  attributed  3  to non-coordinated  H 0.  The  2  compounds  16a-b  solution, giving near-zero molar conductance at mM The  EI-MS of Ru(OEP)Br(L) (L  =  were found  3  peak for either Ru(OEP)Br(NH ) (730 mle)  non-electrolytes in C H C N 3  concentrations at 293 K (see Table 5.2).  vacant, 16a; NH ,  Ru(OEP)Br (713 m/e"), Ru(OEP) (634 m/e")  to be  16c; C H C N ,  16e) show peaks for  3  and the decomposition peaks for Ru(OEP); the parent or Ru(OEP)Br(CH CN) (754 mle)  3  was not observed in  3  the EI-MS or FAB-MS. The same pattern in the EI- and FAB-MS spectra of Ru(OEP)Cl(L) (L vacant, NH , 3  highest-mass  C H C N ) was 3  signal.  (669 mle)  observed, with die parent peak for Ru(OEP)Cl  Again,  no  parent  peak  for Ru(OEP)Cl(NH ) or 3  =  being the  Ru(OEP)Cl(CH CN) 3  was  detected. The FAB-MS of Ru(OEP)Br (16a) and Ru(OEP)Cl (16b) are shown in Figure 5.8. The  UV/visible spectra of 16a-f show broad Soret band absorbencies centered at 390-400  and weak visible bands near 500 and 530 nm  nm  (see Figure 5.9 and Table 5.3). Within one type of  complex (i.e. _16a and 16b or 16c and 16d) the optical spectrum is identical in shape and intensity for each halide analogue. The visible band at 630 nm (log  £  =  characteristic  3.18),  109,110  UV/visible spectrum of R u ( O E P ) C O ( B r ) (d ) has a fairly intense  (log e = 4.04),  n  17b  +  and C o ( O E P ) B r m  +  6  (d ) has a similar band at 680 6  2  nm  suggesting that i f 16a-f were complexes of the type R u ( O E P ) X , a n  n -cation radical band between 630-680 nm  +  would be observed, along with a low-  intensity broad Soret band. Clearly, these features are not observed in die optical spectra of  168  Table 5.2: Microanalyses and conductivity data for several R u ( O E P ) complexes. m  microanalyses data (found/calculated) complex-  %C  %H  %N  % halogen  conducti v i t y -  RuBr, 16a  60.83/60.59  6.27/6.17  8.03/7.85  10.81/11.08  5  RuCl, 16b  64.32/64.57  6.51/6.58  8.30/8.37  5.25/5.23  7  RuBr(NH ).H 0, 16c  57.43/57.75  6.34/6.55  8.89/9.35  10.13/10.55  7  R u C l ( N H ) . H 0 , 16d  61.51/61.10  7.00/6.93  9.62/9.90  RuBr(CH CN), 16e  57.37/57.71  6.16/6.35  9.31/9.07  9.87/10.23  -  R u C l ( C H C N ) . H 0 , 16f 62.86/62.64  6.68/6.73  9.90/9.62  5.21/4.81  —  3  3  2  2  3  3  2  —  ~  5 Ru denotes Ru(OEP). ^ In units of M" cm ohm" at 293 K. 1  Table 5.3:  1  Summary of UV/visible spectroscopic and magnetic moment data for R u ( O E P ) m  complexes. complex-  A  RuBr, 16a  396 (4.61), 500 (3.77), 538 (3.75)  RuCl, 16b  395,500,538  RuBrfNHQ. 16c  385 (4.41), 402 (4.52), 512 (3.79), 550 (sh)  RuCl(NH ). 16d  383,402,513,550  RuBr(CH CN), 16e  381 (sh), 396 (4.60), 519 (3.74), 538 (sh)  R u C l ( C H C N ) , 16f  382,396,519,538  m a x  ?  3  3  (log e) nm*-  corrected 1.78 2.03  1.92  S-Ru denotes Ru(OEP). - Measured in C H . 7  8  - Measured using 5 % f-butanol in C D or C H at 293 K, in units of Bohr magnetons (B.M.). 6  6  n£  7  8  169  ef  Figure 5.8:  FAB-MS of (a) Ru(OEP)Br (16a), and (b) Ru(OEP)Cl (16b).  6 3 4  I 71  T  1  1  1  •80  630 HI/*"  170  1  1—  670  3  Figure 5.9:  UV/visible spectra of (a) Ru(OEP)Br (26.4 /tM), (b) Ru(OEP)Br(NH ) (28.8 /JM), and 3  (c) Ru(OEP)Br(CH CN) (29.2 uM) in C H , cell padilength = 1.00 cm. 3  7  8  WAVELENGTH  of 16a-f. Further, 16a-b are E P R silent at either 293 or 77 K as 2-4 m M C H 7  glass  samples,  respectively.  The E P R spectra of known  111  ir-cation  of an organic free  radical.  Lastiy,  Evans'  method  55  7  8  radical metalloporphyrin  complexes have a sharp signal at g = 2.00 at either 293 or 77 K, presence  solutions or C H  8  17,109  '  110  assigned to the  determination of the solution  magnetic susceptibility of 16a (1.78 B.M.), 16b (2.03 B.M.) and 16c (1.92 B.M., see Table 5.3) using 5% Ru  f-butanol in C H 6  m  or C H  6  7  (d , S = 1/2) oxidation state. 5  agree well with the spin-only value of 1.83 B.M. expected for a  8  56  The infrared spectra of Ru(OEP)X(NH ) (16c and 16d) show the v _ 3  N  (+_ 60 cm ) centered about 3100 cm' , as expected for M-NH -1  1  between 3700-3400 cm" for the i / ^  of free H 0 .  1  81  2  and 16f) have bands at ca. 2260 cm" for v  —  1  c  3  IR bands for f  M  .  x  stretch as a broad band  complexes,  818  and a broad band  The IR spectra of Ru(OEP)X(CH CN) (16c 3  of the coordinated C H C N ,  N  8 1 a  3  spectra of Ru(OEP)X (16a and 16b) are missing the "N.H. "OH The  H  v = c  N  while the I R  bands, as expected.  could not be assigned. The IR spectra of 16a-f had no ring oxidation  marker bands at 1550 cm , -1  82  consistent with the absence of a porphyrin cation-radical and the  -presence of a R u ( O E P ) X ( L ) formulation. in  The  'H N M R spectra of JjSa and 16b in C D 7  8  (see Figure 5.10, and Table 5.4) have four  signals assigned by integration to two types of methylene signal each for the methyl (-1 ppm) and H presence of the paramagnetic  Ru  the O E P macrocycle to shorten, 16a-f. resulting  in broad  111  121  m e s o  protons (6  14 and 0 ppm), and one  (-2 ppm) protons of the O E P macrocycle. The  center causes the normal  relaxation times for the protons of  the effects of which can be seen in the *H N M R spectra of  (100-200 Hz fullwidth at half-height) resonances. Therefore, the J . H  coupling (ca. 6-10 Hz) for the ethyl protons of O E P normally observed in diamagnetic Ru(OEP) complexes are completely eclipsed in 16a-f. The spectra show that the mirror plane of symmetry of the porphyrin is not present in 16a-b. the molecules having two dissimilar axial ligands, and therefore,  two methylene  resonances.  78  The 'H N M R  spectra of 16a-f and of many  Ru (OEP) compounds are similar in pattern, but not necessarily in position (see Table 5.4). in  172  other  H  Figure 5.10:  300 MHz, >H NMR  spectrum of Rtf(OEP)Br (16a) in C D at 293 K. The spectrum of 6  6  Ru(OEP)Cl (16b) is very similar to that of the bromide analogue.  Br  Table 5.4: Summary of *H N M R spectroscopic properties of R u ( O E P ) complexes.m  complex-  *CH  meso  5 H  6 CH,  2 a  b  6 CH  RuBr, 16a  -2.61  14.15  -0.20  -0.90  RuCl. 16b  -2.11  14.13  -0.16  -0.93  RuBr(NH ), 16c  -5.29  11.40  6.10  -2.28  RuCl(NH ), 16d  -5.07  11.24  6.19  -2.31  RuBr(CH CN), 16e  -5.67  10.92  5.80  -2.75  R u C l ( C H C N ) , 16f  -5.85  11.15  5.78  -2.70  RuMe£  -0.24  11.62  5.70  -1.78  RuPh-  1.14  14.13  5.81  -1.02  Ru , 7  3.49  26.25  11.20  10.18  9.90  18.52  8.80  0.53  -5.98  8.50  4.95  -2.75  3  3  3  3  2  RuBr(PPh ), ip> 3  RuBr(py)^ [Ru(py) ] Br"-  -1.82  RuCl(MeOH)2  -5.31  +  f  2  (NH ) 4  +  2  7.05  11.15  4.03  [RuBr ]-, 1 6 ^  -0.22  18.18  6.69  59.68  - Unless stated otherwise, the spectra were measured at 293 K in C D , 300 MHz. 6  ^ Ru denotes Ru(OEP). - From References 5a and 49. - From Reference 28. - Spectrum obtained in C D N , see Section 5.2.d.3. 5  5  - Spectrum obtained in CDC1 , see Sections 5.2.d.3 and 5.2.e.2. 3  s  Spectrum obtained in C D O D , see Section 5.2.d.3. 3  - Spectrum obtained in C D C 1  3>  see Section 5.2.d.3.  174  -2.40  6  3  The  separation  of the two  methylene resonances (about 14 ppm)  in the  H  NMR  spectrum of  Ru(OEP)X (16) is similar, for example, to the separation of the two methylene resonances of the dimer [Ru(OEP)]  2  (7) (about 16 ppm),  and position of the two  25  or Ru(OEP)Br(PPh )  (about 10 ppm).  3  (ca.  methylene resonances of J_6a and 16b  The  28,37  14 and 0 ppm)  different from that of the single methylene resonance observed at 60 ppm  presence are quite  for Ru(OEP)X  (X  2  Br, 8a; CI, 8b), reflecting both the differences in magnetic properties between 8a-b (S = 16a-b  (S  =  =  1) and  1/2) as well as the centrosymmetric nature of 8. These differences in observed  chemical shifts between, for example, 8a and 16a can perhaps be explained in terms of the type of TT -charge transfer involved in 8a (ligand-to-metal charge transfer, L-»M As suggested for 8a,  37  CT).  CT) and J_6a (M-»L  the weak 7r-donor capacity of die halide ligands cause the metal's d , xz  d  y 7  orbitals to increase slightly in energy, such diat the transfer of spin density from the porphyrin 3e  g  (TT) orbitals to the metal is possible.  the 'H N M R  The effect of this spin-density transfer is observed in  spectrum of 8a, with the methylene resonances of OEP  normal diamagnetic position of 4 ppm. one  118  shifting to 60 ppm  In 16a, the further occupancy of die d , d xz  v z  from the orbitals by  electron (d ) causes the energy of these orbitals to increase relative to those in 8a 5  (6 ), A  consequently bringing these orbitals closer in energy to that of the empty 4e„ (TT) orbital of the porphyrin. The effect of the M-»L dramatic upfield shift of the H  CT  m e s o  can be observed in the •H N M R  resonance from 10 ppm  in diamagnetic complexes to -5  in J_6a. The shift of the resonances of the other protons of OEP diamagnetic positions are ascribed to correlation effects. The  spectrum of J_6a, with the  in 8 and in J6 relative to their  118  chemical shifts of the protons of the OEP  macrocycle of 16a-b are temperature-dependent,  as expected for paramagnetic species. Table 5.5 shows the variation of t h e ' H N M R 16a  as  a  function  therefore, is not temperature.  While  of  temperature  shown), and each  data  Figure  (the chloride 5.11  set yields a  analogue  exhibited  identical  resonances of behavior, and  shows the plot of the isotropic shift straight-line  plot  temperature, significant deviation from the zero-intercept at 1/T  175  ppm  =  of  isotropic shift  vs. inverse vs.  inverse  0 is present. This deviation  Table 5.5: Data for the plot of isotropic shift (ppm) vs. 1/T (K" ) for Ru(OEP)Br (16a). 1  «CB, (obs/iso^  8  T(K)  1/T(K)  223  4.48  16.91/12.71  9.19/4.99  -3.95A5.89  -12.12/-22.43  243  4.12  16.58/12.38  10.15/5.95  -2.56/-4.50  -8.87/-19.18  263  3.80  16.26/12.06  10.21/6.01  -1.98/-3.92  -6.74/-17.05  284  3.52  15.81/11.61  10.21/6.01  -1.44/-3.38  -4.19/-14.50  303  3.30  15.69/11.49  11.04/6.84  -0.80/-2.74  -3.10/-13.41  323  3.10  15.42/11.22  11.06/6.86  -0.58/-2.52  -2.12/-12.43  5CHo (obs/iso^  b  n  S Obtained for a 3.52 mM  solution of 16a in C D C 1  3  5CH,(obs/iso)^ * m e s o ( H  in vacuo, ±  positions of the resonances of 16a are different in C D C 1  3  o b s / i s  °)  !  1 K at 300 M H z (FT). The  at 293 K than those reported in  Table 5.4 for 16a i n C D , in keeping with the observed solvent-dependent nature of the 6  !  H  NMR  6  chemical shifts of J_6a. See Section 5.2.d.3 and die other entries in Table 5.4 for  further details. - (Observed/isotropic) chemical shift SCH  2  = 4.20ppm, 6 C H  3  in ppm,  = 1.94ppm, 6 H  e s o  diamagnetic  = 10.31 ppm.  176  correction 122  made from  Rh(OEP)Cl:  Figure 5.11:  Plot of isotropic shift (ppm)  vs. 1/T  (K" ) for Ru(OEP)Br (16a). Solid lines represent 1  the least-square fit of the data, with extrapolation to 1/T = 0.  177  may originate from  such effects as spin-orbit coupling or temperature-independent  The cyclic voltammograms of 16a-b were measured in 0.1 M T B A P in C H C 1 2  paramagnetism.  and C H C N . Two  2  3  reversible (peak-to-peak separations of 65 _+ 5 mV), one-electron oxidation processes are observed in the C V of each complex 16a-b. assigned to the Ru^/Ru  111  (242-312 mV  vs. F c / F c ) and the +  R u ( O E P ) / R u ( O E P ) (779-825 mV vs. F c / F c ) redox processes. These data are presented below: IV  +  IV  +  reduction potentials redox couple  X = Br  [Ru (OEP)X] /Ru (OEP)X IV  +  m  [Ru (OEP )X] /[Ru (OEP)X] I V  +  + 2  I V  +  242  305^  255^  817  779  825^  795^  +  2  4  ^ ± 10 mV vs. Fc /Fc in C H C N in 0.1 M ( n - B u ) N +  3  The  4  metal-centered couple was assigned based  reversible wave at 312 mV  X = CI  312  2 +_ 10 mV vs. F c / F c in C H C 1 in 0.1 M ( n - B u ) N 2  2  +  +  C10 - at 293 K. 4  C10 " at 293 K. 4  on the observation that the potential  for 16a varied as ( n - B u ) N  +  4  expected behavior for a Nernstian process (Figure 5.12a):  B r was added to the cell, following the  84  R u ( O E P ) B r + e - R u ( O E P ) B r + Br"  (5.4)  E = E°' + (RT/nF)ln([Ru(OEP)Br ] / [Ru(OEP)Br][Br"])  (5.5)  IV  m  2  2  Figure 5.12b shows the changes in the C V of 16a upon addition of excess ( n - B u ) N  +  4  cell, die corresponding potential of the Ru^/Ru the  Fc /Fc +  Ru(OEP)Br  2  of the  couple, the final (8b, -154 mV  potential  111  being  couple varying from 312 mV similar  to that  to -165 mV vs.  for the R u / R u IV  vs. F c / F c ) . The irreversible couple observed at 250 mV +  178  B r to the  ni  couple in  vs. Fc /Fc is +  Figure 5.12:  Cyclic voltammograms of (a) Ru(OEP)Br (16a) and, (b) 16a and added excess (n-Bu) N 4  +  Br". X-axis scale is in Volts vs. the F c / F c couple. +  due to the Br /2 Br" couple because the intensity of the C V 2  more ( n - B u ) N  Br" was added to the c e l l .  +  4  84  waves at this potential increased as  However, data for a Nernst plot of E vs. -In [ B r ]  could not be obtained because the Br /Br" couple at 250  mV,  quantitative determination of the change of E from 312 mV  to -165 mV  2  being irreversible, prevented the for the R u / R u I V  m  couple. The  bulk coulometric oxidation of l_6a in the absence of ( n - B u ) N  Br" at 400  +  4  Fc /Fc +  mV  vs. the  couple results in the overall loss of intensity of the UV/visible spectrum of 16a as die  coulometry experiment progresses (Figure 5.13a). However, bulk coulometric oxidation of .16a at T B A P in the presence of 25 equivalents of added  (n-  Br" yields the optical spectrum of 8a. These results show that the couples at 242-312  mV  400 mV Bu) N  vs. F c / F c in C H C 1 +  2  +  4  2  and 0.1 M  for 16a-b are due to the R u / R u couple. I V  m  While the values for the measured potentials of the R u / R u IV  reported values for such compounds, " 100  108  they are ca.  UI  couple in 16a-b are within the  400-500 mV  more positive than that for  the corresponding couple in 8a4). This difference in the value of the Ru^/Ru " couple may 1  due  in part to the different types of charge transfer apparent in 8a-b  L-»M  CT  and  be  16a-b. In 8a-b. the  will increase the spin density at the metal, making die reduction potential of the metal  less favorable. In j_6, the M-»L  CT  removes spin density from  the metal, making any  further  oxidation of die metal unfavorable. Also, the effect of one halide ligand in 16a-b vs. two in 8a-b may  be  significant;  consistent  with  the  the addition lower  of an  extra halide is expected  reduction potentials  implication of this large shift in the R u / R u I V  m  observed  for  to stabilize R u  the  Ru(OEP)X  couple in going to 16a-b  2  from  I V  vs. Ru , 111  systems. 8a-b  will  The be  discussed later in this Chapter. The the C V  second reversible oxidation process observed at approximately 779-825 mV  vs. Fc /Fc in +  of each of 16a-b is assigned to the ring oxidation step because bulk coulometric oxidation  of 16a at 900 mV  vs. F c / F c led to changes in the optical spectrum of 16a which paralleled those +  observed during the coulometric oxidation of 8a at 900. mV  180  vs. F c / F c (see Figure 5.13b). The +  Figure 5.13:  Changes observed in the optical spectrum of 16a upon bulk coulometric oxidation of the solution at (a) +400 mV  vs. F c / F c both in the absence and presence of 25 +  equivalents of (n-Bu) N Br~, (b) coulometric oxidation at 900 mV +  4  vs. F c / F c in the +  absence of added (n-Bu) N Br~. The experiments were conducted in C H C l 2 with +  4  2  0.1 M T B A P electrolyte.  300  450  WAVELENGTH, nm  600  182  couple at ca. -1 V vs. F c / F c may be due to either the R u / R u +  ra  or the R u ( O E P ) / R u ( O E P " )  n  m  ni  couple, but is not definitively assigned. 5.2.d.3. Chemistry of R u ( O E P ) X ( X = Br, 16a; CI, 16b). The five-coordinate 15e" complexes 16a-b are very  stable i n solution. For example, a solution of 16a i n C D 7  heated at 373 K for 24h and then photolyzed  sealed under vacuum was  8  Hg vapor lamp); the U  for 2h (450 W  l  spectrum of the solution remained unchanged. The compounds 16a-b are very and  NMR  soluble in aromatic  halogenated solvents, and are sparingly soluble i n hexanes. In contrast, 8a-b are insoluble in  hexanes,  sparingly  soluble  in aromatic  solvents  and quite  soluble  in halogenated  solvents.  Solutions of 16a and 16b could be stored in closed containers for months without any observed decomposition. The  compounds 16a and 16b. being  six-coordinate  species.  identical, only below  Because  die reactivity  (see Section  coordinatively unsaturated,  the reactivity  of 16a  of Ru(OEP)Br (16a)  2.4 for details  bind  and 16b with  various ligands to form the same  reagents was  is summarized in Scheme 5.1, and discussed  of die reaction  conditions  which  apply  to the reactions  described below). Aerobic  oxidation  of 16a in C D 6  6  in the presence of H B r yields Ru(OEP)Br  quantitative yield within two hours as judged by *H N M R if 16a is reacted with H B r alone, suggesting with  dry 0  2  in C D . 6  6  Addition  spectroscopy;  (8a) in a  2  the reaction is inhibited  0 /HBr is the oxidant. Indeed, !_6a does not react 2  of trace H 0 2  to this  reaction  mixture  induces no further  reactivity, while acidification of the reaction mixture by addition of HBr yields 8a. The bubbling  optical spectrum of 16a at A * M concentrations in C H C 1 NH  3  3  or C H 7  g  immediately changes upon  through the solution, yielding the optical spectrum of Ru(OEP)Br(NH ) (16c). This 3  latter compound and its chloride analogue (16d)  were isolated and fully characterized. The K B r  pellet IR spectrum of 16c and 16d have broad (+_ 60 cm" ) bands, assigned 1  centered  at 3150 cm"  1  (see Figure 5.14). These data, and the microanalyses,  proof of coordination of N H  3  to the i ^ . N  stretch,  are the only direct  to Ru in 16c-d. because the parent peaks of 16c-d were not  183  H  Scheme 5.1: Summary of the reactivity of Ru(OEP)Br (16a).  Figure 5.14:  Infrared spectrum of Ru(OEP)Br(NH ) in the 4000-2500 cm'  1  3  region, as a KBr pellet.  The IR spectrum of Ru(OEP)Cl(NH ) is identical to that of the bromide analogue. 3  detected by FAB-MS nor were the resonance due to the NH3 protons detected by 'H  NMR  spectroscopy. U  The  NMR  l  spectra of 16c and 16d i n C D 6  6  are similar in appearance to those of 16a-b.  having two methylene resonances at 9.2 and 3.8 ppm, the methyl resonances at -2.3 ppm and the resonances at -5.9 ppm. The positions of the resonances of die O E P macrocycle in  Hmeso  16c-d  were found to be similar (_+_ 0.2 ppm) to each other, and both complexes exhibited temperatureand solvent-dependent spectra. The inability to detect the N H the  extreme  broadening  paramagnetic  centre.  of the linewiddi  3  signal i n 16c-d may  due to the proximity  of the N H  3  be due to  ligand  to the  Figure 5.15 shows the relationship between the isotropic shift and 1/T  121  for the O E P resonances of 16a i n the temperature range 203-363 K (see Table 5.6). The isotropic shifts essentially  vary linearly  at 1/T -+ 0, showing may  be  related  with inverse temperature, but have significant non-zero  intercepts  that non-Curie behavior was present. The origin of this non-Curie behavior to  aggregation  effects,  spin-orbit  coupling  or  temperature-independent  paramagnetism. The  'H N M R  spectra of 16c-d indirectly support the formulations proposed for 16c-d in that  the separation between the two methylene resonances of 16a-b (ca. 14 ppm) is reduced to ca. 5 ppm a  in 16c-d upon bubbling N H sixth  ligand.  53  A  similar  3  dirough a solution of 16a-b. consistent with the coordination of  change  in the separation  of the two methylene  Ru(OEP)Ph (8.32 ppm) was observed upon coordination of pyridine (3.70 pprii).  resonances of  53  The compounds 16c-d are air-stable in both the solid state and in solution, and their solubility in various solvents is similar to that of 16a-b. Solutions of 16c-d at A * M concentration in CHC1 or C H 7  8  are unreactive toward added 0 , H , and N 2  2  2  3  as judged by UV/visible spectroscopy. No  substitution of either the coordinated halide or the amine ligand was observed upon addition of approximately ten  equivalents of P P h  3  to 16c i n C H , as judged by UV/visible spectroscopy. 7  8  The protonation of the amine ligand of 16c or 16d in C H C 1  3  with an acid such as H F yields a  reddish solution and an off-white precipitate; filtration of die reaction mixture followed by  186  Table 5.6: Data for the plot of isotropic shift (ppm) vs. 1/T (K' ) for Ru(OEP)Br(NH ) (16c).?1  3  T(K)  1/T(K)  £CH (obs/iso)^  203  4.93  9.48/5.28  -1.14/-5.34  -4.75/-6.69  -17.18/-27.49  223  4.48  9.03/4.83  0.39/-3.81  -4.41/-6.35  -14.02/-24.33  243  4.12  8.83/4.63  1.64/-2.56  -3.86/-5.80  -11.00/-21.31  263  3.80  8.81/4.61  2.54/-1.66  -3.33/-S.27  -8.66/-18.97  284  3.52  8.86/4.66  3.32/-0.88  -2.80/-4.74  -6.53/-16.84  303  3.30  8.89/4.69  3.86/-0.34  -2.40/-4.34  -4.90/-15.21  323  3.10  8.93/4.73  4.31/0.11  -2.06/-4.00  -3.61/-13.92  343  2.92  8.96/4.76  4.70/ 0.50  -1.74/-3.68  -2.37/-12.68  363  2.75  8.97/4.77  4.89/ 0.69  -1.60/-3.54  -1.80/-11.91  5CH, (obs/iso)^ <5CH (obs/iso)^  2n  3  h  5 H  meso(°  5- Obtained for a 2 m M solution of 16c in C D in vacuo, +_ 1 K at 300 M H z (FT). 7  g  - (Observed/isotropic) chemical shift in ppm, diamagnetic correction made from data for Rh(OEP)Cl: c?CH = 4.20 ppm, 5 C H 2  3  = 1.94 ppm, « H  187  m e s o  =10.31 ppm.  122  b s / i s  °)  !  Figure 5.15:  Plot of isotropic shift (ppm) vs. 1/T  (K" ) for Ru(OEP)Br(NH ), 1  3  represent the least-squares fit of the data, with extrapolation to 1/T = 0.  188  16c. Solid  lines  workup yields Ru(OEP)X (T6a-b). and  the precipitate is presumed to be N H  + 4  F\  The  preparative  reaction for the synthesis of Ru(OEP)X(NH ) is, therefore, reversible: 3  NH Ru(OEP)X  Recrystallization of 16a-b of 16c by HF  ^ H  3  Ru(OEP)X(NH )  (5.6)  3  +  from CH CN/CH Cl //i-pentanes or acidification of a C H C N solution 3  2  yields R u ( O E P ) X ( C H C N ) (X 3  2  3  =  Br, 16e; CI, 16$; the products, being isolated and  fully characterized, serve as examples of the association of coordinating solvents to Ru(OEP)X. Again,  the  only  direct  microanalytical data and  evidence  the  "=  mulls (see Figure 5.16). The  *H  Ru(OEP)X(NH ) (see 3  H  m e s o  for  the  association  of  CH CN 3  NMR  Table 5.4),  ppm  of die Ru slightly  111  from ca.  14 ppm  centre.  The  121  in position and  3  each having  in 16a-b. The  two  methylene resonances, and  l  NMR  one  methyl  and  signals appear to be relatively unaffected  by  methylene signals decreases to  3  UV/visible spectrum of 16e  for U  16f as Nujol  C H C N resonance is unobserved due to the presence  extinction coefficient  (see Table 5.4  the  3  (see  is similar to that of 16a, differing only  Figure  5.9  and  data), suggesting  U  Table 5.3).  UV/visible spectra very similar to those of 16e-f were observed when 16a was or C D O D  and  are  spectra of 16e-f in C D C N are quite similar to those for  signal. Again, the position of the latter two  5.4  Ru(OEP)X  N bands observed in the IR spectra of !6e  C  the coordination of a sixdi ligand, while the separation of the two ca.  to  1  NMR  and  dissolved in C D N 5  5  that similar six-coordinate species are  generated in these solvents. The  relatively small changes in A (nm) and log e for Ru(OEP)X(L) species (X  =  Br, CI; L  =  C H C N , py and MeOH), in comparison to data for l_6a, are similar to the changes observed in the 3  optical spectrum of Ru(OEP)CO(MeOH) (3b) upon coordination of diese same and ligands (see Table 3.1 readily  and  Reference 71). The  apparent; for example, the optical  upon coordination of pyridine.  53  In any  other similar  reasons for these unexpected small changes are not  spectrum of Ru(OEP)Ph undergoes immense changes  case, the observed small changes precluded  189  die accurate  Figure 5.16:  Infrared spectrum of Ru(OEP)Br(CH CN) as a Nujol mull. The IR spectrum of 3  Ru(OEP)Cl(CH CN) is identical, except that the i> = is observed at 2250 cm' . 1  3  c  N  measurement of the  for the association equilibria  shown  i n Equation 5.7 by UV/visible  spectroscopy, as was done for several systems in Chapter 3:  Ru(OEP)Br + L ^ Ru(OEP)Br(L) 16a  (5.7)  L = C H C N , py, M e O H 3  However, addition of 1-5 fiL of the reagents C H C N , py, or M e O H to 20-24 / i M solutions of l_6a in 3  CH C1 2  2  (total volume = 4.0 mL) generates the optical spectra of the fully formed corresponding  six-coordinate species, leading to qualitative K g values of the order of 10 -10 M " . 2  3  1  q  Complex 16a dissolved in neat pyridine is suggested also to yield Ru(OEP)Br(py), based on the UV/visible CH C1 2  2  spectrum  containing  generated, which added  was identical to that obtained  pyridine. Of interest, when  for a solution of 16a  16a was dissolved  in pyridine  and  in  the  solution filtered through a short alumina column or refluxed for ten minutes, the end-product was [Ru(OEP)(py) ]  +  2  electrolyte  B r , and not Ru(OEP)Br(py)  complex  can also  as expected (Figure 5.17). This  be prepared by the aerobic  oxidation  six-coordinate 1:1  of Ru(OEP)(py)  2  in  the  presence of H B r acid (see Section 5.2.e). These findings show that substitution of the coordinated halide ligand in 16a is possible only at high temperatures (boiling point of pyridine = 388 K) or by  ligand  exchange  substitution  inert  electrolyte  complexes  temperature.  mediated  than  by chromatographic supports. The Ru system  die analogue upon  addition  Fe(OEP)Cl,  which  of pyridine  or  instantaneously imidazole  forms  more  bis(ligand) 1:1  to Fe(OEP)Cl  at  room  123  The addition of (n-Bu) NBr to a solution of 16a in C H C 1 4  3  leads to changes in the UV/visible  spectrum of 16a which are large enough to measure accurately 5.18  is therefore  an equilibrium constant.  Figure  shows the changes in the UV/visible spectrum of 16a as B r is added, and the corresponding  log plot of relative absorbance changes vs. added B r . The 191  measured at 397 nm and 293 K  Figure 5.17:  300 MHz,  !  H  NMR  spectrum of [ R u ( 0 E P ) ( p y ) ] n,  +  Br", isolated from the reaction of  I  I  2  Ru(OEP)Br with pyridine (see Figure 5.23b).  I  I  | 25  I  I  I  I  | 20  I  I  I  I  | I 15  I  I  I  | 10  I  I  | 5  I  I  I  I  | 0  I  I  I  I  | I I -5 PPM  I  I  | I -10  Figure 5.18:  (a) UV/visible spectral changes observed upon addition of (n-Bu) NBr (68 mM) to 4  Ru(OEP)Br (2.95 x 10 M) in CHCI at 293 K. The total added (n-Bu) NBr present s  3  4  in solution after each addition corresponds to 0, 0.3, 3.4, 10, 24, 52, and 500 equivalents, (b) Plot of log [(A-A )/(A A)] vs. log [Br] for the above titration, 0  r  f  measured at 397 nm.  400 WAVE  450 LENGTH  , nm  500  Figure 5.18b: A  3 9 7 n m  :  Volume of B r 7 C D C l : (in A»L) 3  1.202  1.193  0  1.0  1.162  1.148  10  30  Solid N(n-Bu) Br added. 4  194  1.130 70  1.117 150  1.093 *  from the line drawn i n Figure 5.18b, was 4.8 x 1CT M 4  although the slope of this line from the  1  log-log plot was 0.7 ±_ 0.1.  Ru(OEP)Br + (n-Bu) NBr ^  ( n - B u ) N [Ru(OEP)Br ]" 4  2  16a  The  'H N M R  16g  spectrum of 16a in CDC1  place of (n-Bu) NBr 4  because  (5.8)  +  4  containing added excess N H B r (this being used in  3  4  the presence of the latter would  prevent the observation of the  resonances of 16g) shows only one signal each for the methylene (59.68 ppm), medvyl (6.69 ppm) and H  m e s o  (4.03 ppm) protons of the OEP macrocycle (Figure 5.19 and Table 5.4). The presence  of only one mediylene resonance in the *H N M R centrosymmetric  six-coordinate complex  spectrum of 16g confirms die generation of a  upon association of B r to 16a. These data corroborate -  the changes observed in die C V of 16a upon addition of Br" (Figure 5.12). Similar reactivity has been reported for die association of F" to F e ( T P P ) F  upon addition of H F to [Fe(TPP)] 0 in  m  2  the presence of excess imidazole, the reaction forming [Fe(TPP)F ]".  124  2  The reaction of J_6a with C O ^ in C H C 1 2  2  generates Ru(OEP)(CO)  2  immediately, as judged by  UV/visible spectroscopy (see Section 3.2.b for the optical spectrum of Ru(OEP)(CO) ). 2  reactivity was observed for the reactions of R u ( O E P ) X The  and Ru(OEP)(Ph)  5a 2  with C O in CHC1 . 3  reductant in diese reactions has not yet been identified, but could be the axial anion(s) or  CO, die latter requiring trace OH" (CO + OH" No  C0 + H 2  +  + 2e").  reaction was observed upon addition of a stoichiometric amount of m C P B A to 16a in either  CH C1 , C H 2  37 2  A similar  2  6  6  or C H C N but when 50 equivalents of inCPBA 3  or PhIO was added, a greenish  colored solution was obtained instantly. The optical spectrum of this solution (Figure 5.20) has a single broad band, which remained unchanged when stored for five days under vacuo. This optical  195  Figure 5.19:  'H N M R  spectrum of N H  + 4  [Ru (OEP)Br ]" generated in situ by the association of m  2  Br" to Ru(OEP)Br in CDC1 at 293 K. 3  NH Br(?) 4  HQ 2  CH  2  I I 111 IJ j I I I j 1111 j M I I ] JI 61.0 60.0 59.0  1  I|I  CHCI  3  m  -A. I I I 1  ; 1  I I  1  I  10  I I I I  j  I ! I I  j  I i I I  II  I I 1  I  I I I I  I  I I I I  JI  I I I  I  I I I I j I I I  2 PPM  1  I I  Figure 5.20: UV/visible spectrum of the reaction mixture of Ru(OEP)Br (16a) with excess mCPBA in C H C N . 3  2 .19  ui O Z <  1.0 0  CD  oe O to CD  <  0 .1 5 550  30 0  WAVE LE K G T H . n m  197  80 0  spectrum was similar to that reported by Leung et al. catalyst [ 0 = R u ( O E P ) B r ] . r v  with  +  the formation  destroyed.  for the proposed hydrocarbon oxidation  Exposure of this solution to air led to the bleaching of the solution  of a translucent white precipitate, indicating  that the porphyrin  ring  was  Attempts to isolate the green Ru porphyrin species formed in situ using die methods  described for the isolation of the intermediates 13/14 in Chapter 4, gave only the /i-oxo dinuclear species [ R u ( O E P ) O H ] 0 (9). IV  2  Of interest, this greenish solution, at the m M NMR  resonances in the range  presence of unpaired the *H N M R  m e s o  +_ 150 ppm at 293 K. Morishima et a l .  'H  have shown that the  1 2 5  spin at die macrocycle (i.e. a IT -cation radical) generates marked changes in  spectrum of a precursor such as Ru(OEP)CO (3a). For example, the resonances of  the OEP macrocycle of 3a (5 H H  concentration, did not have any observable  = 10.15; C H  m e s o  2  = 4.00; C H  3  = 1.5) shift to 6 = -35 ppm for the  , to 24 and 30 ppm for the C H , and to 3 ppm for the C H 2  radical species [ R u ( O E P ) C O ( B r ) ] . n  +  +  and broadened,  upon formation of the TT-cation  If additional unpaired spin is present in the same complex  1 2 5  (i.e. there is both metal- and ring-centered oxidation), die OEP further shifted  3  perhaps  resulting  macrocycle resonances may be  in the observation  of a featureless 'H  NMR  spectrum. The addition of 50 equivalents of cyclohexene to a solution of 16a containing 50 equivalents of PhlO did not alter die optical spectrum of the solution shown in Figure 5.20, except for a small dilution effect. Further, even after the solution containing Ru(OEP)Br, C H 6  6  (or CH C1 ) 2  2  was stirred  PhlO  for five days, the gas chromatogram  and cyclohexene in  of the reaction solution  (Figure 5.21) showed that no oxidation of cyclohexene had occurred. A similar result was obtained when the solvent used was C H C N . 3  Alternative methods used to study  include stirring cyclohexene with Kja in C H 6  6  die 'oxidation' reaction  prior to addition of PhlO, heating the solution at  323 K, and using Ru(OEP)Cl (16b) in place of 16a. In all cases, no oxidation of cyclohexene was observed. Cyclohexene was used as the substrate for these studies because of the large database reported for the oxidation of tliis substrate with various metalloporphyrin catalysts. " ' 40  198  42  44  Figure 5.21:  Gas  chromatograms  Ru(OEP)Br (1 mg,  of  (A)  initial  reaction  mixture  HP-17  70 Mmol) in C H C 1 ;  capillary column (15 m  :  (2 mL), and  reaction  of  'Gci  Zrr  , 6 10 C  H  423  2  K  1 minute  \ 3  2  3  K  30 K  199  (B) the final reaction  /minute  detector  t*L sample volun>es were tested.  The temperature program used for each run is shown below.  2  the  x 0.5 nun) was used with a FID  (573 K), the inlet temperature was 473 K, and 0.5  CH CI  from  1.4 ^mol) with excess PhIO (15.6 mg, 70 /jmol) in the presence of  excess cyclohexene (7.3 uL, nuxture. A  the  These reactions vacant coordination The  implications  involving 16a show that 16a-b are capable of chemistry related to both die site trans to the halide, as well as substitution of the halide ligand itself. of the studies  involving  16a-b as possible  catalysts  for the oxidation of  cyclohexene by oxygen atom sources will be discussed in the last section of this Chapter.  5.2.e. Synthesis, characterization and chemistry of [Ru (OEP)(py) ] X (X = CI, 17a; X = B F , m  2  4  17b). 5.2.e.l. Synthesis of 17a-b. The oxidation  of Ru (OEP)(py) n  2  (6a, red-yellow  solution) under  aerobic conditions in the presence of an H X acid yields a deep reddish colored solution when the reaction is conducted in halogenated solvents ( C H C 1 2  when  attempted  in aromatic  solvents  (C H 6  or CHC1 ), and a salmon colored suspension  2  3  or C H ) ,  6  7  the solvents  g  of choice.  An essential  component of this reaction is air or 0 : 2  Ru (OEP)(py) u  2  + HX/0  -  2  [Ru (OEP)(py) ] X + "H0 "  (5.9)  m  2  2  X = CI, 17a; BF , VJb; CI (py-d ), 17c; Br, 17d; F, 17e. 4  5  [ R u ( O E P ) ( C H C N ) ] B r = 17f. +  3  2  When gaseous H X (X = CI, Br) was bubbled through a solution of 6a, its effect was to act as a purge gas for die removal of air from the solution, and some Ru(OEP)X  2  species (8a-b) was  formed along with  6  was saturated  H a and 17d, respectively. If a solution of 6a in C H 6  with  HCl^-, and left for several hours i n the absence of 0 , 8b was formed as die exclusive product 2  of this reaction. Thus, for simplicity, the method used for the syndiesis of 17a-e was to add aqueous H X (X = CI, B F , Br, F) to a C H 4  then sonicated  7  g  solution of Ru(OEP)(py) in air. This mixture was 2  to facilitate complete mixing of the two-phase media, and die resulting suspension  was  filtered to collect the product. The residue was dien purified as described  use  of dilute solutions of Ru(OEP)(py)  reflux  in air for five minutes also  2  in Chapter 2. The  and HX( ^ in C H , or heating the reaction mixture to  gave  aq  7  g  17a-e. the effect of dilution or heating being the  increased solubility of die trace added aqueous acid in C H . 7  200  8  Only the products from the reaction of HCI or H B F and  with Ru(OEP)(py)  4  (6a) were isolated,  2  the spectroscopic characterizations of these two species serve as an example for the others  (17c-e). which were generated in situ at 2-5 m M concentrations. Further, similar oxidation of Ru(OEP)(CH CN) 3  (6b) by HBr/air is proposed to give the analogue [ R u ( O E P ) ( C H C N ) ]  2  3  Br" (_17f),  +  2  based on the similarity of the in situ *H N M R spectrum of this species to those of 17a-e. 5.2.e.2. Spectroscopic characterization of 17a-b. The microanalyses data for each complex (C, H, N analysis for both species and CI analysis for 17a, see Section 2.3.b) show that the products from the aerobic oxidation of Ru (OEP)(py) n  the formulation [ R u ( O E P ) ( p y ) ] m  +  2  data obtained present  2  in the presence of H X  acids (X = CI and B F ) have 4  X" (X = CI, 17a; B F , 17b). In the case of 17b, microanalyses 4  on samples from two separate syndieses  in this product  ( a q )  indicate diat two waters of hydration are  (see also the IR data below).  In C H C N , die molar conductivity data 3  measured for 17a-b and 17f at 293 K (for 17a, 125 M" ohm" cm; 17b, 120 M" ohm" cm; J7f, 1  125  1  1  cm, measured in situ) indicate that diese complexes are 1:1 electrolytes, because  M" ohm" 1  1  1  the values were similar to that measured for the 1:1 electrolyte standard n - B u N C 1 0 " in C H C N +  4  4  3  (120 M' ohm" cm). 1  The  1  infrared spectrum of 17b as a KBr pellet shows a broad band between 3700-3300 cm"  1  assigned  to the presence of free water, as suggested by the microanalysis data. This broad band  is missing in the IR spectrum of l_7a, which from the microanalysis data is known not to have any  water of hydration. Neither compound has die typical strong band at 1550 cm"  1  7r-cation radical,  82  indicating that in the synthesis the oxidation is metal-centered  of macrocycle-centered these  for the O E P (Ru ) instead 111  (Ru (OEP "*"•)). The v _ IR bands could not be assigned in 17b because  bands are typically  u  B  found  between  F  1130-1040 cm" , 1  81  a region  where several  porphyrin  bands are concentrated. The optical spectrum of 17a-b (see Figure 5.22a) confirms that the metalcentered  oxidation product  broad band type Figure 5.3a).  17  is obtained  spectrum normally  because the appearance of the spectrum  is unlike  the  observed for a JT-cation radical complex (see, for example.  The general appearances of the spectra for the two analogues 17a and J J b are  201  Figure 5.22:  (a) Optical spectra of rRu(0EP)(py)2] CI" (17a, [Ru] = 46.5 fiM) measured in CHC1 +  3  with a 1.0 cm pathlength cell, (b) FAB-MS of 17a. The corresponding UV/visible and FAB-MS spectra of [Ru(OEP)(py) ]  +  2  BF " (17b) are identical in pattern, but not 4  necessarily in intensity, to those of the chloride analogue.  (a) LU O < CD  o  CO CD <  0.500.250.00  nm  600  400  WAVELENGTH (b)  79 2  71 2  I  —I  1  620  72 0  67 0 m/c  202  l  7 70  very  similar,  further  complexes having C10 "  or PF '  4  6  porphyrin two  confirming  anions give A  radical s p e c i e s .  2  but  very  are EPR  respectively,  confirming  measurements gave  M  E F F  2 u  which the electron was  Further, 17a-b  different optical  silent at either 293  only to [Ru(OEP)]  (n =  n  '  The  110  terms A 2  spectra  for each  or 77 K  for S = 1/2, low-spin, R u  as mM  type of  CH C1 2  bombardment (FAB)  and  d ) ]Cl 5  2  (17c) has  A  B.M.  BF ", 4  denote the  2 u  radical  to generate  species.  1 7 , 1 0 9  "  0  for magnetic  55  for 17b, reasonably consistent with the 56  show porphyrin  peaks  due  mJe')) and the normally observed 'decomposition  for the pyridine ligands was  mass spectra of  17a-b  observed for each sample. The  (Figure 5.22b and  identical in the pattern of observed signals, but with small differences (+_ positions observed. No  2  Evans' method  oxidation state.  m  radical  solutions or frozen glasses,  2  mass spectra (EI-MS) of 17a-b  1 (634 m/e'), 2 (1268  peaks' of Ru(OEP). A peak at 79 m/e'  l u  removed, the resultant effect being  for JL7a and 2.44  low-resolution, electron-impact  n -cation  Ruthenium(II)  radical species while those having  l u  17,109  state.  the absence of a ff-cation radical. The  of 1.99 B.M.  spin-only value of 1.83 B.M.  fast atom  oxidation 2  characteristic  The  Ru  bromide or chloride anions give A  orbital from  111  the  parent peak for l_7a or 17b  was  observed. The  Section  2.3.b) were  1 m/e')  in the peak  FAB-MS of [Ru(OEP)(py-  peaks at the expected position for the sample having  deuterium  incorporated  (see Section 2.3.b), confirming the assignments made. The  'H  NMR  spectra of Ru(OEP)(py)  2  (6a) and  5.23  (see also Figure 5.17); the corresponding  The  presence of one  having  D  2  ligand are quite dissimilar to those reported by R u ( O E P )CO n  +  (17b) are given in Figure in Table 5.7.  methylene resonance in the spectrum of each complex suggests a structure integration of die coordinated  to those of the macrocycle resonances also confirm  within  4  data for complexes 17a-f are presented  symmetry; the relative intensities and  4h  [Ru(OEP)(py) ]BF  complexes  and,  125  this result. The  resonances of the  Morishima et al. for the n-cation  therefore,  are  consistent  pyridine ligands  with  the  porphyrin  radical moiety proposed  formulation for 17a-b. The  resonances for the coordinated pyridine in Ru (OEP)(py) n  203  2  (Figure 5.23a) are shifted  Ru  111  Figure 5.23:  J  H N M R spectra o f (a) Ru°(OEP)(py) and (b) [Ru (OEP)(py) ] III  2  BF ". Spectra  +  2  4  were recorded in CDC1 under aerobic conditions at 293 K, 300 M H z (FT). 3  (a)  I  py  /  [  C H, HQ 2  C HCI.  P y  11  i  i i i i i I i i i i I i i i i I i i i i j i i i i I  1  B  10  1  1  |  1  1  1  6  1  1  1  ' | ' 1  11  1 11  4  '  1 1  I  2 PPM  0  (b) py  I Ru  H„  C H ,  +  m  \ H.  w  H.  BF  4  T n„  "H  C H. C HCI,  m'  i  j  ^  J. p  i  i  i  i  ^  i  i  i  i  y  i  i  l  i  ^  i  204  l  i  i  ^  l  i  '  i  J jr. j  ' i—I—I—i—|—I—I—i—I—f ' ' r-r-  PPM  -10  Table 5.7: Summary of *H NMR  spectroscopic data for rRu (0EP)(pv) 1 and m  +  2  rRu (OEP)(CH CN)-,l complexes. m  +  8  ?  macrocycle resonances  axial pyridine resonances  complex-  lUmeso  SCU  «CH  SUpara  R u , 6a  9.74  3.98  2.08  4.69  4.18  2.30  rRu lCl. 17a  -1.26  17.21  -0.20  3.21  22.96  -6.99  [ R u ] B F , 17b  -1.88  18.05  -0.33  2.96  24.19  -7.60  [Ru-d )]Cl, 17c  -1.25  17.25  0.23  -  -  fRulBr, 17d  -1.82  18.18  -0.23  3.26  24.32  -7.65  [Ru]F, 17e  -1.79  18.20  -0.23  3.17  24.32  -7.65  [Ru]Br, 17£  23.36  8.48  -2.60  n  m  m  4  10  3  2  *- Measured at 293 K in CDC1 , 300 M H z (FT). 3  ^ Ru denotes Ru(OEP)(py) . 2  - Ru denotes Ru(OEP)(CH CN) .  c  3  2  205  6Wmeta 6 Wortho  —  -  upfield of those observed for free pyridine ( H  8.71, H  p  7.55  m  and H  7.19 ppm)  0  because of the  ring current effect of the macrocycle, as well as the usual upfield shift of the resonances of the ligand  upon  coordination  to a  metal.  16,17  '  The  27  H  and  0  H  resonances  p  for the coordinated  pyridines in 17a-e (Figure 5.23b) are shifted upfield of the positions observed for Ru (OEP)(py) n  in C D C 1  at 293 K, presumably due to the transfer of unpaired spin density from the metal to the  3  pyridine  2  (M-»L  assignments  CT);  the H  m  resonance  is shifted  some  18-20  ppm  downfield. The  of the three resonances for the coordinated pyridine ligands in 17a-e  general  were made  using data for the per-deuterated analogue of 17a. Assignments of the individual resonances to the H utilizing  die known effects of the ring current.  affected the most by  118  0  and H The  of coordinated pyridine were made  p  protons closest to the macrocycle arc  the ring current effect, being shifted upfield  the furthest. Thus, the  resonance of coordinated pyridine is observed to be the furthest upfield resonance and the H  p  H  c  is  least shifted from its 'free' position. Loss of spin density at the mcto-position of the pyridine ring  causes die corresponding resonance for the attached proton to appear well downfield of its  expected position. The  l  H  118  NMR  resonances, both  temperature-dependent,  due  for the  macrocycle  and  the  coordinated pyridines,  to die presence of an unpaired spin at the ruthenium  center.  arc The  chemical shifts of 17a were measured as a function of temperature and these data are presented in Table 5.8. Only die data for _17a are presented because those for 17b were quite similar to 17a. Isotropic shifts were calculated  from  die observed shifts by  subtracting the known diamagnetic  shift contribution based on data for Ru (OEP)(py) . The corresponding plot of the isotropic shift u  2  vs. 1/T is displayed in Figure 5.24. A l l the data sets obtained for 17a shown in Table 5.8 gave straight line plots but deviated, in some cases significantly, from the expected zero-intercept at 1/T of  =  0 for Curie-type behavior. Similar effects were observed in the case of 17b. The influence  factors  such  as  temperature-independent paramagnetism  from Curie law behavior for 17a-b.  206  may  lead  to the observed  deviation  Table 5.8: Data for the plot of isotropic shift (ppm) vs. 1/T (K' ) for rRu(OEP)(py) 1Cl 1  2  (a) macrocyclic resonances c5H (obs/iso£  5CH-,(obs/iso)^  c5CH,(obs/iso)^  -7.79/-17.53  18.94/14.96  -1.64/-3.71  4.11  -5.57/-15.31  18.43/14.45  -1.00/-3.07  267  3.74  -3.49/-13.23  17.99/14.01  -0.68/-2.75  294  3.41  -1.26/-11.00  17.21/13.23  -0.20/-2.27  313  3.19  -0.44/-10.18  17.33/13.35  -0.03/-2.10  331  3.02  0.09/ -9.65  17.33/13.35  0.09/-1.98  SH (obs/iso)^  6HJobs/iso)t  4.69/ 0.00  31.23/27.054  -7.96/-10.26  T(K)  1/T(K)  222  4.50xl0-  244  meso  3  (b) axial ligand resonances T(K)  1/T(K)  5H (obs/iso)^  222  4.50xl0-  244  4.11  4.12/-0.59  28.21/24.03  -7.60/ -9.90  267  3.74  3.49/-1.20  25.62/21.44  -7.60/ -9.90  294  3.41  3.21/-1.48  22.96/18.78  -6.99/ -9.29  313  3.19  2.96/-1.73  22.16/17.90  -7.24/ -9.54  331  3.02  2.90/-1.79  21.39/17.21  -7.24/ -9.54  m  p  3  S Obtained for a 3.8 m M solution of 17a in CDC1 , ± 1 K at 300 M H z (FT). 3  - (Observed/isotropic) chemical shift in _+ 0.01 ppm, diamagnetic correction made from Ru(OEP)(py) : 2  cSH  m e s o  = 9.74 ppm, SCU  ppm, <5H = 4.18 ppm, 6H m  0  2  = 2.30 ppm.  207  = 3.98 ppm, 5 C H  3  = 2.08 ppm, 5 H  p  = 4.69  Figure 5.24:  Plot of isotropic shift (ppm) vs 1/T (K" ) for [Ru(OEP)(py) ] CI", 17a. 1  +  2  represent the least-squaresfitof the data with extrapolation to 1/T = 0.  208  Solid lines  The  1 9  F and B N M R spectra of 17b were measured to confirm the presence of ionic BF . n  4  The N M R  data obtained in CDC1  3  by observing either nuclei indicate diat the BF " in JJb is 4  essentially the same as those in the series of compounds C B F " (see below). A broad singlet at +  4  + 7.07 ppm relative to (n-Bu) NBF in the F spectrum of 17b is assigned to die BF " counterion. 1 9  4  4  4  These experiments were done using (diamagnetic convention) vs. C F C 1 ) .  (n-Bu) NBF 4  as the external standard (set to -146.9 ppm  4  93  3  C BF ": F5,ppm: +  4  19  The  1I  H -145.6  NH + -146.9  +  Cs -141.9  4  B { H } N M R spectrum of 17b in CDC1 1  3  K -152.9  +  Na -158.9  +  +  Rb -149.9  +  run against the standard («-Bu) NBF 4  4  showed a  sharp resonance at 3.51 ppm superposed over a broad resonance which has the appearance of a broad triplet (+48, 0 and -43 ppm, linewidths of approximately 10 ppm at 96 MHz). These data are analogous  to those reported  for the B F " anion,  and concur  94  4  with  the conductivity  data in  supporting die postulated ionic formulation. voltammograms of 17a-b (see Figure 5.25 and data presented below) show two  The cyclic reversible  one-e' couples (peak-to-peak  assigned to the R u / R u m  separation  of approximately 65 +  5 mV) which arc  and the R u ( O E P ) / R u ( O E P ) redox processes. These assignments  u  i n  +  m  reduction potentials redox process -  for 17a^  [Ru ]^!!!! ]  -345  -319  -360  -460£  -410^  -485^  610  710  690  600H  690£  637£  8  111  11  [Ru ( )] /Hiu ] n i  +  + 2  I n  +  for 17t£  - Ru denotes Ru(OEP)(py) . 2  ^ Values _+ 10 mV vs. the F c / F c in 0.1 M T B A P hi CH C1 . +  2  2  £ Values ± 10 mV vs. the F c / F c in 0.1 M T B A P in C H C N . +  3  209  for 6a^  210  were made based on the null potentials and by monitoring the changes generated in the optical spectrum of 17a-b upon bulk coulometry as described for the Ru(OEP)X (n = 1, 2) cases (see n  Sections 5.2.a and 5.2.d.2). The first reduction potential (-345 mV for 17a, -319 mV for Hb and -360 mV for Ru(OEP)(py) (6a) vs. Fc /Fc) for each complex is assigned to die Ru /Rii couple +  in  n  2  because upon one-e" reduction of 17b at a potential of -500 mV vs. Fc /Fc, die optical spectrum +  of  Ru(OEP)(py)  was generated (see  2  Figure 5.26a). The optical spectrum of  17b could be  regenerated by bulk oxidation of this in situ solution at 300 mV vs. Fc /Fc. The changes in the +  optical spectrum show several isosbestic points, indicating clean reversible conversion of ]7b to Ru(OEP)(py) . These reduction potentials for l_7a and 17b are similar to that reported for the 2  Ru /Ru m  n  CH C1 ). 2  couple in Ru(OEP)py(CH CN) (-300 3  mV vs. Fc /Fc +  in 0.1  M (n-Bu) N P F in 4  6  126  2  Similar reversible redox behavior was observed for the bulk coulometric oxidation of J7b at 1200 mV vs. Fc /Fc (Figure 5.26b). The generated product has an optical spectnim that typifies +  the strong Soret absorption bands normally observed when the w-cation radical (OEP ) is formed +  with a BF " counterion. ' 17  109,110  4  The optical spectrum of a solution of 17a electrolyzed at the  same potential as 17b was quite similar to those shown earlier for the Ru (OEP ) and for the lv  +  Ru (OEP ) halide species (Figures 5.3a and 5.13b) Therefore, diis redox process is assigned to ni  +  the R u ( O E P ) ] / [Ru (OEP)] in  +  +2  in  +  couple. The second reversible reduction potential reported for  Ru(OEP)py(CH CN) (743 mV vs. Fc /Fc) was not assigned because die product formed upon bulk +  3  coulometric oxidation of Ru(OEP)py(CH CN) decomposed upon generation.  126  3  A similar result was  observed for the Ru(TPP)(py) analogue.  126  2  Another voltammetric couple could be observed in the CV of 17a-b at +1050-1070 mV vs. Fc /Fc, but this could not be identified by bulk coulometry because the redox couple was too +  close to the solvent discharge range. 5.2.e.3. Chemistry of [Ru(OEP)(py) ]  +  2  X", (17a-b). The substitution chemistry of these complexes  is limited because the two pyridine ligands of 17a-b do not appear even to partially dissociate.  211  Figure 5.26:  Bulk coulometry of [Ru(OEP)(py)2] BF " in 0.1 M TBAP in CH CN to generate +  4  3  (a) Ru^OEPXpyfe, and (b) rRu (OEP Xpy^l+Z. ra  +  0.8  I' '. ,' I. \ I l'  !.  1 •.  U  z <  CD  t w ••"/ --~~.v.  I  OC 0.4 r  O  w.  CD <  W.A A.' V  0.2 — 40 0 1  1  7 00  550  1 .2  S ore I  I I  f  i  O  z <  4-  CD  Ot  O to CO  <  03  -t-  4Q0  -t-  -t-  -t-  '550  WAVELENGTH.nm 212  -t7<J0  These compounds are soluble in chlorinated and coordinating solvents such as T H F stable in solution even at 10" M  and  CH CN, 3  for weeks under aerobic conditions as judged by UV/visiblc  5  spectroscopy, and display no susceptibility to light in solution. The complexes reacted with oxidants such as PhlO or mCPBA in CHC1  3  (about 3 mM)  decompose when  in air, as observed by the  bleaching of the reaction mixture within minutes. This decomposition was observed also when the reaction  was conducted  in C H C N  or under  3  argon  in either of the two solvents or in the  presence of the organic substrate cyclohexene (100 equivalents). One source of interest is that these complexes  can be reduced to the precursor Ru(OEP)(py)  2  by vacuum pyrolysis at 413 K and 1 x 10" torr for one hour. The mechanism of this reduction is 5  not known, but outer-sphere reduction of the cation in 17a-b by the anion seems likely. This reactivity  is dissimilar to that reported for the reduction of R u ( O E P ) B r  under the same conditions to give [Ru (OEP)] 17. > 36  2  The partial auto-reduction of [Ru (OEP)(P(n-Bu) ) ]  37  2  because the halide is uncoordinated to the metal  n  in  (8a) upon pyrolysis  IV  ni  3  the solid state over several weeks has been noted earlier,  17  +  2  B r to Ru"(OEP)(P(«-Bu) ) 3  2  in  the process believed to involve initial  dissociation of P(«-Bu) , followed by coordination of Br" and a reduction step involving phosphine 3  as the reductant:  17  slow [ R u ( O E P ) ( P ( n - B u ) ) ] Br"  Ru (OEP)Br(P(n-Bu) ) + P(n-Bu)  3  (5.12)  P(n-Bu) + 2 [Ru (OEP)(P(7z-Bu) ) ] Br" -> 2 Ru (OEP)(P(n-Bu) ) + P(n-Bu) Br  2  (5.13)  m  -  +  3  2  m  +  3  3  The reduction CH Cl /hexane. 7  IU  3  n  2  3  2  3  process was accelerated by recrystallization of [Ru (OEP)(P(«-Bu) ) ] m  3  17  9  +  2  Br  from  A similar process cannot occur in the case of j j a and 17b because even partial  dissociation of die coordinated pyridine is not observed in solution, and die  pyrolysis reaction  quantitatively gives Ru(OEP)(py) . 2  5.2.f. Summary  of electrochemical  data for Ru(OEP) complexes.  Table 5.9 summarizes the  electrochemical data discussed earlier in this Chapter: Further additions to this Table data for Ru (OEP)Br(PPh ) m  3  (10). The C V for 10 in C H C 1 2  213  2  arc the  is shown in Figure 5.27, and the two  Table 5.9: Summary of electrochemical data for Ru(OEP) complexes. reduction potentials 5  fRu (OEP ')l/rRu OEP)l rRu (OEP ')l/rRu (OEP)l  complex^  IV  +  IV  m  +  m  Ru^/Ru"  1  Ru /Ru" m  Ru^Br^Sa  782  -  -154  Ru^Clj.Sb  694  -  -170  7  -  312  R u ^ l . 16b  779  -  242  EM (py)2,6a  -  690  -  -360  [ E i ^ C p y y C l , 17a  -  600  -  -345  [R» (py)2]BF 17b  -  694  -  -319  R u B r . 16a  .  m  8  D  m  4>  Ru Br(PPh3), 10 m  1  602  -  -222  ?- In mV vs. F c / F c (632 mV vs. NHE) in C H C 1 , 0.1 M T B A P electrolyte at 293 K. +  2  2  ^ Ru denotes Ru(OEP).  214  Figure 5.27:  Cyclic voltammogram of Ru(OEP)BrfPPh ) in 0.1 M TBAP in CH C1 . X-axis scale is 3  in mV vs. the Fc /Fc couple. +  215  2  2  reversible couples observed are assigned centered  (-222 mV  to the ring- (602 mV  on  +  vs. F c / F c ) oxidation. These assignments are based on the observation  diat the  +  redox processes observed at 600-800 mV centered  vs. F c / F c ) and to die metal-  vs. F c / F c for Ru(OEP) complexes arise from the ring+  oxidation couple. The metal-centered couple was assigned  because this couple is observed  the oxidation side of the null potential, and because the potential (-222 mV  similar to that for the R u / R u IV  ra  vs. Fc /Fc) is +  couple in Ru(OEP)X (X = Br, CI). 2  From Table 5.9, it is apparent that the chloride ligand is more capable than die bromide ligand of stabilizing die R u  I V  shift of the R u / R u  oxidation state as judged by the cathodic  I V  i n  couple as the ligand varies from chloride to bromide; such an effect is as expected. Also, within Ru  111  precursor  complexes, those having axial halide ligands coordinated  10) give R u / R u IV  to the metal (16a-b and  couples, while diose having axial pyridine ligands (17a-b) coordinated  ni  to the  metal favor die- reduction process R u / R u . This trend is in keeping with the known ability of m  halide ligands to stabilize higher lower oxidation state.  n  oxidation states at the metal while pyridine ligands stabilize a  127  metal-centered ( R u / R u ) oxidation potentials for Ru(porp)(PR )  Indeed, the first  m  3  +  Lastly, die first oxidation process of Ru (porp)CO complexes yields [ R u ( O E P ) C O ] I1  metal-centered  oxidation  product.  17  These  n  data  show  that  +  the ability  stabilize a higher oxidation state of Ru increases in the order CO < P R  3  couple and -319 to -360 mV  for the R u / R u m  and not the ligands to  vs. F c / F c ) vary to a +  n  vs Fc /Fc for +  couple) showing that axial ligand  substitution has relatively little effect on the potential for die ring-oxidation process. large  variance  for the potential  relative invariance from  for the metal-centered  17  < py -< Br" < CI".  lesser extent than that for the metal-centered oxidation process (-220 to 312 mV m  +  of various  The reduction potentials for the ring-oxidation process (700 _+ 100 mV  I V  2  vs. F c / F c ) show that phosphines also stabilize the lower oxidation states of R u .  (592-462 mV  the R u / R u  complexes  n  oxidation  process  A  (Fe /Fe ) n i  n  similar 1 2 8  and  of the potential for the ring-centered process (porp 7porp) has been noted  electrochemical  +  studies  of Fe(porp)X  complexes where X  216  is varied.  129  Thus, the trends  observed here parallel those observed for the iron porphyrin systems. Of mV  interest, the reduction potential for the 0 7 0 2  2  couple has been shown to vary from -165  vs. F c / F c to +555 mV as the p H is adjusted from 7 to 1 in D M F . +  1 3 0  While this potential will  vary with different solvents and pH, the proposal that HX/air  is the oxidant for the oxidation of  Ru  appears to be correct, because the  precursors  11  to yield R u  complexes in C H C 1  I U  reduction potential of the R u / R u IU  for oxidation of R u to R u 11  m  n  2  or C H 7  8  couple (-320 to -360 mV vs. F c / F c ) is in die correct range +  by H / 0 . +  2  The complexes 8a-b and 17a-b decompose when reacted with w C P B A or PhIO, while complexes Ru(OEP)X  (16a-b) and 10 form green-colored  solutions which are stable under inert conditions.  Thus, no predictable trend in die reactivity of these Ru(OEP) complexes with /rcCPBA or PhIO can be derived from the electrochemical data. Comparison of the reduction potentials of the Ru(OEP) complexes  shown  i n Table  5.9 indicates that  Ru(OEP)Br(PPh ) QO) has the most 3  potentials for the formation  o f a species such as [ R u ( O E P ) X ( L ) ] . Further,  Ru(OEP) complex  to catalyze the oxidation of cyclohexene by PhIO;  I V  reported  +  +  favorable  K) is the only 40  clearly,  it  is  possible that the presence of the phosphine ligand in K> plays a major role in its ability to act as a catalyst for the oxidation of cyclohexene. In die reaction of JO widi m C P B A or PhIO, die oxidation of P P h be  die first  step,  followed  by the oxidation  0 = Ru (OEP )Br. ° Thus, species having 0 = P P h IV  porphyrin  +  4  complexes having  of the 0 = P P h that 0 = P P h  3  3  coordinated  0=PPh  3  3  3  to 0 = P P h  of the remaining  3  was suggested to  Ru(OEP)Br  fragment to  ligands may be present in situ; nithenium nonligands are precedented.  131  The relative ability  ligand to stabilize a high-oxidation state at Ru is unknown; however, considering  would be a weak 7r-acceptor when bound to Ru, lower metal oxidation states should  be favored. Secondly, die 0 = P P h  ligand would have to compete with Br" for the vacant sixth-  3  coordination site in [ 0 = R u ( O E P ) ] . Lastly, the trans effect of the oxo ligand may play an r v  +  +  important role in determining which ligand is coordinated to Ru in tins system. Of  interest,  several  five-coordinate  tetra(perfluorophenyl)porphyrin  217  (an  analogue  of  tetraphenylporphyrin, TPP) complexes of Fe, M n  and Cr having axial halide or azide ligands show  remarkable activity as catalysts for the selective oxidation of, for example, isobutane to /-butyl alcohol at thousands  of turnovers at room temperature utilizing just dioxygen.  avoid the use of expensive oxygen atom sources such as m-CPBA or PhlO. The system  132  These  systems  Ru(OEP)Br(PPh ) 3  for the oxidation of cyclohexene compares poorly with those reported using dioxygen as  40  die oxygen atom source because few turnovers are observed, and the oxidation mechanism is nonselective. alkenes  40  Thus, further studies aimed at developing catalysts for the oxidation of alkanes and  should  perhaps  be  concentrated  on  the  ruthenium.  218  tetra(perfluorophenyl)porphyrin  complexes  of  Chapter 6: General conclusions and recommendations for future work.  The  measurement of the forward and  systems involving the dissociation of a P P h  reverse rate constants and 3  or P P h  for  well  systems,  dissociation  of a  as  PPh  3  ligand. The  3  as  ligand  the  of trace H 0 2  concentrations (mM),  5a  may  be  3  thermodynamic and chemistry  and  4a  of  to yield  the strong  activation parameters measured  these  complexes,  show  that  the  the formally five-coordinate species  (5a) is greatly influenced by solvent effects. The  in solution is shown to be negligible at *H  NMR  effect of the  spectroscopy  sample  but at UV/visible spectroscopy sample concentrations (^L), the formation of  aquated six-coordinate species in and  bond strength in these complexes; die maximum  solution U  from  Ru(OEP)CO (3a) and Ru(OEP)PPh presence  3  indicates a weak bond, but its strength must be influenced by  1  trans effect of the CO these  11; PPh , 4a)  ligand from Ru(OEP)L(PPh3) (L = CO,  has allowed for a crude estimation of the Ru-P value of 64 kJ mol"  equilibrium constants for the  situ occurs. These results show diat while the structure of 3a  five-coordinate, square-pyramidal  in die solid  state, in solution, six-coordinate  octahedral species are formed even if weakly coordinating reagents are present. The the these studies to other ligand systems should be pursued  so that other Ru-L  extension of  bond strengths  (particularly, die Ru-CO bond strength) may be obtained. The mechanism of the oxidation of [Ru(OEP)]  2  (7) by H X  (X = Br, CI) was found to be more  complicated than diought initially. In aromatic solvents, die oxidant is identified as HX not trace X  2  in HX,  directly yielding R u ( O E P ) X IV  used is equal to or below -7 (X major intermediates is observed  =  2  quantitatively when the pK  a  itself and  of the HX  Br, 8a; CI, 8b; SbF , 8d). In C H C 1 , the formation of two 6  2  in the reaction of 7 with HCI,  8b upon aerobic oxidation in the presence of excess HCI.  2  the mixture quantitatively yields  These same intermediates are generated  from die reaction of 7 with CH C1 . Because of the highly reactive nature of the mixture 2  2  intermediates, the individual species could not be believed to be [ R u ( O E P ) ] C H C l 2  2  Q3)  acid  and  separated or isolated; however, the species are  Ru(OEP)H Q4), as determined  219  of  by comparison of their  spectroscopic  properties  with  reaction of 7 with C H C 1 2  with H X in aromatic solution  chemistry.  Ru (OEP)X IV  the  those of known  compounds.  suggest a direct bimolecular  2  Preliminary  The required  2  2  hydrogen  containing  studies  reaction. Radical-based  solvents and in C H C 1 , or of 7 with C H C 1 2  kinetic  2  co-product  reactivity  the  ot  7  itself, are indicated by the i n diese  reactions  giving  has not been identified; however, it is not H . The use of H X may help elucidate 3  2  2  mechanism of this reaction in either type of solvent, as well as identify  generated. The in situ, non-ionic, species Ru(OEP)(X') HX' with 7 (X' =  2  the co-products  have been generated by the reaction of  SbF , 8d) or with the mixture of intermediates from the 7 / C H C 1 T reaction ( X ' ?  6  = B F , 8c). One species, 8d, undergoes facile auto-reduction to give Ru (OEP)SbF  Q5). The  III  4  characterization and chemistry (8e)  on  was isolated  organometallic  of these (X') species should be studied further. Also, Ru(TMP)Br,  and characterized,  chemistry  and its chloride  of Ru(TMP) complexes  organoruthenium complexes of diis porphyrin the mesityl ligand imparts  6  should  analogue  generated  be developed  from  in  situ. The  8c, because few  have been reported. The additional steric bulk  that  to the macrocycle, relative to the substituents of the O E P and T P P  porphyrins, may yield novel chemistry. An  electrochemical study  of Ru(OEP)X  2  (X = Br, CI) reveals that the Ru^/Ru"  these complexes occurs at a low reduction potential, and some chemistry of R u ( O E P ) X  2  1  couple in ( X = Br,  CI, SbF ) confirms this result. The new complexes Ru(OEP)X (X = Br, J_6a; C I , JjSb) have been 6  synthesized by reduction of the parent Ru(OEP)X spectroscopy  2  species using gaseous N H . Initial ' H N M R 3  studies indicate that die reduction of Ru(OEP)X  2  (X = Br, CI) by N H  clean pseudo-first order kinetics, and as such, the complete study the solution Ru-X bond strength. The coordination chemistry  3  may follow  should be undertaken to obtain  at the vacant axial coordination site  in 16a-b is extensive, yielding the isolated six-coordinate species Ru(OEP)X(L) ( X = Br, C I ; L = C H C N , N H ) and the in situ species ( n - B u ) N 3  3  halide ligand in 16a-b occurs media'  such  +  4  only  at high  as a chromatographic  support.  [Ru (OEP)Br ]". Substitution of the coordinated m  2  temperatures or by the assistance of an 'exchange The in situ species  220  [Ru (OEP)(py) ] m  2  +  Br  was  generated by  either method. The  cyclohexene by fluorinated  inability of 16a-b  oxene reagents was  porphyrins  such  as  to perform as catalysts for the oxidation  particularly disappointing. The  the  tetra(perfluorophenyl)porphyrins  use 132  development of suitable catalysts for the oxidation of cyclohexene and desired. These halogen-containing  of complexes of  should  be  highly if  pursued  other organic  of  substrates  the is  complexes have already shown great promise in  metalloporphyrin  utilizing dioxygen as the reagent for the oxidation of organic substrates, instead of the expensive oxene reagents.  The  metadiesis  chemistry  of Ru™  and  of  ]6,  has also been extended, and  the  R u ( O E P ) X complexes (8a-b ra  and  respectively) to generate complexes of alkoxides, azides or hydrides should be studied. The  outer-sphere oxidation of Ru(OEP) complexes by  new  complexes [Ru(OEP)(py) ]  the  outer-sphere  +  2  Ru (OEP)PPh n  3  by  oxidation  X" (X  of  die  =  CI, Ha;  BF , 4  coordinatively  0 /H  +  2  17b) isolated and characterized. Similarly, unsaturated  trace air to give [ R u ( O E P ) O H ] 0 has IV  2  complexes  [Ru (OEP)] n  2  been shown to require both O,  and and  H 0. 2  Electrochemical ligands  favor  studies of Ru  reduction  ligands favor higher requiring  a  much  of  die  and  111  metal  Ru^COEP) complexes have shown that, whereas pyridine to  oxidation states (Ru ). IV  higher  oxidation  the  lower oxidation  The  potential than  electrochemical studies involving other R u  I V  ring-centered the  states (Ru"),  coordinated  oxidation process is less  metal-centered  oxidation process.  and Ru (porp) complexes should be pursued. m  221  halide favored, Further  Chapter 7; References. 1.  Iron Porphyrins. 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The Chemist's Companion.Wiley-InterScience.New York, 1972,pp.54-80.  99.  Cotton,F.A.;Wilkinson,G. Advanced Inorganic Chemistry.4^ Ed.,Wiley-Interscience,New York, 1980,Chapter 9.  100. Che,C.-M.;Tang,T.-W.;Poon,C.-K. J.Chem.Soc.,Chem.Commun., 1984,641. 101. Che,C.-M.;Wong,K.-Y.;Poon,C.-K. Inorg.Chem., 1986,25,1809. 102. Che,C.-M.;Lai,T.-F.;Wong,K.-Y. Inorg.Chem., 1987,26,2299. 103. Llobet,A.;Doppelt,P.;Meyer,T.J. Inorg.Chem., 1988,27,514. 104. Moyer,B.A.;Meyer,T.J. Inorg.Chem., 1981,20,436. 105. Binstead,R.A.;Meyer,T.J. J.Am.Chem.Soc, 1987,109,3287. 106. Groves,J.T.;Gilbert,J.A. Inorg.Chem., 1986,25,123. 107. Calderwood,T.S.;Bruice,T.C. Inorg.Chem.,1986,25,3722. 108. Che,C.-M.;Chung,W.-C. J.Chem.Soc.,Chem.Commun.,l9S6,3S6. 109. Dolphin,D.;Felton,R.H. Acc.Chem.Res., 1974,7,26. 110. Dolphin,D.;Forman,A.;Borg,D.C.;Fajer,J.;Felton,R.H. Proc.Natl.Acad.Sci., 1971,68,614. 111. EPR spectra were run at the University of British Columbia by Mr. Carl Jacobsori, whose  228  help is gratefully acknowledged. 112. Fiuirhop,J.-H.;Kadish,K.M.;Davis,D.G./.Am.CAem.Soc., 1973,95,5140. 113. (a) Scheidt,W.R.;Geiger,D.K.;Lee,Y.L.;Reed,C.A.;Lang,G. J.Am.Chem.Soc, 1985,107,5693. (b) Schol2,W.F.;Reed,C.A.;Lee,Y.L.;Scheidt,W.R.;Lang,G. J.Am.Chem.Soc. 1982.104.6791. (c) l^dmm,J.T.;Grimmett,D.;Haller,K.J.;Scheidt,W.R.;Reed,C.A. J.Am.Chem.Soc.,1981, 103.2640.  114. Kennedy,B.J.;McGram,A.C.;Murray,K.S.;Skelton.B.W.;White,A.H. Inorg.Chem.,1981,26,483. 115. (a) Scheidt,W.R.;Geiger,D.K.;Hayes,R.G.;Lang,G. J.Am.Chem.Soc. 1983.105.2625. (b) Geiger,D.K.;Lee,Y.L.;Scheidt,W.R. J.Am.Chem.Soc, 1984,106,6339. 116. Konig.E. Magnetic Properties of Coordination and Organometallic Transition Metal Compounds.Landolt-Bornstein.New Series,Vol.8,Hellwege,K.-H.;Hellwege,A.M.,Eds., Springer-Verlag.Berlin, 1976.  117. Earnshaw,A.;Figgis,B.N.;Lewis,J.;Peacock,R.D.  J.Chem.Soc, 1961,3132.  118. Horrocks,Jr.,W.D. in N M R of Paramagnetic Molecules. Principles and Applications,LaMar.G.N.; Horrocks,Jr.,W.D.;Holm,R.H.,Eds..Academic Press.New york,1983,pp.86-215. 119. Latimer.W.M. The Oxidation State of the Elements and their Potentials in Aqueous Solution, Prentice-Hall.New York,1938,pp.94-95. 120. Reference 77, pp. 1042-3. 121. Reference 118, Chapter 2. 122. Thackray,D.C;Ariel,S.;Leung,T.W.;Menon,K.;James,B.R.;Trotter,J. Can.J.Chem., 1986,64,2440. 123. Castro.C.E.;Anderson,S.E. Inorg.Chem., 1985,24,1113, and references therein. 124. Scheidt,W.R.;Lee,Y.L.;Tamai,S.;Hatano,K. y.Am.CAm.Soc, 1983,105,778. 125. Morishima,I.;Takamuki,Y.;Shiro,Y. J.Am.Chem.Soc. 1984.106.7666. 126. Brown,G.M.;Hopf,F.R.;Ferguson,J.A.,Meyer,T.J.,Whitten,D.G. J.Am.Chem.Soc, 1973,95,5939. 127. Bottomley,L.A.;01son,L.;Kadish,K.M. in Electrochemical and Spectroelectrochemical Studies of Biological Redox Components.Advances in Chemistry Series,Vol. 210,Kadish.K.M.,Ed.,American  229  Chemical Society .Washington, 1982,pp.279-311. 128. Bottomley,L.A.;Kadish,K.M. Inorg.Chem., 1977,16,711. 128. Phillippi,M.A.;Shimomura,E.T.;Goff,H.M. Inorg.Chem., 1981,20,1322. 130. Reference 127, Chapter 24. 131. Moyer,B.A.;Sipe,B.K.;Meyer,T.J/norg.CAe/w.,1981,20,1475. 132. Ellis,P.E.,Jr.;Lyons,J.E.y.CAem.Soc.,CAm.Commun., 1989,1189.  230  Appendix 1. Information needed for the use of the N M R simulation program DNMR3. A typical input data deck used to simulate the curves described in Chapter 3 is shown below: line 1 2 3 4 5 6 7 8  input 0011201 Ru(OEP)PPh + P P h 18.00 182.00 0101 0.00 200.00 0.180 0.820 0.200 0.70 3  3  1.50  34.00  These lines correspond to the following input parameters: line 1: NRUN,N,NE,MU,NMES (shown here as 0011201). The 001 refers to run number (eg. ran 1 must be input as 001); N is the number of nuclei, ( = 1); N E is the number of chemical configurations (2); M U  is for the mutual exchange case  (0 indicated that it was not  used); N M E S refers to the number of sets of magnetically equivalent nuclei (1). line 2: T E X T (e.g. title). line 3: C H E M I C A L SHIFT for the first chemical configuration (18.00 Hz), line 4: C H E M I C A L SHIFT for the second chemical configuration (182.00 Hz). line 5: NRS, L P U N C H , LPLOT, FR1, FR2, S C A L E , H E I G H T (shown here as 0101  0.00  200.00  1.50 34.00). NRS is the number of sets of rate constants (01); L P U N C H allows die output to be obtained as punched-cards (0 represents no punched-card output); L P L O T gives the option to generate a plot of the calculated data (1 represents plot output is desired); FR1 is the left plot frequency in Hz (0.00); FR2 is the right plot frequency i n Hz (200.00); S C A L E allows the scale to be varied in units of mm/Hz (1.50); and H E I G H T allows the plots to be scaled to any height in mm to a maximum of 240 mm. line  6: POP(l), POP(2). Represents  the populations of each of the nuclei having  chemical configuration, normalized to a total of 1 (0.180 and 0.820). line 7: T refers to the transverse relaxation time in seconds (0.20). 2  line 8: R C represents the rate constants used for the run (0.70). 231  a different  Since D N M R 3 is a general program for the simulation of observed N M R signals, the input deck shown  will  need  significant  modification  before  utilization  to simulate  cases  other  than an  exchange involving just two chemical configurations and one nuclei. The  method for determining  the position and population of each signal involved in die exchange  mechanism at each temperature has already been described  in Chapter 3. The T  2  value used for  the simulation of each spectrum was taken to be the same as that for the solvent, as previously discussed.  The program  DNMR3  utilizes these parameters and a rate constant  function which yields an intensity vs. frequency plot (i.e. an N M R spectrum). Values for the rate constants obtained,  as estimated  to calculate a  64  were chosen on a 'best guess' basis until a reasonable fit was  by comparing the simulated  and actual spectra. The uncertainty  in a rate  constant was found to be +_ 5 % at the 8 0 % level of confidence. Once diree rate constants at three different temperatures were estimated,  an Eyring plot was used to obtain other approximate rate  constants  temperamres. These rate constants  corresponding  to the odier  were then adjusted (a  small correction) individually to obtain a good fit of die simulated and experimental Finally,  these  rate  parameters reported  constants  were  then  used  in a second  Eyring  NMR  spectra.  plot, and the activation  in Chapter 3 were calculated from the slope and the intercept of this plot  using a least-squares fit program. In all cases, it was found that the uncertainty in the slope of the second Eyring plot was less that +_ 3 % at the 9 5 % uncertainty level, and so estimates of the uncertainties in the activation parameters A H J and A S | of +_ 1 0 % and +_ 2 0 % (at the 9 5 % imcertainty level), respectively, were presented with these data reported in Chapter 3. Several  sources of experimental  error contribute  to the imcertainty  limits  of the activation  parameters: (1) while the temperature measurement of the system was calibrated using a sample of neat methanol (this technique is described spectrometer),  in the user manual for the Varian  XL-300  NMR  and found to have an error limit of _+ 1 K, mere are obvious differences such as  sample size and concentration, and the type of N M R  tube used between the standard  sample used  to calibrate the temperature and the actual sample studied. Large errors would originate from the  232  temperature sufficiently  measurement  i f the  sample  were  not  equilibrated  at  each  temperature  for  long enough period of time (20 minutes); (2) shimming the magnet improperly  a was  found to be a critical factor i n determining the shapes of the lines recorded at each temperature. A  technique which proved useful was to adjust the lock shims until the lock signal stabilized for  a  five-minute time  period,  and  adjustment before the sample was was  done by  this  procedure  sometimes  required  20-30  minutes  of  fine  run; (3) the comparison of the simulated and measured spectra  simply superposing one  spectrum  underneath surface, a source of some additional error.  233  over another on  a  table illuminated  via the  Appendix 2; Data obtained from the titration of Ru(OEP)CO by P P h in C H as a function of 3  7  8  Temperature.-  Temperature = 293 K. [Ru] = 7.40 x 10" M, Cell Volume = 3.00 mL, [ P P h ] = 0.0867 M. Volume of PPh , (fth) 0.0 1.0 3.0 10.0 20.0 60.0 80.0 Absorbance (393 nm) 1.860 1.663 1.416 0.965 0.734 0.490 0.460 K = 1.47 x IO" M", slope = 0.77 6  3  stock  3  4  1  [Ru] = 5.74 x 10" M, Cell Volume = 3.00 mL, [ P P h ] = 0.0867 M. Volume of PPh , (/*L) 0.0 1.0 3.0 15.0 30.0 50.0 90.0 Absorbance (393 nm) 1.442 1.306 1.082 0.632 0.477 0.404 0.343 K = 1.57 x 10^ M" , slope = 0.83 6  3  stock  3  1  [Ru] = 3.87 x IO" M, Cell Volume = 3.00 mL, [ P P h ] = 0.0867 M. . 1.0 3.0 15.0 30.0 50.0 90.0 Volume of PPh , (u-L) 0.0 0.878 0.756 0.522 0.328 0.253 0.217 Absorbance (393 nm) 0.9972 K = 1.22 x IO" M" , slope = 0.82 6  3  slock  3  4  1  Temperature = 303 K. = 0.0867 M. [Ru] = 6.57 x IO" M, Cell Volume = 4.00 mL, [ P P h ] 1.0 3.0 10.0 30.0 55.0 80.0 Volume of PPh , ( M L ) 0.0 1.520 1.325 0.974 0.656 0.526 0.475 Absorbance (393 nm) 1.650 K = 1.33 x IO" M" , slope = 0.78 6  3  slock  3  4  1  = 0.0867 M. [Ru] = 2.47 x 10" M, Cell Volume = 4.00 mL, [ P P h ] 1.0 3.0 10.0 30.0 55.0 80.0 Volume of PPh , (fiL) 0.0 0.566 0.486 0.366 0.259 0.216 0.202 Absorbance (393 nm) 0.621 K = 1.16 x I f f M' , slope = 0.78 6  3  stock  3  4  1  Temperature = 313 K. [Ru] = 5.93 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0867 M. Volumeof PPh , (/*L) 0.0 1.0 3.0 10.0 20.0 60.0 80.0 Absorbance (393 nm) 1.310 1.224 1.073 0.785 0.534 0.430 0.393 K = 1.39 x IO" M" , slope = 0.76 6  3  stock  3  4  1  [Ru] = 7.87 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0867 M. Volumeof PPh , ( M L ) 0.0 1.0 3.0 10.0 20.0 60.0 80.0 Absorbance (407 nm) 0.421 0.527 0.676 0.933 1.157 1.240 1.260 K = 1.40 x IO" M" , slope = 0.81 6  3  slock  3  4  1  Temperature = 323 K [Ru] = 2.85 x 10" M, Cell Volume = 4.00 mL, r P P h ] = 0.0599 M. Volumeof PPh , ( M L ) 0.0 1.0 3.0 10.0 30.0 55.0 Absorbance (393 nm) 0.716 0.685 0.625 0.476 0.328 0.253 K = 1.52 x I f f M" , slope = 0.77 6  3  3  4  1  234  stock  80.0 0.208  100.0 0.187  120.0  Appendix 2 continued. [Ru] = 3.77 x 1CT M, Cell Volume = 4.00 mL, [ P P h ] = 0.0599 M. Volumeof PPh , (/*L) 0.0 1.0 3.0 10.0 30.0 55.0 Absorbance (393 nm) 0.948 0.910 0.833 0.655 0.447 0.356 K = 1.59 x 10"* M , slope = 0.77  80.0 -  100.0 -  120.0 0.288  [Ru] = 2.03 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0599 M. Volume of PPh , (/xL) 0.0 1.0 3.0 10.0 30.0 55.0 Absorbance (393 nm) 0.509 0.481 0.432 0.342 0.235 0.188 K = 1.50 x 10" M , slope = 0.91  80.0 -  100.0 0.145  120.0  6  3  s t o c k  3  1  6  3  s t o c k  3  4  1  Uncertainty in temperature +.0.1K. No correction for the amount of coordinated P P h was made for [ P P h ] because the 3  3  f  uncertainty limits for each set of data at one temperature were overlapping with those obtained at the other temperatures, and because the [PPh ] correction was small in comparison with 3  the large scatter in the equilibrium constant.  235  Appendix  3: Data obtained  from the titration of Ru(OEP)CO  by P P h  3  in CDC1  function temperature. 8  Temperature = 293 K [Ru] = 4.10 x 10" M , Cell Volume = 4.00 mL, [ P P h ] = 0,742 M. Volume of PPh , (/xL)* 0.0 1.0 6.0 16.0 40.0 65.0 Absorbance (393 nm) 1.029 0.822 0.694 0.535 0.363 0.282 K = 2.13 10" M " , slope = 0.69  90.0 0.238  [Ru] = 2.81 x IO" M, Cell Volume = 4.00 mL, [PPh;,],^ = 0.742 M . Volume of PPh , ( M L ) 0.0 2.0 10.0 30.0 55.0 80.0 Absorbance (393 nm) 0.707 0.633 0.461 0.287 0.208 0.174 K = 1.97 x 10" M" , slope = 0.79  120.0 0.141  [Ru] = 6.75 IO" M, Cell Volume = 5.00 mL, [ P P h ] = 0.676 M Volume of PPh , ( M L ) 0.0 2.0 8.0 30.0 55.0 Absorbance (393 nm) 1.696 1.580 1.236 0.811 0.617 K = 1.89 x 10" M" , slope = 0.83  80.0 0.513  150.0 0.390  [Ru] = 7.01 x 10" M, Cell Volume = 5.00 mL, [ P P h ] = 0.742 M Volumeof PPh , (ML) 0.0 2.0 10.0 30.0 55.0 80.0 Absorbance (393 nm) 1.762 1.625 1.272 0.859 0.651 0.545 K = 2.14 x 10" M" , slope = 0.85  150.0 0.409  6  3  stock  3  1  3  6  3  3  1  6  3  slock  3  3  1  Temperature = 303 K 6  3  stock  3  3  1  [Ru] = 3.10 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.742 M Volume of PPh , (»L) 0.0 2.0 8.0 30.0 55.0 80.0 Absorbance (393 nm) 0.778 0.703 0.543 0.315 0.229 0.194 K = 2.21 x 10" M" , slope = 0.85 6  3  stock  3  3  150.0 0.137  1  Ru] = 2.50 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.847 M Volume of PPh , (ML) 0.0 2.0 8.0 20.0 45.0 200.0 Absorbance (393 nm) 0.342 0.311 0.249 0.188 0.142 0.105 K = 2.40 x 10" M" , slope = 0.87 [  6  3  stock  3  3  1  Temperature = 313 K [Ru] = 7.36 x IO" M , Cell Volume = 5.00 mL, [ P P h ] = 0.824 M. Volume of PPh , (;tL) 0.0 2.0 8.0 20.0 45.0 70.0 Absorbance (393 nm) 1.847 1.715 1.439 1.120 0.827 0.695 K = 2.51 x 10" M" , slope = 0.88  150.0 0.517  [Ru] = 5.63 x IO" M, Cell Volume = 4.00 mL, [ P P h ] = 0.824 M. Volume of PPh , (uL) 0.0 2.0 8.0 20.0 45.0 70.0 Absorbance (393 nm) 1.415 1.286 1.030 0.789 0.549 0.455 K = 2.51 x 10" M" , slope = 0.86  150.0 0.346  6  3  slock  3  3  1  6  3  3  3  1  * includes 30 A»L of a 0.059 M P P h stock solution. 3  236  slock  3  as a  Appendix 3 continued [Ru] = 3.94 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.824 M. Volume of PPh , (>L) 0.0 2.0 8.0 20.0 45.0 70.0 Absorbance (393 nm) 0.990 0.899 0.715 0.531 0.379 0.308 K = 2.52 x lO" NT , slope = 0.86 6  3  slock  3  3  1  Temperature = 323 K [Ru] = 7.15 x 10' M, Cell Volume = 4.00 mL, [ P P h j ] ^ = 0.690 M. Volume of PPh , (/xL) 0.0 2.0 8.0 20.0 45.0 200.0 Absorbance (393 nm) 1.796 1.665 1.384 1.058 0.756 0.412 K = 2.93 x 10" M" , slope = 0.93 6  3  3  1  [Ru] = 3.29 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.690 M. Volume of PPh , (fth) 0.0 2.0 8.0 20.0 45.0 200.0 Absorbance (393 nm) 0.826 0.765 0.633 0.489 0.359 0.206 K = 3.15 x 10- M-', slope = 1.01 6  3  stC)ck  3  3  [Ru] = 7.04 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.690 M. Volume of PPh , ( M L ) 0.0 2.0 8.0 20.0 45.0 200.0 Absorbance (393 nm) 1.769 1.640 1.366 1.045 0.748 0.418 K = 2.89 x 10" M->, slope = 0.92 6  3  stock  3  3  Uncertainty in temperature _+ 0.1 K. No correction for the amount of coordinated P P h for the calculation of [PPh ] 3  3  was made because die correction was less than 3 %.  237  f  150.0 0.230  Appendix 4: Data obtained from the titration of Ru(OEP)PPh by P P h in C D as a function of 3  3  7  8  temperature.-  Temperature = 293 K [Ru] = 7.43 x 10" M , Cell Volume = 4.00 mL, [ P P h ] = 0.0422 M. Volume of PPh , (uh) 0.0 0.5 1.0 1.5 2.0 25.0 40.0 Absorbance (395 nm) 0.769 0.590 0.514 0.458 0.427 0.298 0.289 Absorbance (422 nm) 1.166 1.443 1.557 1.636 1.683 1.857 1.866 K (at 395 nm) = 8.87 x 10" NT , slope = 0.96 K (at 422 nm) = 8.04 x 10" M" , slope = 0.95 6  3  stock  3  6  1  6  1  [Ru] = 6.34 10" M , Cell Volume = 5.00 mL, [ P P h ] = 0.676 M Volumeof PPh , (/xL) 0.0 0.5 1.0 1.5 2.0 Absorbance (395 nm) 0.699 0.526 0.453 0.412 0.384 Absorbance (422 nm) 0.926 1.199 1.320 1.372 1.418 K (at 395 nm) = 8.20 x 10" M" , slope = 1.01 K (at 422 nm) = 7.52 x 10" M" , slope = 1.00 6  3  stock  3  6  1  6  1  25.0 40.0 0.267 0.259 1.583 1.593  Temperature = 303 K [Ru] = 5.97 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0422 M. Volume of PPh , (fiL) 0.0 0.5 1.0 1.5 2.0 25.0 Absorbance (395 nm) 0.785 0.622 0.539 0.490 0.446 0.268 Absorbance (422 nm) 0.675 0.930 1.077 1.136 1.219 1.485 K (at 395 nm) = 1.20 x 10' M" , slope = 1.01 K (at 422 nm) = 1.15 x 10" M" , slope = 0.97 6  3  slock  3  5  1  5  1  [Ru] = 6.52 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0422 M. Volumeof PPh , ( M L ) 0.0 0.5 1.0 1.5 2.0 25.0 Absorbance (395 nm) 0.847 0.700 0.608 0.539 0.489 0.310 Absorbance (422 nm) 0.741 0.994 1.171 1.291 1.378 1.628 K (at 395 nm) = 1.26 x 10" M" , slope = 0.85 K (at 422 nm) = 1.09 x 10" M" , slope = 0.76  40.0 0.257 1.500  6  3  stock  3  5  40.0 0.299 1.639  1  5  1  Temperature = 313 K [Ru] = 2.93 x 10" M, Cell Volume = 4.00 mL, [ P P h Volumeof PPh , ( / i L ) 0.0 0.5 1.0 Absorbance (395 nm) 0.606 0.521 0.474 Absorbance (422 nm) 0.211 0.338 0.422 K (at 395 nm) = 1.76 x 10" M" , slope = 0.93 K (at 422 nm) = 1.67 x 10" M " , slope = 1.03 6  3  3  5  ] = 0.0422 M. 1.5 2.0 25.0 40.0 0.439 0.393 0.245 0.233 0.466 0.499 0.729 0.736 stock  1  5  1  [Ru] = 8.94 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0422 M. Volumeof PPh , ( / i L ) 0.0 0.5 1.0 1.5 2.0 25.0 40.0 Absorbance (395 nm) 1.371 1.154 0.997 0.887 0.791 0.396 0.373 K (at 395 nm) = 1.62 x 10' M" , slope = 0.87 6  3  3  5  1  238  stock  Appendix 4 continued Temperature = 323 K [Ru] = 6.82 x 10" M, Cell Volume = 4.00 mL, [ P P h Volume of PPh , (^L) 0.0 1.0 2.0 Absorbance (395 nm) 1.134 0.071 0.758 Absorbance (422 nm) 0.507 0.844 1.059 K (at 395 nm) = 2.47 x 10" M" , slope = 0.93 K (at 422 nm) = 2.53 x 10" M" , slope = 0.95 6  3  ]  = 0.0422 M. 3.0 4.0 25.0 40.0 0.680 0.623 0.350 0.327 1.194 1.285 1.665 1.713  3  5  5  stock  1  1  [Ru] = 4.20 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0422 M. Volumeof PPh , (/xL) 0.0 0.5 1.0 1.5 2.0 25.0 40.0 Absorbance (395 nm) 0.814 0.706 0.658 0.606 0.564 0.315 0.298 Absorbance (422 nm) 0.259 0.443 0.507 0.591 0.639 1.019 1.054 K (at 395 nm) = 2.33 x 10" M" , slope = 1.07 K (at 422 nm) = 2.40 x 10" M" , slope = 1.20 6  3  stock  3  5  1  5  1  [Ru] = 4.49 x 10" M, Cell Volume = 4.00 mL, [ P P h ] = 0.0422 M Volume of PPh , (/xL) 0.0 0.5 1.0 1.5 2.0 25.0 40.0 Absorbance (395 nm) 0.804 0.688 0.618 0.536 0.499 0.261 0.231 Absorbance (422 nm) 0.264 0.442 0.553 0.694 0.742 1.108 1.129 K (at 395 nm) = 2.56 x 10" M" , slope = 1.18 K (at 422 nm) = 2.30 x 10" M" , slope = 1.11 6  3  slock  3  5  1  5  1  - Uncertainty in temperature .+ 0.1 K. [PPh ] , the free 3  f  [PPh ] in solution was corrected for partial coordination of 3  die added P P h to Ru(OEP)PPh using [PPh ] = [PPh ] . 3  3  3  f  [(A-A )/(A -Aj)][Ru], as described in Chapter 3. 0  0  239  3  tol  Appendix 5. Raw data for the reaction of C H C 1 with rRu(OEP)l at 293 K, 2  Entry 1  2  Entry 2  2  Entry 4  Entry 3  [Ru ] = 0.17 m M  [Ru ] = 0.17 mM  [Ru ] = 0.19 m M  [Ru ] = 0.19 mM  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  Time, s ^540 nm 0 ~ 0.281 100 0.296 200 0.306 300 0.311 400 0.316 500 0.321 600 0.324 700 0.326 0.328 800 900 0.329 1000 0.331  Time, s ^516 nm 0 ~~ 0.265 100 0.268 200 0.271 300 0.273 400 0.275 500 0.277 600 0.278 700 0.279 800 0.280 900 0.280 0.280 1000  2  2  2  ^540 run  Time.s 0 100 200 300 400 500 600 700 800 900 1000  ~0.235 0.256 0.265 0.272 0.277 0.284 0.287 0.290 0.293 0.295 0.296  Entry 5  2  2  2  Time, s 0 100 200 300 400 500 600 700 800 900 1000  y^516 nm  ~0.212 0.221 0.224 0.226 0.227 0.233 0.234 0.235 0.237 0.237 0.237  Entry 6  2  2  2  2  2  2  Entry 8  Entry 7*  [Ru ] = 0.28 mM  [Ru ] = 0.37 mM  [Ru ] = 0.39 mM  [Ru ] = 0.46 mM  [CH C1 ] = 15.6 M  [CH C1 ] == 15.6M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  Time, s A 0 0.522 84 0.565 168 0.576 252 0.620 336 0.640 420 0.654 504 0.670 588 0.681 0.693 672 0.702 756 840 0.711 924 0.720 0.726 1008 1092 0.736 1176 0.740 00 0.794  Time.s A 0 0.542 200 0.618 400 0.659 600 0.689 800 0.711 0.730 1000 0.748 1200 1400 0.762 1600 0.772 1800 0.783 2000 0.791  2  2  Time.s 0 84 168 252 336 420 504 588 672  00  2  y^540 nm  ^0.390 0.429 0.455 0.475 0.487 0.502 0.509 0.515 0.519 0.575  2  2  2  Time, s 0 260 400 540 680 820 960 1100 1240 1380 1520 1660 1800 2220  00  ^540 nm  ~0.334 0.373 0.409 0.432 0.450 0.469 0.484 0.465 0.505 0.514 0.522 0.529 0.535 0.552 0.585  2  2  2  5 4 0  n m  2  2  2  5 4 0  * These data were used for plot shown in Figure 4.1 l b in Section 4.2.e. 240  n m  Appendix 5 continued. Entry 10  Entry 9  Entry 11  Entry 12  [Ru ] = 0.46 m M  [Ru ] = 0.57 m M  [Ru ] = 0.91 m M  [Ru ] = 0.92 m M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  Time, s A 540 nm 0 ~ 0.931 40 1.050 340 1.197 640 1.284 940 1.341 1240 1.383 1540 1.417 1840 1.444 2140 1.469 2440 1.495 2740 1.517 3040 1.531 00 1.575  Time, s y^540 nm 1.420 0 1.441 300 600 1.459 900 1.475 1200 1.490 1500 1.506 1.520 1800 2100 1.531 2400 1.546 2700 1.557 1.568 3000 3300 1.580 3600 1.593 00 1.895  2  2  2  ^516 nm  Time.s 0 200 400 600 800 1000 1200 1400 1600 1800 2000  ~0.484 0.513 0.529 0.540 0.548 0.554 0.561 0.566 0.571 0.575 0.578  Entry 13  2  2  2  Time, s 0 420 720 1020 1320 1620 1920 2220 2520 2820  00  y^540 nm  ~0.670 0.780 0.849 0.904 0.934 0.972 0.994 1.028 1.045 1.056 1.108  Entry 14  2  2  2  Entry 15  2  2  2  Entry 16  [Ru ] = 0.92 m M  [Ru ] = 1.25 m M  [Ru ] = 4.43 m M  [Ru ] = 0.61 m M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  [CH C1 ] = 15.6 M  [CH C1 ] = 8.87 M  Time, s A 540 nm 0 0.412 300 0.437 600 0.453 1800 0.479 3000 0.497 4200 0.517 5400 0.531 6600 0.562 7800 0.574 9000 0.588 10200 0.603 11400 0.618 12600 0.631 13800 0.640 00 0.668  Time, s ^540 nm 0 ~ 0.840 600 0.855 1200 0.907 1800 0.921 2400 0.939 3000 0.958 3600 0.968 4200 0.981 4800 0.990 5400 1.000 6000 1.009 00 1.053  2  2  Time.s 0 300 600 900 1200 1500 1800 2100 2400 2700 3000 3300 3600  00  2  ^516 nm  1.285  1.294 1.301 1.308 1.315 1.319 1.326 1.332 1.338 1.342 1.349 1.354 1.358 1.687  2  2  2  Time, s 0 720 1320 1920 2520 3120 3720 4320 4920 5520 6120 6720 7320  ^540 nm  ~0.934 1.156 1.249 1.308 1.351 1.383 1.417 1.436 1.459 1.475 1.494 1.503 1.542  2  2  241  2  2  2  2  Entry 17  Entry 18  Entry 19  Entry 20  [Ru ] = 0.73 m M  [Ru ] = 0.73 mM  [Ru ] = 1.20 mM  [Ru ] = 1.20 mM  [CH C1 ] = 1.97 M  [CH C1 ] = 1.97 M  [CH C1 ] = 0.9 M  [CH C1 ] = 0.9 M  Time, s y^540 nm ~~ 1.307 0 600 1.369 1.392 1800 1.415 3000 1.448 4200 1.482 5400 1.524 6600 1.566 7800 9000 1.609 00 1.985  Time, s y^516 nm 0 ~ 1.297 1.342 600 1.356 1800 1.372 3000 1.395 4200 5400 1.423 6600 1.451 7800 1.482 1.512 9000 00 2.073  2  2  Time.s 0 1800 3600 5400 7200 9000 10800 12600 14400 16200 18000  00  2  ^540 nm  ~b.794 0.822 0.843 0.861 0.875 0.886 0.896 0.903 0.910 0.915 0.920 0.922  2  2  2  Time, s 0 1800 3600 5400 7200 9000 10800 12600 14400 16200 18000  00  y^516 nm _  0.810 0.818 0.825 0.832 0.836 0.840 0.843 0.846 0.848 0.851 0.851 0.853  2  2  242  2  2  2  2  

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