Mechanistic aspects of the oxidation of phosphines and related substrates by trans-Ru-VI(TMP)(O)(2); TMP equals dianion of 5,10,15,20-tetramesitylporphyrin

The stoichiometric oxidations of some Pt (p-X-C6H4)(3) compounds (X=OMe, Me, H, F, Cl and CF3), AsPh(3) and SbPh(3) by trans-Ru-VI(TMP)(O)(2) (1) in benzene solution generate the corresponding oxides and Ru-II(TMP)(L) species (L=P(p-X-C6H4)(3), AsPh(3), SbPh(3)). Stopped-flow kinetic data are consistent with a mechanism involving formation (within a k(1) step) of Ru-IV(TMP)(O)(OL) which then reversibly dissociates the OL ligand to generate Ru-IV(TMP)(O); this disproportionates to Ru-VI(TMP)(O)(2) and Ru-II(TMP), which forms Ru-II(TMP)(L). Delta H-1 double dagger values for the phosphine systems vary from 18 to 21 kJ mol(-1), increasing with decreasing electron density at the phosphorus, while Delta S-1 double dagger values become more favorable (-94 to -78 J mol(-1) K-1) with increasing molecular mass of the substituent. Preliminary kinetic data on the O-2-oxidations of the substrates catalyzed by (1) under 1 atm of air are presented.