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

Article abstract of DOI:10.1016/S1381-1169(96)00260-9

The stoichiometric oxidations of some P(p-X-C₆H₄)₃ compounds (X = OMe, Me, H, F, Cl and CF₃), AsPh₃ and SbPh₃ by trans-Ru(VI)(TMPO)₂ (1) in benzene solution generate the corresponding oxides and Ru(II)(TMP)(L) species (L = P(p-X-C₆H₄)₃, AsPh₃, SbPh₃). Stopped-flow kinetic data are consistent with a mechanism involving formation (within a k₁ 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). δH₁(+) values for the phosphine systems vary from 18 to 21 kJ mol^-1, increasing with decreasing electron density at the phosphorus, while ΔS₁(+) values become more favorable (-94 to -78 J mol^-1 K^-1) with increasing molecular mass of the substituent. Preliminary kinetic data on the O₂-oxidations of the substrates catalyzed by (1) under 1 atm of air are presented.