Notes. Oxo transfer reactions. Mechanistic studies on the oxidation of triphenylphosphine by trans-[ RuVIL(O)2]2+(L = 1,4,8,11 -tetramethyl- 1,4,8,11 -tetra-azacyclotetradecane)

Abstract

The mechanism for the oxidation of PPh₃ to OPPh₃ by trans-[ Ru^VIL(O)₂]²⁺(L = 1,4,8,11- tetramethyl- 1,4,8,11 -tetra-azacyclotetradecane) in CH₃CN was studied from 280 to 299 K. The rate law for the reaction is d [Ru^VI]/dt =k₂[PPh₃][Ru^VI]. At 299 K, k₂, is (1.28 ± 0.1)× 10² dm³ mol^–1 s^–1. The ΔH^‡ and ΔS^‡ values are (8.7 ± 0.8) kcal mol^–1 and –20 ± 2 cal K^–1 mol^–1 respectively. A direct comparison between the reactivities of trans-[Ru^VI(O)₂]²⁺ and [Ru^IV(bipy)₂(py)(O)]²⁺(bipy = 2,2′- bipyridine; py = pyridine) towards the oxidation of PPh₃ shows the ruthenium(IV) complex to react 1 000 times faster.