Reaction mechanisms of metal–metal-bonded carbonyls. Part 16. Reversible fragmentation of cyclo-tris[tricarbonyl(triphenylphosphine)-ruthenium](3 Ru–Ru)

Abstract

The kinetics of reaction in decalin of [{Ru(CO)₃(PPh₃)}₃] with oxygen in the presence of triphenylphosphine have been studied and shown to involve reversible fragmentation into two species, only one of which reacts directly with oxygen. It is suggested that the two species are [{Ru(CO)₃(PPh₃)}₂] and high-spin tetrahedral [Ru(CO)₃(PPh₃)]. Kinetic parameters for the fragmentation process are k(100 °C)= 1.1 × 10^–2 s^–1, ΔH^‡= 130.0 ± 2.5 kJ mol^–1, and ΔS^‡= 64.2 ± 7.5 J K^–1 mol^–1. The immediate products of the reaction are triphenylphosphine oxide and an insoluble, involatile, yellow ruthenium complex that has not yet been characterized. When generated at low concentrations in toluene, the yellow complex changes to a green one that catalytically oxidizes PPh₃.