Oxygenation studies. Part I. Rhodium(I)-promoted oxygenation of terminal olefins to methyl ketones

Abstract

Hex-1-ene, hept-1-ene, and oct-1-ene are converted to the corresponding methyl ketones with dioxygen at ambient temperature and pressure in benzene solutions of the complexes [RhH(CO)(PPh₃)₃], (I), and [RhCl(PPh₃)₃], (II). Small quantities of hexanal and heptanal respectively are also formed from hept-1-ene and oct-1-ene. Higher yields of ketone (70–88% based on the complex) are obtained when [RhCl(PPh₃)₃] is used. Radical-chain processes have not been detected and the reactions appear to involve co-oxygenation of co-ordinated PPh₃ and olefin at the metal centre. Evidence for the formation from [RhCl(PPh₃)₃] of several complexes which can produce ketones has been obtained. The course of the reaction of the complex [RhCl(PPh₃)₃] with dioxygen is sensitive to the concentration of the latter.