The reaction of [RhH(PPh 3) 4] with thiols: a 1H and 31P NMR study

Abstract

In toluene or THF at −40°C [RhH(PPh 3) 4] reacts with RSH (R = Pr i, Ph, CH 2Ph) to give the unstable dihydro complex [RhH 2(SR)(PPh 3) 3]. At 20°C decomposition of this complex with loss of H 2 occurs via a five-coordinate species [RhH 2(SR)(PPh 3) 2] to give [Rh(SR)(PPh 3) 3], which then dimerises to give the stable product [Rh 2(μ-SR) 2(PPh 3) 4]. In toluene/pyridine the initial product is [RhH 2(SR)(PPh 3) 2(py)]. Loss of H 2 gives [ cis-Rh(SR)(PPh 3) 2(py)], which then undergoes further reaction with thiol. Where the formation of a five-coordinate dihydro species is prevented by the presence of a chelating ligand NArS- (NArS = 2-pyridylmethanethiolate, pyrimidine-2-thiolate, benzthiazole-2-thiolate and purine-6-thiolate) a thermally stable dihydrobis(triphenylphosphine)rhodium thiolate complex can be isolated.