Reduction–oxidation properties of organotransition-metal complexes. Part 6. The isomerization, and one-electron oxidation, of syn- and anti-di-µ-arylthio-bis[(η-cyclopentadienyl)rhodium

Abstract

The reaction of [Rh(η-C5H5)(CO)2] with R1SSR1 affords [{Rh(µ-SR1)(η-C5H5)}2](R1= Ph or C6H4Me-p) as a mixture of syn and anti isomers. Each isomer is not fluxional but syn–anti isomerization, via a bridge-opening mechanism, occurs at room temperature. The isomerization process has been studied by 1H n.m.r. spectroscopy and by cyclic voltammetry which also reveals that both isomers undergo irreversible one-electron oxidation at the platinum electrode in CH2Cl2. The complex syn-[{Rh(µ-SC6H4Me-p)(η-C5H5)}2] reacts with di-p-tolyl disulphide, in the presence of [NO][PF6], to give [Rh2(µ-SC6H4Me-p)3(η-C5H5)2][PF6], and with [N(C6H4Br-p)3]-[SbCl6] to give [Rh2(µ-Cl)(η-SC6H4Me-p)2(η-C5H5)2][SbCl6], via one-electron oxidation followed by insertion into the metal-metal bond of the radical cation [{Rh(µ-SC6H4Me-p)(η-C5H5)}2]+.