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]⁺.