Preparation of chalcogenolato-bridged dinuclear Tp*Rh–Cp*Ru complexes (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate, Cp* = η5-pentamethylcyclopentadienyl) and binding of dioxygen to their Ru sites

Abstract

Reactions of [Tp*Rh(coe)(MeCN)] (1; Tp* = hydrotris(3,5-dimethylpyrazol-1-yl); coe = cyclooctene) with one equiv of diphenyl dichalcogenides PhEEPh (E = Se, Te) afforded the mononuclear Rh^III complexes [Tp*Rh(EPh)₂(MeCN)] (2b: E = Se; 2c: E = Te), as reported previously for the formation of [Tp*Rh(SPh)₂(MeCN)] (2a) from the reaction of 1 and PhSSPh. Complexes 2a–2c were treated with the Ru^II complex [(Cp*Ru)₄(µ₃-Cl)₄] (Cp* = η⁵-C₅Me₅) in THF at room temperature, yielding the chalcogenolato-bridged dinuclear complexes [Tp*RhCl(µ-EPh)₂RuCp*(MeCN)] (3). Complex 3a (E = S) in solution was converted slowly into a mixture of 3a and the sterically less encumbered dinuclear complex [Tp*RhCl(SPh)(µ-η¹-S-η⁶-Ph)RuCp*] (4a) at room temperature. In 4a, one SPh group binds only to the Rh center as a terminal ligand, while the other SPh group bridges the Rh and Ru atoms by coordinating to the former at the S atom and to the latter with the Ph group in a π fashion. The Se analogue 3b also underwent a similar transformation under more forcing conditions, e.g. in benzene at reflux, whereas formation of the µ–η¹-Te-η⁶-Ph complex was not observed for the Te analogue 3c even under these forcing conditions. When complexes 3 was dissolved in THF exposed to air, the MeCN ligand bound to Ru was substituted by dioxygen to give the peroxo complexes [Tp*RhCl(µ-EPh)₂RuCp*(η²-O₂)] (5a: E = S; 5b: E = Se; 5c: E = Te). X-Ray analyses have been undertaken to determine the detailed structures for 2c, 3a, 3b, 4a, 5a, 5b, and 5c.