Organosulphur–transition-metal chemistry. Part 4. The isomerism of µ-thio- and µ-seleno-bis[carbonyl(η-cyclopentadienyl)ruthenium] complexes

Abstract

Complexes [Ru(CO)₂(ER)(η-C₅H₅)] and [{Ru(CO)(µ-ER)(η-C₅H₅)}] are formed when mixtures of [{Ru(CO)₂-(ηC₅H₅)}₂] and E₂R₂(ER = SMe, SCH₂Ph, SPh, or SePh) are subjected to U.V. irradiation. With S₂Bu^t₂, [Ru(CO)₂(SBu^t)(η-C₅H₅)], [Ru(CO)₂(S₂Bu^t)(η-C₅H₅)], and [Ru₂(CO)₂(µ-SBu^t)(µ-S₂Bu^t)(η-C₅H₅)₂] are produced. On heating or irradiating, [Ru(CO)₂(ER)(η-C₅H₅)] is converted into [{Ru(CO)(µ-ER)(η-C₅H₅)}₂]. The diruthenium complexes, which are concluded to contain a non-planar Ru₂E₂ ring, exist as isomers in which the cyclopentadienyl ligands are cis or trans with respect to the ring, with additional isomerism arising from the relative orientation of the R groups. Interconversion of cis and trans isomers occurs on irradiation or heating, relative stabilities depending on the nature of the bridging ER group. Isomers varying only in R-group orientation, however, may be interconverted on the n.m.r. time scale. This is so with trans-[{Ru(CO)(µ-SCH₂Ph)(η-C₅H₅)}₂], and with cis- and trans-[{Ru(CO)(µ-SePh)(η-C₅H₅)}₂], each of which exists as a rapidly interconverting mixture of two such isomers, attributed to inversion at sulphur or selenium.