Thioxoethenylidene (CCS) as a Bridging Ligand

Abstract

The reaction of [Mo(≡CBr)(CO) 2 (Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with [Fe 2 (μ-SLi) 2 (CO) 6 ] affords, inter alia, the unsymmetrical binuclear thioxoethenylidene complex [Mo 2 (μ,σ( C ):η 2 ( C ′ S )-CCS)(CO) 4 (Tp*) 2 ], which may be more directly obtained from [Mo(≡CBr)(CO) 2 (Tp*)] and Li 2 S. The reaction presumably proceeds via the intermediacy of the bis(alkylidynyl)thioether complex S{C≡Mo(CO) 2 (Tp*)} 2, which was, however, not directly observed but explored computationally and found to lie 78.6 kJ mol –1 higher in energy than the final thioxoethenylidene product. Computational interrogation of the molecules [M 2 (μ-C 2 S)(CO) 2 (Tp*) 2 ] (M = Mo, W, Re, Os) reveals three plausible coordination modes for a thioxoethenylidene bridge which involve a progressive strengthening of the C–C bond and weakening of the M–C and M–S bonds, as might be expected from simple effective atomic number considerations.