Transition metal complexes with sulphur ligands. Part 67. A novel type of reaction: nucleophilic alkylation of thiolato ligands by carbanions via intramolecular electron transfer. Alkylation and reduction of [W(S2C6H4)3] by lithium alkyls

Abstract

The reaction of [W(S₂C₆H₄)₃]1 with LiMe depends on the concentration of the latter and yields either the anionic tungsten(IV) complex [NR₄][W(S₂C₆H₄)₂(MeSC₆H₄S)](R = Me, 2a; or Et, 2b) or the anionic tungsten(V) complex [NMe₄][W(S₂C₆H₄)₃]3b. This novel type of reaction demonstrates the reactive versatility of transition-metal sulphur centres and is of importance for the understanding of trans-methylation reactions catalysed by oxidoreductases with sulphur-co-ordinated transition-metal centres, e.g. CO dehydrogenase. When 1 is treated with LiEt, LiCH₂Bu^t or LiPh only a reduction of 1 takes place yielding 3b. The reaction of complex 1 with 2 equivalents of LiBuⁿ affords the dianionic tungsten(IV) complex [NMe₄]₂[W(S₂C₆H₄)₃]4. The electrophilic alkylation of 4 by 2 equivalents of R₃OBF₄(RMe or Et) or of 2b by 1 equivalent of Me₃OBF₄ leads to the doubly alkylated complexes [W(S₂C₆H₄)(RSC₆H₄S)₂](R = Me, 5a; or Et, 5b).