TRANSITION-METAL COMPLEXES WITH SULFUR LIGANDS .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

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 LiBu(n) affords the dianionic tungsten(iv) complex [NMe4]2[W(S2C6H4)3] 4. The electrophilic alkylation of 4 by 2 equivalents of R3OBF4 (R = Me 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).