Sulphur-containing metal complexes. Part 9. Synthesis of trisubstituted aminocarbene–thioether chelates of chromium(0) and tungsten(0)

Abstract

Several isocyanide–thioether complexes, cis-[M(CNR)(CO)₄{S(R¹)CH₂R²}][M = Cr: R = Bu^t, R¹R²=(CH₂)₃S; R = R¹= Ph, R²= SPh; R = cyclo -C₆H₁₁ or CH₂Ph, R¹R²=(CH₂)₃S. M = W : R = Bu^t, R¹R²=(CH₂)₃S] were prepared by u.v. irradiation of the corresponding pentacarbonyl(isocyanide) complexes in the presence of the thioether compounds. Deprotonation of two of these, cis-[M(CNBu^t)(CO)₄{[graphic omitted]H₂}](M = Cr or W), with LiBu and addition of PEt₃, resulted (via consecutive carbonylation and isocyanide insertion into a metal–carbene bond) in the formation of the evasive trisubstituted aminocarbene–thioether chelates, fac-[[graphic omitted]}(PEt₃)], upon alkylation with [Et₃O][BF₄]. Replacement of the phosphine by 1,3-dithiolane-2-thione under similar reaction conditions yielded, unexpectedly, the substitution products cis-[Cr(CNR)(CO)₄{S[graphic omitted]}](R = Bu^t or Ph). When in addition, the isocyanide had been substituted for CO, the first saturated cyclic dithiocarbene complex of chromium, [Cr(CO)₅{[graphic omitted]}], was formed.