The reaction of molybdenum and tungsten carbyne complexes with sulphur and selenium; crystal structures of [Mo{η2-(S2CCH2But)}-(CO)2(η-C5H5)] and [W{η2-(S2CC6H4Me-4)}(CO)2(η-C5H5)]

Abstract

Reaction of [M(CR)L₂(η-C₅H₅)][M = Mo, R = CH₂Bu^t, L = P(OMe)₃ or CO; M = W, R = C₆H₄Me-4, L = CO] with sulphur affords the complexes [M{η²-(S₂CR)}L₂(η-C₅H₅)]. Similar reactions between [Mo(CCH₂Bu^t)(CO)₂(η-C₅H₅)] or [W(CC₆H₄Me-4)(CO)₂(η-C₅H₅)] and selenium give the related complexes [M{η₂-(Se₂CR)}(CO)₂(η-C₅H₅)](M = Mo, R = CH₂Bu^t; M = W, R = C₆H₄Me-4). X-Ray diffraction studies on the isostructural products obtained from sulphur and the molybdenum or tungsten carbonyl carbyne complexes show that a M(CO)₂(η-C₅H₅)(M = Mo or W) moiety is bonded to a thioacetate ligand forming a planar MS₂C ring of dimensions M–S 2.47, C–S 1.68 Å, S–M–S 68, and S–C–S 110 °. The metal atom can be regarded as seven-co-ordinate with the cyclopentadienyl group occupying three co-ordination sites. Both structures are monoclinic, space group P2₁/c; the molybdenum compound has been refined to R 0.033 for 2 165 reflections and the tungsten compound to R 0.042 for 2 382 reflections. The mechanism of formation of these complexes is discussed in terms of initial electrophilic attack on the carbyne carbon.