SCHEDULED MAINTENANCE
Synthesis and characterization of bis(xanthate) complexes of MoII and WII. Crystal structure of [W(S2COPri-S)(S2COPri-SS′)(CO)2(PMe3)2]
Abstract
The reactions of [MoCl2(CO)2(PMe3)2] with potassium xanthates, K(S2COR), give the red crystalline compounds [Mo(S2COR)2(CO)(PMe3)2][R = Me (1), Et (2), Pri(3), or But(4)] in which the xanthate groups seem to act as η3-(S,S′,C) pseudo-allylic ligands. Formation of the dicarbonyl species [Mo(S2COR)2(CO)2(PMe3)] is not detected, but the isopropyl derivative [Mo(S2CO-Pri)2(CO)2(PMe3)](5) can be obtained by carbonylation of (3) under relatively forcing conditions. The tungsten complex [WCl2(CO)2(PMe3)3] reacts similarly with K(S2COR) but gives mixtures of [W(S2COR)2(CO)2(PMe3)n](n= 1 or 2). The monophosphine derivatives [R = Et (6) or Pri(7)] exhibit n.m.r. spectroscopic features similar to those of (1)–(5), but for the bis(phosphine) species a formulation containing uni- and bi-dentate xanthate groups, [W(S2COR-S)(S2COR-SS′)(CO)2(PMe3)2][R = Et (8) or Pri(9)] is proposed, and this has been confirmed by an X-ray crystal structure determination of complex (9). Formation of the dithiocarbonate complexes, [M(S2CO)(CO)2(PMe3)2][M = MO (11) or W (12)] during the reactions leading to the above xanthates has also been observed. Complex (9) is triclinic, space group P1, with unit-cell constants a= 8.775(2), b= 14.027(5), c= 11.806(5)Å, α= 106.09(2), β= 75.74(3), γ= 109.06(4)°, and Z= 2. The structure was refined to an R value of 0.032 by using 2 878 independent observed reflections.
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