REACTIONS OF SULFUR-CONTAINING HETEROCUMULENES WITH LOW-VALENT MOLYBDENUM AND TUNGSTEN COMPLEXES - OXIDATIVE CLEAVAGE OF A HEAD-TO-TAIL CARBON-DISULFIDE DIMER IN A MOLYBDENUM COMPLEX

Head-to-tail carbon disulfide dimers of composition M(C2S4)(C2H4)(PMe3)3 (M = Mo (3), W (4)) have been prepared by action of CS2 on the ethylene complexes trans-M(C2H4)2(PMe3)4 (M = Mo (1), W (2)). An X-ray analysis, carried out on complex 3, shows the C2S4 unit is acting formally as a four-electron donor ligand, bonded to the metal through one of the carbon and two of the sulfur atoms. The complex is monoclinic, C2/c, with a = 26.633 (7) Å, b = 8.615 (4) Å, c = 19.903 (6) Å, β = 103.51 (2) °, and D(caled) = 1.60 g cm-3 for Z = 8 and R(F0) = 0.048. The analogous reactions of 1 and 2 with SCNPh provide related head-to-tail dimers, [equation omitted] (7); x = 2 (8)) and [equation omitted] (9); x = 2 (10)). Treatment of 3 with MeX (X = I, OSO2CF3), followed by anion exchange with NH4PF6, gives [Mo-(C2S4Mc)(C2H4)(PMe3)3]PF6 (11), which has a structure similar to that found for 3 (as determined by X-ray studies) but with a methyl group bonded to the exocyclic sulfur atom of the C2S4 unit. 11 is monoclinic, P21/c, with a = 13.726 (2) Å, b = 14.272 (3) Å, c = 14.686 (4) Å, β = 106.28 (2)°, and D(calcd) = 1.509 g cm-3 for Z = 4 and R(F0) = 0.058. Complex 3 reacts with CNBu1 to afford a complex mixture of compounds from which the substitution product Mo(C2S4)(CNBu2)(PMe3)3 (12) can be isolated. With carbon monoxide, however, a molybdenum(0) complex, Mo(S2CPMe3)(CO)2(PMe3)2 (13), is formed in an unprecedented reaction that corresponds to an oxidative symmetric cleavage of the MC2S4 linkage. © 1990, American Chemical Society. All rights reserved.