Syntheses and NMR studies of mono alkyne complexes of molybdenum and tungsten

Reactions of [MCl(CO)(PhCCPh)(?⁵-C₅H₅)] (M = Mo, 1a; W, (1b) with TISR (R = ME, Et, ⁿPr, ⁱPr and ^tBu) give thiolate complexes [MSR(CO)(PhCCPh)(?⁵-C₅H₅)] which according to IR and NMR spectroscopy exist in two isomeric forms as a result of restricted rotation about the MSR bond. Reactions of [WCl(CO)(PhCCPh)(?⁵-C₅H₅)] and metal salts ML-L, {(ML-L = TlS2-Ph, TlS4-Py. Tlacac, TlOAc, TlS₂P(OMe)₂} (acac = 2,4-pentanedionato, Py = C₅H₄N) give similar monoalkyne complexes [WL-L(CO)(PhCCPh)(?⁵-C₅H₅)] (3 in which the L-L species functions as a monodentate ligand. In contrast 1a and 1b react with NaS₂CNMe₂{d2H₂O to give carbonylfree derivatives [M(S₂CNMe₂)(PhCCPh)(?⁵-C₅H₅)] containing a bidentate dithiocarbamate ligand. Oxidation of [W{(S₂P(OMe)₂}(CO)(PhCCPh)(?⁵-C₅H₅)] in air gives the oxo complex [W{(S₂P(OMe)₂}(O)(PhCCPh)(?⁵-C₅H₅)], thought to contain a monodentate S₂P(OMe)₂ ligand. © 1991.