CATIONIC BIS(BUT-2-YNE) COMPLEXES OF THE TYPE [W(CO)(NCME)(S2CX)(ETA-2-MEC2ME)2][BPH4]

The compounds [WI(CO)(S2CX)(eta2-MeC2Me)2] (X = NC4H8, NMe2, NEt2, N(CH2Ph)2, OEt) react with Na[BPh4] in acetonitrile at room temperature to give the new cationic bis(but-2-yne) complexes[W(CO)(NCMe)(S2CX)(eta2-MeC2Me), [BP (1-5) in high yield. X-ray single-crystal studies were carried out on [W(CO)(NCMe)(S2CNC4H8)(eta2-MeC2Me)2][BPh4](1). The crystals are monoclinic, space group P2(1)/a, Z = 4, in a unit cell of dimensions a = 12.944 (13) angstrom, b = 26.671 (25) angstrom, c = 11.090 (1 3) angstrom, and beta = 105.71 (1)-degrees. The structure was refined to R = 0.085 (R(w) = 0.087) for 1989 independent reflections above background. The coordination geometry about the tungsten can be considered to be pseudooctahedral with the midpoints of the two cis-but-2-yne ligands in the same plane as the sulfur atoms of the dithiocarbamate ligand. Acetonitrile and carbon monoxide occupy the axial sites. Selected reactions of 1-5 with both monodentate (CO, CNBu(t), P(OMe)3) and bidentate (Ph2P(CH2)nPPh2 (n = 1-6), [Fe(eta5-C5H4-PPh2)2], 2,2'-bpy, 1,10-phen) ligands are also described. The fluxionality of several of the complexes has been investigated by variable-temperature H-1 NMR spectroscopy. C-13 NMR spectroscopy has been used to suggest the number of electrons donated to the tungsten by the alkyne in selected compounds.