BIS(ALKYNE) COMPLEXES OF THE TYPE [WI2(CO)(NCR)(ETA(2)-R'C(2)R')(2)] (R=ET, (T)BU, PH OR CH(2)PH, R'=ME OR PH) - X-RAY CRYSTAL-STRUCTURE OF [WI2(CO)(NC(T)BU)(ETA(2)-MEC(2)ME)(2)]

Reaction of [WI2(CO)(3)(NCR)(2)] (R = Et, (t)Bu, Ph or CH(2)Ph) with an excess of but-2-yne or two equivalents of PhC(2)Ph in CH2Cl2 at room temperature gave the bis(alkyne) complexes [WI2(CO)(NCR)(eta(2)-R'C(2)R')(2)] (R' = Me or Ph) (1-8). The crystal structure of the (t)butylnitrile complex [WI2(CO)(NC(t)Bu)(eta(2)-MeC(2)Me)(2)] (3) was determined by X-ray crystallography. The geometry about the tungsten can be considered to be octahedral, with the but-2-yne ligands, as expected, cis- and parallel to each other and trans- to the two iodo-ligands, leaving the acetonitrile and carbonyl ligands mutually trans-. The alkyne ligands in these complexes donate a total of six-electrons to the metal, as suggested by C-13 NMR spectroscopy.