CARBON-CARBON COUPLING OF A MU-ETHYNYL LIGAND WITH AN ISOCYANIDE AT ADITUNGSTEN CENTER - PREPARATION AND STRUCTURE OF W(2)(MU-CCCNHXYL)(OSIME2BUT)5(CNXYL)4, WHERE XYL = 2,6-ME2C6H3

The ethynyl-bridged complex W2(mu-CCH)-(OsiMe2But)5 reacts in hydrocar bon solvents with xylyl isocyanide, 2,6-Me2C6H3NC, to give W2(mu-CCCNH Xyl)-(OSiMe2But)5(CNXyl)4 which has been characterized by NMR spectros copy and a single-crystal X-ray study. The bridging mu-CCCNHXyl ligand may be viewed as an eta2-aminoalkyne to one tungsten and an alkylidyn e to the other. One tungsten is in a pseudooctahedral environment bein g coordinated to four isocyanide ligands, one siloxide, and an eta2-al kyne moiety while the other is a five-coordinate pseudo-square-based p yramid having four siloxides in the basal plane and the alkylidyne car bon at the apical site. Crystal data for 2(mu-CCCNHXyl)-(OSiMe2BUt)5(C NXYl)4(.1/2)(toluene) at -158-degrees-C: a = 21.3.54(7) angstrom, b = 17.095(6) angstrom, c = 24.288(9) angstrom, beta = 100.18-(2)-degrees, d(calcd) = 1. 347 g cm-3 Z = 4, and space group P2(1)/n.