3-Hexyne Complexes of M olybdenum(II) and Tungsten(II) Containing 2, 2 '-Bipyridine. X-Ray Crystal Structure of [MoI2(CO)(bipy)(η2-EtC2Et)]

Reaction of [MI2(Co)(NCMe)(?(2)-EtC2Et)(2)] (M = Mo,W) with one equivalent of 2,2'-bipyridine (bipy) in CH2Cl2 at room temperature gives either the neutral complex, [MoI2(CO)(bipy)-(?(2)-EtC2Et)] (1) or the cationic complex, [WI(CO) (bipy)(?(2)-EtC2Et)(2)]I (2). The neutral molybdenum complex 1, has been crystallographically characterised, and has a pseudo-octahedral geometry with the iodo-ligand trans to the 3-hexyne, and with the bipy, carbon monoxide and other iodo-ligand occupying the equatorial face. C-13 NMR studies show the 3-hexyne is donating four electrons to the molybdenum in 1.