NITRILE EXCHANGE-REACTIONS OF [MI(2)(CO)(3)(NCME)(2)] (M=MO OR W) - X-RAY CRYSTAL-STRUCTURES OF THE MIXED-LIGAND 7-COORDINATE COMPLEXES [WI2(CO)(3)(NCR)(ASPH(3))] (R=ET OR PH)

Reaction of [MI(2)(CO)(3)(NCMe)(2)] (M = Mo or W) with an excess of NCR (for M = W, R = Et, (t)Bu, CH(2)Ph or Ph; for M = Mo, R = Ph) in CH2Cl2 at room temperature gives the nitrile-exchanged products [MI(2)(CO)(3)(NCR)(2)] (1-5). Equimolar quantities of 1-5 and L (L = PPh(3), AsPh(3) or SbPh(3)) react in CH2Cl2 at room temperature to afford the mixed ligand complexes [MI(2)(CO)(3)(NCR)L] (6-20). X-ray single crystallographic studies were carried out on both the tungsten complexes [WI2(CO)(3)(NCR)(AsPh(3))] (R = Et and Ph). The metal atoms in both complexes have the same seven-coordinate, slightly distorted monocapped trigonal prismatic, coordination geometry, with very similar ligand dispositions. Low temperature C-13 NMR spectroscopy was used to correlate the solution and solid-state structures of several of these seven-coordinate complexes. The reactions of the bis(propionitrile) complex [WI2(CO)(3)(NCEt)(2)] with neutral monodentate donor ligands are also described.