ORGANOMETALLIC NITROSYL CHEMISTRY .51. NEW ORGANOMETALLIC NITROSYL CATIONS CONTAINING THE GROUP-6 ELEMENTS

{Treatment of the dihalo nitrosyl complexes of molybdenum and tungsten, Cp’M(NO)X2 (Cp’ = Cp (eta(5)-C5H5), Cp* (eta(5)-C5Me5); M = Mo, W;X = Cl, Br, I), in CH3CN with NO+ or Ag+ salts affords a series of new diamagnetic cationic nitrosyl complexes, [Cp*Mo(NO)(NCCH3)3]2+ and [Cp’M(NO)X(NCCH3)2]+. Eight such complexes have been isolated analytically pure as either their PF6- or BF4- salts by crystallization from CH3CN/Et2O. The physical and spectroscopic properties of these organometallic cations are consistent with their possessing four-legged piano stool molecular structures. This conclusion has been confirmed by single-crystal X-ray crystallographic analyses of [Cp*Mo(NO)(NCCH3)3][PF6]2 and [CpMo(NO)Cl-(NCCH3)2]BF4 which also establish that the acetonitrile ligands are coordinated linearly through their N atoms to the metal centers. Crystal data for [Cp*Mo(NO)(NCCH3)3][PF6]2: monoclinic