Imido and oxo compounds of chromium-(V) and -(VI) and of molybdenum- and tungsten-(VI)

Abstract

The interaction of 1,1,1,3,3,3-hexamethyldisilazane and CrO₂Cl₂ gives the amido complex CrO₂[N(SiMe₃)₂] whereas MoO₂Cl₂ gives the imido complex Mo(NSiMe₃)₂(OSiMe₃)₂ and WO₂Cl₂(dme)(dme = 1,2-dimethoxyethane) gives a red oil that reacts with pyridine (py) to give WCl(NSiMe₃)(OSiMe₃)₃(py). Interaction of CrO₂[N(SiMe₃)₂] with pyridine and 4-methylpyridine (L) leads to reduction to the chromium(V) species [CrO(NSiMe₃)L]₂(µ-OSiMe₃)₂. Interaction of CrO₂Cl₂ with 2,2,6,6-tetramethyl-piperidine gives the amido species CrO₂Cl(NC₉H₁₈) while SiMe₂(NHBu^t)₂ gives Cr(NBu^t)₂Cl₂(NH₂Bu^t). The crystal structures of the compounds [CrO(NSiMe₃)(py)]₂(µ-OSiMe₃)₂, CrO₂Cl(NC₉H₁₈) and WCl(NSiMe₃)(OSiMe₃)₃(py) have been determined. In the centrosymmetric dimeric complex the Cr atom is five-co-ordinate with a geometry intermediate between trigonal bipyramidal and square pyramidal. The crystals of CrO₂Cl(NC₉H₁₈) contain two chemically equivalent tetrahedral molecules, while WCl(NSiMe₃)(OSiMe₃)(py) is octahedral with the pyridine ligand trans to the imido group.