N,N '-bis(trimethylsilyl)benzamidinato complexes of vanadium(V), niobium(V) and tantalum(V)

N,N'-Bis(trimethylsilyl)benzamidinato complexes of vanadium(V), niobium(V) and tantalum(V) have been prepared starting from (BuN)-Bu-t=MCl3 . n py and (BuN)-Bu-t=MCpCl2, respectively: (BuN)-Bu-t=V[PhC(NSiMe3)(2)] Cl-n(3)-n (n = 1, 2); (BuN)-Bu-t=M[RC(NSiMe3)(2)]Cl-2 . py [M = Nb, Ta; R = C6H5, C6H4( 4-CF3)]; (BuN)-Bu-t=MCp[RC(NSiMe3)(2)]Cl [M = V, Nb, Ta; R = C6H5, C6H4-(4- CF3)]; (BuN)-Bu-t=VCp[PhC(NSiMe3)(2)]((OBu)-Bu-t). The syntheses of silylat ed tert-butylamido complexes (BuN)-Bu-t=M[(NBu)-Bu-t-SiMe2-(NHBu)-Bu-t]Cl-2 . py (M = Nb, Ta), (BuN)-Bu-t=V[(NBu)-Bu-t-SiMe2-(OBu)-Bu-t]Cl-2 and (BuN) -Bu-t=M[(NBu)-Bu-t-SiMe2-(OBu)-Bu-t]Cl-2 . py [M = Nb, Ta (20)] are also de scribed. The compounds have been investigated by H-1 NMR data, V-51 NMR dat a, mass spectra, X-ray data diffraction analysis.