Quantitative Oxidation of Organovanadium( I V ) and -niobium( I V ) Complexes: Synthesis of cp2v( SbF,)*, [ cp2Vc12][ A#,], and [ Cp2V(ASF&][ ASF,]. Crystal Structure of [ Cp2NbC12][ SbF6]Niobocene dichloride, Cp,NbC12 (l), reacts with SbF, to give [Cp2NbC12] [SbF6] (2). The X-ray structure of 2 has been determined and shows 2 to consist to discrete SbF, anions, which show the usual octahedral geometry but are slightly disordered in the crystal, and CpZNbCl2+ cations with an approximate tetrahedral coordination of the Nb atom. The average Nb-Cl distance is 2.341 A; the Nb-C distances range from 2.354 to 2.455 A with an average of 2.404 A. The mean distance from Nb to the Cp ring centroids is 2.087 A.The angle C1-Nb-Cl is 98.10'; the average of the centroid-Nb-C1 angles is 106', the angle at Nb between the centroids 131°, and the angle between the ring planes 51.4'. 2 crystallizes in the orthorhombic space group mlcn with cell constants a = 8.557 (3) A, b = 12.753 (4) A, c = 13.839 (6) A, V = 1510.2 A3, 2 = 4, and R(F) = 3.3%. The oxidation of vanadocene dichloride, Cp2VClz (3), which is not possible by common agents such as Ag+, with AsF, has been estimated to be thermodynamically favored by simple Born-Haber cycles and has been proved to be a convenient and quantitative synthesis of novel organovanadium(V) species. [Cp2VC12] [AsF,] (5) and [Cp2V(AsF,),] [A#,] (6) were prepared and characterized by elemental analysis, IR, 'H NMR, and l9F NMR spectroscopy (5: 6 = -58.75 ppm, q; relative to CFC1,; J = 937 f 5 Hz). The preparation and characterization of the paramagnetic Cp,V(SbF6), (4) is also reported. The EPR spectrum of 4 shows a nicely resolved eight-line spectrum (B = 1.9738), indicating that the unpaired electron is mainly localized at the V.
