CATIONIC DERIVATIVES OF NIOBOCENE(IV) - CRYSTAL-STRUCTURES OF [CP2NBL2][BF4]2 (L = CNME, NCME)

The isomeric cationic derivatives of niobocene, [Cp2Nb(NCMe)2][BF4]2 a nd [CP2Nb(CNMe)2][BF4]2, were prepared from [Cp2NbCl2] and the ligands in the presence of TlBF4. The crystal structure determination made on both complexes shows that the cations are isostructural, with pseudo- tetrahedral symmetry and linear ligands. Although the C=N distances ar e normal, the Nb-N and Nb-C distances are at the short end of the rang e found for niobium complexes of these ligands.