NEW METALLOCENE COMPLEXES OF NB AND TA WITH FUNCTIONALIZED DIAZOALKANES

The reaction of Cp2MH3, where M = Nb or Ta, with N2CPh2, N2CPh(o-C6H4B r) and N2CHCOOEt was thoroughly studied. It was shown that the primary products of the reaction are the complexes Cp2M(H)(eta1-N2CRR') (2). The complexes 2 are readily oxidized by air to give polymeric (Cp2MO)n , N2CRR' and RR'CN2CRR'. Interaction of an excess of N2CPh(o-C6H4Br) w ith Cp2NbH3 leads to a 17-electron complex Cp2Nb(-N-N=CPh-o-C6H4)2 (6) with two sigma-N pyrazole ligands. Finally the reaction of Cp2NbH3 wi th N2CHCOOEt gives an unusual dimeric complex Cp2Nb2(eta5-C5H4C(COOEt) =N-mu-N)2. The complexes 2 were found to undergo easily substitution o f a hydride ligand for a halogen atom. The results of X-ray analysis o f the complexes 6 and Cp2Nb(Cl)-eta1-N2CPh(o-C6H4Br) are provided.