MOLECULAR-REARRANGEMENTS OF A LOW-VALENT NIOBIUM AMIDE - LIGAND C-H BOND OXIDATIVE ADDITION AND REDUCTIVE ELIMINATION

Reaction of the dinuclear and divalent (TMEDA)(2)Nb2Cl5Li(TMEDA) with Ph2NK led to the formation of three different compounds. The rst compl ex contains no amide ligands. It is a mixed-valence dinuclear and para magnetic species with a typical face-sharing bioctahedral structure Cl 2Nb2(mu-Cl)(3)(TMEDA)(2) (1). The second complex, a trivalent and dinu clear -eta(1);eta(2)-C6H4)](mu-H)}{Li(TMEDA)(2)}.toluene (2) with one hydride and one cyclometalated aromatic ring, is the result of oxidati ve addition of the two metal centers to the C-H bond. In a subsequent reaction step, the oxidative addition is followed by reductive elimina tion to restore the C-H bond to form the neutral, dinuclear, and diama gnetic (Ph2N)(2)Nb{[mu-NPh(eta(6)-C6R5)](2)Nb}.ether (3) containing th e two metals in formal oxidation states of +4 and 0. Ab initio and EHM O calculations have been carried out in an attempt to clarify the natu re of the Nb-Nb interaction in the three complexes.