HALF-SANDWICH AND ANSA-NIOBIOCENES - SYNTHESIS AND REACTIVITY

The reaction of [Nb(NMe2)(3)(=N-2,6-iPr(2)C(6)H(3))] 1 with the cyclop entadienyl-indenyl isopropylidene ligand 2 gave the new half-sandwich niobium complex [Nb(eta(5)- C5H4R)(NMe2)(2)(=N-2,6-iPr(2)C(6)H(3))] (R = CMe2C9H7) 3 in high yield. The new ansa-type niobiocene [Nb(NMe2)(= N-2,6-i-Pr2C6H3)(eta 5:eta(1)-{C5H4}C(CH3)(2){C9H6}] 4 was obtained at higher temperatures by an intramolecular deprotonation with concomita nt coordination of the indenyl group. The reactivity of the new ansa-n iobiocene 4 towards electrophilic reagents, giving chloro- and cationi c ansa-type niobium complexes is described. (C) 1998 Elsevier Science S.A. All rights reserved.