Cyclic Organohydroborate Complexes Of Metallocenes Part Vi. Syntheses And Structures Of Cp2m{(Mu-H)(2)Br2} (M = Ti, Nb; R-2 = C4h8, C5h10, C8h14)

The complexes, Cp2M{(mu -H)(2)BC4H8} (1: M = Ti; 2. M = Nb), Cp2M{(mu -H)(2)BC5H10} (3: M = Ti; 4: M = Nb), and Cp2M{(mu -H)(2)BC8H14} (5: M=Ti; 6: M=Nb), were prepared from the reactions of Cp2MCl2 with the organohydroborate salts, K[H2B2(mu -H)(mu -C4H8)(2)], K[H2BC5H10], and K[H2BC8H14], respectively. In these reactions, the transition metal is reduced from M(IV) to M(III), producing 17-electron, paramagnetic titanocene complexes (1, 3 and 5) and eighteen electron, diamagnetic niobocene complexes (2, 4 and 6). Single crystal X-ray structures of 1-6 were determined. The molecular structure of Cp2Nb{(mu -H)(2)BH2} (7) was redetermined using modern CCD techniques. (C) 2001 Elsevier Science B.V. All rights reserved.