Cyclic organohydroborate complexes of metallocenes: Part VI. Syntheses and structures of Cp2M{(μ-H)2BR2} (M=Ti, Nb; R2=C4H8, C5H10, C8H14)

The complexes, Cp2M{(μ-H)2BC4H8} (1: M=Ti; 2: M=Nb), Cp2M{(μ-H)2BC5H10} (3: M=Ti; 4: M=Nb), and Cp2M{(μ-H)2BC8H14} (5: M=Ti; 6: M=Nb), were prepared from the reactions of Cp2MCl2 with the organohydroborate salts, K[H2B2(μ-H)(μ-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{(μ-H)2BH2} (7) was redetermined using modern CCD techniques.