Christine E. Plecnik

A neutron diffraction study of Cp2Ti{(μ-H)2BC8H14}

Abstract The structure of Cp2Ti{(μ-H)2BC8H14} has been determined by single-crystal neutron diffraction methods. The geometrical parameters of the central four-atom core, Ti(μ-H)2B, are: Tiue5f8H=1.904(15), 1.933(17) A; Bue5f8H=1.298(15), 1.333(13) A; Tiue5f8Hue5f8B=94.1(8)°, 96.7(9)°; Hue5f8Tiue5f8H=65.3(6)°, Hue5f8Bue5f8H=103.8(9)°; Ti⋯B=2.426(12) A; H⋯H=2.071(19) A. The final weighted agreement factor is Rw=8.7% for 2635 unique reflections collected at 20 K from a crystal of volume 0.8 mm3 at the Argonne Intense Pulsed Neutron Source (IPNS). This structure determination represents the first neutron diffraction analysis of a Tiue5f8H bonding distance in a molecule, as well as the first neutron analysis of a Tiue5f8Hue5f8B bridge bond.

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

Abstract 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.