Low-Valent Titanium Species Stabilized with Aluminum/Boron Hydride Fragments |
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| Authors: | Estefanía del Horno Dr. Jesús Jover Dr. Miguel Mena Dr. Adrián Pérez-Redondo Prof. Dr. Carlos Yélamos |
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| Affiliation: | 1. Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química “Andrés M. del Río” (IQAR), Universidad de Alcalá, 28805 Alcalá de Henares-Madrid, Spain;2. Secció de Química Inorgànica, Departament de Química Inorgànica i Orgànica, Institut de Química Teòrica i Computacional (IQTC-UB), Universitat de Barcelona, Martí i Franquès 1–11, 08028 Barcelona, Spain |
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| Abstract: | Low-valent titanium species were prepared by reaction of [TiCp*X3] (Cp*=η5-C5Me5; X=Cl, Br, Me) with LiEH4 (E=Al, B) or BH3(thf), and their structures elucidated by experimental and theoretical methods. The treatment of trihalides [TiCp*X3] with LiAlH4 in ethereal solvents (L) leads to the hydride-bridged heterometallic complexes [{TiCp*(μ-H)}2{(μ-H)2AlX(L)}2] (L=thf, X=Cl, Br; L=OEt2, X=Cl). Density functional theory (DFT) calculations for those compounds reveal an open-shell singlet ground state with a Ti−Ti bond and can be described as titanium(II) species. The theoretical analyses also show strong interactions between the Ti−Ti bond and the empty s orbitals of the Al atom of the AlH2XL fragments, which behave as σ-accepting (Z-type) ligands. Analogous reactions of [TiCp*X3] with LiBH4 (2 and 3 equiv.) in tetrahydrofuran at room temperature and at 85 °C lead to the titanium(III) compounds [{TiCp*(BH4)(μ-X)}2] (X=Cl, Br) and [{TiCp*(BH4)(μ-BH4)}2], respectively. The treatment of [TiCp*Me3] with 4 and 5 equiv. of BH3(thf) produces the diamagnetic [{TiCp*(BH3Me)}2(μ-B2H6)] and paramagnetic [{TiCp*(μ-B2H6)}2] complexes, respectively. |
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| Keywords: | aluminum boron density functional calculations reduction titanium |
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