Tetra-, Penta-, and Hexanuclear Yttrium Hydride Clusters from Half-Sandwich Bis(aminobenzyl) Complexes Containing Various Cyclopentadienyl Ligands

The novel series of half-sandwich tetrahydrofuran (THF)-free yttrium bis(aminobenzyl) complexes [(C5Me4R)Y(CH2C6H4NMe2-o)2] (R = SiMe3 (1a), Me (1b), Et (1c), H (1d)) was prepared by treatment of [Y(CH2C6H4NMe2-o)3] with C5Me4RH, and their reactions with H2 and with PhSiH3 in aromatic solvents or in THF were examined. The reaction of 1a with H2 in benzene gave the pentanuclear yttrium decahydride complex [{Cp′Y(μ-H)2}5] (Cp′ = η5-C5Me4SiMe3) (3), which could not be obtained by the reaction of the corresponding THF-coordinated dialkyl complex [Cp′Y(CH2SiMe3)2(THF)] with H2. The reaction of 1b with H2 in toluene gave the partially hydrogenated tetranuclear mixed aminobenzyl/hydride complex [(Cp*Y)2(CH2C6H4NMe2-o)(μ-H)3]2 (4; Cp* = η5-C5Me5), and no further hydrogenation reaction occurred, whereas the corresponding reaction of 1b with H2 in THF gave the pentanuclear yttrium polyhydride complex [{Cp*Y(μ-H)2}5(THF)2] (5). Hydrogenolysis of the sterically less demanding C5Me4H-ligated complex 1d with H2 in THF gave the tetranuclear octahydride complex [{CpHY(μ-H)2}4(THF)4] (6; CpH = η5-C5Me4H), which has one coordinating THF ligand on each metal atom. The hexanuclear yttrium dodecahydride complex {[Cp*Y(μ-H)2]6} (7) was obtained by treatment of 1b with PhSiH3 in benzene. The structures of 1a,b,d, 3, 4, [{(C5Me4Et)Y(μ-H)2}5(THF)2] (5′), 6, and 7 were determined by X-ray single-crystal diffraction studies.