Novel Ruthenium(II) Aluminate Anions: Building Blocks of Unique Cage Structures

New anionic ruthenium­(II) aluminohydrides were synthesized from [Cp*RuCl]4, LiAlH4, and lithium alkyls. The reaction of [Cp*RuCl]4 with 8 equiv of LiAlH4 afforded the lithium salt [Li­(DME)3]­[Cp*2Ru2(μ-H)­(μ-AlH4)2] (1) in 65% isolated yield. Reactions of [Cp*RuCl]4, LiAlH4, and RLi (R = Me, Et, iPr, nBu) in THF yielded the new compounds [Li5(THF)2Cp*6Ru6Al4Me4H19] (2) and [Li2(THF)2Cp*RuAl2R2H7)]2 (3–5, R = Et, iPr, tBu). The compounds were characterized by single-crystal X-ray crystallography, multinuclear liquid and solid-state NMR spectroscopy, IR spectroscopy, and microanalysis. The molecular structures of 1–5 display novel anionic ruthenium­(II) aluminate frameworks. In the case of 2–5, these anions associate into unusual cage structures via Li–H interactions in the solid state. Variable-temperature 1H and 7Li NMR studies on the fluxional complex 5 in deuterated toluene show that the cage structure of this compound is retained at low temperature in solution.