Synthesis and reactivity of new ruthenium alkyls and hydrides. Protonation of Cp*Ru(Me₂PCH₂PMe₂)Me and x-ray crystal structure of Cp*₂Ru₂(μ-Ph₂PCH₂PPh ₂)(AIH₅)

Treatment of the pentamethylcyclopentadienylruthenium chloride tetramer [Cp*RuCl]₄ with bis(dimethylphosphino)methane (dmpm) in tetrahydrofuran affords three ruthenium(II) phosphine complexes, Cp*Ru(dmpm)Cl, [Cp*Ru(dmpm)(η¹-dmpm)]Cl, and Cp*₂Ru₂(μ-dmpm)₂-Cl₂. Similar treatment of [Cp*RuCl]₄ with bis(diphenylphosphino)methane (dppm) in tetrahydrofuran or diethyl ether affords the dinuclear species Cp*₂Ru₂(μ-dppm)(μ-Cl)₂; in acetonitrile, this same reaction yields the mononuclear product Cp*Ru(dppm)Cl in high yield. The mononuclear complexes Cp*Ru(P-P)Cl (where P-P is dmpm or dppm) can be alkylated with dimethylmagnesium in diethyl ether to give the methyl complexes Cp*Ru(dmpm)Me and Cp*Ru(dppm)Me. Protonation of these Cp*Ru(P-P)Me complexes with trifluoroacetic acid results in the rapid reductive elimination of methane and formation of the trifluoroacetato complexes Cp*Ru(P-P)(η¹-O₂CCF₃); no ruthenium(IV) hydridomethyl intermediates could be detected. Treatment of Cp*₂Ru₂(dppm)₂Cl₂ with LiAlH₄ in diethyl ether yields the ruthenium aluminohydride complex Cp*₂Ru₂(μ-dppm)(μ-AlH₅), which can be converted to the ruthenium polyhydride complex Cp*₂Ru₂(μ-dppm)H₆ by treatment with methanol at low temperatures. The crystal structure of Cp*₂Ru₂(μ-dppm)(μ-AlH₅) shows that the aluminohydride unit is bound in a (μ-H)₂AlH(μ-H)₂ fashion.