Rare Earth/d-Transition Metal Heteromultimetallic Polyhydride Complexes Based on Half-Sandwich Rare Earth Moieties

The reaction of half-sandwich rare earth metal bis(alkyl) complexes Cp′Ln(CH2SiMe3)2(THF) (Cp′ = η5-C5Me4SiMe3; Ln = Y, Lu) with 1 equiv of the binuclear tungsten octahydride complex [Cp*WH4]2 (Cp* = η5-C5Me5) readily gave the corresponding Ln/W2 heterotrimetallic hexahydride complexes Cp′Ln(THF)(μ-H)6(WCp*)2 (Ln = Y (1a), Lu (1b)) with release of SiMe4. A similar reaction of (C5Me4R)Ln(CH2SiMe3)2(THF) with the binuclear osmium tetrahydride complex [Cp*OsH2]2 gave the Ln/Os2 heterotrimetallic trihydride complexes [(Cp*Os){(μ-η5:η1-C5Me4CH2)Os}Ln(C5Me4R)(THF)(μ-H)3] (2a, Ln = Y, R = SiMe3; 2b, Ln = Lu, R = Me), in which one methyl carbon atom of the Cp* ligand on an Os center is bonded to the Ln atom through activation of the CH bond. In contrast, the analogous reaction of (C5Me4R)Ln(CH2SiMe3)2(THF) with the binuclear ruthenium tetrahydride complex [Cp*RuH2]2 gave the corresponding Ln/Ru4 heteropentametallic heptahydride complexes (Cp*Ru)4(C5Me3RCH2)Ln(μ-H)7 (3a, Ln = Y, R = SiMe3; 3b, Ln =Lu, R = Me) as a result of removal of two protons from two molecules of [Cp*RuH2]2 by one molecule of (C5Me4R)Ln(CH2SiMe3)2(THF) followed by oxidative addition of a methyl C−H bond of the (C5Me4R)Ln unit to a Ru center. The 1H NMR spectra of 3a and 3b showed that oxidative C−H addition and C−H reductive elimination at the Ru atom are reversible in solution. Hydrogenolysis of 3a and 3b gave the decahydride complexes (Cp*Ru)4(Cp′Y)(μ-H)10 (4a) and (Cp*Ru)4(Cp*Lu)(μ-H)10 (4b), respectively. The molecular structures of 1b, 2b, 3a, 3b, 4a, and 4b were determined by X-ray analyses.