Ln₄(CH₂)₄ Cubane-Type Rare-Earth Methylidene Complexes Consisting of “(C₅Me₄SiMe₃)LnCH₂” Units (Ln = Tm, Lu)

Tetranuclear cubane-type rare-earth methylidene complexes consisting of four “Cp′LnCH2” units, [Cp′Ln(μ3-CH2)]4 (4-Ln; Ln = Tm, Lu; Cp′ = C5Me4SiMe3), have been obtained for the first time through CH4 elimination from the well-defined polymethyl complexes [Cp′Ln(μ2-CH3)2]3 (2-Ln) or mixed methyl/methylidene precursors such as [Cp′3Ln3(μ2-Me)3(μ3-Me)(μ3-CH2)] (3-Ln). The reaction of the methylidene complex 4-Lu with benzophenone leads to CO bond cleavage and CC bond formation to give the cubane-type oxo complex [Cp′Lu(μ3-O)]4 and CH2CPh2, while the methyl/methylidene complex 3-Tm undergoes sequential methylidene addition to the CO group and ortho C−H activation of the two phenyl groups of benzophenone to afford the bis(benzo-1,2-diyl)ethoxy-chelated trinuclear complex [Cp′3Tm3(μ2-Me)3{(C6H4)2C(O)Me}] (6-Tm).