Hydrogenolysis and Protonation of Polymetallic Lutetium Methylidene and Methyl Complexes

We report the hydrogenolysis and protonation reactions of a tetrametallic lutetium tetramethylidene complex [Cp′Lu­(μ3-CH2)]4 (Cp′ = C5Me4SiMe3) (1) and a trimetallic lutetium hexamethyl complex [Cp′Lu­(μ2-CH3)2]3 (2) with H2 and ammonium borate compounds. The hydrogenolysis of 1 with H2 afforded the corresponding tetrahydride tetramethyl complex [Cp′4Lu4(μ4-H)­(μ3-H)­(μ2-H)2(μ2-Me)4] (3) in 87% yield. In this transformation, each of the four [Lu-μ2-CH2] methylidene groups in 1 reacted with one molecule of H2 to give a mixed methyl/hydride “Lu­(H)­CH3” unit. The reaction of 1 with [PhMe2NH]­[B­(C6F5)4] gave the cationic tetrametallic lutetium monomethyl trimethylidene complex [Cp′4Lu4(μ3-CH2)3(μ3-CH3)]­[B­(C6F5)4] (4) in 85% yield, through protonation of one of the four methylidene units in 1 with the anilinium borate. In contrast, the reaction of the trimetallic hexamethyl complex 2 with H2 led to formation of a tetrametallic lutetium monohydride heptamethyl complex [Cp′4Lu4(μ4-H)­(μ3-Me)­(μ2-Me)6] (5) in 65% yield, while the protonation reaction of 2 with 3 equiv of [Et3NH]­[BPh4] gave a monometallic lutetium monomethyl contact-ion-pair complex [Cp′LuMe­(η6-Ph)­(η1-Ph)­BPh2] (6) in 81% yield. Complexes 3–6 were fully characterized by 1H and 13C NMR, single-crystal X-ray diffraction, and micro elemental analyses.