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.