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(mu(3)-CH2)](4) (Cp' = C5Me4SiMe3) (1) and a trimetallic lutetium hexamethyl complex [Cp'Lu(mu(2)-CH3)(2)](3) (2) with H-2 and ammonium borate compounds. The hydrogenolysis of 1 with H-2 afforded the corresponding tetrahydride tetramethyl complex [Cp-4'Lu-4(mu(4)-H)(mu(3)-H)(mu(2)-H)(3)(mu(2)-Me)(4)] (3) in 87% yield. In this transformation, each of the four [Lu-mu(2)-CH2] methylidene groups in 1 reacted with one molecule of H-2 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-4'Lu-4(mu(3)-CH2)(3)(mu(3)-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 H-2 led to formation of a tetrametallic lutetium monohydride heptamethyl complex [Cp-4'Lu-4(mu(4)-H)(mu(3)-Me)(mu(2)-Me)(6)] (5) in 65% yield, while the protonation reaction of 2 with 3 equiv of [Et3NH][BPh4] gave a monometallic lutetitun monomethyl contact-ion-pair complex [Cp'LuMe(eta(6)-Ph)(eta(1)-Ph)BPh2] (6) in 81% yield. Complexes 3-6 were fully characterized by H-1 and C-13 NMR, single-crystal X-ray diffraction, and micro elemental analyses.