Reactivity of lanthanide and yttrium hydrides and hydrocarbyls toward organosilicon hydrides and related compounds

The reaction of lanthanide and yttrium hydrocarbyls {Cp*(2)Ln(mu-Me)}(2) (Cp* = (BuC5H4)-Bu-t (Cp'), Ln = Y (1), Tb (2), Yb (3), Lu (4); Cp* = Me3SiC5H4 (CP ''), Ln = Lu (5)), one of which, 2, has been characterized by X-ray crystal analysis, with various organosilicon, -germanium, and -tin hydrides (as well as some organoaluminum and -gallium hydrides) in hydrocarbon solution was found to yield the corresponding unsolvated dimeric lanthanide and yttrium hydrides (Cp*(2)Ln(mu-H)}(2) rather than compounds with lanthanide-element (Si, Ge, Sn) bonding. Thus, the reaction involves hydride transfer to Ln rather than the silyl transfer studied earlier for pentamethylcyclopentadienyllanthanide hydrocarbyls. Dimeric compounds Cp*(2)Ln(mu-H)(mu-Me)LnCp*(2) with different bridging ligands were isolated; they are intermediates in this reaction. Dimeric lanthanide and yttrium hydrides catalyze the H/D exchange in silanes. This catalytic reaction is most correctly described by a mechanism involving nucleophilic substitution at the silicon atom. Yttrium and lutetium hydrocarbyls 1 and 4 react with various alkoxysilanes to produce the dimeric alkoxides (Cp'(2)Ln(mu-OR)}(2) or the hydrocarbyl alkoxides Cp'(2)Ln(mu-Me)(mu-OR)LnCp'(2) (R = Me, Et), depending on the reaction conditions. The reaction of 4 with (MeO)(4)Si provided Cp'Lu-2(mu-Me)(mu-OMe)LuCp'(2), which has been characterized by X-ray crystal analysis. This compound contains one methyl bridge (Lu-C 2.57(2) and 2.58(2) Angstrom) and nonsymmetrically bonded mu-OMe ligand (Lu-O 2.20(2) and 2.12(2) Angstrom). The reaction of 1 and 4 with Me3SiCl leads to the corresponding dimeric chlorides (Cp'(2)Ln(mu-Cl)}(2) only. Thus, the reaction of lanthanide and yttrium hydrocarbyls with various heterosubstituted organosilanes R3SiX, where X = H, OR, or Cl, is a selective and convenient synthetic method in the chemistry of the group 3 elements. Complexes with Ln(mu-H)(mu-Me)Ln and Ln(mu-H)(mu-Cl)Ln bridging were prepared in high yield by the exchange reactions between the corresponding dimeric compounds (Cp*(2)Ln(mu-X)}(2) (X = H, Me, Cl) in a hydrocarbon solution. The capacities of various bridging fragments to undergo reversible cleavage (dissociation) in the hydrocarbon solution increase in the sequence Ln-O(Me)-Ln much less than Ln-Cl-Ln < Ln-H-Ln < Ln-Me-Ln.