Silica-Grafted Lanthanum Benzyl Species: Synthesis, Characterization, and Catalytic Applications

The grafting of a lanthanum trisbenzyl derivative onto dehydroxylated silica affords a mixture of [(SiO)2La­(CH2Ph)­(THF)n] and [(SiO)­La­(CH2Ph)2(THF)m] surface sites, in respective proportions of 80 and 20%, as evidenced from mass balance analyses, IR and 1H, 13C and 29Si 1D and 2D solid-state NMR spectroscopy. Significant transfer of alkyl groups from lanthanum to the surface was demonstrated. The grafting mechanism was also probed by DFT calculations, which confirm that benzyl group transfer from the lanthanum to the surface (via Si–O–Si cleavage) occurs readily. This material proved to be active in alkyne dimerization and in ethylene, styrene, and ε-caprolactone homopolymerization.