Syntheses of bis- and tetra(trimethylsilyl) substituted lanthanocene methyl complexes and their catalyses for polymerizations of methyl methacrylate, ε-caprolactone and L-lactide

Bis- and tetra(trimethylsilyl) substituted lanthanocene methyl complexes, [(Me3SiC5H4)(2)SmMe](2) (2) {[1,3-(Me-3-Si)(2)C5H3](2)SmMe}(2) (4) and {[1,3(Me3Si)(2)C5H3](2)NdMe}(2) (5) were prepared in high yield from trimethylsilyl- or bis(trimethylsilyl)cyclopentadienyllithium and LnCl(3)(THF)(2) followed by the reaction with a stoichiometric amount of MeLi. The molecular structures of 2 and 4 as well as their precursors, [(Me3SiC5H4)(2)SmCl](2) (1) and [1,3-(Me-3,Si)(2)C5H3](2)SmCl2Li(THF)(2) (3) were determined by X-ray crystallographic analyses. The complexes 2, 4 and 5 perform the living polymerization of methyl methacrylate and the block copolymerizations Of L-lactide with epsilon-caprolactone in high yields in the absence of any cocatalysts. (C) 2002 Elsevier Science B.V. All rights reserved.