Synthesis, structure, and catalytic activity of tetracoordinate lanthanide amides [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Nd, Sm, Eu)

Interaction of anhydrous lanthanide(III) chlorides (Ln = Nd, Sm, Eu) with 3 equiv. of lithium bis(trimethylsilyl)amide (Me3Si)(2)NLi in THF, followed by recrystallization from toluene, produced tetracoordinate lanthanide amides [(Me3Si)(2)N](3)Ln(mu-Cl)Li(THF)(3) (Ln = Nd (1), Sm (2), Eu. (3)). Sublimation of 1, 2 and 3 afforded the corresponding complexes [(Me3Si)(2)N](3)Ln (Ln = Nd, Sm, Eu). The structures of complexes 2 and 3 were determined by the single-crystal X-ray diffraction. These complexes can function as single-component MMA polymerization catalysts in THF, DME, toluene and n-hexane. It was found that the activities of the catalysts, stereo-regularity of PolyMMA, and the molecular weight of polymers were dependent on the solvents, temperatures, and the catalyst/MMA mole ratios. (C) 2003 Published by Elsevier Science Ltd.