Bridged bis(amidinate) lanthanide complexes: Synthesis, molecular structure and reactivity

The yttrium chloride with the bridged bis(amidinate) L (L = Me3SiNC(Ph)N(CH2)(3)NC(Ph)NSiMe3) LYCl(DME) (2) was synthesized and structurally characterized. Treatment of LLnCl(sol)(x) (Ln = Yb, sol = THF, x = 2 1; Ln = Y, sol = DME, x = 1 2) with the dilithium salt Li2L(THF)(0.5) afforded the novel bimetallic lanthanide complexes supported by three ligands, Ln(2)(mu(2)-L)(3)center dot DME (Ln = Yb 3, Y 4; DME = dimethylether), instead of the designed complex LLn(mu(2)-L)LnL via the ligand redistribution reaction. Complexes 3 and 4 were fully characterized including X-ray analysis and H-1 NMR spectrum for 4. Reaction of LnCl(3) (Ln = Yb, Y) with 2 equiv. of Li2L(THF)(0.5) gave the anionic complexes [Li(DME)(3)] [L(2)Ln] (Ln = Yb 5, Y 6), which were confirmed by a crystal structure determination. The further study indicated that complexes 3 and 4 can also be synthesized by reaction of LnCl(3) (Ln = Yb, Y) with 1.5 equiv. of Li2L(THF)0.5 or reaction of 1 and 2 with anionic complexes 5 and 6. Complexes 3, 4, 5 and 6 were found to be high active catalysts for ring-opening polymerization of c-caprolactone (CL). (C) 2008 Elsevier Ltd. All rights reserved.