Synthesis, structure and catalytic activity of alkali metal-free bent-sandwiched lanthanide amido complexes with calix[4]-pyrrolyl ligands

摘要

Simple silylamine elimination reactions of calix[4]-pyrrole [R _2C(C_4H_2NH)]_4 (R = Me (1), {-(CH _2)_5-}_(0.5) (2)) with 2 equiv. of [(Me _3Si)_2N]_3Ln(μ-Cl)Li(THF)_3 (Ln = Nd, Sm, Dy) in reflux toluene, afforded the novel dinuclear alkali metal-free trivalent lanthanide amido complexes (η~5:η~1: η~5:η~1-R_8-calix[4]-pyrrolyl) {LnN(SiMe_3)_2}_2 (R = Me, Ln = Nd (3), Sm (4), Dy (5); R = {-(CH_2)_5-}_(0.5), Ln = Nd (6), Sm(7)). The complexes were fully characterized by elemental analyses, spectroscopic analyses and single-crystal X-ray analyses. X-ray diffraction studies showed that each lanthanide metal was supported by bispyrrolyl anions in an η~5 fashion and along with three nitrogen atoms from N(SiMe _3)_2 and two other pyrroyl rings in η~1 modes formed the novel bent-sandwiched lanthanide amido bridged trivalent lanthanide amido complexes, similar to ansa-cyclopentadienyl ligand-supported lanthanide amides with respect to each metal center. The catalytic activities of these organolanthanide complexes as single component l-lactide polymerization catalysts were studied.