Synthesis and Characterization of Organolanthanide Complexes with a Calix[4]-pyrrolyl Ligand and Their Catalytic Activities toward Hydrophosphonylation of Aldehydes and Unactivated Ketones

Abstract

The alkali metal salt free dinuclear trivalent lanthanide amido complexes (η5:η1:η5:η1-Et8-calix[4]-pyrrolyl){LnN(SiMe3)2}2 (Ln = Nd (2), Sm (3), Gd (4)) were prepared through the silylamine elimination reactions of calix[4]-pyrrole [Et2C(C4H2NH)]4 (1) with 2 equiv of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Nd, Sm, Gd) in toluene at 110 °C. The complexes were fully characterized by elemental, spectroscopic, and single-crystal X-ray analyses. Studies on the catalytic activity of the new lanthanide amido complexes revealed that these complexes can be used as efficient catalysts for hydrophosphonylation of aldehydes and unactivated ketones, affording the products in high yields by employing a low catalyst loading (0.1 mol %) at room temperature in a short time (20 min). Noteworthy is that it is the first application of calix[4]-pyrrolyl-supported lanthanide amides as catalysts to catalyze the hydrophosphonylation of aldehydes and unactivated ketones under mild conditions.