Anionic Bridged Bis(amidinate) Lithium Lanthanide Complexes: Efficient Bimetallic Catalysts for Mild Amidation of Aldehydes with Amines

Anionic bridged bis(amidinate) lithium lanthanide complexes have been found to be efficient catalysts for the amidation of aldehydes with amines under mild conditions. The activity follows the order: yttrium < neodymium < europium approximate to ytterbium. The catalysts are available for the formation of benzamides derived from pyrrolidine, piperidine, and morpholine with good to excellent yields. In comparison with the corresponding neutral complexes, the anionic complexes show higher activity and a wider range of scope for the amines. A cooperation of the lanthanide and lithium metals in this process is proposed to contribute to the high activity of the present catalyst.