Syntheses and structures of lanthanide complexes containing a bis(imidazolin-2-imino) pyridine pincer ligand

The Lewis acid-base reaction of 2,6-bis[1,3-di-tert-butylimidazolin-2-imino) methyl] pyridine (TL(tBu)) and LnCl(3) in THF leads to the corresponding neutral lanthanide complexes of type [(TL(tBu)) LnCl(3)], Ln = Y (1a), Er (1b), Lu (1c). The yttrium and lutetium complexes have been characterized by X-ray diffraction analysis. The solid state structures reveal that the bulky TL(tBu) ligand causes steric crowding around the lanthanide atoms by coordinating to the metal center in a tridentate fashion. In addition, remote C-H center dot center dot center dot Ln interactions (H center dot center dot center dot Ln ca. 2.7 angstrom) involving one of the (t)Bu methyl groups are observed in both cases. A DFT (density functional theory) calculation on 1a was able to reproduce this interaction, which was additionally characterized by means of an H center dot center dot center dot Y compliance constant and by employing the AIM (atoms in molecules) theory. (C) 2007 Elsevier B. V. All rights reserved.