Complexation-Induced N‒P Axial Chirality in Sm(II) N-Phosphine-Oxide-Substituted Imidazolylidene and Imidazolinylidene Complexes

Abstract

Two types of Sm(II) complexes bearing either an N-phosphine-oxide-substituted imidazolylidene (PoxIm) or the corresponding imidazolinylidene (SPoxIm) were successfully prepared and characterized using single crystal X-ray diffraction analysis. The general formula of the structures of the complexes was found to be (anti-k-O-(S)PoxIm)nSmX2(THF)m where X = I, n = 2, m = 2 or X = pentamethylcyclopentadienyl, n = 1, m = 0. The carbene carbon atoms remained intact in these complexes. In some cases, axial chirality was clearly induced around the N‒P bonds due to the restricted rotation of the N-phosphinoyl moieties, which arises from the formation of N-phosphinoyl oxygen‒Sm(II) bonds. This work highlights a rare example of complexation-induced N‒P axial chirality and new aspects regarding lanthanide complexes of multifunctional multipurpose carbenes.