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-κ-O-(S)PoxIm) n SmX2(THF) m where X = I, n = 2, and m = 2 or X = pentamethylcyclopentadienyl, n = 1, and 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.