Determination of the Absolute Configuration of CN-Palladacycles by 31P{1H} NMR Spectroscopy Using (1R,2S,5R)-Menthyloxydiphenylphosphine as the Chiral Derivatizing Agent: Efficient Chirality Transfer in Phosphinite Adducts

Abstract

A series of (1R)-MenOPPh2 phosphinite derivatives of α-arylalkylaminate CN-palladacycles of known absolute configuration was prepared. Their structure and stereochemistry were determined using different experimental (NMR spectroscopy and X-ray diffraction) and theoretical (density functional theory calculation) methods. Despite the conformational mobility of the phosphinite reagent and the highly remote position of its stereocenters from those of the cyclopalladated amine, efficient chirality transfer in the phosphinite cyclopalladated complexes was established. On the basis of these results, a new method for the determination of the absolute configuration of chiral CN-palladacycles was elaborated using the (1R)-MenOPPh2 phosphinite as a highly sensitive referee ligand and in situ 31P{1H} NMR spectroscopy as a control method. The proposed approach is a remarkable addition to the classical NMR techniques, increasing their versatility and excluding the isolation of the phosphinite derivatives.