Nickel pincer model of the active site of lactate racemase involves ligand participation in hydride transfer

Pincer complexes are widely applied in homogeneous catalysis. However, only very recently has the first pincer complex been discovered in the active site of a metalloenzyme, namely, lactate racemase. Here, we report a synthetic model of the active site of lactate racemase. The nickel pincer model not only reproduces some key structural features of the active site, but also mediates the dehydrogenation of alcohols, a reaction relevant to lactate racemization. Our work suggests a mechanism in which the unique pyridinium-derived SCS pincer ligand actively participates in the hydride transfer. This work not only represents a successful biomimetic study of this enzyme but also lays the foundation for the development of new bioinspired pincer ligands.