Carbenes. Pincers, chelates, and abnormal binding modes

Abstract

Routes to pincer and chelate carbene complexes of Pd, Rh, and Ir include double geminal CH activation, metallation, and CH activation. Abnormal binding via imidazole C5 can occur, and ion pairing can strongly influence C2 vs. C5 binding. Prior ligand binding via pyridine N before metallation is not essential. Computational methods are used extensively, for example, to compare N vs. C binding in imidazole. The possibility of C binding by histidine in metalloenzymes is discussed.