Synthesis and Characterisation of a Novel Chiral Bidentate Pyridine-N-Heterocyclic Carbene-Based Palladacycle

A novel chiral six-membered bidentate pyridine-N-heterocyclic carbene palladacycle was prepared via optical resolution of the racemic palladacycle. This is the first successful demonstration of the synthesis of a chiral carbene palladacycle via fractional crystallization of its chiral amino acid derivatives. Upon formation of (R-C,S-C) and (S-C,S-C)-phenylalanate derivatives, the (R-C,S-C)-phenylalanate diastereomer crystallized out spontaneously. Optically active (R)- and (S)-dichloropalladacycles can then be achieved by subsequent cleavage of the chiral amino acid auxiliary in the presence of aqueous HCl from their respective diastereomers. The absolute configurations of both the (R)- and (S)-palladacycles were determined by X-ray diffraction studies.