Proline and α‐Methylproline as Chiral Auxiliaries for the Synthesis of Enantiopure Bis‐Cyclometalated Iridium(III) Complexes

Abstract

A convenient proline‐ and α‐methylproline‐mediated method for the synthesis of enantiomerically pure bis‐cyclometalated iridium(III) complexes is reported. The reactions of l ‐proline or l ‐α‐methylproline with [Ir(µ‐Cl)(C^N) 2 ] 2 (C^N = cyclometalating 2‐phenylpyridine, 2‐phenylbenzoxazole, or 2‐phenylbenzothiazole ligand) afforded diastereomeric mixtures of intermediate prolinatoiridium(III) complexes from which the Λ‐( S ) diastereomers were isolated with excellent diastereomeric purity by washing, precipitation, or crystallization. A subsequent trifluoroacetic acid (TFA) induced substitution of the prolinate ligands with 2,2′‐bipyridine with the retention of configuration provided the chiral‐only‐at‐metal complexes with >99 % ee .