Transition metal complexes with chirality at the metal as well as chiral ligands

Abstract

Chiral ruthenium N-heterocyclic carbene (NHC) complexes form a diverse and versatile class of organometallic compounds with a wide range of structural variations and applications. This study presents our attempts on the separation of diastereomers of thermally stable octahedral Ru(II)-CNC pincer complexes.1 However, diastereomer separation proved unsuccessful utilizing camphor sulfonate as a chiral auxiliary. Consequently, the approach shifted towards pre-reported Ru(II)-NHC-DMSO and Ru(II)-NHC-DMS complexes2 with alternative chiral auxiliaries, including R-BINAP, S-BINAP, SBINAM, and R-BINAM. Both photochemical and thermal synthetic routes were explored. 1H NMR spectroscopy indicated a 3:1 diastereomeric ratio, though repeated attempts at physical separation were unsuccessful, so far. All complexes were thoroughly characterized using ¹H, ¹³C, and ³¹P NMR spectroscopy. The broad utility of chiral Ru-NHC complexes stems from their customizable steric and electronic environments, which make them highly suitable for fine-tuning in asymmetric catalysis and bioinorganic chemistry. Ongoing research is directed at expanding their applications and deepening the understanding of structure–property relationships.