Studies of the Electronic Properties of N‐Heterocyclic Carbene Ligands in the Context of Homogeneous Catalysis and Bioorganometallic Chemistry

Abstract

AbstractN‐heterocyclic carbenes (NHCs) have been dominating the world of homogeneous catalysis in an unprecedented manner in the last two decades. Understanding the underlying reasons behind catalysis with NHC ligands has thus become of significant interest. Subscribing to this view, we strive to identify the key attributes of N‐heterocyclic carbene ligands through a combination of experimental and computational studies. Rational catalyst design, by appropriate functionalization of N‐heterocyclic carbene ligands to investigate their utility in a host of catalytically relevant transformations of interest to contemporary organic synthesis, is thus central to our efforts. From this perspective, a variety of C–C and C–N bond forming reactions, namely, the Suzuki–Miyaura, Sonogashira, and Hiyama cross‐couplings, the base‐free Michael additions, the alkene and alkyne hydroaminations, the formation of β‐enaminones from 1,3‐dicarbonyl compounds and primary amines, and the environmentally important ring‐opening polymerizations (ROP) of L‐lactides, which produce biodegradable polylactide polymers from renewable resources, have been studied. The metal–carbene interaction in these catalysts has been probed with the aid of computational studies, which suggest that strong σ‐donor N‐heterocyclic carbene ligands bind tightly to the metal center and thereby impart the much needed stability to these catalysts. Even going beyond catalysis, we investigated the potential of N‐heterocyclic carbene complexes in biomedical applications particularly for their antimicrobial and anticancer properties.