Historical Introduction to Nitrosyl Complexes

Abstract

This review provides a historical introduction to nitrosyl complexes. In the 1960s and 1970s, the renaissance of coordination chemistry led to the detailed study of nitrosyl complexes, and the emerging of new spectroscopic and structural techniques were used to define the metrics of nitric oxide when coordinated to transition metals and established that unlike CO and CN⁻, NO adopted alternative geometries. The development of theoretical models to account for this geometric ambivalence was initially based on semiempirical molecular orbital calculations in the early 1970s. Subsequently more accurate and sophisticated calculations have deepened our understanding of the bonding in transition metal-nitrosyl complexes. The discovery in the 1980s of the key importance of these complexes as models for the biological functions and transformations of NO encouraged these studies. NO is produced in vivo by the nitric oxide synthase (NOS) family of enzymes and plays a key role in the nerve-signal transreduction, vasodilation, blood clotting, and immune response by white blood cells. In these biological processes, the coordination of nitric oxide to metal centres is crucial, and therefore, their detailed study is essential for an understanding of nitric oxide’s functions at the molecular level.