Reactivity and Structure of Complexes of Small Molecules: Nitric Oxide

Nitric oxide (NO) is the classic non-innocent ligand, and its coordination chemistry has both fascinated and perplexed scientists for the last > 150 years, starting with the discovery of sodium nitroprusside, Na2[Fe(CN)5(NO)], by Playfair in 1849. This is not only due to the fact that this ligand can change oxidation state upon binding to transition metal centers, but also the often highly covalent bonds that originate from this interaction. The coordination chemistry of NO with iron, but also copper and cobalt, then experienced a revival in the 1980s when the biological significance of NO for mammalian physiology was recognized. This article summarizes key accomplishments in the field of the coordination chemistry of NO in the last 10–15 years, and points toward biological relevance wherever appropriate.