Redox Reactivity of Coordinated Ligands in Pentacyano(L)Ferrate Complexes

Abstract

This chapter discusses redox chemistry of small nitrogen-containing L ligands with bioinorganic relevance, particularly nitric oxide, NO, and its redox-interconverted forms NO+ (nitrosyl) and NO- (nitroside, or its protonated form, HNO, nitroxyl). The coordination chemistry of transition metal cyanometallates has been of great and long-standing matter because of the fundamental issues related to their electronic structure and reactivity. The chemistry of redox-active ligands L in the pentacyano(L) ferrate(II) and -(III) complexes is of fundamental concern for disclosing the mechanistic features which are operative in stoichiometric and catalytic processes associated with oxidation, reduction, and disproportionation of L. This is particularly important for small molecules displaying a versatile coordination behavior, such as the N-binding species associated with the nitrogen redox cycle, which display complex, multi-electronic paths for oxidation or reduction in most cases, generally under kinetic rather than thermodynamic control. Another crucial factor influencing the redox reactivity of cyano complexes is the possibility of bridging one (or more) cyano ligands to an acceptor moiety.