Peroxynitritometal complexes

Peroxynitrite as a ligand can be formed (1) from the reaction of a superoxometal complex with nitrogen monoxide, or (2) as an intermediate in the catalysis of the isomerization to nitrate or the reduction to nitrogen dioxide. With one exception, namely [(CN)(5)ONOOCo](3-), such complexes have not been isolated. The instances where peroxynitrito complexes have been described or invoked so far are limited to two proteins, (haemoglobin and myoglobin), three macrocyclic complexes, (a rhodium tetraazacyclotetradecane, and manganese and iron porphyrins), cobalt, chromium, and titanium. Upon formation of the complex, isomerization to nitrate can occur within the coordination sphere, or the O-O bond breaks to yield an oxometal complex and nitrogen dioxide. The latter two can recombine to form a nitratometal complex, which subsequently dissociates. (C) 2004 Elsevier B.V. All rights reserved.