Mechanism of Reduction of the Nitrite Ion by Cu I Complexes

The reaction of Cu + aq with NO 2 − was studied. The results are consistent with the mechanism: Cu + aq + NO 2 − → ← (Cu + NO 2 − ), K = 140 ± 30 M −1 ; (Cu + NO 2 − ) + H + → Cu 2+ + NO + OH − , k = 4.6 × 10 5 M −1 s −1 . It is proposed that the copper is bound to the nitrogen in the transient complex (Cu + NO 2 − ). In addition, the reaction was studied with (Cu I L i ) + complexes. The results show that the ligands reduce the value of K and that their effect on k depends on the redox potential of the (Cu II/I L i ) couple. This reaction is the simplest model for the CuNIR (NIR = Nitric reductase) enzymes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)