Mechanistic Studies on the Activation of NO by Iron and Cobalt Complexes

Abstract

In this review, the reactions of nitric oxide with selected Fe and Co complexes of biological and environmental importance are reviewed. Fundamental chemical kinetics and mechanisms of reactions that lead to the formation and decay of nitrosyl complexes are illustrated and discussed on the basis of studies on Fe II and the release of NO from metal complexes and on the nature of the stable metal-NO complexes produced in solution.As will be seen for most of the presented reactions, the interaction of NO with the metal complex involves activation of the small NO molecule so that charge transfer occurs as a result of the formation of the metal-NO bond.

Distorted tetrahedral nickel-nitrosyl complexes: spectroscopic characterization and electronic structure

“…NO can react with both organic and oxygencentered radicals to yield many highly reactive intermediates. Moreover, NO can also interact with transition-metal ions to make a variety of coordination compounds [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The ν(N-O) stretching energies should provide straightforward insight into the geometric and electronic structure of nitrosyl complexes.…”

Reactivity of Inorganic Radicals in Aqueous Solution

“…Several review articles have been published on aspects of this subject recently. [143][144][145][146][147][148][149] In many cases the reactions are reversible, so binding equilibrium constants and rate constants for binding and release (k on and k off ) have been measured. A selection of these data is presented in Table 9.12.…”

“…201 Reductive nitrosation of [Ru(NH 3 ) 6 ] 3 þ produces [Ru(NH 3 ) 5 N 2 ] 2 þ with base-catalyzed kinetics; the coordinated N 2 is produced by hydrolysis after the nitrosation step. 170 Reductive nitrosylation occurs for several Fe III porphyrins, 145,147,159 where the net reaction is LFe III ðH 2 OÞ þ 2NO ! ½LFeðNOÞ À þ NO 2 À þ 2H þ ð9:36Þ…”

“…Co(III) porphyrins react with NO in excellent analogy with the stoichiometry of Equation 9.36, but the rates are not catalyzed by nucleophiles; the proposed mechanism is quite different from that for the Fe(III) reactions and involves substitution at both axial sites. 147,176 In another class of reactions, NO is oxidized to NO 3 À or its equivalent by metal-(O 2 /O 2 À ) complexes. In these reactions, NO first adds to the O 2 À moiety to form a peroxynitrito intermediate that can decompose in various ways.…”

Review: Recent advances in the investigations of NO activation on cobalt and manganese porphyrins: a brief review

“…Over the past dozen years a number of reviews have been devoted to the mechanisms of the interactions occurring in such a system, taking into account both NO itself and its endogenous and exogenous donors [11][12][13][14][15][16][17][18] biological scavenger [19,20]. The complex structure of cobalamin which increases the probability of the interference from the background reactions encourages taking advantage of simpler model systems, based mainly on symmetric synthetic porphyrins [21].…”