The oxidation of Fen(L) complexes by molecular oxygen is significantly enhanced by the presence of a chelating ligand L. The kinetics of this reaction was studied for L = ethylenediaminetetraacetate, jV-(hydroxyethyl)ethylenediaminetriacetate, and diethylenetriaminepentaacetate as a function of [FeK(L)], [02], pH, temperature, and pressure. All the observed kinetic relationships can be accounted for in terms of a mechanism in which 02 rapidly reacts with Fe"(L) to produce Fen(L)02, followed by three parallel reaction steps. These include spontaneous and acid-catalyzed electron transfer, as well as a reaction with Fel!(L) to produce (L)Fe,,,-022"-Fe,II(L). The results are discussed in reference to the available literature data for these and related oxidation processes.

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NO, HONO, and N02" react with Fen(edta) in aqueous solution to produce Fen(edta)NO. The reaction with NO is too fast for conventional stopped-flow and -jump techniques, whereas the reaction with H0N0/N02" can be followed kinetically by using stopped-flow techniques. This reaction occurs in two parallel paths of different order, viz. pseudo first and pseudo zero order in Fen(edta) concentration, respectively. The contribution of each path strongly depends on the pH and total nitrite concentration employed. The kinetics of the reaction can be described by the rate law -d[Fen(edta)]/dr = U, [HONO]2 + kb[Fen(edta)][HONO], where ka and kb have the values 62 ± 12 and 90 ± 16 M"1 s'1, respectively, at 25 °C and 0.5 M ionic strength. The suggested mechanism involves the rate-determining formation of NO+ and the reduction of HONO to NO by Fen(edta), to account for the parallel reaction paths. The results are discussed in comparison to the available literature data.

Chelate ring closure in (vl-bid)M(CO)5 complexes (bid = bidentate, potentially chelating ligand; M = Cr, Mo, W; eq 1)