Kinetics and mechanism of nitrite reduction by trichloro-oxobis(triphenylphosphine oxide)molybdenum(V)

Abstract
In the presence of excess of nitrite ion the complex [MoOCl3(OPPh3)2] is completely oxidised to MoVI in CH2Cl2. The reaction proceeds by three observable stages. Data for the first stage correspond to co-ordination of nitrite at molybdenum(V), via a limiting SN1 mechanism, involving loss of a triphenylphosphine oxide molecule. At 25 °C, k1= 51·8 ± 2·1 s–1, ΔH1 = 12·6 ± 0·3 kcal moh–1, and ΔS1 =–8·2 ± 1·0 cal K–1 mol–1. The data for the second stage of reaction are taken to indicate chelation and/or isomerisation of co-ordinated nitrito-ligand into a position cis to the oxo-group, followed by rapid non-rate-determining electron transfer. The third and final stage of reaction appears to involve co-ordination of the available nitrite to the primary molybdenum(VI) product, and subsequent rearrangement of these molybdenum(VI) products.

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