A polystyrene-supported molybdenum peroxo material (Mo-Y(s)) was applied towards the oxidative degradation of the organophosphate neurotoxin O, S – diethylphenyl phosphonothioate (DEPP) through ethanolysis. In addition to the operational advantages of heterogeneous reactivity, the oxidative ethanolysis with 10 fold excess of H2O2 yields only P – S bond scission to yield diethylphenyl phosphonate and ethyl sulfate. This is the first report of a molybdenum solid support that promotes the degradation of sulfur-containing organophosphate with the turnover benefits of heterogeneous catalysis. Activation parameters of DEPP ethanolysis by Mo-Y(s) (Ea =57 ± 6 kJ/mol and △S‡ = -124 ± 21 J/mol●K) and by the model compound oxodiperoxo(pyridine-2-carboxylato)molybdate(VI) bis(pyridine-2-carboxylic acid) monohydrate (1) (Ea =55 ± 5 kJ/mol and △S‡ = -154 ± 15 J/mol●K) are almost identical for the oxidation of thioanisole by 1. This suggests the rate determining step for DEPP ethanolysis is sulfur oxidation to form an intermediate phoshonothioate S-oxide that subsequently undergoes nucleophilic attack by the ethanol solvent to form diethylphenyl phosphonate and ethyl sulfate. Evidence for formation of this S-oxide intermediate and the postulated ethanolysis mechanism is provided.

Heterogeneous and homogeneous phosphonothioate alcoholysis by supported molybdenum-peroxo complexes

253rd National Meeting (2017)

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