5 research outputs found

    Stereochemical Inversion of Phosphonothioate Methanolysis by La(III) and Zn(II): Mechanistic Implications for the Degradation of Organophosphate Neurotoxins

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    The utility of phosphonothioate methanolysis to degrade organophosphate neurotoxins has prompted the stereochemical investigation of this useful transformation. The methanolysis of enantiomerically pure <i>O</i>,<i>S</i>-diethyl phenylphosphonothioate (<b>5</b>) was studied both in the presence and in the absence of metal ions known to catalyze the phosphonothioate → phosphonate transformation. This report outlines the syntheses of enantiomerically pure <b>5</b> and its methanolysis product <i>O</i>-ethyl <i>O</i>-methyl phenylphosphonate (<b>7</b>). Compound <b>7</b> results from exclusive P–S scission of <b>5</b>, which is the desired mode of phosphonothioate methanolysis (<i>E</i><sub>a</sub> = 14.5 ± 0.5 kcal/mol). The stereochemical analysis of the phosphonothioate methanolysis was done for the first time with β-cyclodextrin, and it shows complete inversion on the phosphorus center upon methoxide displacement of ethanethiolate. The presence of La­(III) or Zn­(II) complexes do not alter this S<sub>N</sub>2-like substitution which sheds new light on the mechanism of methanolysis of phosphonothioates

    Stereochemical Inversion of Phosphonothioate Methanolysis by La(III) and Zn(II): Mechanistic Implications for the Degradation of Organophosphate Neurotoxins

    No full text
    The utility of phosphonothioate methanolysis to degrade organophosphate neurotoxins has prompted the stereochemical investigation of this useful transformation. The methanolysis of enantiomerically pure <i>O</i>,<i>S</i>-diethyl phenylphosphonothioate (<b>5</b>) was studied both in the presence and in the absence of metal ions known to catalyze the phosphonothioate → phosphonate transformation. This report outlines the syntheses of enantiomerically pure <b>5</b> and its methanolysis product <i>O</i>-ethyl <i>O</i>-methyl phenylphosphonate (<b>7</b>). Compound <b>7</b> results from exclusive P–S scission of <b>5</b>, which is the desired mode of phosphonothioate methanolysis (<i>E</i><sub>a</sub> = 14.5 ± 0.5 kcal/mol). The stereochemical analysis of the phosphonothioate methanolysis was done for the first time with β-cyclodextrin, and it shows complete inversion on the phosphorus center upon methoxide displacement of ethanethiolate. The presence of La­(III) or Zn­(II) complexes do not alter this S<sub>N</sub>2-like substitution which sheds new light on the mechanism of methanolysis of phosphonothioates

    Aqueous Chemistry of the Metallocene [Cp<sub>2</sub>MoCl<sub>2</sub>]BF<sub>4</sub>: Evidence of Autocatalytic Molybdenum(V) Reduction in Water

    No full text
    The aqueous chemistry of the air-stable Mo­(V) metallocene [Cp<sub>2</sub>MoCl<sub>2</sub>]­BF<sub>4</sub> (<b>1</b>) yields an unexpected autocatalytic reduction when water is added to an acetonitrile solution of <b>1</b>. While <b>1</b> yields the expected stable Cp–Mo ligation and rapid chloride hydrolysis in water, a Mo­(V) → Mo­(IV) reduction to the metallocene Cp<sub>2</sub>MoCl<sub>2</sub> (<b>2</b>) was evident. Under acidic conditions (pH ∼2) or trace amounts of water this reduction was slow enough to be monitored spectroscopically, and it is shown to be autocatalytic in aqueous <b>2</b>. No reaction occurs when <b>1</b> and <b>2</b> are in the dichloride form in acetonitrile (i.e., no water). It is hypothesized that the added water serves two roles. First it initially reduces a small population of <b>1</b> to <b>2</b>, and then as the aquated Mo­(IV) metallocene, it catalyzes the reduction of the remaining Mo­(V) in water. This is the first aqueous investigation of the Mo­(V) metallocene, and it shows a novel and unprecedented autocatalytic reduction that is mediated by water

    Phosphonothioate Hydrolysis Turnover by Cp<sub>2</sub>MoCl<sub>2</sub> and Silver Nanoparticles

    No full text
    The metallocene bis­(cyclopentadienyl)­molybdenum­(IV) dichloride (Cp<sub>2</sub>MoCl<sub>2</sub>; Cp = η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>) is the first organometallic compound to promote the hydrolysis of phosphonothioates with selective P–S scission in a stoichiometric fashion. This report shows that silver nanoparticles capped with borohydride ions promote turnover in this hydrolytic process, as indicated by <sup>31</sup>P NMR studies on the reaction of <i>O</i>,<i>S</i>-diethyl phenylphosphonothioate (DEPP) with Cp<sub>2</sub>MoCl<sub>2</sub> (pH 7). This is the first example of the joint use of nanoparticles and molybdenum metallocenes to promote phosphonothioate hydrolysis. Initial results indicate the turnover may be due to free Ag<sup>+</sup>(aq) ions present in the solution that arise either from the slow dissolution of the nanoparticles or from interactions with the Ag nanoparticle surface

    Phosphonothioate Hydrolysis Turnover by Cp<sub>2</sub>MoCl<sub>2</sub> and Silver Nanoparticles

    No full text
    The metallocene bis­(cyclopentadienyl)­molybdenum­(IV) dichloride (Cp<sub>2</sub>MoCl<sub>2</sub>; Cp = η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>) is the first organometallic compound to promote the hydrolysis of phosphonothioates with selective P–S scission in a stoichiometric fashion. This report shows that silver nanoparticles capped with borohydride ions promote turnover in this hydrolytic process, as indicated by <sup>31</sup>P NMR studies on the reaction of <i>O</i>,<i>S</i>-diethyl phenylphosphonothioate (DEPP) with Cp<sub>2</sub>MoCl<sub>2</sub> (pH 7). This is the first example of the joint use of nanoparticles and molybdenum metallocenes to promote phosphonothioate hydrolysis. Initial results indicate the turnover may be due to free Ag<sup>+</sup>(aq) ions present in the solution that arise either from the slow dissolution of the nanoparticles or from interactions with the Ag nanoparticle surface
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