| Abstract
| - This is the first case of an organometallic complex that hydrolyzes thiophosphinates which is the key functional group for many neurotoxins. The metallocene bis(cyclopentadienyl) molybdenum(IV) dichloride, Cp2MoCl2, hydrolyzes a variety thioaryl diphenylphosphinates in an aqueous THF solution with a 102 rate acceleration that proceeds through intermolecular P−S bond scission.
- Thiophosphinate hydrolysis involving P−S bond scission is desirable for the degradation of organophosphateneurotoxins, and we report the first case for such a hydrolytic process by an organometallic compound. Themetallocene, bis(cyclopentadienyl)molybdenum(IV) dichloride, Cp2MoCl2 (Cp = η5-C5H5), hydrolyzes a variety ofthioaryl diphenylphosphinates in an aqueous THF solution. P−S scission of p-methoxythiophenyl diphenylphosphinatehas a 500-fold rate of acceleration in the presence of Cp2MoCl2(aq) with activation parameters of 20(3) kcal mol-1and −15(3) cal mol-1 K-1 for ΔH‡ and ΔS‡, respectively. These activation parameters and the rate accelerationare consistent with an intermolecular hydrolytic process in which the Cp2Mo serves as a Lewis acid to activate thephosphinate for nucleophilic attack. Furthermore, ρ = 2.3 (25 °C) which indicates a single nonconcerted mechanismin which the rate determining step is the nucleophilic attack on the activated phosphinate.
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