Thiophosphinate hydrolysis involving P-S bond scission is desirable for the degradation of organophosphate neurotoxins, and we report the first case for such a hydrolytic process by an organometallic compound. The metallocene, bis(cyclopentadienyl)molybdenum(IV) dichloride, Cp2MoCl2 (Cp = eta(5)-C5H5), hydrolyzes a variety of thioaryl diphenylphosphinates in an aqueous THF solution. P-S scission of p-methoxythiophenyl diphenylphosphinate has a 500-fold rate of acceleration in the presence Of Cp2MoCl2(aq) with activation parameters of 20(3) kcal mol(-1) and -15(3) cal mol(-1) K-1 for Delta H-double dagger and Delta S double dagger respectively. These activation parameters and the rate acceleration are consistent with an intermolecular hydrolytic process in which the Cp2Mo serves as a Lewis acid to activate the phosphinate for nucleophilic attack. Furthermore, p = 2.3 (25 degrees C) which indicates a single nonconcerted mechanism in which the rate determining step is the nucleophilic attack on the activated phosphinate.