P-S Bond scission by bis(cyclopentadienyl)molybdenum(IV) dichloride, Cp(2)MoCl(2)(aq): first documented example of an organometallic complex hydrolyzing thiophosphinates.
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, Cp(2)MoCl(2) (Cp = eta(5)-C(5)H(5)), 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 Cp(2)MoCl(2)(aq) with activation parameters of 20(3) kcal mol(-)(1) and -15(3) cal mol(-)(1) K(-)(1) for DeltaH(double dagger) and DeltaS(double dagger), respectively. These activation parameters and the rate acceleration are consistent with an intermolecular hydrolytic process in which the Cp(2)Mo serves as a Lewis acid to activate the phosphinate for nucleophilic attack. Furthermore, rho = 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.
Kuo
Louis Y
LY
Department of Chemistry, Lewis & Clark College, Portland, Oregon 97219, USA. kuo@clark.edu
Blum
Angela P
AP
Sabat
Michal
M
D018360:Crystallography, X-Ray; D006868:Hydrolysis; D008958:Models, Molecular; D008968:Molecular Conformation; D008982:Molybdenum / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010721:Phosphinic Acids / Q000138:chemical synthesis*; D010758:Phosphorus / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*; D013816:Thermodynamics
D009942:Organometallic Compounds; D010721:Phosphinic Acids; C024389:molybdocene dichloride; D010758:Phosphorus; D013455:Sulfur; D008982:Molybdenum