THE [CU(TMEN)(OH)(OH2)](-DINITROPHENYL DIETHYL PHOSPHATE AND O-ISOPROPYL METHYLPHOSPHONOFLUORIDATE (SARIN) (TMEN = N,N,N'N'-TETRAMETHYL-1,2-DIAMINOETHANE)() PROMOTED HYDROLYSIS OF 2,4)

The hydrolysis of the phosphate triester 2,4-dinitrophenyl diethyl pho sphate to diethyl phosphate is catalysed by [Cu(tmen)(OH)(OH2)](+) in the pH range 6.5 to 8.0. At pH 7 with a catalyst concentration of 2.5 x 10(-3) mol dm(-3) the rate enhancement is ca 10(4) fold. The pH depe ndence of the catalysis is consistent with the hydroxoaqua complex bei ng the active species in the hydrolysis. The greater kinetic effective ness of this weak base, compared with hydroxide ion on a molar basis, indicates a bifunctional mechanism in which bound hydroxide acts as a nucleophile in conjunction with electrophilic catalysis by copper at t he phosphoryl oxygen. The copper complex is an excellent catalyst for the hydrolysis of O-isopropyl methylphosphonofluoridate (Sarin). At pH 7 and 25 degrees C using a Sarin concentration of 4.5 x 10(-2) mol dm (-3) and a [Cu(tmen)(OH2)(2)](2+) concentration of 5 x 10(-3) mol dm(- 3), complete hydrolysis (9 turnovers) occurs in 13 min. (C) 1998 Elsev ier Science Ltd. All rights reserved.