CuII—diamine complex catalyzed hydrolysis of phosphate triesters adsorbed on strong-base ion exchange resins. 31P NMR relaxation measurements

Abstract

The Cu^II—diamine complexes, (bipy)CuSO₄ and (tmen)CuSO₄, catalyze the hydrolysis of p-nitrophenyl diphenyl phosphate (PNDP) adsorbed on a strong-base ion exchange resin. Turnover is observed. The major hydrolysis products are diphenyl phosphate, p-nitrophenyl phenyl phosphate, and the ethanolysis product ethyl diphenyl phosphate (EDPP) which are observed in similar amounts in both the presence and absence of the Cu^II—diamine catalysts. The apparent bimolecular rate constants found for the (bipy) CuSO₄ and (tmen)CuSO₄ catalysts are 0.023 and 0.024 M⁻¹ s⁻¹, respectively. CuSO₄ is inactive as a catalyst. ³¹P MAS NMR relaxation measurements of the stable EDPP product reveal that the Cu^II—diamine complexes greatly enhance T₁ relaxation, whereas CuSO₄ has only minimal effect. These results are consistent with the complexation of neutral phosphorus esters by the Cu^II—diamine catalysts. ³¹P T₁ measurements of hydrolytically-stable dimethyl methylphosphonate (DMMP) in water solutions of Cu²⁺, (tmen)Cu²⁺, and Mn²⁺ suggest that DMMP exchanges rapidly between inner-sphere and outer-sphere complexes in a nearly identical manner with each of these paramagnetic species.