Altered mechanisms of reactions of phosphate esters bridging a dinuclear metal center.
Kinetic isotope effects in the nucleophile and leaving group were obtained for the reaction of p-nitrophenyl phosphate monoester coordinated to a dinuclear Co(III) complex. The metal complex of the p-nitrophenyl phosphate monoester was found to hydrolyze by a single-step concerted mechanism, with significant nucleophilic participation in the transition state. By contrast, the hydrolysis of uncomplexed p-nitrophenyl phosphate occurs by a very loose transition state with little bond formation to the nucleophile. Previously, the metal complex of the diester methyl-p-nitrophenyl phosphate was found to hydrolyze via a two-step addition-elimination mechanism, in contrast to the concerted hydrolysis mechanism followed by uncomplexed diesters with the p-nitrophenolate leaving group. These results show that coordination to a metal complex can significantly alter the mechanism of phosphoryl transfer.
Humphry
Tim
T
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA.
Forconi
Marcello
M
Williams
Nicholas H
NH
Hengge
Alvan C
AC
D003035:Cobalt / Q000737:chemistry*; D006868:Hydrolysis; D007700:Kinetics; D009596:Nitrophenols / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry; D010755:Organophosphates / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010103:Oxygen Isotopes; D013816:Thermodynamics
D009596:Nitrophenols; D009942:Organometallic Compounds; D010755:Organophosphates; D009943:Organophosphorus Compounds; D010103:Oxygen Isotopes; C008644:nitrophenylphosphate; D003035:Cobalt