title: Altered mechanisms of reactions of phosphate esters bridging a dinuclear metal center.
abstract: 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.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA.
authors.forename: Tim
authors.initials: T
authors.lastname: Humphry
authors.forename: Marcello
authors.initials: M
authors.lastname: Forconi
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Williams
authors.forename: Alvan C
authors.initials: AC
authors.lastname: Hengge
mesh_terms: 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
chemical_list: D009596:Nitrophenols; D009942:Organometallic Compounds; D010755:Organophosphates; D009943:Organophosphorus Compounds; D010103:Oxygen Isotopes; C008644:nitrophenylphosphate; D003035:Cobalt