Mechanism and Transition State Structure of Aryl Methylphosphonate Esters Doubly Coordinated to a Dinuclear Cobalt(III) Center
作者:Guoqiang Feng、Eric A. Tanifum、Harry Adams、Alvan C. Hengge、Nicholas H. Williams
DOI:10.1021/ja904134n
日期:2009.9.9
to that of a phosphate monoester complex with the same leaving group, rather than the isoelectronic diester complex. The data from these model systems parallel the observation that in protein phosphatase-1, which has an active site that resembles the structures of these complexes, the catalyzed hydrolysis of aryl methylphosphonates and aryl phosphates are much more similar to one another than the uncomplexed
研究了每种与双核 Co(III) 配合物配位的五种膦酸酯的反应性 ([Co(2)(tacn)(2)(OH)(2)O(2)P(Me)OAr}](3+ ); tacn = 1,4,7-三氮杂环壬烷; 取代基 = mF, p-NO(2) (1a); p-NO(2) (1b); m-NO(2) (1c); p-Cl ( 1d);未取代的(1e))。1a 到 1e 中膦酸酯的水解是特定碱催化的,并通过分子内氧化物攻击桥接膦酸酯而发生。这些数据定义了 -1.12 的 Brønsted beta(lg),比未复合的膦酸酯的水解 (-0.69) 更负面。对于 1b,离去基团中的动力学同位素效应为 (18)k(lg) = 1.0228 和 (15)k = 1.0014,在非桥连磷酰氧 (18)k(nonbridge) = 0.9954 和亲核氧( 18)k(nuc) = 1.0105。KIE 和 beta(lg)