Characterization of transition states in dichloro(1,4,7-triazacyclononane)copper(II)-catalyzed activated phosphate diester hydrolysis
Characterization of transition states in dichloro(1,4,7-triazacyclononane)copper(II)-catalyzed activated phosphate diester hydrolysis
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DOI：
10.1021/ja952306p
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发表时间：
1996-02-21
影响因子：
15
通讯作者：
Burstyn, JN
中科院分区：
文献类型：
--
作者：
Deal, KA;Hengge, AC;Burstyn, JN
通过动力学同位素效应和同位素交换实验，探讨了铜[9]-N(3)-氯(2)催化间-硝基苯基磷酸乙酯的反应机理。溶剂的氚同位素效应((D)k=1.14)，再加上4-硝基苯酚中没有O-18的掺入，表明水解是通过磷中心的金属配位氢氧化物的分子内攻击进行的。二次N-15同位素效应((15)k=1.0013+/-0.0002)意味着离开基团的损失发生在限速步骤，在过渡态大约有50%的键断裂。这项研究是首次将二次N-15同位素效应应用于简单的金属促进的水解反应，其结果与协作键的形成和断裂是一致的。提出了与同位素研究相一致的机理。
The reaction mechanism for Cu[9]aneN(3)Cl(2)-catalyzed hydrolysis of ethyl it-nitrophenyl phosphate was probed using kinetic isotope effects and isotope exchange experiments. The solvent deuterium isotope effect ((D)k = 1.14), combined with the absence of O-18 incorporation into 4-nitrophenol, suggests that hydrolysis proceeds through intramolecular attack of the metal-coordinated hydroxide at the phosphorus center. The secondary N-15 isotope effect ((15)k = 1.0013 +/- 0.0002) implies that loss of the leaving group occurs at the rate-limiting step with approximately 50% bond cleavage in the transition state. This study is one of the first applications of the secondary N-15 isotope effect to simple metal-promoted hydrolysis reactions, and the result is consistent with concerted bond formation and cleavage. A mechanism consistent with the isotope studies is presented.