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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Kinetic and mechanistic study on the reaction of alkylcobaloximes with azoles
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Kinetic and mechanistic study on the reaction of alkylcobaloximes with azoles

机译：烷基钴氧肟与唑类反应的动力学和机理研究

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摘要

The kinetics of axial water substitution by azoles ( pyrazole and 1,2,4-triazole) in three different cobaloximes, viz. trans-[Co(Hdmg)(2)(R) H2O] where Hdmg = dimethylglyoximate, R = PhCH2, Et and CF3CH2, were studied as a function of azole concentration, temperature and pressure in aqueous solution. The second order rate constants for the substitution of water in trans-[Co(Hdmg)(2)(R) H2O] for R = Et at pH 6.0, 25degreesC and I = 0.1 M (NaClO4), were found to be 1309 and 1200 M-1 s(-1) for pyrazole (Pz) and 1,2,4-triazole (Tz), respectively, and those obtained for R = PhCH2 were found to be 755 and 691 M-1 s(-1), respectively. The second order rate constants in the case of R = CF3CH2 were found to be 0.358 and 0.348 M-1 s(-1) for Pz and Tz, respectively. The relative order of reactivity for the different alkyls being Et > PhCH2 > CF3CH2. The activation parameters (DeltaH(not equal), DeltaS(not equal) and DeltaV(not equal)) obtained for these reactions were found to be in the range of 65 - 87 kJ mol(-1), 24 - 47 J mol(-1) K-1 and 2.5 - 7.7 cm(3) mol(-1), respectively. These data suggest that an Id substitution mechanism operates where the azoles participate in the transition state.
机译：在三种不同的钴肟中，用唑类（吡唑和1,2,4-三唑）进行轴向水置换的动力学。研究了反式-[Co（Hdmg）（2）（R）H2O]（其中Hdmg =乙二酸二甲酯），R = PhCH2，Et和CF3CH2作为水溶液中吡咯浓度，温度和压力的函数。发现在pH 6.0、25°C和I = 0.1 M（NaClO4）下，反式[Co（Hdmg）（2）（R）H2O]中的水替代R = Et的水的二级速率常数为1309和吡唑（Pz）和1,2,4-三唑（Tz）分别为1200 M-1 s（-1），R = PhCH2获得的那些分别为755和691 M-1 s（-1） ， 分别。在R = CF3CH2的情况下，Pz和Tz的二阶速率常数分别为0.358和0.348 M-1 s（-1）。不同烷基的反应性相对顺序为Et> PhCH2> CF3CH2。这些反应获得的活化参数（DeltaH（不等于），DeltaS（不等于）和DeltaV（不等于））被发现在65-87 kJ mol（-1），24-47 J mol（ -1）K-1和2.5-7.7 cm（3）mol（-1）。这些数据表明，Id取代机制在唑类参与过渡态的地方起作用。

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