Methyl transfer reactivity of pentachloromethylplatinate(IV) anion with a series of N-nucleophiles
Methyl transfer reactivity of pentachloromethylplatinate(IV) anion with a series of N-nucleophiles
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DOI：
10.1016/j.jorganchem.2018.10.020
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发表时间：
2019-02-01
影响因子：
2.3
通讯作者：
Vedernikov, Andrei N.
中科院分区：
文献类型：
--
作者：
Adams, Daniel J.;Johns, Brian;Vedernikov, Andrei N.
研究了K-2[（PtCH_3Cl_5）-C-IV]对一系列取代N，N-二甲基苯胺1a-1g、N，N-二异丙基苯胺1h和2，6-取代吡啶2a-2b的反应性。丙酮水溶液。反应产生相应的N-甲基铵或N-甲基吡啶鎓产物3或4，对底物1a-1g和2b具有高选择性，并遵循总体2级动力学，Pt-IV络合物和胺均为1级。胺的电子性质和空间体积的反应性进行了讨论。对于N，N-二甲基苯胺系列1a-1g，Me_2NC_6H_4R（R = H，m-Cl，p-Cl，m-Me，p-Me，p-MeO，p-Me_2N），反应二级速率常数log（k（2））与pK（a）之间存在良好的线性关系。同时，体积较大的N，N-二异丙基苯胺底物1h的反应性比使用该相关性预测的低约3个数量级。最后，吡啶2a-2b的反应性比具有类似pK（a）的N，N-二甲基苯胺低3-4个数量级。有趣的是，K2[（PtCH 3Cl 5）-C-IV]对N，N-二甲基苯胺的反应性与标准有机甲基化剂硫酸二甲酯Me 2SO 4的反应性具有相同的数量级或稍大。标题反应的计算（DFT）模型与五配位PtIVMe亲电试剂[PtIVCH_3Cl_4]（-）的形成一致，该亲电试剂参与亲核胺对S（N）_2甲基碳的攻击。(C)2018 Elsevier B. V.版权所有。
Reactivity of K-2[(PtCH3Cl5)-C-IV] toward a series of substituted N, N-dimethylanilines 1a-1g, N, N-diisopropylaniline 1h and 2,6-substituted pyridines 2a-2b was investigated in 60% (vol.) aqueous acetone solutions. The reactions result in corresponding N-methylammonium or N-methylpyridinium products, 3 or 4, with high selectivity for the substrates 1a-1g and 2b, and follow an overall 2nd order kinetics, 1st order in both the Pt-IV complex and the amines. The reactivity is discussed in terms of the amine electronic properties and steric bulk. For the series of N, N-dimethylanilines 1a-1g, Me2NC6H4R (R = H, m-Cl, p-Cl, m-Me, p-Me, p-MeO, p-Me2N), a high quality linear correlation was found between logarithm of the reaction second order rate constant, log(k(2)), and pK(a) of the anilines. At the same time, the reactivity of the bulkier N,N-diisopropylaniline substrate 1h is about 3 orders of magnitude lower than predicted using this correlation. Finally, the pyridines 2a-2b are 3-4 orders of magnitude less reactive than N,N-dimethylanilines of similar pK(a). Interestingly, the reactivity of K2[(PtCH3Cl5)-C-IV] toward N,N-dimethylanilines is of the same order of magnitude or slightly greater than that of a standard organic methylating agent, dimethylsulfate Me2SO4. A computational (DFT) modeling of the title reaction is consistent with the formation of five-coordinate PtIVMe electrophile, [PtIVCH3Cl4](-), which is involved in S(N)2 attack at its methyl group carbon by nucleophilic amines. (C) 2018 Elsevier B.V. All rights reserved.