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首页> 外文期刊>Chemistry: A European journal >A computational study of rhodium pincer complexes with classical and nonclassical hydride centres as catalysts for the hydroamination of ethylene with ammonia
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A computational study of rhodium pincer complexes with classical and nonclassical hydride centres as catalysts for the hydroamination of ethylene with ammonia

机译：铑钳夹配合物的经典和非经典氢化物中心作为乙烯与氨加氢胺化反应的计算研究

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The catalytic hydroamination of ethylene with ammonia was investigated by means of density functional theory (DFT) calculations. An initial computational screening of key reaction steps (C-N bond formation, N-H bond cleavage), which are assumed to be part of a catalytic cycle, was carried out for complexes with the [M (L)]-complex fragment (M = Rh, Ir; L = NCN, PCP; NCN = 2, 5-bis (dimethylaminomethyl) benzene, PCP = 2, 5-bis-(dimethylphosphanylmethyl) benzene). Based on the evaluation of activation barriers, this screening showed the rhodium compound with the NCN ligand to be the most promising catalyst system. A detailed investigation was carried out starting with the hypothetical catalyst precursor [Rh-(NCN) (H)_2 (H_2)] (1). A variety of activation pathways to yield the catalytically active species [Rh (NCN) (H) (NH2)] (5), as well as [Rh (NCN) (C_2H_5) (NH_2)] (17), were identified. With 5 and 17 several closed catalytic cycles could be calculated. One of the calculated cycles is favoured kinetically and bond-forming events have activation barriers low enough to be put into practice. The calculations also show that for experimental realisation the synthesis of 1 is not necessary, as the synthesis of 17 would establish an active catalyst directly without the need for activation. Oligomerisation of ethylene would be possible in principle and would be expected as a competitive side reaction. Accordingly not only ethylamine would be observed in an experimental system, as amines with longer carbon chains also can be formed.
机译：通过密度泛函理论（DFT）计算研究了乙烯与氨的催化加氢胺化反应。初步计算了关键反应步骤（CN键形成，NH键断裂）的初步计算筛选，这些步骤被认为是催化循环的一部分，用于与[M（L）]络合物片段的络合物（M = Rh， Ir; L ＝ NCN，PCP; NCN ＝ 2，5-双（二甲基氨基甲基）苯，PCP ＝ 2，5-双-（二甲基膦基甲基）苯）。根据活化障碍的评估，该筛选显示具有NCN配体的铑化合物是最有希望的催化剂体系。从假设的催化剂前体[Rh-（NCN）（H）_2（H_2）]（1）开始进行了详细的研究。确定了多种激活途径，以产生催化活性物质[Rh（NCN）（H）（NH2）]（5）以及[Rh（NCN）（C_2H_5）（NH_2）]（17）。用5和17可以计算出几个封闭的催化循环。动力学上有利于计算的循环之一，并且键形成事件的激活势垒足够低，无法付诸实践。计算还表明，对于实验实现而言，不需要合成1，因为17的合成将直接建立活性催化剂而无需活化。乙烯的低聚原则上是可能的，并且可以预期作为竞争性副反应。因此，不仅会在实验系统中观察到乙胺，因为还会形成具有更长碳链的胺。

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