Density Functional Theory Study on [Ni0(1,10-Phenanthroline)]-Catalyzed Reductive Carboxylation of Alkyl and Aryl Halides with CO2: Effect of the Lewis Acid and β-H Elimination Side Reaction in the Crucial CO2 Insertion Step,Inorganic Chemistry

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Density Functional Theory Study on [Ni0(1,10-Phenanthroline)]-Catalyzed Reductive Carboxylation of Alkyl and Aryl Halides with CO2: Effect of the Lewis Acid and β-H Elimination Side Reaction in the Crucial CO2 Insertion Step
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2022-11-22 , DOI: 10.1021/acs.inorgchem.2c03340
Prabha Vadivelu ₁ , Krithika Ganesan ₁

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The [Ni⁰(phen)] (1)-catalyzed reductive carboxylation of propyl and phenyl chloride with a CO₂ molecule has been compared using the density functional theory method. The reactivity of 1 in the initial oxidative addition with the propyl and phenyl chloride and in the subsequent single electron transfer step to form the Ni^I intermediates, [Ni^I(phen)(R′-CH₂)], 4, (R′ = CH₃–CH₂−), and [Ni^I(phen)(C₆H₅)], 4′, is almost the same. However, an apparent reactivity difference is interpreted in the CO₂ insertion step, which involves the Ni^I and the Ni^II intermediates. In both propyl and phenyl chloride, the Ni^I-mediated CO₂ insertion is kinetically more preferred than that mediated by the analogues Ni^II intermediates (3 and 3′) by +5.0 and +33.4 kcal/mol, respectively. This trend in energetics clearly shows that the CO₂ insertion of phenyl chloride exclusively occurs via the Ni^I-mediated pathway, whereas in propyl chloride, it follows both Ni^I- and Ni^II-mediated pathways. Overall, the catalytic efficacy of 1 is found to be higher in phenyl chloride (by +11.3 kcal/mol) than that in propyl chloride. Furthermore, the effect of a plausible β-H elimination side reaction in the CO₂ insertion step is modeled for propyl chloride. Herein, the β-H elimination of the Ni^II propyl species (3) is kinetically more feasible than its CO₂ insertion, while the β-H elimination of Ni^I propyl (4) is rather difficult compared to its CO₂ insertion by +16.3 kcal/mol. This strongly supports the suitability of the Ni^I intermediate in the CO₂ insertion step. In addition, the role of the Lewis acid (X) in the CO₂ insertion step is tested by incorporating various Lewis acids (X = MgCl₂, ZnCl₂, AlCl₃, and LiCl) in the Ni^II propyl (7) and Ni^I propyl (5) intermediates. The Lewis acids effectively facilitate the CO₂ insertion step, and the effect due to MgCl₂ is found to be more evident. MgCl₂ enhances the CO₂ insertion of 5 and 7 by 89 and 84%, respectively, and hence, the Ni^I-mediated CO₂ insertion of propyl halide (ΔG^⧧ = +1.4 kcal/mol) is now comparable with that of phenyl halide (ΔG^⧧ = +0.9 kcal/mol). This suggests that in the presence of Lewis acids, the catalytic efficacy of 1 is enhanced for the reductive carboxylation of propyl halide and exhibits similar reactivity to that of phenyl halide.

中文翻译：

[Ni0(1,10-菲咯啉)]-催化烷基和芳基卤化物与 CO2 的还原羧基化的密度泛函理论研究：关键 CO2 插入步骤中路易斯酸和 β-H 消除副反应的影响

使用密度泛函理论方法比较了[Ni ⁰ (phen)] ( 1 )-催化的丙基和苯基氯与CO _{2分子的还原羧化。}1在与丙基氯和苯氯的初始氧化加成反应以及随后的单电子转移步骤中形成 Ni I^中间体[Ni ^I (phen)(R'-CH ₂ )], 4 , (R' = CH ₃ –CH ₂ −), 和 [Ni ^I (phen)(C ₆ H ₅ )], 4′，几乎是一样的。然而，在涉及 Ni ^I和 Ni ^II中间体的 CO ₂插入步骤中解释了明显的反应性差异。在丙基氯和苯基氯中，Ni ^I介导的 CO _{2插入在动力学上比由类似物 Ni}^II中间体（3和3' ）介导的插入更优选，分别为 +5.0 和 +33.4 kcal/mol。这种能量学趋势清楚地表明，苯基氯的 CO ₂插入完全通过 Ni ^I介导的途径发生，而在丙基氯中，它遵循 Ni ^I - 和 Ni^II介导的途径。总体而言，发现1在苯基氯中的催化功效（+11.3 kcal/mol）高于丙基氯。此外，针对丙基氯模拟了CO ₂插入步骤中可能发生的 β-H 消除副反应的影响。^{在此，Ni II}丙基物质 ( 3 )的 β-H 消除在动力学上比其 CO _{2插入更可行，而 Ni}^I丙基 ( 4 )的 β-H 消除与其 CO ₂插入相比通过+ 16.3 大卡/摩尔。^{这强烈支持 Ni I}中间体在 CO ₂中的适用性插入步骤。此外，路易斯酸 (X) 在 CO _{2插入步骤中的作用通过在 Ni}^II丙基 ( 7 ) 和 Ni中加入各种路易斯酸（X = MgCl ₂、ZnCl ₂、AlCl ₃和 LiCl）来测试^一丙基（5）中间体。路易斯酸有效地促进了CO ₂插入步骤，并且发现由于MgCl ₂引起的效果更加明显。MgCl _2分别将5和7的 CO ₂插入增强了89% 和 84%，因此，Ni ^I介导的 CO₂丙基卤化物 (Δ G ^⧧ = +1.4 kcal/mol) 的插入现在与苯卤化物 (Δ G ^⧧ = +0.9 kcal/mol) 相当。这表明在路易斯酸存在的情况下，1对卤代丙烷的还原羧化作用的催化效果增强，并表现出与卤代苯相似的反应活性。

更新日期：2022-11-22

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