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首页> 外文期刊>Catalysis science & technology >Computational investigation of the ligand effect on the chemo/regioselectivity and reactivity of cobalt-catalysed hydroformylation
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Computational investigation of the ligand effect on the chemo/regioselectivity and reactivity of cobalt-catalysed hydroformylation

机译：计算配位效应的调查化疗/区域选择性和反应cobalt-catalysed加氢甲酰化

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摘要

The ligand effect on the chemo/regioselectivity and reactivity of cobalt-catalysed hydroformylation has been discussed. The results of the unmodified cobalt carbonyl catalyst showed that the regioselectivity of the terminal alkene substrate was mainly affected by the steric hindrance of the bulky alkyl substitution group and was insensitive to the elongation of the carbon chain. Regarding the addition of Co-H onto the alkene, modifying the cobalt carbonyl catalyst with a phosphine ligand led to more distinct differences between the Markovnikov and anti-Markovnikov pathways with respect to both the energy barrier and the reaction free energy. Among the four selected phosphines, PBu3 and a(5)-PhobPC(5) with large Tolman cone angles favoured anti-Markovnikov-type Co-H addition, which is beneficial for the generation of a linear product. The modification with phosphine also promoted the oxidative addition of H-2 on the Co(i) centre by lowering the energy barrier of H-2 splitting and generating a more stable Co(iii)-dihydride complex but retarded the reductive elimination step by elevating its activation energy and reaction energy. On the whole, the hydroformylation mechanism is similar for both modified and unmodified cobalt carbonyl catalysts. Moreover, PBu3 modification on the catalyst does not intrinsically change the chemoselectivity of alkene but indeed improves the subsequent alcohol and formic ester formation.
机译：配体对化疗/区域选择性的影响和反应的cobalt-catalysed探讨了加氢甲酰化。显示未修改的羰基钴催化剂烯烃的区域选择性终端基质主要是受到空间的影响笨重的烷基取代集团的阻碍麻木不仁的伸长碳链。烯烃,修改羰基钴膦配体导致更多的催化剂马氏和截然不同的区别anti-Markovnikov通路对两者能量势垒和反应自由能。在四个选择膦类化合物,PBu3和(5) -PhobPC(5)与大型杜尔曼锥角支持anti-Markovnikov-type Co-H之外,这是有益的一代吗线性的产品。也促进了2的氧化加成有限公司(i)中心通过降低能量势垒2分裂和生成更稳定有限公司(iii)二氢化物复杂但迟钝一步提升其还原消除活化能和反应能量。整体,加氢甲酰化机制是相似的修改和未修改的钴羰基催化剂。催化剂没有本质上的改变chemoselectivity烯烃,但的确提高了随后的酒精和甲脂形成。

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