Benefit of a hemilabile ligand in deoxygenation of fatty acids to 1-alkenes†,Faraday Discussions

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Benefit of a hemilabile ligand in deoxygenation of fatty acids to 1-alkenes†
Faraday Discussions ( IF 3.3 ) Pub Date : 2019-06-05 , DOI: 10.1039/c9fd00037b
Sondre H. Hopen Eliasson _{1,

2,

3,

4} , Vidar R. Jensen _{1,

2,

3,

4}

Affiliation

One of the most important tasks for chemistry in our time is to contribute to sustainable chemical production. A green industrial process for linear α-olefins, the arguably most important class of petrochemical intermediates, from renewable resources would be a major contribution to this end. Plant oils are attractive renewable feedstocks for this purpose because their triglycerides can be hydrolyzed to fatty acids that contain valuable long-chain hydrocarbons (C16–C22). These hydrocarbons may, in turn, be converted to α-olefins by the deoxygenation of the fatty acids. For the most selective of these deoxygenation reactions, transition-metal catalyzed decarbonylative dehydration, the density functional theory (DFT) calculations have just started to offer valuable mechanistic insight, and the use of this insight in rational catalyst design has been facilitated by the arrival of the first well-defined precatalyst for this reaction, Pd(cinnamyl)Cl(DPEphos) (1). Here, we present DFT calculations showing how, in 1, the hemilability of DPEphos, a classical P–O–P diphosphine, contributes to a low overall barrier and high α-selectivity. DPEphos facilitates decarbonylation by first switching from bidentate to monodentate binding to create a coordination site for CO. The recoordination of the dangling phosphine displaces the Pd-bound CO, a co-product that must leave the reactor for the reaction to proceed, and the escaping CO is here modelled using a low pressure in the calculation of its thermochemical corrections. Finally, the role of the hemilabile ligand suggests that further improvements in the decarbonylative dehydration of fatty acids to α-olefins might be achieved by exploring new, potentially asymmetric, hemilabile ligands.

中文翻译：

半不稳定配体在脂肪酸脱氧为1-烯烃方面的优势†

在当今时代，化学领域最重要的任务之一就是为可持续的化学生产做出贡献。线性α-烯烃（可以说是石油化工中间体中最重要的一类）的绿色工业生产方法将是为此目的的重要贡献。为此，植物油是有吸引力的可再生原料，因为它们的甘油三酸酯可以水解为包含有价值的长链烃（C16–C22）的脂肪酸。这些烃又可以通过脂肪酸的脱氧而转化为α-烯烃。对于这些脱氧反应中最具选择性的，过渡金属催化的脱羰脱水，密度泛函理论（DFT）的计算才刚刚开始提供有价值的机理见解，1）。在这里，我们本DFT计算示出了如何在1，DPEphos，一个经典的P-O-P的二膦，有助于的hemilability到低的总屏障和高α-选择性。DPEphos首先从二齿结合转变为单齿结合，以形成一氧化碳的配位部位，从而促进脱羰作用。在此，在计算其热化学校正值时使用低压对CO进行建模。最后，半不稳定配体的作用表明，通过探索新的，可能不对称的半不稳定配体，可以进一步改善脂肪酸脱羰基脱水成α-烯烃的能力。

更新日期：2019-12-04

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