Stannyl Cations for the Hydrogenation of Carbon Dioxide to Methanol and Methyl Formate

甲锡烷基阳离子用于二氧化碳加氢生成甲醇和甲酸甲酯

• 批准号: 1829051
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1829051
• 关键词: Stannyl; Cations; Hydrogenation; Carbon; Dioxide

The principal goal of this proposal is to develop novel stannyl cation-based Lewis pair catalysts [R3Sn(dot)L]+ (L = 2electron oxygen donor) which are capable of rapidly activating H2 with concomitant reduction of CO2, to selectively form the commodity chemicals methanol (CH3OH) or methyl formate (HCO2CH3), at lower temperatures and pressures than currently used for their industrial-scale production. The activation of H2 by these main-group based systems is based on an extension of 'frustrated Lewis pair' (FLP) chemistry, albeit using catalysts that more closely resemble 'classical' donoracceptor adducts. This research builds upon our extremely promising preliminary results which demonstrate the competence of a Bu3SnH/catalytic [Bu3Sn]+ system for the rapid hydrostannylation of CO2 under mild conditions to methoxide (CH3O-) and oxide (O2-) equivalents, in addition to free HCO2CH3. Excitingly, reaction of this mixture with hydrogen (H2) liberates CH3OH, H2O and HCO2CH3, and regenerates the Bu3SnH reductant. This demonstrates that all stages of a catalytic protocol for CO2 hydrogenation can be achieved, although hydrogenolysis is at present too slow. The approach outlined in this work is to rationally modify the stannyl cation by increasing the size of the pendant alkyl groups and hence increase the amount of 'frustration' in the Lewis pair adducts. This is expected to markedly improve the kinetics of both H2 activation and subsequent CO2 reduction steps. Fundamentally new (water-tolerant) hydrogenation catalysts based on inexpensive and abundant Sn compounds will naturally develop during the course of this work programme, which will undoubtedly find use in other industrially relevant transformations (e.g. organic carbonyl hydrogenation to alcohols).The specific key objectives to achieve the main aim are:1. Synthesise new precursors (R3SnH, R3SnX; R = alkyl, X = NTf2, OTf) incorporating bulky R groups.2. Investigate stannyl cation Lewis pair adducts, [R3Sn(dot)L]+ (L = R3SnOCH3, R3SnOSnR3), for their ability to activate H2, and correlate observed rates with structure.3. Conduct detailed mechanistic studies on the hydrostannylation of both CO2 and proposed reaction intermediates.4. Investigate the mechanism of Sn-O bond hydrogenolysis, and establish the relevant experimental parameters (e.g. temperature, pressure) which favour the production of either CH3OH or HCO2CH3.5. Consolidation of rate data, mechanistic information, and experimental variables obtained from objectives 1-4 in order to optimise the best [R3Sn]+ species for selective catalytic hydrogenation of CO2 to CH3OH and/or HCO2CH3.

这项建议的主要目标是开发新型锡阳离子路易斯对催化剂[R3Sn(点)L]+(L=2电子给氧体)，能够快速活化H2，伴随着二氧化碳的还原，在低于目前工业规模生产的温度和压力下，选择性地生成商品化学品甲醇(CH3OH)或甲酸甲酯(HCO2CH3)。这些基于主基的体系对H2的活化是基于‘受挫Lewis对’(FLP)化学的延伸，尽管使用的催化剂更接近于‘经典’的供体受体加合物。这项研究建立在我们非常有希望的初步结果的基础上，这些结果表明，除了游离的HCO2CH3之外，Bu3SnH/催化[Bu3SnH]+体系还能够在温和的条件下将二氧化碳快速氢化为甲醇(CH3O-)和氧化物(O2-)的等价物。令人兴奋的是，这种混合物与氢(H2)反应，释放出CH3OH、H2O和HCO2CH3，并再生Bu3SnH还原剂。这表明，二氧化碳加氢的催化方案的所有阶段都可以实现，尽管目前氢解太慢。在这项工作中概述的方法是通过增加侧链烷基的大小来合理地修饰锡阳离子，从而增加Lewis对加合物中的‘受挫’量。预计这将显著改善氢气活化和随后的二氧化碳还原步骤的动力学。基于廉价和丰富的锡化合物的新型(耐水)加氢催化剂将在本工作计划的过程中自然开发，这无疑将用于其他工业相关的转化(例如，有机羰基加氢为醇)。实现主要目标的具体关键目标是：1.合成含有大量R基团的新前体(R3SnH，R3SnX；R=烷基，X=NTf2，OTf)。研究锡阳离子Lewis对加合物[R3Sn(点)L]+(L=R3SnOCH3，R3SnOSnR3)活化H2的能力，并将观察到的速率与结构关联起来。对二氧化碳和建议的反应中间体的氢化锡化反应进行详细的机理研究。研究了锡-氧键氢解的机理，建立了有利于生成CH3OH或HCO2CH3.5的相关实验参数(如温度、压力)。综合从目标1-4获得的速率数据、机理信息和实验变量，以优化二氧化碳选择性催化加氢为CH3OH和/或HCO2CH3的最佳[R3Sn]+物种。

项目成果

Base-induced reversible H 2 addition to a single Sn( ii ) centre

碱诱导可逆 H 2 加成到单个 Sn( ii ) 中心

• DOI: 10.1039/c8sc03110j
• 发表时间: 2018
• 期刊: Chemical Science
• 影响因子: 8.4
• 作者: Turnell-Ritson R

Hydrogen activation using a novel tribenzyltin Lewis acid.

• DOI: 10.1098/rsta.2017.0008
• 发表时间: 2017-08-28
• 期刊: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
• 作者: Cooper RT;Sapsford JS;Turnell-Ritson RC;Hyon DH;White AJP;Ashley AE
• 通讯作者: Ashley AE