Carbon Dioxide Hydrogenation to Formate Catalyzed by a Bench-Stable, Non-Pincer-Type Mn(I) Alkylcarbonyl Complex.

Sylwia Kostera,Stefan Weber,Karl Kirchner,Luca Gonsalvi,Luis F Veiros,Maurizio Peruzzini

doi:10.1021/acs.organomet.0c00710

Sylwia Kostera, Stefan Weber + Show 4 more

Open Access

https://doi.org/10.1021/acs.organomet.0c00710

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Abstract

The catalytic reduction of carbon dioxide is a process of growing interest for the use of this simple and abundant molecule as a renewable building block in C1-chemical synthesis and for hydrogen storage. The well-defined, bench-stable alkylcarbonyl Mn(I) bis(phosphine) complex fac-[Mn(CH2CH2CH3)(dippe)(CO)3] [dippe = 1,2-bis(diisopropylphosphino)ethane] was tested as an efficient and selective non-precious-metal precatalyst for the hydrogenation of CO2 to formate under mild conditions (75 bar total pressure, 80 °C), in the presence of a Lewis acid co-catalyst (LiOTf) and a base (DBU). Mechanistic insight into the catalytic reaction is provided by means of density functional theory (DFT) calculations.

Highlights

In recent years, the increasing concentration of CO2 in the atmosphere and its contribution to climate change made decision makers and society at large more aware of the need to curb emissions of this greenhouse gas
HCO2H is currently obtained industrially from the hydrolysis of HCO2Me, in turn derived from fossil feedstock as one of the products of methanol carbonylation
The dark brown color of the solutions and the presence of a dark precipitate at the end of the tests indicate that the activated form of 1 decomposes in these solvents under catalytic conditions

Summary

■ INTRODUCTION

The increasing concentration of CO2 in the atmosphere and its contribution to climate change made decision makers and society at large more aware of the need to curb emissions of this greenhouse gas. Two CO2 utilization pathways are possible: a nonreductive approach, involving the incorporation of CO2 in reactive organic molecules such as epoxides, aziridines, alkenes, etc., and a reductive approach, to obtain simple C1 molecules such as formic acid (HCO2H), formaldehyde (HCHO), methanol (CH3OH), dimethyl ether (CH3OCH3), methane (CH4), or higher hydrocarbons.2 Among these products, methanol and formic acid find large use as bulk chemicals in industrial and laboratory applications and are receiving attention as fuels (MeOH) and as highly promising liquid organic hydrogen carriers (LOHC), to generate H2 on demand by dehydrogenation reactions in the presence of suitable homogeneous or heterogeneous catalysts.. The results of the catalytic tests, including a screening of the reaction conditions and the effect of a Lewis acid co-catalyst, are hereby presented

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES