Researchers at the University of Cincinnati, Ohio, report on the development of a catalytic hydroboration system for the “highly efficient” reduction of CO2 with a borane and subsequent hydrolysis of the resulting methoxyboryl species to produce methanol (CH3OH) in good yield.
A paper on their work was published online 14 June in the ACS journal Energy & Fuels.
Transforming CO2 into methane, the most reduced form of carbon, under homogeneous conditions can be accomplished using silanes as the reducing reagents. Reducing CO2 to methanol would be even more desirable for the advantages of transporting a liquid fuel rather than a gas.
Catalytic hydrosilylation of CO2 to methoxysilyl species is feasible with Ir(CN)(CO)(dppe) [dppe=1,2-bis(diphenylphosphino)ethane] at 40 °C, albeit with limited turnover numbers. More efficient hydrosilylation reactions are catalyzed by N-heterocyclic carbenes (metal-free) at ambient temperature with turnover frequencies (TOFs) as high as 25.5 h-1 (based on Si-H), and methanol is produced from the hydrolysis of the initial reduction products. The recent development of frustrated Lewis acid-base pair (FLP) chemistry has led to alternative strategies for the reduction of CO2 to the methoxide level given either H2 or H3NBH3 9 as a hydrogen source.
In this paper, we report a highly efficient nickel system for the catalytic hydroboration of CO2 to methoxyboryl species using a simple borane. The reactions operate at room temperature with TOFs [495 h-1 based on B-H] at least 1 order of magnitude higher than those of the related reactions described above.
Further studies to elucidate the mechanistic details and improve the catalytic efficiencies are in progress.
Sumit Chakraborty, Jie Zhang, Jeanette A. Krause and Hairong Guan (2010) An Efficient Nickel Catalyst for the Reduction of Carbon Dioxide with a Borane. J. Am. Chem. Soc., Article ASAP doi: 10.1021/ja103982t