Effective Pincer Cobalt Precatalysts for Lewis Acid Assisted CO2 Hydrogenation

Effective Pincer Cobalt Precatalysts for Lewis Acid Assisted CO2 Hydrogenation

Ariana Z. Spentzos, Charles L. Barnes, and Wesley H. Bernskoetter*

University of Missouri

http://pubs.acs.org/doi/pdf/10.1021/acs.inorgchem.6b01454

Inorg. Chem. 

DOI: 10.1021/acs.inorgchem.6b01454

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Abstract:

The pincer ligand MeN[CH2CH2(PiPr2)]2 (iPrPNP) was employed to support a series of cobalt(I) complexes, which were crystallographically characterized. A cobalt monochloride species, (iPrPNP)CoCl, served as a precursor for the preparation of several cobalt precatalysts for CO2 hydrogenation, including a cationic dicarbonyl cobalt complex, [(iPrPNP)Co(CO)2]+. When paired with the Lewis acid lithium triflate, [(iPrPNP)Co(CO)2]+ affords turnover numbers near 30 000 (at 1000 psi, 45 °C) for CO2-to-formate hydrogenation, which is a notable increase in activity from previously reported homogeneous cobalt catalysts. Though mechanistic information regarding the function of the precatalysts remains limited, multiple experiments suggest the active species is a molecular, homogeneous [(iPrPNP)Co] complex.