Sequential Hydrogenation of CO2 to Methanol Using a Pincer Iron Catalyst

Methanol is a crucial precursor for the preparation of many high-value commercial chemicals and synthesizing it from an inexpensive and renewable carbon source such as carbon dioxide (CO2) could have significant benefits. Herein, a homogeneous iron(II) pincer complex for the catalytic generation of methanol from CO2 and H-2 via a two-step process is described. The CO2 reduction process occurs through initial coupling with H-2 and an amine to give a formamide. Subsequently, the formamide undergoes catalytic deaminative hydrogenation to afford methanol and regenerate the amine. A net turnover number of 590 is obtained for CO2 and H-2 to methanol using this method. The primary obstacle to a single-batch catalytic process is CO2 poisoning of the catalyst in the formamide hydrogenation step, and mechanistic investigations suggest that this CO2 inhibition results from the formation of a stable iron(II) formate complex.