Reduction of CO_2 to free CO by a Pd(Ⅰ)-Pd(Ⅰ) dimer

摘要

Reduction of carbon dioxide (CO_2) to carbon monoxide (CO) is an important fundamental chemical transformation that potentially provides a path for utilization of CO_2 in making value-added chemicals and a path for storing solar energy in the form of chemical fuels. In biology, this conversion is efficiently and reversibly catalysed by the carbon monoxide dehydrogenase (CODH) enzyme. Synthetic electrocatalysts for reduction of CO_2 to CO have also been developed, most notably using Re, Ni, Pd, and Ru complexes. Stoichiometric chemical reduction of CO_2 to free CO has been accomplished using a variety of transition metal complexes, uranium, as well as main group elements. In general, these reactions are successful when the formal equivalent of oxide (O~(2-)) generated in the CO_2 reduction is trapped by making strong bonds to oxophilic elements (e.g., metal-oxos or Si-O and Al-O bonds) and when the transition metal compounds involved have a low affinity for binding CO as a ligand. The catalytic chemical reduction of CO_2 to CO by Sadighi et al. exemplifies this well: a Cu(Ⅰ) catalyst mediates reduction of CO_2 to CO with pinB-Bpin as the reductant, consuming the oxide equivalent to form pinB-O-Bpin. A conceptually related CsF-catalyzed conversion of CO_2 to CO with PhMe_2Si-SiMe_2Ph as the reductant was very recently disclosed.