Multi-electron reduction of CO_2 via Ru-CO_2, -C(O)OH, -CO, -CHO, and -CH_2OH species

摘要

A series of [Ru (bpy)_2(CO)L]~n+ (L=CO_2, C(O)OH, CO, CHO, CH+2OH, CH_3, and C(O)CH_3; n=0,1,2) were prepared and their molecular structures determined by X-ray analyses. These complexes are reasonable models of reaction intermediates in the mulit-electron reduction of CO_2 catalyzed by metal complexes, since reductive cleavage of the Ru-L bonds of the complexes in protic media affords HCOOH, CO, HCHO, CH_3HO, and CH__4 as two, four-, xis-and eight-electron reduction products of CO_2. Thermodynamically, the free energy required in the reduction of CO_2 progressively decreases with an increase of the number of Electrons participating in the reduction of CO_2.