Synthesis and reactions of fac-[Re(dmbpy)(CO)3X] (dmbpy=4,4′-dimethyl-2,2′-bipyridine; X = COOH, CHO) and their derivatives

Reactions of fac-[Re(dmbpy)(CO)(3)COOH] (1) alone or together with fac-[Re(dmbpy)(CO)(3)CHO] (4) or other compounds which could be generated in photocatalytic reductions of CO2 from fac- [Re(dmbpy)(CO)(3)Cl] have been studied to establish possible routes to CO and formate. The results suggest that the reactions of 1 are governed by complex equilibria involving its ionization to Re(dmbpy)(CO)(4)(+) and OH- or proton transfer to highly basic species. Parallel reaction paths, emanating from Re(dmbpy)(CO)(4)(+), are suggested to account for the formation of CO and formate in the catalytic reactions and support the proposal that 4 is a likely catalytic intermediate in addition to 1. New compounds have been isolated or prepared in order to support proposals about reaction pathways: {fac-[Re(dmbpy)(CO)(3)](2)-(OCO2)} (5), fac-[Re(dmbpy)(CO)(3)OH].2.5H(2)O (8a), {fac,fac-[Re(dmbpy)(CO)(3)](2)(H)}[OTf] (11), fac,fac-[Re(dmbpy)(CO)(3)CO2Re(bpy)(CO)(3)] (13), fac- [Re(bpy)(CO)(3)OH] (17) and {fac,fac,fac[Re(dmbpy)(CO)(3)](3)(OCO2)}[ReO4] (18). Compounds 8a,and 18 have been characterized by X-ray crystallography.