Synthesis and Reactions of <i>fac</i>-[Re(dmbpy)(CO)₃X] (dmbpy = 4,4‘-Dimethyl-2,2‘-bipyridine; X = COOH, CHO) and Their Derivatives

Abstract

Reactions of fac-[Re(dmbpy)(CO)3COOH] (1) alone or together with fac-[Re(dmbpy)(CO)3CHO] (4) or other compounds which could be generated in photocatalytic reductions of CO2 from fac-[Re(dmbpy)(CO)3Cl] 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)3OH]·2.5H2O (8a), {fac,fac-[Re(dmbpy)(CO)3]2(H)}[OTf] (11), fac,fac-[Re(dmbpy)(CO)3CO2Re(bpy)(CO)3] (13), fac-[Re(bpy)(CO)3OH] (17) and {fac,fac,fac-[Re(dmbpy)(CO)3]3(OCO2)}[ReO4] (18). Compounds 8a and 18 have been characterized by X-ray crystallography.