ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
[fac-Re(bpy) (CO)3Cl] (bpy = 2,2′-bipyridine) is an efficient homogeneous catalyst for the selective and sustained photochemical or electrochemical reduction of CO2 to CO. A quantum yield of 14% and a faradic efficiency of 98% were measured in the presence of excess Cl- ions. The photochemical process took place under visible-light irradiation and consumed a tertiary amine as electron donor. A formato-rhenium complex was isolated in the absence of excess Cl- ions. Substitution by Cl- ion generated free formate, but no CO was detected. Luminescence measurements showed that the tertiary amine quenches the metal-to-ligand charge-transfer excited state of the rhenium complex via a reductive mechanism, with a rate constant of 3.4 × 107M-1S-1. The 19e-complex [Re(bpy) (CO)3X]- produced either photochemically or electrochemically appears to be the active precursor in the CO-generation process. Detailed spectroscopic studies on 13C-enriched carbonyl-rhenium and formato-rhenium complexes derived from 13C-enriched CO2 were performed in order to confirm the origin of the products and to study the exchange of the ligands. A mechanism for the present CO2 photoreduction process is presented; it involves separate pathways for CO and formate generation, in which the [Re(bpy) (CO)3X] complex plays the role of both the photoactive and the catalytic center.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19860690824