An in situ infrared study of CO2 reduction catalysed by rhenium tricarbonyl bipyridyl derivatives

Abstract

The electrochemical reduction of CO, by derivatives of rhenium carbonyl bipyridyl at carbon cathodes in acetonitrile solution is shown to take place by different routes depending on the concentration of water in the system. In the absence of water and CO,, reduction of fac-[Re(dmbipy)(CO),CI] (dmbipy = 4,4'dimethyl-2,Z'-bipyridyl) leads first to fac-[ Re(dmbipy'-) (CO),CI] followed by elimination of CI-and partial dimerisation of t h e resultant five-co-ordinate species to give both fac-[Re(dmbipy) (CO),] and [{Re(drnbipy)(CO),},]. Further reduction gives rise to fa~-[Re(dmbipy'-)(CO)~], which is the final product. Cathodic reduction of [Re(dmbipy) (CO),CI] in the presence of CO, and absence of water leads to direct attack of CO, on fac-[Re(dmbipy'-) (CO),CI] to give [Re(dmbipy)(CO),(CO,H)] E, which can undergo further reduction to give [Re(dmbipy'-) (CO),(CO,H)]. By contrast, in the presence of H,O, the complex E can be protonated to yield [ Re(dmbipy) (CO),(CO,H,)] + which is attacked by acetonitrile to yield [Re(dmbipy) (CO),(MeCN)] + and CO, this latter complex being identified unambiguously by comparison with the species formed in the oxidation of the original rhenium complex.

A complete series of tricarbonylhalidorhenium(I) complexes (abpy)Re(CO)3(Hal), Hal=F, Cl, Br, I; abpy=2,2′-azobispyridine: Structures, spectroelectrochemistry and EPR of reduced forms

“…All three structures confirm the facial arrangement of the three carbonyl groups at rhenium(I). The abpy ligand adopts an s-cis/E/s-trans conformation as already observed for the related (abpy)Mo(CO) 4 [12].…”

“…Since the discovery that (bpy)Re(CO) 3 Cl can act as an efficient electrocatalyst for the reduction of CO 2 [1,2] many complexes of the type (N Ù N)Re(CO) 3 (Hal) with N Ù N = a-diimine or related chelate ligand have been the subject of studies in the context of photoor electrocatalyzed CO 2 reduction [3][4][5]. The primary activation mechanism involves the addition of an electron to the p * orbital of the N Ù N ligand with the result of a labilization of the halide as essential step [5][6][7].…”

A novel tricarbonyl rhenium complex of 2-benzoylpyridine – Synthesis, spectroscopic characterization, X-ray structure and DFT calculations

“…The excited states of [Re(CO) 3 (L-L)(E)] 0/+ complexes are often sufficiently long-lived to become engaged in energy transfer reactions. Currently, several facRe(CO) 3 + complexes are used as electroluminescent materials in OLED-type devices [1][2][3][4][5][6][7][8][9][10][11][12].…”

Electrochemical triggered O-atom transfer reaction in nitrocarbonyl rhenium(I) complexes: An IR spectroelectrochemical investigation

“…Voltammetry experiments were carried out using BAS Epsilon EC equipment, with vitreous C as working electrode, Pt wire as auxiliary electrode, and Ag/AgCl (3 M NaCl) as reference electrode. In cyclic voltammetry experiments the concentrations were c = 10 À3 M for the complexes and 0.1 M for TBAPF 6 . For spectroelectrochemistry experiments the concentrations of the complexes were 3Á10 À3 M and 0.3 M for TBAPF 6 .…”

“…These complexes have led to applications such as sensors [3], molecular switches [4], building blocks in mixed-valent asymmetric dinuclear complexes [5] and catalysis [6,7]. Thus, for [Re(diimine)(CO) 3 (X)] + complexes, electrochemical oxidations and reductions have been widely investigated, undergoing irreversible metal-based one electron oxidations and one-electron reductions that are centered on the a-diimine.…”