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Title: Electrochemical Reduction of CO 2 Catalyzed by Re(pyridine-oxazoline)(CO) 3 Cl Complexes

In a series of rhenium tricarbonyl complexes coordinated by asymmetric diimine ligands containing a pyridine moiety bound to an oxazoline ring were synthesized, structurally and electrochemically characterized, and screened for CO 2 reduction ability. We reported complexes are of the type Re(N-N)(CO) 3Cl, with N-N = 2-(pyridin-2-yl)-4,5-dihydrooxazole (1), 5-methyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (2), and 5-phenyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (3). The electrocatalytic reduction of CO 2 by these complexes was observed in a variety of solvents and proceeds more quickly in acetonitrile than in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The analysis of the catalytic cycle for electrochemical CO 2 reduction by 1 in acetonitrile using density functional theory (DFT) supports the C–O bond cleavage step being the rate-determining step (RDS) (ΔG = 27.2 kcal mol –1). Furthermore, the dependency of the turnover frequencies (TOFs) on the donor number (DN) of the solvent also supports that C–O bond cleavage is the rate-determining step. Moreover, the calculations using explicit solvent molecules indicate that the solvent dependence likely arises from a protonation-first mechanism. Unlike other complexes derived from fac-Re(bpy)(CO) 3Cl (I; bpy = 2,2'-bipyridine), in which one of the pyridyl moieties in the bpy ligand is replaced by another imine, no catalytic enhancement occurs during the first reductionmore » potential. Remarkably, catalysts 1 and 2 display relative turnover frequencies, (i cat/i p) 2, up to 7 times larger than that of I.« less
Authors:
 [1] ;  [1] ;  [2] ; ORCiD logo [1] ;  [3] ; ORCiD logo [4] ;  [3] ;  [5] ; ORCiD logo [1]
  1. Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemistry
  2. Vassar College, Poughkeepsie, NY (United States). Dept. of Chemistry
  3. DePaul Univ., Chicago, IL (United States). Dept. of Chemistry
  4. Yale Univ., New Haven, CT (United States). Dept. of Chemistry
  5. Yale Univ., New Haven, CT (United States). Dept. of Chemistry; Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Division
Publication Date:
Report Number(s):
BNL-113673-2017-JA
Journal ID: ISSN 0020-1669; R&D Project: CO026; KC0304030
Grant/Contract Number:
SC00112704; SC0001059
Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 56; Journal Issue: 6; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1349563