TY - JOUR
T1 - Controlling Hydrogen Evolution during Photoreduction of CO2 to Formic Acid Using [Rh(R-bpy)(Cp∗)Cl]+ Catalysts
T2 - A Structure-Activity Study
AU - Todorova, Tanya K.
AU - Huan, Tran Ngoc
AU - Wang, Xia
AU - Agarwala, Hemlata
AU - Fontecave, Marc
N1 - Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/5/20
Y1 - 2019/5/20
N2 - The photochemical reduction of CO2 to formic acid catalyzed by a series of [Rh(4,4′-R-bpy)(Cp∗)Cl]+ and [Rh(5,5′-COOH-bpy)(Cp∗)Cl]+ complexes (Cp∗ = pentamethylcyclopentadienyl, bpy = 2,2′-bipyridine, and R = OCH3, CH3, H, COOC2H5, CF3, NH2, or COOH) was studied to assess how modifications in the electronic structure of the catalyst affect its selectivity, defined as the HCOOH:H2 product ratio. A direct molecular-level influence of the functional group on the initial reaction rate for CO2 versus proton reduction reactions was established. Density functional theory computations elucidated for the first time the respective role of the [RhH] and [Cp∗H] tautomers, recognizing rhodium hydride as the key player for both reactions. In particular, our calculations explain the observed tendency of electron-donating substituents to favor CO2 reduction by means of decreasing the hydricity of the Rh-H bond, resulting in a lower hydride transfer barrier toward formic acid production as compared to substituents with an electron-withdrawing nature that favor more strongly the reduction of protons to hydrogen.
AB - The photochemical reduction of CO2 to formic acid catalyzed by a series of [Rh(4,4′-R-bpy)(Cp∗)Cl]+ and [Rh(5,5′-COOH-bpy)(Cp∗)Cl]+ complexes (Cp∗ = pentamethylcyclopentadienyl, bpy = 2,2′-bipyridine, and R = OCH3, CH3, H, COOC2H5, CF3, NH2, or COOH) was studied to assess how modifications in the electronic structure of the catalyst affect its selectivity, defined as the HCOOH:H2 product ratio. A direct molecular-level influence of the functional group on the initial reaction rate for CO2 versus proton reduction reactions was established. Density functional theory computations elucidated for the first time the respective role of the [RhH] and [Cp∗H] tautomers, recognizing rhodium hydride as the key player for both reactions. In particular, our calculations explain the observed tendency of electron-donating substituents to favor CO2 reduction by means of decreasing the hydricity of the Rh-H bond, resulting in a lower hydride transfer barrier toward formic acid production as compared to substituents with an electron-withdrawing nature that favor more strongly the reduction of protons to hydrogen.
UR - http://www.scopus.com/inward/record.url?scp=85065778544&partnerID=8YFLogxK
U2 - 10.1021/acs.inorgchem.9b00371
DO - 10.1021/acs.inorgchem.9b00371
M3 - Article
C2 - 31050296
AN - SCOPUS:85065778544
SN - 0020-1669
VL - 58
SP - 6893
EP - 6903
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 10
ER -