TY - JOUR
T1 - Mechanistic studies on the pH-controllable interconversion between hydrogen and formic acid in water
T2 - DFT insights
AU - Zhang, Dandan
AU - Chen, Xiankai
AU - Liu, Huiling
AU - Huang, Xuri
N1 - Publication details (e.g. title, author(s), publication statuses and dates) are captured on an “AS IS” and “AS AVAILABLE” basis at the time of record harvesting from the data source. Suggestions for further amendments or supplementary information can be sent to [email protected].
PY - 2015/7/30
Y1 - 2015/7/30
N2 - A complete reaction mechanism for interconversion between hydrogen and formic acid catalyzed by [C,N] cyclometallated organoiridium complex [IrIII(Cp∗)(4-(1H-pyrazol-1-yl-κN2)benzoic acid-κC3)(H2O)]2·SO4, i.e. [Ir-1]2·SO4, has been revealed by density functional theory (DFT) calculations. For both the hydrogen storage catalytic cycle I and hydrogen evolution catalytic cycle II, the detailed reaction profiles with the key transition states and intermediates are revealed. Catalytic cycle I shows that the dihydrogen heterolysis facilitated by OH- gives the considerable stable iridium hydride intermediate M-4, followed by an outer-sphere hydrogen transfer to afford a metal-formate complex M-6. Upon the increasing of pH, catalytic cycle II occurs via the generation of the metal-formate complex M-7, followed by the outer-sphere β-H elimination to form a metal-hydride complex M-9, which is subsequently protonated by the hydrated proton H3O+ to afford dihydrogen. The decomposition of bicarbonate and the β-hydride elimination of formate are believed to be the rate-determining steps for cycle I and II, respectively. The acid-base equilibrium between the hydroxy and oxyanion form on the catalyst [C,N] ligand has a considerable influence on the catalytic hydrogen transfer. Our studies are in good agreement with experimental results. Remarkably, the new theoretically designed low-cost cobalt(iii) complex, as a promising catalyst, exhibits catalytic activity for the interconversion between hydrogen and formic acid.
AB - A complete reaction mechanism for interconversion between hydrogen and formic acid catalyzed by [C,N] cyclometallated organoiridium complex [IrIII(Cp∗)(4-(1H-pyrazol-1-yl-κN2)benzoic acid-κC3)(H2O)]2·SO4, i.e. [Ir-1]2·SO4, has been revealed by density functional theory (DFT) calculations. For both the hydrogen storage catalytic cycle I and hydrogen evolution catalytic cycle II, the detailed reaction profiles with the key transition states and intermediates are revealed. Catalytic cycle I shows that the dihydrogen heterolysis facilitated by OH- gives the considerable stable iridium hydride intermediate M-4, followed by an outer-sphere hydrogen transfer to afford a metal-formate complex M-6. Upon the increasing of pH, catalytic cycle II occurs via the generation of the metal-formate complex M-7, followed by the outer-sphere β-H elimination to form a metal-hydride complex M-9, which is subsequently protonated by the hydrated proton H3O+ to afford dihydrogen. The decomposition of bicarbonate and the β-hydride elimination of formate are believed to be the rate-determining steps for cycle I and II, respectively. The acid-base equilibrium between the hydroxy and oxyanion form on the catalyst [C,N] ligand has a considerable influence on the catalytic hydrogen transfer. Our studies are in good agreement with experimental results. Remarkably, the new theoretically designed low-cost cobalt(iii) complex, as a promising catalyst, exhibits catalytic activity for the interconversion between hydrogen and formic acid.
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U2 - 10.1039/c5nj01740h
DO - 10.1039/c5nj01740h
M3 - RGC 21 - Publication in refereed journal
SN - 1144-0546
VL - 39
SP - 8060
EP - 8072
JO - New Journal of Chemistry
JF - New Journal of Chemistry
IS - 10
ER -
