Developing efficient dehydrogenation is critical to understanding organic hydride hydrogen storage. The catalytic mechanism of the pH-dependent acceptorless-alcohol-dehydrogenation in aqueous solution catalyzed by a novel [C,N] cyclometalated Cp*Ir-complex, [IrIII(Cp*)-(4-(1H- pyrazol-1-yl-κN2)benzoic acid-κC3)(H 2O)]2SO4, has been investigated using density functional theory (DFT) with the M06 dispersion-corrected functional. Using water as the solvent with liberation of dihydrogen represents a safe and clean process for such oxidations. The overall catalytic cycle has been fully characterized. The pre-catalyst AIr first reacts with the ethanol in basic solution to generate an active hydride complex DIrvia an inner-sphere mechanism, involving the hemi-decoordination of [C,N] ligand followed by the β-H elimination. Subsequently, the complex DIr interacts with the protons in acid solution to generate H2 molecules, which is a downhill process nearly without an energy barrier. The present theoretical results have shown that both the hydroxyl in basic solution and the proton in acidic solution play a crucial role in promoting the whole catalytic cycle. Therefore, our results theoretically demonstrated a significant dependence of the reaction system studied on pH value. The present study also predicts that the FIr (at the first triplet excited state, T 1) formed from DIr under laser excitation can catalyze the dehydrogenation of ethanol. Remarkably, the replacement of Ir by Ru may yield an efficient catalyst in the present system.
All Science Journal Classification (ASJC) codes
- Materials Chemistry