Pd -Initiated Formic Acid Decomposition: Plausible Pathways for C-H Activation of Formate.

Formic acid (HCOOH, FA) has long been considered as a promising hydrogen-storage material due to its efficient hydrogen release under mild conditions. In this work, FA decomposes to generate CO and H selectively in the presence of aqueous Pd complex solutions at 333 K. Pd(NO ) was the most effective in generating H among various Pd complexes explored. Pd complexes were in situ reduced to Pd species by the mixture of FA and sodium formate (SF) during the course of the reaction. Since C-H activation reaction of Pd -bound formate is occurred for both Pd reduction and H /CO gas generation, FA decomposition pathways using several Pd species were explored using density functional theory (DFT) calculations. Rotation of formate bound to Pd , β-hydride elimination, and subsequent CO and H elimination by formic acid were examined, providing different energies for rate determining step depending on the ligand electronics and geometries coordinated to the Pd complexes. Finally, Pd reduction toward Pd pathways were explored computationally either by generated H or reductive elimination of CO and H gas.