Highly efficient dehydrogenation of formic acid in aqueous solution catalysed by an easily available water-soluble iridium(iii) dihydride

Abstract

The new water-soluble cis-mer-[IrH₂Cl(mtppms)₃] (mtppms = monosulfonated triphenylphosphine) was employed as a catalyst for selective decomposition of formic acid to H₂ + CO₂ in aqueous solution at T = 30–100 °C. The easily synthesized compound showed high catalytic activity (TOF up to 298 000 h⁻¹) and could be reused several times with no loss of activity (total TON = 67 650). A sharp maximum in the reaction rate was observed at pH = 3.75; its coincidence with the pK_a of formic acid shows that both H⁺ or HCOOH and HCOO⁻ play important roles in the reaction mechanism.