Hydrogen Liberation from Formic Acid Mediated by Efficient Iridium(III) Catalysts Bearing Pyridine‐Carboxiamide Ligands

Gabriel Menendez Rodriguez; Chiara Domestici; Bucci Alberto; Massimiliano Valentini; Cristiano Zuccaccia; Alceo Macchioni

Index: 10.1002/ejic.201701458

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Abstract

Herein it is shown that complexes [Cp*Ir(R‐pica)Cl] {R‐pica = R‐picolinamidate = κ2‐R‐pyridine‐2‐carboxamide, ion(−1), 1 R = H and 2 R = Me } catalyze the liberation of H2 from formic acid in water, at ambient temperature and pressure, in the absence of any addictive/promoter, with performances comparable with those of the best catalysts reported so far. TOF approaching 30000 h‐1 were observed for 1 and 2 (pH = 3.7, [HCOOH] + [HCOO‐] = 1 M, [Cat] = 250 μM, T = 60 °C), whereas TON was only limited by the amount of HCOOH used and increase of pH during with the progress of reaction, which makes the protonation of Ir‐H little probable. Catalyst 2, bearing the most electrondonating ligand, exhibited higher TOF than 1, especially at acidic pH (< 5).