A Low-Coordinate Iridium Complex with a Donor-Flexible O,N-Ligand for Highly Efficient Formic Acid Dehydrogenation

Formic acid is one of the most promising hydrogen carriers. Here, we report on a highly productive iridium-based catalyst for formic acid dehydrogenation, which is based on an underligated iridium­(III) center containing a donor-flexible pyridylidene-amine ligand containing a chelating phenolate. This complex reaches temperature-dependent turnover frequencies from 2000 (40 °C) to 280000 h–1 (100 °C) and up to 3 million turnover numbers, thus outperforming state-of-the-art systems. The high efficiency together with the remarkably low cost and easy accessibility of the complex (<$100/g) are attractive features for industrial applications.