Cyclometalated iridium complexes for transfer hydrogenation of carbonyl groups in water

Cyclometalated iridium complexes are shown to be excellent catalysts for transfer hydrogenation of carbonyl compounds in water using formate as a hydrogen source. A wide range of ketones and aldehydes have been reduced at 0.05% catalyst loading with no need for any organic solvents. Solution pH is found to play a critical role, with acidic conditions needed for fast transfer hydrogenation.