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.

The reversible storage of hydrogen through the intermediate formation of Formic Acid (FA) is a promising solution to its safe transport and distribution. However, the common necessity of using bases or additives in the catalytic dehydrogenation of FA is a limitation. In this context, two new cobalt complexes (1 and 2) were synthesized with a pincer PP(NH)P ligand containing a phosphoramine moiety. Their reaction with an excess FA yields a cobalt(I)-hydride complex (3). We report here the unprecedented catalytic activity of 3 in the dehydrogenation of FA, with a turnover frequency (TOF) of 4000 h-1 and a turnover number (TON) of 454, without the need for bases or additives. A mechanistic study reveals that the ligand has a non-innocent behaviour due to intermolecular hydrogen bonding, which is influenced by the concentration of formic acid.

Copper(i) complexes featuring N-heterocyclic carbenes (NHCs) in which the nitrogen atoms are substituted by a 9-ethyl-9-fluorenyl group (EF) have been synthesised and tested in the hydrosylilation of functionalized and/or sterically demanding ketones and aldehydes. These reactions, carried out with triethylsilane as hydride source, were best achieved with the imidazolylidene copper complex in which the EF substituents can freely rotate about the corresponding N-CEF bonds. The remarkable stability of the active species, which surpasses that of previously reported Cu-NHC catalysts is likely to rely on the ability of the NHC side arms to protect the copper centre during the catalytic cycle by forming sandwich-like intermediates, but also on its steric flexibility facilitating approach of encumbered substrates. TONs up to 1000 were reached.

Heteroleptic organogermylenes containing a sulfoxide donor function were used for application in coordination chemistry with [W(cod)(CO)4], [Mo(nbd)(CO)4] and [Ru(PPh3)3Cl2].