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submitted on 01.09.2020 and posted on 02.09.2020by Nicolas Lentz, Alicia Aloisi, Pierre Thuéry, Emmanuel Nicolas, Thibault Cantat
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