Formic acid dehydrogenation (FAD) is considered as a promising process in the context of hydrogen storage.

This work updates the first non-phosphine-based Mn complex able to perform the formic acid dehydrogenation (FA DH) in the presence of amines. Significant improvements were achieved regarding TON (>7500), gas evolution (>20 L), and lower CO content.

Hydrogen utilization as a sustainable energy vector is of growing interest. We report herein a cyclometalated ruthenium complex [Ru(κ 3 -CNN)(dppb)Cl], originally described by Baratta, to be active in the selective dehydrogenation (DH) of formic acid (FA) to H 2 and CO 2 . TON′s of more than 10000 were [a] 1293 achieved under best conditions without observation of CO (detection limit 10 ppm). The distinguished behavior of the catalyst was explored varying the starting conditions. Our observation revealed the complex [Ru(κ 3 -CNN)(dppb)(OOCH)] as key species in the catalytic cycle. Scheme 1. Selected systems for the Ru catalyzed DH of FA. [21] . Additional phosphine based tridentate ligands were developed such as [Ru(acac) 3 ] in the presence of bis(diphenylphos-Scheme 3. Synthesis of the ligand and Ru-CNN complex.