Phosphine Ligand Hemilability as a Route Towards Robust and Efficient Hydrogenation with Mn(I) Complexes

The foremost requirement for any catalyst to be

implemented in practice is its efficiency and stability. This

requirement is particularly valid for manganese hydrogenation catalysts representing more sustainable alternatives to conventional noble metal-based systems. Herein, we report a highly efficient Mn(I)-CNP pre-catalyst featuring phosphine arm hemilability, which gives rise to the excellent productivity (TOF° up to 41 000 h-1) and outstanding stability (TON up to 200 000) in hydrogenation catalysis. This system enables near-quantitative hydrogenation of ketones, imines, aldehydes, and esters at the catalyst loadings as low as 5-200 ppm. Our analysis points to the crucial role of the phosphine hemilability for the catalyst activation step and the stability of the reactive species under the catalytic conditions. Unprecedented in

manganese hydrogenation catalysis, this unusual coordination behavior might have general utility for improving catalysis by Mn complexes and bringing them yet another competitive advantage.