Hydrogenation of Alkenes Catalyzed by a Non‐pincer Mn Complex

Hydrogenation of substituted styrenes and unactivated aliphatic alkenes by molecular hydrogen has been achieved using a Mn catalyst with a non‐pincer, picolylphosphine ligand. This is the second reported example of alkene hydrogenation catalyzed by a Mn complex. Mechanistic studies showed that a Mn hydride formed by H2 activation in the presence of a base is the catalytically active species. Based on experimental and DFT studies, H2 splitting is proposed to occur via a metal‐ligand cooperative pathway involving deprotonation of the CH2 arm of the ligand, leading to pyridine dearomatization.