Single-Step Synthesis of Ni^I from Ni^II with H₂

Chemists have long sought to regulate the reactivity of H₂ , to yield hydride ions, hydrogen atoms, or electrons on demand. One source of inspiration for achieving this control is [NiFe]hydrogenase ([NiFe]H₂ ase), which reacts with H₂ to form various hydrogen active species such as Ni^III hydride species, Ni^II hydride species, and Ni^I low-valent species. Chemists have attempted to synthesize these hydrogen active species not only as models for the active species of [NiFe]H₂ ase, but also as electron transfer catalysts. However, the synthesis of Ni^I complex directly from H₂ has not been reported. This paper reports the first example of a single-step synthesis of a Ni^I complex, via reaction of a Ni^II complex with H₂ , stable for over 3 months at room temperature and we further demonstrate a reductive coupling of acridinium ions as part of a reaction cycle.