Takeshi Yatabe

Chemists have long sought to regulate the reactivity of H 2 , to yield hydride ions, hydrogen atoms, or electrons on demand. One source of inspiration for achieving this control is [NiFe]hydrogenase ([NiFe]H 2 ase), which reacts with H 2 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]H 2 ase, but also as electron transfer catalysts. However, the synthesis of Ni I complex directly from H 2 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 H 2 , stable for over 3 months at room temperature and we further demonstrate a reductive coupling of acridinium ions as part of a reaction cycle.