Catalytic transfer hydrogenation of N(2) to NH(3) via a photoredox catalysis strategy

Inspired by momentum in applications of reductive photoredox catalysis to organic synthesis, photodriven transfer hydrogenations toward deep (>2 e(−)) reductions of small molecules are attractive compared to using harsh chemical reagents. Noteworthy in this context is the nitrogen reduction reaction (N(2)RR), where a synthetic photocatalyst system had yet to be developed. Noting that a reduced Hantzsch ester (HEH(2)) and related organic structures can behave as 2 e(−)/2 H(+) photoreductants, we show here that, when partnered with a suitable catalyst (Mo) under blue light irradiation, HEH(2) facilitates delivery of successive H(2) equivalents for the 6 e(−)/6 H(+) catalytic reduction of N(2) to NH(3); this catalysis is enhanced by addition of a photoredox catalyst (Ir). Reductions of additional substrates (nitrate and acetylene) are also described.