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.