Developing more sustainable processes for ammonia synthesis

This paper describes a recent advance on the conversion of molecular dinitrogen into ammonia or ammonia equivalent, silylamine, by using transition metal–dinitrogen complexes. Two effective systems for the catalytic transformation of molecular dinitrogen under ambient reaction conditions have been achieved by the use of molybdenum and iron complexes as catalysts. The former system employs a molybdenum–dinitrogen complex bearing two ferrocenyl diphosphines or an iron complex such as iron carbonyl or substituted ferrocene as a catalyst to afford up to 226 equiv of silylamine based on the catalyst. The latter system employs a dinitrogen-bridged dimolybdenum complex bearing two PNP-type pincer ligands as a catalyst to afford up to 23 equiv of ammonia based on the catalyst. Both systems provide a new aspect in the development of novel nitrogen fixation under mild reaction conditions.

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► Recent advance on metal-promoted mild conversion of N2 into NH3 or N(TMS)3 is noted.
► Mo complex with two Fc diphosphines catalyzes transformation of N2 into N(TMS)3.
► Fe complexes such as Fe(CO)5 and FeCp2 catalyze transformation of N2 into N(TMS)3.
► Mo complex with two PNP-type pincer ligands catalyzes transformation of N2 into NH3.