Direct synthesis of cyanate anion from dinitrogen catalysed by molybdenum complexes bearing pincer-type ligand

Abstract

Dinitrogen is an abundant and promising material for valuable organonitrogen compounds containing carbon–nitrogen bonds. Direct synthetic methods for preparing organonitrogen compounds from dinitrogen as a starting reagent under mild reaction conditions give insight into the sustainable production of valuable organonitrogen compounds with reduced fossil fuel consumption. Here we report the catalytic reaction for the formation of cyanate anion (NCO−) from dinitrogen under ambient reaction conditions. A molybdenum–carbamate complex bearing a pyridine-based 2,6-bis(di-tert-butylphosphinomethyl)pyridine (PNP)-pincer ligand is synthesized from the reaction of a molybdenum–nitride complex with phenyl chloroformate. The conversion between the molybdenum–carbamate complex and the molybdenum–nitride complex under ambient reaction conditions is achieved. The use of samarium diiodide (SmI2) as a reductant promotes the formation of NCO− from the molybdenum–carbamate complex as a key step. As a result, we demonstrate a synthetic cycle for NCO− from dinitrogen mediated by the molybdenum–PNP complexes in two steps. Based on this synthetic cycle, we achieve the catalytic synthesis of NCO− from dinitrogen under ambient reaction conditions.