Direct Synthesis of Organonitrogen Compounds from Dinitrogen Using Transition Metal Complexes: Leap from Stoichiometric Reactions to Catalytic Reactions

Abstract

Organonitrogen compounds are of vital importance to our lives. For almost all organonitrogen compounds, ammonia is only the feedstock as a nitrogen source. Ammonia is produced from dinitrogen (N2) and dihydrogen (H2) by the Haber‐Bosch process, which consumes an enormous amount of energy. As an alternative method to convert N2 into organonitrogen compounds under milder conditions, various stoichiometric reactions with transition metal complexes have been explored for the last 50 years. However, the field of catalytic formation of organonitrogen compounds directly from N2 with transition metal complexes is still in its infancy. This short review summarizes strategies to achieve the direct synthesis of organonitrogen compounds from N2 under mild reaction conditions using transition metal complexes ranging from stoichiometric reactions to catalytic reactions.

Catalytic Nitrogen Fixation Using Well‐Defined Molecular Catalysts under Ambient or Mild Reaction Conditions

“…Next target molecules can be nitriles and amines, which are very important in modern nitrogen chemistry for manufacturing plastics and polymers. Nitriles and amines have been already prepared from N 2 via stepwise stoichiometric reactions by using transition metal complexes under ambient reaction conditions [20,21] . B−N bond formation under ambient reaction conditions via radical reactions has been also recently achieved for borylation of N 2 , and the next target reaction can be catalytic hydroboration of N 2 .…”

“…Several C−N bond forming reactions for N 2 ‐derived transition metal dinitrogen, hydrazide, or nitride complexes under ambient reaction conditions have been reported including addition with carbon‐centered electrophiles such as acyl or alkyl halides, condensation with ethers or ketones, and addition or insertion with unsaturated compounds such as CO, CO 2 , or alkynes [20,21] . Early examples of acylation or alkylation of coordinated N 2 were reported by Chatt and co‐workers, who demonstrated stepwise alkylation of the W(0) dinitrogen complex 21 with MeBr at the distal N atom, for example, where a stoichiometric amount of dimethylamine was obtained as the major product on further treatment with LiAlH 4 (Figure 10a).…”

“…As shown in Figures 10a–10d, several pseudo‐catalytic cycles to produce nitrogen‐containing compounds with C−N bond formation have been portrayed. However, all these reactions summarized here are aggregation of reaction steps, [20,21] and construction of single catalyses is still left to be demonstrated.…”

“…This review is intended to give an overview on recent advances on the catalytic conversion of N 2 into nitrogen‐containing compounds with N−H, [4,5,15–18] Si−N, [18–20] or C−N bonds [20,21] under ambient or mild conditions by using well‐defined molecular complexes as homogeneous catalysts.…”

Synthesis of Collidine from Dinitrogen via a Tungsten Nitride

“…In nature and in industry, molecular dinitrogen is reduced either to NH 4 + (via nitrogenase and/or via nitrate assimilation) or to NH 3 (via the Haber–Bosch process) in order to eventually assemble N-containing molecules in countless follow-up reactions. To cleave N 2 and couple this cleavage step directly to an N–C bond formation step in a catalytic cycle is therefore regarded as one of the long-term goals in homogeneous N 2 functionalization . In this context, a number of stoichiometric N–C coupling reactions that rely on N 2 -derived nitrido complexes have been reported, and closed synthetic (noncatalytic) cycles have been established in some cases. , Most often, alkyl amines, nitriles, isocyanates, and carboxylic amides have been prepared stoichiometrically, while only one example for the synthesis of anilines via an N 2 -derived μ-nitrido tri-iron complex has been discovered so far .…”