Scandium-Promoted Direct Conversion of Dinitrogen into Hydrazine Derivatives via N-C Bond Formation

Direct conversion of dinitrogen (N-2) into organic compounds, not through ammonia (NH3), is of great significance both fundamentally and practically. Here we report a highly efficient scandium-mediated synthetic cycle affording hydrazine derivatives (RMeN-NMeR') directly from N-2 and carbon-based electrophiles. The cycle includes three main steps: (i) reduction of a halogen-bridged discandium complex under N-2 leading to a (N-2)(3-)-bridged discandium complex via a (N-2)(2-) intermediate; (ii) treatment of the (N-2)(3-) complex with methyl triflate (MeOTf), affording a (N2Me2)(2-)-bridged discandium complex; and (iii) further reaction of the (N2Me2)(2-) complex with the carbon-based electrophile, producing the hydrazine derivative and regenerating the halide precursor. Furthermore, insertion of a CO molecule into one Sc-N bond in the (N2Me2)(2-)-scandium complex was observed. Most notably, this is the first example of rare-earth metal-promoted direct conversion of N-2 to organic compounds; the formation of C-N bonds by the reaction of these (N-2)(3-) and (N2Me2)(2-) complexes with electrophiles represents the first case among all N-2-metal complexes reported.