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

Direct
conversion of dinitrogen (N2) 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 N2 and carbon-based electrophiles. The cycle
includes three main steps: (i) reduction of a halogen-bridged discandium
complex under N2 leading to a (N2)3–-bridged discandium complex via a (N2)2– intermediate; (ii) treatment of the (N2)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 N2 to organic compounds; the formation
of C–N bonds by the reaction of these (N2)3– and (N2Me2)2– complexes
with electrophiles represents the first case among all N2–metal complexes reported.