Diazene Chemistry: Metal-Free Models of N 2 Reduction Intermediates.

Interest in main group chemistry related to the Haber-Bosch process has drawn less attention than that of transition metal species. Herein, we show that the steric demands in ( t BuO2 CN)2 block initial interaction of B(C6 F5 )3 with nitrogen and prompt loss of methylpropene and CO2 to diazene (N2 H2 ) borane adduct 1 and the analogous hydrazine (N2 H4 ) adduct 2 . These species react with basic phosphines to give anions of 3 and 5 containing N2 H and N2 H3 fragments, respectively. While these species are not derived directly from N2 , they represent metal-free species containing N2 H n ( n = 1-4) fragments, which model plausible intermediates in the reduction of N2 .