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 BuO 2 CN) 2 block initial interaction of B(C 6 F 5 ) 3 with nitrogen and prompt loss of methylpropene and CO 2 to diazene (N 2 H 2 ) borane adduct 1 and the analogous hydrazine (N 2 H 4 ) adduct 2 . These species react with basic phosphines to give anions of 3 and 5 containing N 2 H and N 2 H 3 fragments, respectively. While these species are not derived directly from N 2 , they represent metal-free species containing N 2 H n ( n = 1-4) fragments, which model plausible intermediates in the reduction of N 2 .