Borane Adducts of Hydrazoic Acid and Organic Azides: Intermediates for the Formation of Aminoboranes

The reaction of HN 3 with the strong Lewis acid B(C 6 F 5 ) 3 led to the formation of a very labile HN 3 ⋅B(C 6 F 5 ) 3 adduct, which decomposed to an aminoborane, H(C 6 F 5 )NB(C 6 F 5 ) 2 , above −20 °C with release of molecular nitrogen and simultaneous migration of a C 6 F 5 group from boron to the nitrogen atom. The intermediary formation of azide–borane adducts with B(C 6 F 5 ) 3 was also demonstrated for a series of organic azides, RN 3 (R=Me 3 Si, Ph, 3,5‐(CF 3 ) 2 C 6 H 3 ), which also underwent Staudinger‐like decomposition along with C 6 F 5 group migration. In accord with experiment, computations revealed rather small barriers towards nitrogen release for these highly labile azide adducts for all organic substituents except R=Me 3 Si (m.p. 120 °C, T dec =189 °C). Hydrolysis of the aminoboranes provided C 6 F 5 ‐substituted amines, HN(R)(C 6 F 5 ), in good yields.