Mechanism of B‐H Redistribution during Reduction of Polyborazylene by Hydrazine

Abstract

AbstractDensity functional theory has been used to elucidate the mechanistic underpinnings of the regeneration of ammonia‐borane (H3B−NH3, AB) from polyborazylene (BxNxHx, PBz) in the presence of hydrazine (H2N−NH2, Hz). Herein, borazine (B3N3H6, Bz) is used as the simplest relevant model of PBz for the regeneration process. Digestion of Bz using Hz was found to occur by a string of Lewis acid base adduct (between B atoms of Bz and Hz molecule) formation and Hz assisted proton transfer processes. Later, B−H bonds of HB(NHNH2)2, the Bz digested product, are redistributed to form hydrazine‐borane (H3B−NH2NH2, HzB) and B(NHNH2)3. Redistribution of B−H bonds occurs through hydroboration and concerted proton‐hydride transfer. Another B−H redistributed product, B(NHNH2)3, produces HzB as a result of proton and hydride transfer from cis‐diazene (Dz), the oxidized product of Hz in presence of O2.