Hydrodechlorination of Et₃NBCl₃ Catalyzed by Amorphous Nickel Boride – A Mechanistic Approach

Abstract

The catalytic hydrodechlorination of BCl 3 with molecular hydrogen in the presence of tertiary amines is a viable strategy for the energy-efficient generation of valuable B-H bonds. A mechanistic study based on experiments with isolated intermediates and deuterium labeling experiments is presented. The occurrence of the rate-limiting reverse reaction from the insoluble Et 3 NHCl adduct was identified as a major cause of [a]

The Recycling of Spent Ammonia Borane with HBr/AlBr3 and Other HX/AlX3‐Based Schemes

“…In contrast to the analogous chloride case investigated in Ref. [34], a control experiment between Et 3 NHBr and Et 3 NBH 3 at a temperature of T = 160°C and a reaction period of 48 h showed no formation of any lower hydrogenated boron species. Due to the reduced reverse reaction rate, the overall reaction rate of the hydrodehalogenation of the Et 3 NBBr 3 or Et 3 NBI 3 adducts is enhanced compared to the one observed for the Et 3 NBCl 3 adduct and the final Et 3 NBH 3 yield is higher.…”

“…There is a third major step which is the replacement of the auxiliary base by ammonia in order to arrive eventually at ammonia borane. However, in case of a successful hydrodehalogenation, this step is identical to the corresponding one in the recycling procedure based on HCl ,…”

“…However, in case of a successful hydro-dehalogenation, this step is identical to the corresponding one in the recycling procedure based on HCl. [29,34]…”