In a previous episode Sutton et al. introduced a new method for the regeneration of ammonia borane (AB) using hydrazine. Bad idea! say Reller and Mertens because hydrazine is (1) a hazardous material and (2) therefore predominantly sold as the less hazardous hydrate. And the hydrate cannot be used in AB regeneration. In their recent publication (DOI) Reller and Mertens suggest an alternative scheme for AB regeneration featuring an entirely different intermediate as summarized below:
Bottlenecks reported: small window of opportunity in step 4 as dehydrogenation sets in already at 90°C but eventually ammonia can replace triethylamine.
Lucky breaks reported: despite its abundance chlorine did not poison the nickel boride catalyst.