A tert-butyl-substituted amino-borane bound to an iridium fragment: A latent source of free H2BNtBuH

Release of the primary amino-borane H2BNtBuH from [Ir(PCy3)2(H)2(η2-H2BNtBuH)][BAr4F], formed from dehydrogenation of [Ir(PCy3)2(H)2(η2-H3B·NtBuH2)][BAr4F], results in the eventual formation of the corresponding cyclic borazine [HBNtBu]3. Observations point to the fact that off-metal hydrogen redistribution reactions play a major role in the final product formation, with H3B·NtBuH2 being formed alongside [HBNtBu]3.

Graphical abstractRelease of the primary amino-borane H2BNtBuH from [Ir(PCy3)2(H)2(η2-H2BNtBuH)][BAr4F] results in the eventual formation of the cyclic borazine [HBNtBu]3 via a pathway that involves off-metal hydrogen redistribution reactions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New amine (H3BNtBuH2) and amino-borane (H2BNtBuH) sigma complexes of Ir synthesized. ► Addition of MeCN releases free amino-borane H2BNtBuH. ► Oligomerisation results in the formation of the corresponding cyclic borazine. ► Off-metal hydrogen redistribution reactions play a major role. ► The implications for the overall mechanism of dehydrocoupling are discussed.