A Highly Active PBP–Iridium Catalyst for the Dehydrogenation of Dimethylamine–Borane: Catalytic Performance and Mechanism

A long‐tethered boron‐containing (P‐B‐P) pincer ligand with an aliphatic backbone was synthesized. Oxidative addition of the B−H bond in the ligand to [Ir(coe)2Cl]2 (coe=cyclooctene) afforded the (P‐B‐P)Ir(H)Cl complex. A catalyst system comprising the iridium complex and KOtBu showed excellent performance in the dehydrocoupling of N,N‐dimethylamine–borane (DMAB), releasing 1 equivalent of dihydrogen gas from a concentrated solution of DMAB at a low catalyst loading of 0.05 mol % and with an initial turnover frequency of approximately 3400 h−1. The dihydride (P‐B‐P)Ir(H)2 complex also catalyzed the dehydrogenation of DMAB and was postulated as one of the intermediates in the catalytic cycle. Stuck like PB: A newly synthesized boron‐containing pincer ligand with an aliphatic backbone is treated with [Ir(coe)2Cl]2 (coe=cyclooctene) to result in (P‐B‐P)Ir(H)Cl. A catalyst system comprising this Ir complex and KOtBu shows excellent performance in releasing 1 equivalent of H2 from the N,N‐dimethylamine–borane complex at a low catalyst loading (0.05 mol %) with an initial turnover frequency (TOF) of approximately 3400 h−1.