LAUSR

Dibenzobarrelene-based PC s p 3 P pincer iridium complex bearing dangling CH2OH groups, ( ( PC s p 3 P CH 2 OH ) IrH ( Cl ) , catalyzes the dehydrogenation of amine–boranes at the reaction rate changing counter intuitively in the order: Me2NH·BH3 > > ButNH2·BH3 > NH3·BH3. The spectral (IR and NMR) data and DFT/M06 calculations have revealed that the binding of amine–boranes to the dangling OH group leads to an additional stabilization of the Ir···OH bond, thus hampering the dehydrogenation reaction, whereas the amine–borane coordination to iridium entails a fac- to mer-transformation of the complex and initiates the catalytic H2 evolution.