Dehydrogenation of N-ethyl perhydrocarbazole catalyzed by PCP pincer iridium complexes: Evaluation of a homogenous hydrogen storage system

The iridium complexes IrH2{C6H3-2,6-(CH2PBut2)2 (1), IrH2{C6H3-2,6-(CH2PPri2)2 (2), and IrHCl{C6H3-2,6-(OPBut2)2 (3) have been found to be highly active catalysts for the dehydrogenation of N-ethyl perhydrocarbazole at 200 °C. However, dehydrogenation to the fully unsaturated ethyl carbazole does not occur in most instances. Complex 3 is the most active catalyst and shows reasonable activity even at 150 °C. No signs of dehydrogenation were found in experiments conducted at 100 °C. This apparently reflects the thermodynamic constraints imposed by the high enthalpy of dehydrogenation of the substrate.