Synthesis, hemilability, and catalytic transfer hydrogenation activity of iridium(III) and ruthenium(II) complexes containing oxygen-functionalised triazolylidene ligands

Abstract

The synthesis and characterisation of iridium(III) and ruthenium(II) complexes bearing pendant hydroxy- and ether-wingtip substituents is described. Both monodentate and C,O-bidentate binding modes were observed for these O-functionalised triazolylidene complexes. The two bonding modes are interconvertible, which demonstrates the hemilability of this coordinating group. The catalytic activity of the complexes was compared in transfer hydrogenation, revealing that pendant hydroxy-functionalities are beneficial for enhancing the performance of triazolylidene iridium(III) catalysts, while they have no effect in ruthenium-catalysed transfer hydrogenation. Accordingly, this functional group may serve as a probe to distinguish inner sphere from outer sphere transfer hydrogenation.