Redox Activity of IrIII Complexes with Multidentate Ligands Based on Dipyrido‐Annulated N‐Heterocyclic Carbenes: Access to High Valent and High Spin State with Carbon Donors

Abstract

AbstractSynthetic strategies to access high‐valent iridium complexes usually require use of π donating ligands bearing electronegative atoms (e. g. amide or oxide) or σ donating electropositive atoms (e. g. boryl or hydride). Besides the η5‐(methyl)cyclopentadienyl derivatives, high‐valent η1 carbon‐ligated iridium complexes are challenging to synthesize. To meet this challenge, this work reports the oxidation behavior of an all‐carbon‐ligated anionic bis(CCC‐pincer) IrIII complex. Being both σ and π donating, the diaryl dipyrido‐annulated N‐heterocyclic carbene (dpa‐NHC) IrIII complex allowed a stepwise 4e− oxidation sequence. The first 2e− oxidation led to an oxidative coupling of two adjacent aryl groups, resulting in formation of a cationic chiral IrIII complex bearing a CCCC‐tetradentate ligand. A further 2e− oxidation allowed isolation of a high‐valent tricationic complex with a triplet ground state. These results close a synthetic gap for carbon‐ligated iridium complexes and demonstrate the electronic tuning potential of organic π ligands for unusual electronic properties.