Carbon monoxide induced double cyclometalation at the iridium center

Abstract

Bubbling of CO into a dichloromethane solution of [Ir(COD)(CH₃CN)₂][BF₄] followed by the addition of 2-phenyl-1,8-naphthyridine (LH) at room temperature results in the bis-cyclometalated IrIII complex [Ir(C^∧N)₂(CO)(LH)][BF₄] (C^∧N = L). The observed cyclometalation contradicts the classical role of CO, which is to hinder oxidative addition by lowering electron density on the metal. DFT calculations reveal that the first cyclometalation involves oxidative addition of the ligand. Subsequently, preferential electrophilic activation of the second ligand followed by elimination of dihydrogen affords the bis-cyclometalated Ir^III complex.