Carbon Monoxide Induced Double Cyclometalation at the Iridium Center

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 IrIII complex.