Cyclometalated half‐sandwich iridium complexes: Synthesis, characterization, and catalytic activity in preparation of esters from halides by using formate as both CO source and coupling partner

Abstract

A highly efficient carbonylation of aryl halides using half‐sandwich iridium catalysis was developed, providing a new avenue for synthesizing carboxylic ester derivatives and yielding consistently impressive results. These iridium complexes demonstrated remarkable catalytic performance in the coupling reaction using phenyl formate derivatives as the source of CO, phenol, and aryl halides as the starting material in the presence of air and possessed good air and moisture stability properties. Ester products with different substituents were synthesized at low reaction temperatures without the need for an inert atmosphere, leading to high yields. The broad substrate scope, impressive catalytic activity, and mild reaction conditions suggest promising industrial applications for this catalytic system. The desired metal complexes 1–4 have been well proven by attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR), nuclear magnetic resonance (NMR), and elemental analysis (EA). The molecular structure of the cyclometalated iridium complexes 2 and 3 was proven through X‐ray crystallography. Additionally, the possible mechanism of this Ir‐catalyzed process is further supported by the density functional theory (DFT) study.