Exploring the Site Selectivity of Arene Oxidation in [(η⁵-C₅Me₅)Ir(η⁶-arene)](OTf)₂ Complexes

The oxidation selectivity of the η6-arene ligand in a series of [(η5-C5Me5)Ir(η6-arene)](OTf)2 complexes to the corresponding [(η5-C5Me5)Ir(η5-phenoxo)](OTf) derivatives was studied as a complementary protocol to metal-catalyzed borylation-oxidation. A series of representative [(η5-C5Me5)Ir(η6-arene)](OTf)2 compounds was prepared with mono-, di-, and trisubstituted arenes as well as two examples with biphenyls to rationally explore the site selectivity of C(sp2)–H oxidation. The isolated organometallic arene complexes were treated with NaClO2 and formed the desired iridium η5-phenoxo products. While site-selective oxidation was observed for some compounds, most of the iridium complexes yielded a mixture of regioisomers. Regioselectivity was primarily determined by electronic factors, while sterics influenced sites that were electronically similar.