Photochemical reaction of Cp*Ir(CO)2 with C6F5X (X = CN, F) : formation of diiridium(II) complexes

Visible light irradiation of Cp*Ir(CO)(2) (1) in pentafluorobenzontrile resulted in the formation of the two isomeric diiridium(II) complexes [Cp*Ir(mu-CO)(C6F4CN)](2) (3) and [Cp*Ir(CO)(C6F4CN)](2), (4), while the analogous reaction of 1 in hexafluorobenzene to give [Cp*Ir(mu-CO)(C6F5)](2) (3a) required UV irradiation. Complex 4 isomerizes to 3 under visible light irradiation. A reaction pathway to 4 involving aromatic nucleophilic substitution has been proposed on the basis of experimental and computational data. The isomerization of 4 to 3 is believed to proceed via a radical species resulting from homolytic fission of the Ir-Ir bond.