A Cyclometalated NHC Iridium Complex Bearing a Cationic (η⁵ -Cyclopentadienyl)(η⁶ -phenyl)iron Backbone*

Nucleophilic substitution of [(η⁵ -cyclopentadienyl)(η⁶ -chlorobenzene)iron(II)] hexafluorophosphate with sodium imidazolate resulted in the formation of [(η⁵ -cyclopentadienyl)(η⁶ -phenyl)iron(II)]imidazole hexafluorophosphate. The corresponding dicationic imidazolium salt, which was obtained by treating this imidazole precursor with methyl iodide, underwent cyclometallation with bis[dichlorido(η⁵ -1,2,3,4,5-pentamethylcyclopentadienyl]iridium(III) in the presence of triethyl amine. The resulting bimetallic iridium(III) complex is the first example of an NHC complex bearing a cationic and cyclometallated [(η⁵ -cyclopentadienyl)(η⁶ -phenyl)iron(II)]⁺ substituent. As its iron(II) precursors, the bimetallic iridium(III) complex was fully characterized by means of spectroscopy, elemental analysis and single crystal X-ray diffraction. In addition, it was investigated in a catalytic study, wherein it showed high activity in transfer hydrogenation compared to its neutral analogue having a simple phenyl instead of a cationic [(η⁵ -cyclopentadienyl)(η⁶ -phenyl)iron(II)]⁺ unit at the NHC ligand.