A Cyclometalated NHC Iridium Complex Bearing a Cationic (η5‐Cyclopentadienyl)(η6‐phenyl)iron Backbone. Issue 61 (5th October 2021)

• Record Type: Journal Article
• Authors: Malchau, Christian; Milbert, Tom; Eger, Tobias R.; Fries, Daniela V.; Pape, Pascal J.; Oelkers, Benjamin; Sun, Yu; Becker, Sabine; Prosenc, Marc H.; Niedner‐Schatteburg, Gereon; Thiel, Werner R.
• Is Part Of: Chemistry. Volume 27:Issue 61(2021)
• Page Start: 15209
• Page End: 15217
• Publication Date: 2021-10-05
• Subjects: cyclometallation -- iridium -- iron -- N-heterocyclic carbenes -- transfer hydrogenation; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202102520
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Nucleophilic substitution of [(η 5 ‐cyclopentadienyl)(η 6 ‐chlorobenzene)iron(II)] hexafluorophosphate with sodium imidazolate resulted in the formation of [(η 5 ‐cyclopentadienyl)(η 6 ‐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(η 5 ‐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 [(η 5 ‐cyclopentadienyl)(η 6 ‐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 [(η 5 ‐cyclopentadienyl)(η 6 ‐phenyl)iron(II)] + unit at the NHC ligand. Abstract : Iron power : A cyclometalated Fe(II) and Ir(III) complex based on the cationic (η 5 ‐cyclopentadienyl)(η 6 ‐phenyl)iron(II)]imidazole skeleton is reported. Compared to its neutral analogue without the [CpFe] + fragment, it is surprisingly active in the transfer hydrogenation of ketones. Mechanistic investigation on the reaction paths performed by DFT calculations provided a better understanding of the reaction mechanism, possible intermediates and the active species.