NHC Versus Pyridine: How “Teeth” Change the Redox Behavior of Iron(II) Complexes

http://pubs.acs.org/doi/10.1021/acs.organomet.5b00732


NHC Versus Pyridine: How “Teeth” Change the Redox Behavior of Iron(II) Complexes
Daniel T. Weiss†, Markus R. Anneser†, Stefan Haslinger†, Alexander Pöthig‡, Mirza Cokoja§, Jean-Marie Basset∥, and Fritz E. Kühn*†

† Chair of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany
‡ Catalysis Research Center, Technische Universität München, Ernst-Otto-Fischer-Straße 1, D-85747 Garching bei München, Germany
§ Chair of Inorganic & Organometallic Chemistry, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany
∥ KAUST Catalysis Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
Organometallics, 2015, 34 (20), pp 5155–5166
DOI: 10.1021/acs.organomet.5b00732
Publication Date (Web): October 6, 2015








A series of octahedral iron(II) complexes with tetradentate NHC/pyridine hybrid ligands containing up to three pyridyl units was designed to study the influence of NHC and pyridine donors on the electronic structure of the metal center. Structural analysis of the iron complexes by NMR spectroscopy and single-crystal X-ray diffraction reveals different coordination modes of the ligand depending on the linkage of the different donor moieties. The oxidation potentials of all complexes correlate linearly with the number of NHC moieties coordinated to iron, as shown by cyclic voltammetry. The influence, although minor, of structural properties on the oxidation potential and (in one case) the influence of the oxidation state of the coordination geometry of the hybrid ligand are also demonstrated.