Redox‐Active Triazole‐Derived Mesoionic Imines with Ferrocenyl Substituents and their Metal Complexes: Directed Hydrogen‐Bonding, Unusual C−H Activation and Ion‐Pair Formation

Abstract

We present herein the synthesis, characterization and complexation of ferrocenyl‐substituted MIIs (mesoionic imines) and their metal complexes. In the free MIIs, strong hydrogen bonding interactions are observed between the imine‐N and the C‐H bonds of the ferrocenyl substituents both in the solid state and in solution. The influence of this hydrogen bonding is so strong that complexation of the MIIs with [IrCp*Cl2]2 yields unique six‐membered iridacycles via C‐H‐activation of the corresponding C‐H‐site at the Fc‐substituent and not the Ph‐substituent. This result is in contrast to previous reports in which always a preferential C‐H activation at the phenyl substituent is observed in competitive reactions in the presence of ferrocenyl substituents. The corresponding Ir complexes formed after in‐situ halide exchange reaction exist in either [Ir‐I] contact or as [Ir]+I‐ solvent separated ion‐pairs depending on the solvent polarity. The iodide coordinated and solvent separated ion‐pairs display drastically different physical properties. The TEP (Tolman‐electronic‐parameter) of these ligands was determined and lines up with previously reported MII‐ligands. The redox properties were investigated by a combination of electrochemical and spectroelectrochemical methods. We show here how non‐covalent interactions can have a drastic influence on the physical and chemical properties of these new class of compounds.