M(0)- Aminocarbene Complexes (M=Cr,W,Fe) : Redox Behaviour Tuned by Metal and/or Ligand Modification

Abstract

Series of chromium, tungsten and iron aminocarbene complexes were prepared and electrochemically investigated. The influence of the type of coordination, of the substituent on the ligand phenyl ring and of the central metal atom on oxidation and reduction potentials was followed electrochemically using the Linear Free Energy Relationship (LFER) approach. The difference between the oxidation and reduction potentials reflects the energy of the HOMO-LUMO gap. The reduction of carbene derivatives strongly depends only on the nature of ligands and their substitution, but not on the nature of the central metal. On the other hand, the oxidation is practically independent of the ligand substitution, being influenced by both the nature of the central metal atom and the number of carbonyl groups (i.e. strong π-acceptors) present.