Observation of Carbodicarbene Ligand Redox Noninnocence in Highly Oxidized Iron Complexes

摘要

To probe the possibility that carbodicarbenes (CDCs) are redox active ligands, all four members of the redox series [Fe(1)(2)](n+) (n = 2-5) were synthesized, where 1 is a neutral tridentate CDC Through a combination of spectroscopy and DFT calculations, the electronic structure of the pentacation is shown to be [Fe-III (1(center dot)(+))(2)](5)(+) (S = 1/2). That of [Fe(1)(2)](4+) is more ambiguous, but it has significant contributions from the open-shell singlet [Fe-III(1)(1(center dot)(+))](4+) (S = 0). The observed spin stales derive from antiferromagnetic coupling of their constituent low-spin iron(III) centres and cation radical ligands. This marks the first time redox activity has been observed for carbones and expands the diverse chemical behaviour known for these ligands.