Observation of Carbodicarbene Ligand Redox Noninnocence in Highly Oxidized Iron Complexes. Issue 48 (2nd November 2018)

• Record Type: Journal Article
• Authors: Chan, Siu‐Chung; Gupta, Puneet; Engelmann, Xenia; Ang, Zhi Zhong; Ganguly, Rakesh; Bill, Eckhard; Ray, Kallol; Ye, Shengfa; England, Jason
• Is Part Of: Angewandte Chemie international edition. Volume 57:Issue 48(2018)
• Page Start: 15717
• Page End: 15722
• Publication Date: 2018-11-02
• Subjects: carbodicarbenes -- cationic ligands -- iron -- radical ions -- redox noninnocence; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201809158
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: 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, where1 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 .+ )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 .+ )] 4+ ( S =0). The observed spin states 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. Abstract : Carbones contain C atoms possessing two lone pairs of electrons. Thus, along with σ‐coordination to a metal ion, they have a further pair of electrons, rendering them capable of π‐donation or geminal coordination to a second metal. Via formation of a [Fe(1 )2 ] n + ( n =2–5) redox series, where1 is a tridentate carbodicarbene ligand, it is shown that this second pair of electrons also allows them to be redox‐active.