Noninnocent β-Diiminate Ligands: Redox Activity of a Bis(alkylimidazole)methane Ligand in Cobalt and Zinc Complexes

Pradip Ghosh; Richard Naastepad; Charl F Riemersma; Martin Lutz; Marc-Etienne Moret; Robertus J M Klein Gebbink

doi:10.1002/chem.201701215

Noninnocent β-Diiminate Ligands: Redox Activity of a Bis(alkylimidazole)methane Ligand in Cobalt and Zinc Complexes

Chemistry. 2017 Aug 10;23(45):10732-10737. doi: 10.1002/chem.201701215. Epub 2017 Jun 14.

Authors

Pradip Ghosh¹, Richard Naastepad¹, Charl F Riemersma¹, Martin Lutz², Marc-Etienne Moret¹, Robertus J M Klein Gebbink¹

Affiliations

¹ Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands.
² Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, The Netherlands.

PMID: 28543845
DOI: 10.1002/chem.201701215

Abstract

A new β-diiminate ligand (the bis(1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methane anion, BMIM^Ph2- ) is introduced, in which the ligand framework bears an extended imidazole-based π-system in conjugation with a formal β-diketiminates (NacNac) backbone. Bis-ligated transition metal complexes (Co, Zn) featuring this anionic ligand undergo a series of four consecutive single-electron oxidations that are all ligand-based. The singly and doubly oxidized complexes can be synthesized on a preparative scale and have been fully characterized by various spectroscopic techniques. This is in sharp contrast to the corresponding NacNac-based complexes in which only singly oxidized complexes were isolated and characterized. Single crystal X-ray structure determination revealed a correlation between the intra-ligand metrical parameters and the oxidation state of BMIM^Ph2- . These structural changes in the ligand framework make BMIM^Ph2- as a perceptible non-innocent ligand in contrast to NacNac type ligands.

Keywords: bis(alkylimidazole)methane; cobalt and zinc complexes; redox noninnocence; β-diiminate; π-radical ligand.