Issue 47, 2021

Revealing redox isomerism in trichromium imides by anomalous diffraction


In polynuclear biological active sites, multiple electrons are needed for turnover, and the distribution of these electrons among the metal sites is affected by the structure of the active site. However, the study of the interplay between structure and redox distribution is difficult not only in biological systems but also in synthetic polynuclear clusters since most redox changes produce only one thermodynamically stable product. Here, the unusual chemistry of a sterically hindered trichromium complex allowed us to probe the relationship between structural and redox isomerism. Two structurally isomeric trichromium imides were isolated: asymmetric terminal imide (tbsL)Cr3(NDipp) and symmetric, μ3-bridging imide (tbsL)Cr33–NBn) ((tbsL)6− = (1,3,5-C6H9(NC6H4-o-NSitBuMe2)3)6−). Along with the homovalent isocyanide adduct (tbsL)Cr3(CNBn) and the bisimide (tbsL)Cr33–NPh)(NPh), both imide isomers were examined by multiple-wavelength anomalous diffraction (MAD) to determine the redox load distribution by the free refinement of atomic scattering factors. Despite their compositional similarities, the bridging imide shows uniform oxidation of all three Cr sites while the terminal imide shows oxidation at only two Cr sites. Further oxidation from the bridging imide to the bisimide is only borne at the Cr site bound to the second, terminal imido fragment. Thus, depending on the structural motifs present in each [Cr3] complex, MAD revealed complete localization of oxidation, partial localization, and complete delocalization, all supported by the same hexadentate ligand scaffold.

Graphical abstract: Revealing redox isomerism in trichromium imides by anomalous diffraction

Supplementary files

Article information

Article type
Edge Article
31 Aug 2021
02 Nov 2021
First published
03 Nov 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2021,12, 15739-15749

Revealing redox isomerism in trichromium imides by anomalous diffraction

A. K. Bartholomew, R. A. Musgrave, K. J. Anderton, C. E. Juda, Y. Dong, W. Bu, S. Wang, Y. Chen and T. A. Betley, Chem. Sci., 2021, 12, 15739 DOI: 10.1039/D1SC04819H

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity