Does Reduction-Induced Isomerization of a Uranium(III) Aryl Complex Proceed via C-H Oxidative Addition and Reductive Elimination across the Uranium(II/IV) Redox Couple?

Michael A Boreen; Christopher Z Ye; Andrew Kerridge; Karl N McCabe; Brighton A Skeel; Laurent Maron; John Arnold

doi:10.1021/acs.inorgchem.2c01563

Does Reduction-Induced Isomerization of a Uranium(III) Aryl Complex Proceed via C-H Oxidative Addition and Reductive Elimination across the Uranium(II/IV) Redox Couple?

Inorg Chem. 2022 Jun 13;61(23):8955-8965. doi: 10.1021/acs.inorgchem.2c01563. Epub 2022 Jun 2.

Authors

Michael A Boreen^{1

2}, Christopher Z Ye¹, Andrew Kerridge³, Karl N McCabe⁴, Brighton A Skeel¹, Laurent Maron⁴, John Arnold^{1

2}

Affiliations

¹ Department of Chemistry, University of California, Berkeley, California 94720, United States.
² Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
³ Department of Chemistry, Lancaster University, Lancaster LA1 4YB, U.K.
⁴ LPCNO, Université de Toulouse, INSA Toulouse, 135 Avenue de Rangueil, Toulouse 31077, France.

PMID: 35654478
DOI: 10.1021/acs.inorgchem.2c01563

Abstract

Reaction of the uranium(III) bis(amidinate) aryl complex {TerphC(NⁱPr)₂}₂U(Terph) (2, where Terph = 4,4″-di-tert-butyl-m-terphenyl-2'-yl) with a strong reductant enabled isolation of isomeric uranium(III) bis(amidinate) aryl product {TerphC(NⁱPr)₂}₂U(Terph*) (3, where Terph* = 4,4″-di-tert-butyl-m-terphenyl-4'-yl). In terms of connectivity, 3 differs from 2 only in the positions of the U-C and C-H bonds on the central aryl ring of the m-terphenyl-based ligand. A deuterium labeling study ruled out mechanisms for this isomerization involving intermolecular abstraction or deprotonation of the ligand C-H bonds activated during the reaction. Due to the complexity of this rapid, heterogeneous reaction, experimental studies could not further distinguish between two different intramolecular C-H activation mechanisms. However, high-level computational studies were consistent with a mechanism that included two sets of unimolecular, mononuclear C-H oxidative addition and reductive elimination steps involving uranium(II/IV).