Isomerization reactions in anionic mesoionic carbene-borates and control of properties and reactivities in the resulting coII complexes through agostic interactions

Jessica Stubbe, Nicolás Neuman, Ross McLellan, Michael Sommer, Maite Nößler, Julia Beerhues, Robert Mulvey, Biprajit Sarkar Sarkar

Research output: Contribution to journalArticlepeer-review

Abstract

We present herein anionic borate-based bi-mesoionic carbene compounds of the 1,2,3-triazol-4-ylidene type that undergo C−N isomerization reactions. The isomerized compounds are excellent ligands for Co II centers. Strong agostic interactions with the “C−H”-groups of the cyclohexyl substituents result in an unusual low-spin square planar Co II complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. This complex displays a high-spin tetrahedral Co II center, which is reactive towards external substrates including dioxygen. To the best of our knowledge, this is also the first investigation of agostic interactions through single-crystal EPR spectroscopy. We conclusively show here that the structure and properties of these Co II complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these classes of anionic mesoionic carbene-based ligands.

Original languageEnglish
Pages (from-to)499-506
Number of pages8
JournalAngewandte Chemie International Edition
Volume60
Issue number1
Early online date20 Oct 2020
DOIs
Publication statusPublished - 4 Jan 2021

Keywords

  • cobalt
  • mesoionic carbene
  • EPR spectroscopy
  • ligand rearrangement
  • spin state
  • reactivity

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