Issue 26, 2019

Cyclometallation reactions of a three-coordinate cobalt(i) complex bearing a nonsymmetric N-heterocyclic carbene ligand

Abstract

The reactions of a three-coordinate cobalt(I) complex [(IAdMes)(PPh3)CoCl] (1) (IAdMes = 1-mesityl-3-adamantyl-4,5-dimethylimidazol-2-ylidene) with LiCH3, LiCH2SiMe3 and NaCp gave ligand-based C(sp3)–H bond activation products [(IAd′Mes)Co(η6-C6H5PPh2)] (2), [(IAdMes′)(PPh3)Co(CH2SiMe3)] (4) and [(IAd′Mes)Co(η5-Cp)] (5), respectively (IAd′Mes and IAdMes′ denote adamantyl- and mesityl-cyclometallated N-heterocyclic carbene (NHC) ligands, respectively). All the cobalt–NHC complexes have been characterized by various spectroscopic methods, and their structures have been established by single-crystal X-ray diffraction studies. These cyclometallation reactions are among the rare examples of C(sp3)–H bond activation reactions observed in structurally well-defined low-valent cobalt complexes. Different cyclometallated NHC ligands ([IAd′Mes]1−versus [IAdMes′]1−) and different oxidation states of the metal center (cobalt(I) versus cobalt(II)) in the resultant cobalt complexes hint at different mechanisms for these cobalt-mediated C(sp3)–H bond activation reactions.

Graphical abstract: Cyclometallation reactions of a three-coordinate cobalt(i) complex bearing a nonsymmetric N-heterocyclic carbene ligand

Supplementary files

Article information

Article type
Paper
Submitted
18 feb 2019
Accepted
15 mar 2019
First published
18 mar 2019

Dalton Trans., 2019,48, 9676-9683

Cyclometallation reactions of a three-coordinate cobalt(I) complex bearing a nonsymmetric N-heterocyclic carbene ligand

Y. Gao, Q. Chen, X. Leng and L. Deng, Dalton Trans., 2019, 48, 9676 DOI: 10.1039/C9DT00731H

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