Intramolecular C(sp<sup>3</sup>)–H Bond Activation Reactions of Low-Valent Cobalt
Complexes with Coordination Unsaturation
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Abstract
Intramolecular C(sp<sup>3</sup>)–H bond activation
reactions mediated by low-valent cobalt, both Co(I) and Co(0), have
been observed in the reactions of the three-coordinate cobalt complex
[Co(IMes)<sub>2</sub>Cl] (IMes = 1,3-dimesitylimidazol-2-ylidene)
with alkylation reagents and sodium amalgam. The reactions with alkylation
reagents gave [Co(IMes)(IMes′)(N<sub>2</sub>)], featuring a
metalated IMes′ anion, whereas the one-electron-reduction reaction
afforded [Co(IMes′)<sub>2</sub>]. The Co(II) complex can react
with CO, isocyanide, and a diazo compound to furnish interesting cobalt
complexes bearing functionalized N-heterocyclic carbene ligands. The
establishment of these conversions demonstrates the capability of
low-valent cobalt with coordination unsaturation to mediate C(sp<sup>3</sup>)–H bond activation and functionalization