Intramolecular C(sp3)–H Bond Activation Reactions of Low-Valent Cobalt Complexes with Coordination Unsaturation

Intramolecular C­(sp3)–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)2Cl] (IMes = 1,3-dimesitylimidazol-2-ylidene) with alkylation reagents and sodium amalgam. The reactions with alkylation reagents gave [Co­(IMes)­(IMes′)­(N2)], featuring a metalated IMes′ anion, whereas the one-electron-reduction reaction afforded [Co­(IMes′)2]. 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(sp3)–H bond activation and functionalization.