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Cobalt-Catalyzed C(sp2)–H Borylation with an Air-Stable, Readily Prepared Terpyridine Cobalt(II) Bis(acetate) Precatalyst

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posted on 13.10.2016, 19:05 by Nadia G. Léonard, Máté J. Bezdek, Paul J. Chirik
A bench-stable, 4-aryl-substituted terpyridine supported, high-spin cobalt­(II) bis­(acetate) complex, (ArTpy)­Co­(OAc)2 (ArTpy = 4′-(4-N,N′-dimethylaminophenyl)-2,2′:6′,2″-terpyridine), is active for the C­(sp2)–H borylation of arenes and heteroarenes with B2Pin2 (Pin = pinacolato). Optimization of the catalytic borylation reaction revealed improved performance in the presence of LiOMe and turnover numbers of up to 100 have been observed using all air-stable components. EPR specstroscopy identified formation of inactive cobalt species, promoted by excess HBPin. A high-spin cobalt­(II) bis­[(diacetoxy)­pinacolatoborate−κ3O,O,O] compound has been isolated and characterized by X-ray diffraction and is the result of catalyst deactivation.