Building Square Planar Cobalt (II) Complexes via Sodium Mediated Cobaltation of Fluoroarenes

• Published in: Angewandte Chemie International Edition 2022-12, Vol.61 (49), p.e202213246-n/a
• Main Authors: Logallo, Alessandra, Mu, Manting, García‐Melchor, Max, Hevia, Eva
• Format: Article
• Language: English
• Subjects: Cobalt; Cobalt compounds; Cooperative Bimetallics; Density functional theory; Fluoroarene; Intermediates; Non-Covalent Interactions; Sodium; Stoichiometry; Substrates
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202213246

While cobalt complexes have already shown their potential for C−H and C−F bond activation of fluoroarenes, their reactivity as metalating agents via Co−H exchange towards these substrates has not been explored. Herein, we report a Co(HMDS)2 [HMDS=N(SiMe3)2] system which, when synergistically enhanced via sodium amide Na(HMDS) mediation, can render chemo‐ and regioselective cobaltation of a series of fluoroarenes to produce a new class of homoleptic square planar [Na2CoAr4] complexes. Density functional theory calculations elucidate the key roles of the Na/Co counterparts in a stepwise sodiation/cobalt transmetalation process, leading to this novel C−H metalation. Depending on the reaction stoichiometry, this process can occur inter‐ or intramolecularly, furnishing transient [NaCo(HMDS)2Ar] intermediates which can undergo ligand rearrangement to afford [Na2CoAr4] with concomitant formation of Co(HMDS)2 and [NaCo(HMDS)3]. Using a mixed Na/CoII tris(amido) base enables the selective cobaltation of a range of fluoroarenes furnishing a new family of square planar tetra(aryl) complexes. Mechanistic investigations shed light on the key roles played by each metal, uncovering two alternative types of bimetallic cooperation for the metalation step, which is then followed by a fast ligand rearrangement driven by the coordination preference of the alkali‐metal.