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

Abstract

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].