Umpolung of an Aliphatic Ketone to a Magnesium Ketone‐1,2‐diide Complex with Vicinal Dianionic Charge

The new β‐diketimine ( iPrDip)nacnacH, HC(iPrCNDip)(2)H, Dip=2,6‐iPr(2)‐C(6)H(3), was converted to the magnesium(I) complex [{(( iPrDip)nacnac)Mg}(2)] and reaction with 2‐adamantanone (OAd) afforded the ketone‐1,2‐diide complex [{(( iPrDip)nacnac)Mg}(2)(μ‐OAd)]. The complex contains the first stable dianion of an aliphatic ketone with an electropositive metal and shows an OAd(2−) unit with long C−O bond and pyramidal carbon centre. DFT studies reveal an anionic charge on both neighbouring C and O atoms. Reductions of aliphatic ketones with magnesium(I) complexes show that these likely proceed via highly reactive dianions and afforded a 1 : 1 mixture of an alkoxide and an enolate when an enolisable ketone was used, and rapid CH activations reactions, e.g., of stabilising ligand moieties, when non‐enolisable ketones were employed.