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

The new beta-diketimine (iPrDip)nacnacH, HC(iPrCNDip)(2)H, Dip=2,6-iPr(2)-C6H3, 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)(mu-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.

Automated summary

The study presents a new magnesium complex containing a stable dianion of an aliphatic ketone. The complex undergoes reduction reactions or CH activation reactions when reacted with aliphatic ketones.