Unusual trimetallic magnesium cations and adamantyl anions of aluminum and gallium

Reaction of adamantylmagnesium bromide, AdaMgBr (Ada=C10H15) with aluminum(III) chloride, gallium(III) chloride, dimethylgallium chloride, or dimethylaluminum chloride gives [Mg3BrCl3(OEt)(OEt2)6][Ada3AlBr] (I), [Mg3Br2Cl3(OEt2)6][Ada2GaBr2] (II), [Mg3Br4(OEt)(OEt2)6][Ada2GaMe2] (III), and [Mg3Br4(OEt)(OEt2)6][Ada2AlMe2] (IV), respectively. These ionic compounds, characterized by 1H- and 13C-NMR, elemental analyses, and single crystal X-ray diffraction, contain trimetallic magnesium cations with each alkaline earth metal residing in a distorted octahedral environment. The aluminum and gallium atoms in the adamantyl-based anions reside in distorted tetrahedral environments. These substances are the first examples of adamantyl-based Group 13 organometallic compounds.