Solvent-free and TMEDA-solvated mixed alkali metal-magnesium tris-diisopropylamides

A trio of heterobimetallic tris-diisopropylamides, the solvent-free potassium-magnesium amide [{KMg(NiPr2)(3)}(infinity)], its TMEDA solvate [KMg(NiPr2)(3).TMEDA] and the sodium congener [NaMg(NjPr(2))(3).TMEDA] has been synthesised by mixing the appropriate metal alkyl reagents with three molar equivalents of diisopropylamine in a hydrocarbon medium, to which, in the last two cases, TMEDA is added. All three amides have been successfully crystallographically characterised by X-ray diffraction studies. Representing the first pure s-block mixed-metal diisopropylamide free of solvent molecules or other stabilising anionic co-ligands, the first compound adopts an infinite spiral chain of ...K-(mu-N)(2)-Mg-N... links, the metal-N framework of which is supported by agostic K...C intra-dinuclear and inter-dinuclear contacts. The dinuclear tris-amido motif is maintained in both TMEDA complexes, the metal-N cores of which are essentially isostructural, but the presence of the chelating diamine blocks the propagating terminal site on the alkali metal and so gives rise to discrete molecular structures

Synthesis of the mixed lithium-potassium-(bis)magnesium N-metallated / N, C-dimetallated amide [Li2K2Mg4 {But(Me3Si)N} 4{But[Me2(H2C)Si]N}4] : an inverse crown molecule with an atomless cavity

Unlike previous members of the inverse crown family, which are heterobimetallic and have cationic rings surrounding anionic cores, the title compound is heterotrimetallic and its "guest" anion is intramolecularly stitched into the complex fused-ring structure of its cationic "host"