Synthesis, structure and characterisation of magnesium and calcium β-diketonate complexes [Ca 3 (tmhd) 6 ] and [Ca 2 (tmhd) 4 (EtOH) 2 ](Htmhd = 2,2,6,6-tetramethylheptane-3,5-dione)

The reaction of the oligomeric Group 2 metal ethoxide complexes [{Mg(OEt)2}n] and [{Ca(OEt)2(EtOH)4}n] with 2 equivalents of 2,2,6,6-tetramethylheptane-3,5-dione (Htmhd) yielded the homoleptic β-diketonate compounds [{M(tmhd)2}n](M = Mg 1 or Ca 2). An intermediate en route to complex 2 is the ethanol-solvated species [Ca2(tmhd)4(EtOH)2]3. The reaction of 1 with triglyme (2,5,8,11-tetraoxadodecane, C8H18O4) yielded the air- and moisture-stable derivative [{[Mg(tmhd)2]2(C8H18O4)}n]4. The calcium complexes 2 and 3 were characterised structurally by X-ray crystallography: 2 is the first structurally characterised homoleptic β-diketonate of calcium and has a novel triangular core, with all the calcium ions six-co-ordinate and held together by tmhd ligands in a wide range of co-ordinating modes; 3 has a dimeric structure with both chelating and bridging tmhd ligands and two terminal ethanol molecules.