Synthesis and characterization of new alkaline earth metal β-ketoiminates. The first structurally characterized strontium β-ketoiminate

The β-ketoimine MeC(O)CHCMeNH(CH2CH2NiPr2) (HLiPr) was prepared and used for the synthesis of new calcium, strontium and barium β-ketoiminates. These were characterized by elemental analysis, FT-IR, 1H NMR, and, for the strontium bis-N,N-di(isopropyl)aminoethylamino-2-penten-4-onate, by single-crystal X-ray diffraction. Two molecular units having similar conformations are present in the asymmetric unit cell. Both molecules are linear trimers with six-coordinate strontium atoms and bond lengths spreading over the range 2.454(4)–2.511(4) Å and 2.572(6)–2.635(4) Å for the Sr–O and Sr–N linkages, respectively. All ketoiminate ligands are bonded in μ,η2-mode leading to an unprecedented structural motif, with the amine functionality remaining pendant, probably due to the steric hindrance of the diisopropylamino moiety.