Synthesis and characterization of alkaline earth metal trichloroacetates

• Hydrated alkaline earth metal trichloroacetates were synthesized and characterized.
• Single crystal X-ray studies of magnesium, calcium and strontium compounds are reported.
• Six water molecules coordinated to metal ion in the ionic magnesium compound.
• Bridging trichloroacetate ligand form 1D polymers in calcium/strontium compounds.

Alkaline earth metal trichloroacetates M(O2CCCl3)2·nH2O where M = Be (1), n = 4; M = Mg (2), n = 6; M = Ca (3) or Sr (4) or Ba (5), n = 4 were synthesized by reacting BeSO4 with hydrated barium trichloroacetate for 1 and neutralization of respective metal carbonates with trichloroacetic acid for 2–5. The desired products were characterized by elemental analysis, physiochemical studies, FT-IR, 13C NMR and single crystal X-ray studies (in case of 2, 3 and 4). The spectroscopic data reveals bidentate bridging CCl3COO groups and coordinated water molecules in Be(O2CCl3)2·4H2O. The compound 2 crystallizes in triclinic crystal system with space group, P1¯. The crystal structure reveals that magnesium cation is coordinated to six water molecules with regular octahedral geometry. All water molecules are involved in hydrogen bonding with oxygens of CCl3CO2 groups in 2. The compounds 3 and 4 are isostructural and each compound crystallizes in monoclinic crystal system with space group, P21/c, having similar cell parameters and showing the same spatial arrangement. The central metal ions are octacoordinated in 3 and 4. The bridging trichloroacetate ligand in 3 and 4 results in the formation of polymeric chains giving rise to 1D infinite polymers. Similar environment is anticipated around barium cation in 5 as that of metal ion in 3 or 4 on the basis of similar physiochemical and spectroscopic results.

Hydrated alkaline earth metal trichloroacetates have been synthesized. The magnesium cation is fully hydrated having perfect octahedral geometry with no direct interaction with the anion. The calcium and strontium compounds are isostructural with eight coordinated metal ion in a polymeric structure.Figure optionsDownload as PowerPoint slide