Synthesis, structure and electrochemical properties of metal malonate Na2M(H2C3O4)2·nH2O (n = 0, 2) compounds and comparison with oxalate Na2M2(C2O4)3·2H2O compounds

• We prepare new malonate compounds by hydrothermal method.
• Na2M(H2C3O4)2·2H2O malonate compounds crystallize in an orthorhombic structure.
• The removal/uptake of water from the malonate members was found to be reversible.
• We report the crystal structure of Na2Mn(H2C3O4)2 from X-rays powder diffraction.

Oxalate and malonate based compounds were prepared by hydrothermal method. The crystal structure of oxalate compounds of formulae Na2M2(C2O4)3·2H2O (with M = Mn, Fe, Co, Ni and Mg) was confirmed from single crystal diffraction. We report here a series of new malonate compounds Na2M(H2C3O4)2·2H2O with M = Mn, Fe, Co, Ni, Zn and Mg, whose structure, thermal and electrochemical performances are presented. Metal malonate compounds crystallize in an orthorhombic structure built upon MO6 octahedra connected with malonate groups to form a layered structure. The removal/uptake of water from the malonate members was found to be reversible and the crystal structure of the anhydrous Na2Mn(H2C3O4)2 is solved from powder diffraction and presents similarities with the hydrated phase. However, sodium 3d-metal oxalates/malonates compounds show poor electrochemical activity.

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