Ternary copper(II) malonato complexes with alkali metals:: K2Cu(mal)2 • 3H2O, Rb2Cu(mal)2 • H2O, Cs2[Cu(H2O)2(mal)2] 2H2O

Reactions of copper(II) chloride and malonic acid with the corresponding alkali metal carbonate in the presence of imidazole in aqueous methanol at pH = 4.2-6.0 yielded K2Cu(mal)(2) center dot 3H(2)O (1), Rb2Cu(mal)(2) center dot H2O (2) and Cs-2[Cu(H2O)(2)(mal)(2)] center dot 2H(2)O (3) (H(2)mal = malonic acid). In 1, octahedrally coordinated Cu atoms are interlinked by malonate anions to generate 2D (2)(infinity)[Cu(mal)(4/2)](2-) anionic layers, between which the K+ cations are sandwiched. The 1D anionic (1)(infinity)[Cu(mal)(mal)(2/2)](2-) chain in 2 is generated from square pyramidally coordinated Cu atoms bridged by malonate anions and is held together by Rb+ cations. The cesium compound consists of Cs+ cations and trans-[Cu(H2O)(2)(mal)(2)](2-) anions with Cu atoms octahedrally coordinated. Diminution in dimensionality from the 2D (2)(infinity)[Cu(mal)(4/2)](2-) anionic layer in 1 through the 1D anionic (1)(infinity)[Cu(mal)(mal)(2/2)](2-) chain in 2 to trans-[Cu(H2O)(2)(mal)(2)](2-) anions in 3 could be attributed to the replacement of the smaller alkali cation by the larger one. IR spectroscopic, magnetic and thermal data are discussed.