Preparation, crystal structures, and thermal studies of alkaline earth nitrocarboxylates

Abstract

The preparation, crystal structures, and thermal properties of [Ca(pyr)(2)(4-nba)(2)](n)(1)(pyr = pyrazole; 4-nba = 4-nitrobenzoate) {[Ca(H2O)(2)(3-npth)].H2O}(n) (2) (3-npth = 3-nitrophthalate), [Mg(H2O)(5)(3-npth)].2H(2)O (3), and [Mg(H2O)(4)(2-nba)(2)] (4) (2-nba = 2-nitrobenzoate) are reported. The anhydrous Ca-II compound 1 and the diaqua Ca-II-3-nitrophthalate monohydrate 2 are one-dimensional coordination polymers containing a hexacoordinate Ca-II ion located on a center of inversion in 1 and a heptacoordinated Ca-II ion in 2. In 1, the 4-nitrobenzoate moiety acts as a mu(2)-bridging bidentate ligand, whereas the 3-nitrophthalate anion exhibits a mu(3)-bridging pentadentate coordination mode in 2. The hexacoordinate Mg-II-containing compounds 3 and 4 do not contain a [Mg(H2O)(6)](2+) unit and the central Mg-II ion is coordinated to at least one monodentate carboxylate unit namely the monodentate 3-npth molecule in 3 and two trans monodentate 2-nba molecules in 4. Hydrogen bonding between the lattice water molecules results in the formation of a water dimer in 3. A comparative study of 17 alkaline earth nitrocarboxylates is described.