Earth alkaline tetrathiosquarates:: Syntheses and crystal structures of M9C4S4 • 6 H2O and CaC4S4 • 4 H2O

Concentrated aqueous solutions of magnesium chloride and calcium nitrate, respectively, allow on addition of the potassium salt of tetrathiosquarate, K2C4S4 center dot H2O, the isolation of the earth alkaline salts MgC4S4 center dot(6) H2O (1) and CaC4S4 center dot(4) H2O (2) as orange and red crystals. The crystal structure determinations (1: monoclinic, C2/c, a = 17.2280(7), b = 5.9185(2), c = 13.1480(4) angstrom, beta = 104.730(3)degrees, Z = 4; 2: monoclinic, P2(1)/m, a = 7.8515(3), b = 12.7705(5), c = 10.6010(4) angstrom, beta = 93.228(2)degrees, Z 4) show the presence of C4S42- ions with almost undistorted D-4h symmetry having average C-C and C-S bond lengths of 1.451 angstrom and 1.659 angstrom for land 1.451 angstrom and 1.655 angstrom for 2. The structure of 1 contains discrete, octahedral [Mg(H2O)(6)](2+) complexes. Several O-H center dot center dot center dot center dot O and O-H center dot center dot center dot center dot S bridges with H center dot center dot center dot center dot O and H center dot center dot center dot center dot S distances of less than 2.50 angstrom connect cations and anions. The structure of 2 is built of concatenated, edge-sharing Ca(H2O)(6)S-2 polyhedra. The Ca 21 ions have the coordination number eight, C4S42- act as a chelating ligands towards Ca2+ with Ca-S distances of 3.14 angstrom. The infrared and Raman spectra show bands typical for the molecular building units of the two compounds.