[NA(12-CROWN-4)2]2[NI(SE4)2].DMF - SYNTHESIS, CRYSTAL-STRUCTURE, AND MAGNETIC-BEHAVIOR

The title compound has been prepared from NiCl2 and sodium polyselenide in dimethylformamide solution in the presence of 12-crown-4, forming black crystal needles. They were characterized by an X-rav structure determination, by FIR spectroscopy as well as by the magnetic behaviour. [Na(12-crown-4)2]2[Ni(Se4)2] . DMF crystallizes monoclinically in the space group P2(1), 3650 observed unique reflections, R = 0.046. Lattice dimensions at -80-degrees-C: a = 1020.3(2); b = 1889.5(2); c = 1498.7(3) pm; beta = 108.29(1)-degrees. The compound has an ionic structure, in which the sodium atoms of the [Na(12-crown-4)2]+ cations are coordinated by the oxygen atoms of the crown ether molecules in an antiprismatic fashion. The nickel atom of the anion [Ni(Se4)2]2- is surrounded by four selenium atoms of the tetraselenide chelates in an almost planar environment. The DMF molecules are inserted in the lattice without a bonding interaction. The magnetic susceptibility observed in the temperature interval 4.2 to 330 K can be interpreted by means of a 3E ground term and D2 as local symmetry, which was established by X-ray crystallography.