SYNTHESES AND CRYSTAL STRUCTURES OF Di-μ-CHLORO-BIS [DITHIOCYANATOSELENATE(II)] AND Di-μ-BROMO-BIS [DITHIOCYANATOSELENATE(II)] SALTS

Abstract

The compounds were prepared by oxidation of elemental selenium with halogen and addition of |C6H5(CH3)3N|SCN or |(CH3)3NH|SCN. The crystal structures have been determined by X-ray methods. |C6H5(CH3)3N|2|Se2(μ-CI)2(SCN)4| (1) and |C6H5(CH3)3N|2|Se2(μ-Br)2(SCN)4| (2) are isotypic, and so are |(CH3)3NH|2|Se2(μ-CI)2(SCN)4| (3) and |(CH3)3NH|2|Se2(μ-Br)2(SCN)4| (4) The anions are cis-SeX2(SCN)2 squares (X = CI or Br) dimerised by the halogen atoms. The terminal bonds, Se-S, are in the narrow range 2.252(1) - 2.295(2) Å whereas the bridging bonds are in the wider range; Se-CI = 2.885(1) - 3.041(1) Å and Se-Br = 2.971(1) - 3.117(1) Å. In the structures of the isotypic pair 3 and 4 there are N-H…X hydrogen bonds between the (CH3)3NH+cations and the halogen atoms. N…CI = 3.114(3) Å and N…Br = 3.270(3) Å. The bridging bonds of these compounds are increased by an average of 0.087 Å compared to the corresponding bonds of the isotypic pair 1 and 2.