Synthesis and Properties of Tris[Bis(2-Hydroxy-Ethyl)Dithiocarbamato]Haloditellurium(II) (Halo = Scn-, Br-, I-) and the Crystal-Structure of the Thiocyanato-S Complex, [Te-2((Hoch2ch2)2ncs2)3scn]

Abstract

Mixed halo dithiocarbamate complexes of Te^II were synthesized for the first time. Complexes of the general formula Te₂L₃X (X = SCN^-, Br^- and I^-) were obtained from the parent compound TeL₂[L = bis (2- hydroxyethyl ) dithiocarbamate ] and potassium thiocyanate or halides in acetic acid medium. Their chemical and physical properties were studied and the crystal structure of the thiocyanate compound determined. The crystals of the thiocyanate complex are monoclinic, with space group P2₁/n, a 14.056(3), b 9.599(2), c 22.519(6) Ǻ, β 105.71(2)°, V 2924.8 Ǻ³, Z 4, F(000) 1672, the final R and R_w values being 0.042 and 0.041 respectively for 1209 unique reflections. Many novel aspects were observed in the structure. The two tellurium atoms display entirely different coordinations. One of them, namely, Te(1), has two unequal bidentate dithiocarbamate groups chelated to it in planar-trapezoidal coordination similar to the geometry found in the parent TeL₂ complex. It is also linked to Te(2) by a short contact [3.221(3)Ǻ] to complete the fifth coordination. The second tellurium atom Te(2) exhibits trapezoidal four-coordination with an equal bidentate dithiocarbamate group, an S-bonded thiocyanate group, and interestingly with Te(1). The Te(1)-Te(2) axis is inclined with respect to the Te(1)-S(1)-S(2)-S(3)- S(4) plane (trapezoid) by 67.6°.