Synthese und Kristallstruktur von Te4 2+(MoOCl4)2 2- / Synthesis and Crystal Structure of Te4 2+(MoOCl4)2 2-

MoOCl4 reacts with two equivalents of tellurium in a sealed evacuated ampoule at 250 C to give Te4 2+(MoOCl4)2 2- in quantitative yield. Te4(MoOCl4)2 forms black crystals which rapidly decompose in moist air. The crystal structure determination (lattice constants a = 1192.9(3), b = 683.7(2), c= 1049.8(2) pm, β = 90.08(2) , Ζ = 2, monoclinic space group P21/n, 1907 unique reflections for 73 parameters, final R = 0.013) shows, that Te4(MoOCl4)2 consists of nearly ideal square Te4 2+ cations with Te–Te distances of 269.1 and 269.9 pm and dimeric (MoOCl4)2 2- anions, in which Mo atoms are linked by asymmetric chloro bridges (Mo–Cl = 278.3 and 241.0 pm). The oxygen ligand (Mo–O = 164.7 pm) is located in the trans position to the longer Mo–Cl bond. Close contacts as short as 315.8 pm between chlorine and oxygen to the cation show considerable anion-cation charge-transfer interaction.