Synthese und Kristallstruktur von Te₄ ²⁺(WCl_6-)₂ / Synthesis and Crystal Structure of Te₄ ²⁺(WCl₆ ^-)₂

Abstract

WCl 6 reacts with two equivalents of tellurium in a sealed evacuated ampoule in the temperature range from 170 to 190 °C to give Te 4 2+ (WCl 6 - ) 2 . Under the same conditions with one equivalent of tellurium WCl 5 yields Te 4 2+ (WCl 6 - ) 2 and WCl 4 . Te 4 (WCl 6 ), formes black crystals, which are sensitive to moist air. It decomposes at temperatures above 300° C to Te and WCl 6 . The crystal structure determination (lattice constants a = 638.9(1), b = 753.2(2), c = 1102.0(5) pm, α = 101.19(2)°, β = 102.85(2)°, γ = 90.21(1)°, Z = 1, triclinic space group P 1̄, 3572 unique reflections for 82 parameters, final R = 0.026) shows the nearly ideal square Te 4 2+ cation with Te–Te distances of 268.8 and 268.7 pm and markedly distorted WCl 6 – octaedra with W–Cl bond length from 227.5 to 237.3 pm. The structure involves interionic Te–Cl contacts as short as 319 pm.