Graphit einlagerungsverbindungen mit thallium(III) chlorid

Abstract

Whilst graphite lamellar compounds with AlCl 3, GaCl 3 and InCl 3[1,2] have been extensively studied, the analogous compounds with TlCl 3 have received scant attention although it has been known for many years that TlCl 3 forms intercalation compounds [4,5]. As a part of a systematic investigation of metal halide graphite compounds [8] we studied the system TlCl 3/graphite in detail. TlCl 3-graphite compounds were prepared by heating mixtures of anhydrous TlCl 3 and graphite in sealed tubes. The reaction conditions are summarized in Table 1. In method (I) the tubes had been evacuated, in (II) filled with nitrogen, and in (III) filled with chlorine. In (IV) the tubes contained 2 ml liquid chlorine before sealing. In (V) TlCl instead of TlCl 3 was heated with graphite in chlorine vapor. The samples were washed with methanol saturated with chlorine. Table 1 shows that the preparation of TlCl 3-graphite is best affected by heating up to 150°C in the presence of chlorine. Samples 10 and 11, obtained in inert atmosphere, were only of the 2nd stage type. They were contaminated with TlCl and mixed Tl(I)-Tl(III) chlorides. In this case the chlorine, the presence of which is a basic requirement for intercalation, had been generated by dissociation of TlCl 3. The metal: chlorine ratios in samples having been prepared in chlorine vapor resemble those in AlCl 3-graphite[2]. Accordingly the TlCl 3-graphite can be formulated as C n +[ TlCl 4 −]· XTlCl 3 ( X = 2.5–3). Preparation of TICl 3-graphite (1st stage) was also accomplished by refluxing a solution of TlCl 3 in SOCl 2 or in SO 2Cl 2 with graphite with or without bubbling chlorine through the solution. The results are listed in Table 2. Reaction of graphite with TlCl 3 in nitromethane gave only a 2nd stage compound. The ease of intercalation of TlCl 3 in the three solvents follows the order: SO 2 Cl 2 > SOCl 2 > NM. This is explained with the different Gutmann donor numbers [11] of the solvents. Compound formation was verified by means of X-ray diffraction. The reflexes of a 1st stage compound are listed in Table 5. The identity period along the c-axes is I c = 977 ± 5 pm for the 1st stage, 1312 pm for the 2nd stage, and 1645 pm for the 3rd stage. The intercalated TlCl 3 is considerably more stable than the free TlCl 3 which decomposes above 100°C. No explanation can be given why AlCl 3, GaCl 3, and TlCl 3 form the 1st stage compound whereas with InCl 3 only the 2nd stage could be obtained.