S. S. BATSANOV, N. A. SHESTAKOVA, L. A. KHRIPIN

TIN CHALCOGENOCHLORIDES

(Presented by Academician I. I. Chernyaev, 3 VI 1963)

1. Tin salts with mixed anions have been known for a long time—the mixed halides SnCl₂Br₂, SnCl₂J₂, as well as the oxychloride SnOCl₂, were synthesized as early as the last century (¹–³), and all these compounds were obtained by the direct action of oxidizing agents on crystalline salts of divalent tin. Owing to the high electronegativity of tin \((\chi = 1.7\) for Snᴵᴵ), the chemical bonds in a molecule, for example SnCl₂, have 30% ionicity (see (⁴), p. 167). In crystalline SnCl₂, assuming c.n. = 9 (⁵), the ionicity of the Sn—Cl bond will be equal to 67%; hence the effective coordination charge of tin will be equal to (see (⁴), pp. 104–106):

\[ z = -0.33 \cdot 9 + 2 = -0.97e. \]

This latter circumstance, in accordance with the criterion proposed by us (⁶,⁷), accounts for the possibility of direct oxidation of the metal without displacement of anions according to the reaction:

\[ 2\mathrm{SnCl}_2 + \mathrm{Y}_2 = 2\mathrm{SnCl}_2\mathrm{Y}, \]

where Y is, for example, oxygen.

It is obvious that analogous reactions can also be carried out with chalcogens, which is the subject of the present work.

1. The addition of sulfur to SnCl₂ was carried out by melting mixtures of SnCl₂ + S and SnCl₂ + 2S in sealed ampoules at a temperature of 140–150° for 8 hr.

As a result of the reaction, a liquid appeared among the contents of the ampoules; it fumed on contact with air (like tin tetrachloride or sulfur); this liquid was removed in a vacuum desiccator. The remaining dark-gray powder did not dissolve either in cold or in hot water, nor in hydrochloric and sulfuric acids or toluene, but dissolved slowly in nitric acid and more rapidly in alkalis. This behavior distinguishes the resulting substance from the initial reagents, as well as from SnCl₄ and SnS₂.

The product obtained was analyzed for tin by dissolving a 0.15–0.2 g sample in nitric acid, precipitating tin hydroxide with ammonia, and subsequently igniting at 900° to SnO₂; it was analyzed for chlorine by precipitation as AgCl from a nitric-acid solution, and for sulfur by precipitation of BaSO₄ from a solution of the fusion of the sample with sodium peroxide. The analytical results correspond to the formula Sn₂Cl₂S₃.

Found, %: Sn 58.82; Cl 17.59; S 22.11.
Calculated, %: Sn 58.69; Cl 17.53; S 23.78.

Thus, the reaction of sulfur addition to tin dichloride proceeds either according to the scheme:

\[ 3\mathrm{SnCl}_2 + 3\mathrm{S} = \mathrm{Sn}_2\mathrm{Cl}_2\mathrm{S}_3 + \mathrm{SnCl}_4, \]

or

\[ 2\mathrm{SnCl}_2 + 4\mathrm{S} = \mathrm{Sn}_2\mathrm{Cl}_2\mathrm{S}_3 + \mathrm{SCl}_2. \]

The formation of a substance of one and the same composition in the interaction of SnCl₂, regardless of the amount of sulfur, is sufficient grounds for considering Sn₂Cl₂S₃ an individual compound. To confirm this conclusion, we carried out a physicochemical study of tin sulfochloride.

The density of Sn₂Cl₂S₃ is 3.48 g/cm³; moreover, it did not change upon heating the sample at a temperature of 140° for another 12 hr, which indicates completion of the reaction.

The X-ray diffraction pattern of this compound is given in Table 1 together with the X-ray diffraction pattern of SnCl₂; they were obtained in a camera of 57 mm diameter, with copper radiation.

Table 1

X-ray constants of tin chloride and chalcogenochlorides

Comparison of the X-ray patterns of Sn₂Cl₂S₃ with SnCl₂, and also with the values of \(d/n\) for SnS₂ (8), shows that more than one third of the lines (and, moreover, the most intense ones) of tin sulfochloride are specific; half of the lines, either in magnitude or in magnitude and intensity, are close to the values for SnCl₂, while one quarter of the lines resemble the X-ray pattern of SnS₂, including four lines characteristic simultaneously of the X-ray patterns of SnCl₂ and SnS₂. There are no sulfur lines in the X-ray pattern. Hence it may be concluded that the newly obtained compound has certain structural features in common with the starting substance and with tin disulfide.

The thermogram of the sulfochloride, recorded on a Kurnakov pyrometer in the temperature range 25–800° at a heating rate of 15°/min, is reproduced in Fig. 1 together with the curve for SnCl₂. The figure clearly shows the individuality of the product obtained.

The reactions of interaction of SnCl₂ with selenium and tellurium were likewise carried out by fusion (1 : 1 mixtures) in sealed ampoules for 20 hr at temperatures of 240 and 480°, respectively. The reaction products were dried in a vacuum oven and then analyzed (in the same way as the sulfochloride).

The results of the analysis lead to the following formulas:

\[ \begin{array}{rll} \mathrm{Sn_3Cl_2Se_5} & \text{Found \%:} & \mathrm{Sn}\ 40.35;\ \mathrm{Cl}\ 8.68;\ \mathrm{Se}\ 47.54. \\ & \text{Calculated \%:} & \mathrm{Sn}\ 43.33;\ \mathrm{Cl}\ 8.63;\ \mathrm{Se}\ 48.04. \\ \mathrm{Sn_4Cl_2Te_7} & \text{Found \%:} & \mathrm{Cl}\ 5.37;\ \mathrm{Te}\ 62.24. \\ & \text{Calculated \%:} & \mathrm{Cl}\ 4.93;\ \mathrm{Te}\ 62.08. \end{array} \]

The chemical properties of the seleno- and tellurochlorides are qualitatively similar to the properties of tin sulfochloride, except that Sn₄Cl₂Te₇

dissolves in alkalis only on heating and with liberation of tellurium. The density of $\mathrm{Sn_3Cl_2Se_5}$ is 5.32; that of $\mathrm{Sn_4Cl_2Te_7}$ is 6.15 g/cm$^3$.

Thermograms of the seleno- and tellurochlorides, reproduced in Fig. 1, show complete specificity. The X-ray patterns of these substances are given in Table 1, from which it is seen that approximately $^{2}/_{5}$ of all their lines are specific, while the rest are close in magnitude or in intensity to the lines of $\mathrm{SnCl_2}$; there are no Se and Te lines.

Fig. 1

The totality of the physical and chemical characteristics of these substances unambiguously indicates their individuality.

In conclusion, it is useful to compare the compositions of the oxy- and chalcogenochlorides of tin, which change in a quite regular manner:

\[ \mathrm{SnCl_2O \rightarrow Sn_2Cl_2S_3 \rightarrow Sn_3Cl_2Se_5 \rightarrow} \]

\[ \mathrm{\rightarrow Sn_4Cl_2Te_7,} \]

namely, on going from O to Te, the compositions of the mixed salts successively change by $\mathrm{SnY_2}$.

In other words, the compounds synthesized by us may be represented as derivatives of the $\mathrm{SnY_2}$ structure, in which, for $Y = O$, every second $Y$ is replaced by $2\mathrm{Cl}$; for $Y = S$, $^{1}/_{4}$ of all $Y$ is replaced; for $Y = Se$, $^{1}/_{6}$ of all $Y$ is replaced; and for $Y = Te$, $^{1}/_{8}$ of all $Y$ is replaced. Naturally, it should be assumed that such a regularity is due to the requirements of the densest packing of atoms in the crystal structures of tin chalcogenochlorides.

To confirm the considerations expressed, we shall give some qualitative results of analysis of the X-ray patterns of tin sulfo-, seleno-, and tellurochlorides. Thus, in the case of $\mathrm{Sn_2Cl_2S_3}$, of 14 lines close to the lines of $\mathrm{SnCl_2}$, $^{2}/_{3}$ are also close in intensity; in the case of $\mathrm{Sn_3Cl_2Se_5}$, of 18 lines only $^{1}/_{3}$ are close in intensity, while for $\mathrm{Sn_4Cl_2Te_7}$, of 17 lines close to the lines of $\mathrm{SnCl_2}$, not one is close in intensity. Thus, in going from S to Te, the structure of the chalcogenochlorides increasingly departs from the structure of stannous chloride.

$\mathrm{Sn_2Cl_2S_3}$, $\mathrm{Sn_3Cl_2Se_5}$, and $\mathrm{Sn_4Cl_2Te_7}$ have been synthesized; their physicochemical properties have been studied—their thermograms and X-ray patterns have been taken, their densities measured, and the behavior of the chalcogenochlorides toward various media investigated.

Institute of Inorganic Chemistry
Siberian Branch of the Academy of Sciences of the USSR

Received
30 V 1963

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