Chalcogenide halides

Copper chalcogenide halides have been prepared by this method for the first time. Tables I and II give the data. The conditions for the preparation of these compounds are listed in Table II. 

The crystals are stable in air. The tellurium compounds are stable in alkaline solutions but decompose in concentrated nitric and sulfuric acid. The selenium compounds decompose readily in alkaline solutions. 

All compounds exhibit a temperature-independent diamagnetism which suggests copper to be monovalent. 

The phases form part of pseudobinary systems between the copper(I) halide and selenium or tellurium, respectively. 

The optical band gaps at room temperature from spectral reflectance measurements5 are 1.4 e.V. for the CuTeX compounds, 1.2 e.V. for the CuTe2X compounds, 1.6 e.V. for CuSe2Cl, and about 2.0 e.V. for CuSe3Br and CuSe3I. Thermal stabilities and crystallographic data are summarized in Table I. 

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Despite the tremendous amount of work on the binary compounds, copper chalcogenide halides were first reported in 1969 (304). Nine compounds of selenium and tellurium have been found, and they are listed in Table 1. Copper sulfide halides are still unknown. 

Fig. 1. Chalcogenide halides in ternary systems having the components the Group IB elements Cu, Ag, and Au, the chalcogens S, Se, and Te, and the halogens Cl, Br, and I, They are indicated as M , Y, and X ", respectively. (Redrawn from A. Rabenau, H. Rau, and G. Rosenstein, J. Less-Common Metals 21, 395 (1970), Fig. 4, p. 401.)...

Due to the high heats of formation of the binary components, these small values seem to be representative for most of the chalcogenide halides discussed in this article. 

Many of the chalcogenide halides mentioned in the different Sections have been obtained in this way. As this method is not yet com-... 

No chalcogenide halides of zinc and cadmium are known. The phase diagrams of CdS-CdCl (7, 198, 210), CdSe-CdCl (220, 314), CdTe-CdClj 368), CdTe-CdBr2 (368), and CdTe-Cdl (323) are of a simple, eutectic type. The system CdS-CdCl shows a range of solubility of CdS in solid CdClj that extends to 5% of CdS at room temperature, and increases to a maximum of 12.5% of CdS at 500°C (7,210). 

The most important mercury chalcogenide halides are of the type HgaYjXj (Y = S, Se, Te X = Cl, Br, I). The corresponding sulfide halides have been known for over 150 years (326). Quite a lot of work has been performed concerning the preparation, structures, electronic and optical properties, and phototropic behavior of these compounds. Mercury chalcogenide halides of other compositions have been mentioned in the literature (141). As most of these compounds are not well established, they will not be treated in detail, with the exception of the latest contributions (see Table V). 

Table VI summarizes the structural data on mercury chalcogenide halides.

The phototropic behavior of the mercury chalcogenide halides has received particular attention. This interest was stimulated by the hope that these materials might allow the preparation of photolayers capable of repeated use for the production of images. 

Chalcogenide Halides of Group IIIB and Lanthanides Bibliography... 

Fig. 16. Preparation of lanthanide chalcogenide halides experimental arrangement.

Very little is known about chalcogenide halides of Group IVB elements. Although the existence of sulfide chlorides (45, 274, 329, 365) and of a selenide chloride (329) of titanium was claimed in early publications, their true composition, and even their existence, remains doubtful. They have usually been obtained by the reaction of titanium chlorides with sulfur and selenium, respectively, or with hydrogen sulfide. The synthesis of a pure compound, TiSClj, was published in 1959 (113). It is an intermediate of the reaction of TiCU with HjS. 

Nothing has thus far been reported concerning chalcogenide halides of other elements of Group IVB. 

Although not yet published in a journal, according to thesis work, the vanadium compounds VSCl (11), VSBr, and VSI (208) seem to exist. Numerous niobium chalcogenide halides have been reported, and among these are the best characterized examples of Group VB (see Table X). Only two tantalum compounds, TaSjCU (361) and TaSCls (13) have thus far been described in the literature. 

Just as, in Group VB, niobium, so, in this Group, molybdenum provides most of the examples of the chalcogenide halides. The occurrence and preparation of such compounds are described in numerous publications. In most cases, they have been obtained as powders, with the composition based on chemical analyses only. The presence of defined, homogeneous phases is, therefore, in many cases doubtful. In addition, some published results are contradictory. A decision is possible where a complete structure analysis has been made. As will be shown later, the formation of metal-metal bonds (so-called clusters), as in the case of niobium, is the most characteristic building-principle. Such clusters... 

In this section, a review is given of preparative work on chalcogenide halides. Table XIII summarizes the proposed compositions thus far described in the literature. 

Metal-Metal Bonds in Molybdenum Chalcogenide Halides... 

Only two compounds, W2S7CI8 (362) and W4S9CI6 (97) are mentioned in the older literature, their true nature being uncertain. The existence of the other compounds in Table XV seems to be well established. All of them were reported by the same group, and, with few exceptions, it remains the only work (57, 58, 131). This example illustrates that the lack of information on chalcogenide halides, especially of transition elements, has its main origin in the lack of systematic investigations. 

All of the known rhenium chalcogenide halides are stable in air. With the exception of RegSgCU, they are insoluble in water, acids, and the common organic solvents. They dissolve readily in hot, 50% KOH (263, 264). Re2S3Cl4 is soluble in water, and ethanol, but insoluble in nonpolar organic solvents. With acids, alkalis, or hot water, hydrolytic decomposition takes place. Alkaline solutions can be oxidized to produce perrhenate compounds. 

The structures of the rhenium chalcogenide halides have not been studied. X-Ray powder data were collected, in order to prove the homogeneity of the compounds 140, 263, 264, 353). 

Only chalcogenide halides of palladium and platinum are mentioned in the literature. 

Thiele and co-workers 389) prepared the only known palladium chalcogenide halides, PdTel and Pd Sels, by hydrothermal synthesis in HI (see Section II,D,2) at 300°C, starting with the elements. Crystalline PdzSelj is better obtained by reaction of Pdl2 with Se and an excess of iodine in a closed ampoule at 250°C (reaction time, 2 days). 

No platinum chalcogenide halides of invariable, exact, stoichiometric compositions are known. 

Thiele and co-workers, who tried to prepare platinum chalcogenide halides, could neither isolate nor identify any pure, homogeneous compound (389). 

The gallium chalcogenide halides are hygroscopic compounds that decompose (without melting) at temperatures between 240 and 380°C to a mixture of chalcogenide and halide (see Table XVIII). The tel-luride halides are yellow, and the other compounds are colorless 160, 165). 

Again, the complete series of InYX compounds (Y = S,Se,Te X = Cl,Br,I) exists. Of the Group IIIA chalcogenide halides, the indium compounds have been the most extensively studied. 

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