Selenium IV Chloride

Submitted by Henry G. Nowak and John F. Suttle Checked by William E. Parker and Jacob Kleinberg  

Selenium(IV) chloride has been prepared by direct chlorination of either elemental selenium or selenium(I) chloride (diselenium dichloride), Se2Cl2.1,2 Elemental selenium is first converted to selenium(I) chloride, which then combines with more chlorine to give selenium(IV) chloride. 

An all-pyrex apparatus of the type shown in Fig. 12 is constructed. Bulb A, of 125 ml. capacity, has sealed to it 

A weighed ampoule is broken in a closed flask containing aqueous sodium hydroxide solution. Chlorine is determined by the Mohr method, and selenium is weighed as the metal after reducing an aliquot with hydroxylammo- 

Selenium(IV) chloride is a bright yellow, crystalline solid which sublimes at 196°. The solid contains [SeCl3]+ and Cl- groups.3 In the vapor state, it is completely dissociated into selenium(II) chloride and chlorine, the vapor density being half that for selenium(IV) chloride, and the vapor pressure of the solid being depressed in the presence of excess chlorine.2 The heat of formation of the solid is 46.12 kcal./mol at 18°. Selenium(IV) chloride hydrolyzes readily in moist air but is stable indefinitely in an atmosphere of dry chlorine. With anhydrous aluminum chloride it forms an addition compound which has the structure [SeCUJ+lAlCU]-.4 

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Aluminum acetylacetonate, 2 25 Aluminum bromide, 3 30 of high purity, 3 33 Aluminum chloride, compound with selenium(IV) chloride, 5 127 Aluminum complex compounds, anions, oxalato, K3[A1(Cs04)3]-3HsO, 1 36... 

Samarium (III) nitrate, analysis of anhydrous, 6 41 Selenic acid, crystalline, 3 137 Selenides, precipitation of pure metallic, from solutions of hydrogen selenide, 2 185 Selenium, red and gray, 1 119 Selenium (II) chloride, formation of, by selenium(IV) chloride, 6 127... 

Selenium(IV) chloride, 5 125 analysis of, 6 126 compound with aluminum chloride, 5 127... 

The addition of selenium tetrachloride to two equivalents of a symmetrical alkene can theoretically result in the formation of ten stereoisomers of the bis-adduct two me so forms and four diastereomeric pairs. It was, however, found that the addition of selenium tetrachloride to two equivalents of (Z)-2-butene in dichloromethaiie at 25 °C gives only two products, bis(l R, 2R )-4 and [(12 , 2J XlS, 2S )]-4 in approximately 90% and 10% yields, respectively83. The reaction of selenium(IV) chloride with ( )-2-butene under the same conditions also affords two different products namely a mixture of bis(lS, 2/ )-4 and [(lS, 2/ )(l/ , ,2S )]-4in 90% and 10% yields, respectively83. 

Addition of Selenium(IV) Chloride to Alkenes General Procedure83 ... 

Fig. 2. Comparison of the molecular structures of the tellurium(IV) fluoride, chloride, and iodide types in the solid state. The selenium(IV) chlorides and bromides as well as tellurium(IV) bromide and one of the five forms of tellurium(lV) iodide are isostructural to the cubane-like Te4Cli6 molecules (244).

The formation of aqueous selenium(IV)-chloride complexes in solutions of high hydrochloric acid concentration has been studied by Milne and LaHaie [79M1L/HA1] and by Milne [87MIL]. The studies are based on Raman spectroscopic measurements and, in [79MIL/HAI], the occurrence of bands at 152, 265, and 336 cm were interpreted as originating from a species SeOCl2(aq). The intensities of these bands were significant at HCl concentrations of 7 M and above, and were used to deduce an equilibrium constant for the reaction... 

To minimize entrainment of sublimed selenium (IV) chloride, a flow rate not in excess of 1 or 2 bubbles of chlorine every 2 seconds through a 6-mm. orifice in the exhaust line is maintained. 

AlCl4] [SeCl3]+ Aluminum chloride compound, with selenium-(IV) chloride, 5 127 AlCs(S04)2-12H20 Cesium alum, 4 8... 

SeCl2 Selenium (II) chloride, 5 127 [SeCl3]+[AlCl4]- Selenium (IV) chloride, compound with aluminum chloride, 6 127 SeCl4 Selenium (IV) chloride, 5 125, 126... 

Selenium(IV) oxychloride was syntheazed first by Weber in 1859 by heating together the vapors of selenium(IV) oxide and selenium (IV) chloride. It was later prepared by Michaelis by the interaction of selenium(IV) oxide and phosphorus(V) chloride. Cameron and Macallam allowed a mixture of selenium(IV) oxide and sodium chloride to interact and obtained sodium selenite and selenium(IV) oxychloride. 

The classical researches of Victor Lenher on selenium(IV) oxychloride (reviewed by Smith ) were begun about 1919 at the University of Wisconsin. Lenher suggested the following practical laboratory methods for the preparation of selenium(IV) oxychloride (1) union of selenium(IV) oxide and selenium(IV) chloride (2) partial hydrolysis of sele-nium(IV) chloride, and (3) dehydration of Se02 2HCl (dichloroselenious acid, H2Se02Cl2). ... 

The dehydrated product is chlorinated at this pmnt to convert any selenium(II) chloride that may be present into selenium(IV) chloride. The latter will react with sele-... 

Tellurium(IV) chloride is most conveniently prepared by the direct union of the elements, but is also obtainable by the reaction of elemental tellurium or tellurium(IV) oxide with various anhydrous chlorides such as sulfur chloride, iron(III) chloride, and selenium(IV) chloride. " Tellurium of 99.96 per cent purity and chlorine of similar purity are easily obtainable. The absence of other reaction products in the direct union simplifies the purification problem. 

On the other hand selenium(IV) chloride, tellurium(IV) chloride andphosphorus(V) chloride act as bases... 

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