Selenium monochloride

Selenium monochloride, Se2Cl2 m.p. —85 C 130°C (decomp.). Reddish liquid, a good chlorinating agent (CI2 plus Se). 

Selenium and precious metals can be removed selectively from the chlorination Hquor by reduction with sulfur dioxide. However, conditions of acidity, temperature, and a rate of reduction must be carefliUy controlled to avoid the formation of selenium monochloride, which reacts with elemental selenium already generated to form a tar-like substance. This tar gradually hardens to form an intractable mass which must be chipped from the reactor. Under proper conditions of precipitation, a selenium/precious metals product substantially free of other impurities can be obtained. Selenium can be recovered in a pure state by vacuum distillation, leaving behind a precious metals residue. 

Selenium-containing donors, synthesis and manufacture of, 22 212 Selenium dichloride, 22 75t Selenium diethyldithiocarbamate, 22 73t Selenium dioxide, 22 73t, 75t, 88 toxicify of, 22 95 Selenium disulfide, 22 73t Selenium hexafluoride, 22 75t, 87 toxicify of, 22 96 Selenium hypofluorite, 22 75t Selenium iodides, 22 87 Selenium monobromide, 22 75t, 88 Selenium monochloride, 22 75t, 87 in selenium recovery, 22 85 Selenium monoxide, 22 88 Selenium oxidation, selenium recovery via, 22 81-83... 

Scheme 73 shows the reaction of l-hydroxyethyl-6-aminouracil with sulfur monochloride giving the [l,2,5]thiadia-zolo[3,4-,7lpyrimidine-A -oxide in good yield <2005RJC493>. An analogous transformation with selenium monochloride was reported in the same paper, and is given in Scheme 77. 

Yavolovskii et al. have reported the synthesis of several [l,2,5]selenadiazolo[3,4-rf pyrimidines (e.g., Scheme 77) and [l,2,5]thiadiazolo[3,4-<71pyrimidines (e.g., Scheme 73) using respective sulfur and selenium monochloride reactions with nitrosopyrimidinamines <2005RJC493>. 

The ease with which selenium combines with many other elements to form binary compounds has already been mentioned (p. 299). Only one compound with hydrogen is known, but a series of polyselenides of the alkali metals corresponding to the polysulphides has been obtained. Selenium forms a hexafluoride, SeFG, but no other hexalialide has been isolated. The tetrahalides arc the most stable, and mixed chloro-bromides of quadrivalent selenium, SeCl Br, are known. Selenium monochloride, SeaCla, and selenium monobromide, Se2Br2, also exist as comparatively stable liquids at ordinary temperatures. No compound of selenium and iodine is known. Selenium oxychloride, SeOCl2, and the oxybromide, SeOBr2, are extremely reactive and useful compounds. 

Selenium Monochloride, Se2Cla.—This chloride is most easily obtained by the action of chlorine on heated selenium, but it is always accompanied by a certain quantity of the more stable tetrachloride which, however, is less volatile.2 It may be prepared by saturating with chlorine a suspension of selenium or a selenium mineral in carbon tetrachloride.3 The selenium monoehloride is soluble in carbon tetrachloride, whilst the chlorides of other elements present are insoluble. The monochloride is therefore obtained by evaporation of the solvent after filtration. 

Selenium monochloride behaves as a strong chlorinating agent towards metals, metallic selenides and hydrocarbons.3 Phosphorus displaces selenium from the chloride with formation of phosphorus trichloride.4 Chlorine converts it into the tetrachloride. 

By the action of excess of chlorine on selenium or on selenium monochloride in carbon tetrachloride solution the tetrachloride is insoluble and precipitates as rapidly as it is formed as a white powder ... 

Selenium Trichlorobromide, SeCl3Br, Selenium Dichlorodi-bromide, SeCl2Br2, and Selenium Chlorotribromide, SeClBr3, have been described as yellow crystalline compounds, the first being obtained by the action of chlorine on selenium monobromide and the last by the action of bromine on selenium monochloride, while the intermediate body has been obtained by the action of chlorine on a mixture of selenium tetrabromide and monobromide.3... 

Sulphur, selenium and tellurium are soluble in the oxychloride in the cold, but on heating, reaction may take place. Sulphur interacts to form selenium monochloride, sulphur monochloride and sulphur dioxide. Tellurium is converted into its tetrachloride. Both red and yellow phosphorus react violently with the oxychloride, forming phosphorus pentoxide and selenium mono- and tetra-chlorides. Carbon, silicon and boron are unattacked. 

Selenium and tellurium are attacked at room temperature, arsenic being liberated and selenium monochloride or tellurium tetrachloride formed.6... 

These compounds are produced by the interaction of selenium monochloride, Se2Cl2, and the unsaturated hydrocarbon.2 The complete... 

The production of these compounds is considered to be evidence of the unsymmetrical structure, Se SeCl2, for selenium monochloride. 

The formation of diselenium fo sacetylacetone from selenium monochloride and copper acetylacetone in molecular proportions may be expressed as follows ... 

Selenium monochloride is required for this method, and is prepared by dissolving the requisite amount of selenium in selenium 1 Morgan, Drew and Barker, loc. cit. 

Selenium monochloride reacts with antipyrine1 as though it were 66 selenoselenyl dichloride, Se SeCl2. When a concentrated solution of the chloride in carbon tetrachloride is added to a concentrated solution of antipyrine in chloroform at 0° C., diantipyryl diselenide (or selenoselenide) is deposited,... 

Treatment of disilametallacycles 32a and 32b with selenium monochloride at —78°C affords the dithiadiselenadisilacyclohexane 33c in 90-100% yield. Compound 33c is stable at room temperature, but decomposes under irradiation, liberating selenium as a red precipitate to yield dithiaselenadisilacyclopentane. The reaction of 32a with dichlorodiphenylgermane gives a corresponding dithiadisilagermacyclopentane... 

Selenium dioxide and tellurium dioxide react with 1,3-diketone dioximes unsubstituted at position 2, to give compounds (198) and (199), respectively. Selenium monochloride and tellurium tetrachloride give identical results (Scheme 88) (49JCS274, 79BSF(2)199). 

The use of selenium monochloride in reaction with 6-amino-1,4-diazepinium perchlorate led to an isoselenazole condensed with a diazepine ring (Scheme 48) <1996KGS997>. 

The reaction of selenium monochloride with propylene was also shown to give the two isomeric bis(/ -chloroalkyl)selenides (86) and (87) via the episelenium intermediate (85) (Scheme 17) <69JOC4003>. As compared to the reaction of propylene with sulfur monochloride, the isomer distribution (86) and (87) remains essentially identical to that observed in the sulfur case within experimental limits. On the other hand, the reaction of 1,5-cyclooctadiene (88) with selenium monochloride was reported to result in the formation of 2,6-dichloro-9-seleno-bicyclo[3.3.1]nonane (89), which can be transformed into the starting cyclooctadiene (88) by treatment with potassium cyanide or lithium aluminum hydride via the episelenium intermediate (90) and episelenide (91) as shown in Scheme 18 <69JOC4003>. 

Since the last review of this system only one 1,2,5-selenadiazole without a fused ring has been reported. When a 1,2-diketone dioxime is treated with selenium monochloride in dimethylformamide, the 1,2,5-selenadiazole N-oxide (200) is formed [Eq. (48)]. 

Benzoselenadiazole-N-oxide (210) was prepared by Pedersen through the reaction of o-benzoquinone dioxime (209) with selenium monochloride [Eq. (50)]. 

The synthesis of only two selenadiazine derivatives have been described. The 6-chloromethyldihydro(2//)-l,2,4-selenadiazine-3(4H)-thione (231) was prepared by Apostolescu through treatment of allylthiourea with selenium monochloride. [Eq. (54)]. The NMR spectrum of 231 and the activation energy for the decomposition and dehydration of its dihydrate have been studied. 

Wolesensky J. Am. Chem. Soc. 291 215 (1907) by the action of dry ammonia on a dilute soln of selenium monochloride in carbon disulfide van Valkenburg, Bailar ibid. 47, 2134 (1925) by the action of dry ammonia on diethyl Selenite or dimethyl selenite dissolved in benzene and washing with potassium cyanide Strecker Schwarzkopf Z, Anorg. Chem. 221, 193 (1934) by reacting anhydr, liquid ammonia with selenium dioxide Jander Doetsch, Ber. 93, 561 (1960), Crystal structure Baernighausen et al. Acta Cryst 15 615 (1962) 21, 571 (1966),... 

Older names selenium monochloride and selenous chloride. 

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