Rhenium chloride, decomposition

If a pure product is desired, the tube is sealed off at the first constriction after all of the pentachloride has been decomposed. The product is shaken into bulb D, the tube inclined at an angle of 45°, and the chloride sublimed under reduced pressure at a temperature of 450°C. An asbestos shield placed at the point where the tube enters the furnace will assure condensation of trichloride just beyond the edge of the furnace. The product is sublimed twice, allowed to cool to room temperature, and the tube broken just above and below the point where the trichloride has formed. The dark-red crystalline mass may be powdered, transferred to a weighing bottle, and stored in a desiccator without fear of decomposition. Exposure to direct sunlight should be avoided because of the formation of oxychlorides under such conditions. The yield is usually about 60 to 65 per cent based upon the quantity of rhenium used. In one experiment, 38 g. of twice resublimed rhenium trichloride was prepared with a yield of 68 per cent. 

The method to be described is a significant modification of the synthesis outlined by Hurd and Brimm2 and is derived from the apparatus of Geilmann and Wrigge.6 This procedure allows for the decomposition of large quantities of rhenium(V) chloride in a short period (approximately an hour for a 14-g. sample), in high yield (of the order of 90%) and by an inexperienced person. 

The rhenium (V) chloride can be prepared by standard methods6,7 or purchased commerciallyf and then stored in a screw-capped vial until needed. The movement of the rhe-nium(V) chloride into bulb 1 and subsequent decomposition are accomplished by the heat of a medium Bunsen flame. The temperature is not critical, but a very hot flame should be avoided, as some of the unreacted rhenium(V) chloride will be lost and some decomposition of the nonachlorotrirhenium(III) will occur. The nitrogen flow rate during the decomposition should be two to three bubbles per second. The flow rate can be doubled during the movement of the sample into bulb 1 to aid in the transfer process. 

In a typical run, the decomposition apparatus is flushed with dry nitrogen, and then 14.0 g. of rhenium(V) chloride is transferred to the apparatus by removal of stopper 1 and quick insertion of the opened vial-t Upon heating the tube directly... 

The use of 10-mm. tubing alleviates obstruction of the connecting tubes. Elevation of the connecting tube in the fashion illustrated in Fig. 19 allows condensation of the rhenium (V) chloride vapor in the first bulb and facilitates the decomposition. 

If the procedure and apparatus of Hurd and Brimm are used for the production of the rhenium(V) chloride, the decomposition train, from point A to point B, is attached to the combustion tube in place of tubes D to I. The bottom of the combustion tube and the connecting tube of bulb 1... 

Rhenium pentachloride is obtained as black crystals. The solid melts at 261° with decomposition. It fumes in air, evolving hydrogen chloride and chlorine. 

Rhenium oxide tetrafluoride and rhenium oxide pentafluoride can be used as selective fluorination agents reacting with CH2C12 by chlorine-fluorine exchange with > 90% selectivity and, in the case of ReOF5, subsequent decomposition of the unstable Revu chloride species results in ReOCl4 [348]. 

An example of a chemically induced substitution reaction is represented by the halide removal in MnCl(CO)5 by AICI3 leading to the hexacarbonylmanganese(I) cation. The driving force of this reaction, carried ont at room temperature, is represented by the high affinity of aluminum for chloride. Similarly, the corresponding rhenium(I) derivative [Re(CO)6]AlCLi can be prepared. This complex has considerable stability in that it can be dissolved in water without prompt decomposition (equation 32). 

SAFETY PROFILE Poison by intraperitoneal route. When heated to decomposition it emits toxic fumes of Cl . See also RHENIUM and CHLORIDES. 

Shortly after rhenium was discovered, rhenivim trichloride was prepared by thermal decomposition of rhenium pentachloride (172, 205). Reaction of rhenium trichloride with cesium chloride in hydrochloric acid produced a dark red salt of stoichiometry CsReCli ... 

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