Tungsten Pentachloride
Introduction
Name: Tungsten Pentachloride
CAS: 13470-14-9
Formula: WCl5
Molecular weight：361.2
Melting Point: 243℃
Boiling Point: 275.6℃
Nature
Tungsten pentachloride is a flash dark green crystal, which is easily decomposed when exposed to the air. It is very sensitive to moisture and water, green surface film will generated when placed in the air; besides, it will decompose in the water to get the W 2 O 5. When heated in air, it generates WOCl 4. It can decompose in most polar solvents; however, it also slightly soluble in non-polar solvents, such as carbon disulfide. Its vapor appears in light blue-green.
Tungsten pentachloride can be dissolved in acetonitrile, benzene, chloroform, carbon disulfide and other organic solvents; easy to form amine compound with the primary amine. It will carry out hydrolysis in water to produce blue tungsten oxide; also generate WOCl 4 in the air when heated.
Preparation method
It can be obtained by using red phosphorus or hydrogen to reduce tungsten hexachlorideat at 250~280℃ and 380~400℃; also, it can generate by the disproportionation reaction of tungsten tetrachloride; and as well as the red-hot decomposition of trichloride tungsten.
Method 1: 2WCl 6 + H2 → 2WCl5 + 2HCl
Heating the tungsten hexachloride at 410~425℃ in a quartz tube to get a reduction while introducing hydrogen. The products should be purified by sublimation in a stream of nitrogen and then stored in a sealed tube, because WCLO, WCl 4 and WCl 2 generated at the same time.
Method 2: 2WCl6 + C2Cl4 → 2WCl5 + C2Cl6
Using the same equipment of preparing tungsten tetrachloride, the yield of WCl5 will be higher if the reaction conditions changed. 4~7g of tungsten hexachloride and 25mL of tetrachlorethylene are carried out a oil bath at 100℃ for 24 hours with the 100W bulbs irradiating. The initially red-brown solution is changed to blue-green, and resulted in fine dark powder at the end of the reaction.
The steps are exactly the same as in the preparation of tungsten tetrachloride; however it can not contact with the air and should be sufficiently dried saved, because the product is highly hygroscopic. In the purifying process, the product can be placed in a hard glass tube to make it staying in the airflow of vacuum, nitrogen or carbon dioxide, the glass tube is placed in an electric furnace and form temperature gradient of 180℃~25℃, then tungsten pentachloride will be the first precipitated, and tungsten tetrachloride turns to black and eventually survived. Finally, the products should be removed with the exiting of inert gas and stored in the absence of air.