Tungsten Dichloride Dioxide
Tungsten dichloride dioxide is the chemical compound with the formula WO2Cl2. It is a yellow-colored solid. It is used as a precursor to other tungsten compounds. Like other tungsten halides, WO2Cl2 is sensitive to moisture, undergoing hydrolysis.
WO2Cl2 is prepared by ligand redistribution reaction from tungsten trioxide and tungsten hexachloride:
2 WO3 + WCl6 → 3 WO2Cl2
Using a two-zone tube furnace, a vacuum-sealed tube containing these solids is heated to 350 °C. The yellow product sublimes to the cooler end of the reaction tube. No redox occurs in this process. An alternative route highlights the oxophilicity of tungsten:
WCl6 + 2 O(Si(CH3)3)2 → 3 WO2Cl2 + 4 ClSi(CH3)3
This reaction, like the preceding one, proceeds via the intermediacy of WOCl4.
The compound is a polymer consisting of distorted octahedral W centres. The monomer is characterized by two short W-O distances, typical for a multiple W-O bond, and two long W-O distances more typical of a single or datice W-O bond.
Other tungsten oxy chlorides and related oxy halides
Tungsten forms a number of oxyhalides including WOCl4, WOCl3, WOCl2. The corresponding bromides (WOBr4, WOBr3, WOBr2) are also known as is WO2I2.
WO2Cl2 is a Lewis acid, forming soluble adducts of the type WO2Cl2L2, where L is a donor ligand such as bipyridine and dimethoxyethane. Such complexes often cannot be prepared by depolymerization of the inorganic solid, but are generated in situ from WOCl4.