Tungsten hexafluoride

Chemical formula is WF6. The molecular weight is 297.84. It is colorless gas or light yellow liquid. It has strong irritant. It is poisonous, its toxicity is similar with fluorine. When the temperature is very low, it is white solid. It is soluble in organic solvents and then generate a special color. When meet water, it can decompose. In the air, it can decompose with strong smoke by moisture, and generate yellow tungstate or tungsten trioxide. Chemical properties is lively. And almost all metals (except gold and platinum) can react with it. It is also corrosive for nickel, monel and stainless steel, but Ni and stainless steel have resistance for corrosion. When dry, it is less corrosive to glass, while in moisture, it is able to react quickly. It can react strong with gaseous ammonia. Ammonia or an alkali can absorb it . It can generate double salt with alkali metal fluoride. It is soluble in benzene and other organic solvents.
[Density] 3.44×103kg/m3 (15℃, liquid)
[Melting point] 2.5℃ (5.6 × 104 Pa)
[Boiling point] 17.5℃
[Critical temperature] 171℃
[Critical pressure] 445.8kPa
[Preparation method] Metal tungsten powder and elemental fluorine can react to synthesize it directly.
[Application] (1) It is strong fluorinating agent, it can synthesize tungsten film in vapor deposition method. (2) it is used in the microelectronics industry for chemical vapor deposited tungsten silicide or tungsten, to produce a low resistance, a high melting point interconnects.

Figure 1 shows the molecular structure of tungsten hexafluoride.

When meet moisture, air or water, it will decompose and emit toxic and corrosive hydrogen fluoride fumes. It can cause very serious burns for skin, eyes, mucous membranes. When high concentrations expose, it can cause nausea, vomiting, abdominal pain, convulsions, kidney damage.
The above information is edited by the chemicalbook of Wang Xiaodong.

It shoud be packed in special cylinders and stored in a cool, ventilated coffers. Avoid direct sunlight. Keep away from heat and sources of ignition. Prevent moisture. Metal, glass should be isolated storage. "poison gas" signs should be affixed. Aviation, railway transportation is prohibited. When other combustibles on fire around, dry powder, carbon dioxide can be used to extinguish. Water can be used to cool cylinder, and then close the valve quickly.

It has eye irritation and can lead to blind, eyes should continue to be rinsed, go to the hospital fast for treatment. After corrosion, skin and mucous membranes is difficult to heal, it should be washed with water, and then coated with magnesium oxide ointment or glycerol dilute ammonia, and seek medical advice.

Compressed gas and liquefied.

When meet water, it can decompose into toxic hydrogen fluoride gas and tungstate.

Treasury ventilation low-temperature drying.

Water.

TLV-TWA 5 mg (tungsten)/cubic meter; STEL 10 mg (tungsten)/cubic meter.

Tungsten(VI) fluoride, also known as tungsten hexafluoride, WF6, is a toxic, corrosive, colorless gas, with a density of about 13 g/L (roughly 11 times heavier than air). It is one of the densest gases known under standard conditions. WF6 is frequently used by the semiconductor industry to form tungsten films, through CVD. The WF6 molecule is octahedral with the symmetry point group of Oh. The W-F bond distances are 183.2 pm. Between 2.3℃ and 17℃, tungsten hexafluoride condenses into a pale-yellow liquid with a density of 3.44 g/cm3 at 15℃. At 2.3℃ it freezes into a white solid with a cubic crystalline structure, with lattice constant of 628 pm and a calculated density of 3.99 g/cm3 . At 29℃ this structure converts to an orthorhombic solid with lattice constants of a = 960.3 pm, b = 871.3 pm, and c = 504.4 pm and a density of 4.56 g/cm3 . In this phase, the W-F distance is 181 pm, and the mean closest intermolecular contacts are 312 pm. 

Colorless gas or light-yellow liquid.

Tungsten hexafluoride is a toxic, colorless gas or a light yellow liquid.

In the electronics industry as a source of tungsten metal that connects the aluminum layers within semiconductor devices.

A toxic corrosive light yellow liquid or gas. Boiling point 67°F. Melting point 37°F. Noncombustible. Used in the manufacture of other chemicals and in the manufacture of electronics.

Decomposes in water giving hydrofluoric acid, another corrosive material.

Tungsten hexafluoride emits very toxic and irritating fumes containing metallic tungsten and tungsten fluorides when heated to decomposition. Reacts violently with tetramethoxysilane [Jacob, E., Angew. Chem., 1982, 21, p. 143].

TOXIC; may be fatal if inhaled, ingested or absorbed through skin. Vapors are extremely irritating and corrosive. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.

Some may burn but none ignite readily. Vapors from liquefied gas are initially heavier than air and spread along ground. Some of these materials may react violently with water. Cylinders exposed to fire may vent and release toxic and/or corrosive gas through pressure relief devices. Containers may explode when heated. Ruptured cylinders may rocket.

A poison and corrosive liquid or gas.

WF6 is usually produced by the exothermic reaction of F2 gas with tungsten powder between 350℃ and 400℃.
W +3F2→WF6

A strong halogenating agent. Used to apply tungsten coatings to other surfaces by vapor deposition process; making electronics and components; in the manufacture of other chemicals.

UN2196 Tungsten hexafluoride, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 8-Corrosive material, Inhalation Hazard Zone B. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.

Decomposes on contact with water and moist air, forming highly corrosive hydrofluoric acid. Violent reaction on contact with methyl silicate.

Return refillable compressed gas cylinders to supplier. Nonrefillable cylinders should be disposed of in accordance with local, state and federal regulations. Allow remaining gas to vent slowly into atmosphere in an unconfined area or exhaust hood. Refillabletype cylinders should be returned to original supplier with any valve caps and outlet plugs secured and valve protection caps in place.