Chromium hexacarbonyl

Reaction

1. Reagent for the preparation of Fischer carbenes.
2. Reagent for the preparation of arenechromium complexes.

Description

Chromium carbonyl is a colorless crystallinesubstance which sinters (forms a coherent mass withoutmelting) at 90℃. Molecular weight =220.06; Freezing/Melting point =110℃ (decomposes). Boilingpoint 5 explodes (in lieu of boiling) at 210℃. HazardIdentification (based on NFPA-704 M Rating System):Health 2, Flammability 1, Reactivity 0. Insoluble in water;possible reaction.

Chemical Properties

Chromium carbonyl is a colorless crystalline substance which sinters (forms a coherent mass without melting) @ 90°C.

Chemical Properties

white crystals or powder

Physical properties

White orthogonal crystal; density 1.77 g/cm³; sublimes at ordinary temperatures; vapor pressure 1 torr at 48°C; decomposes at 130°C; insoluble in water and alcohols; soluble in ether, chloroform and methylene chloride.

Uses

It is used as a catalyst for polymerization andisomerization of olefins. It is also used as anadditive to gasoline, to increase the octanenumber.

Uses

Chromiumhexacarbonyl is a volatile; air stable precursor of Chromium(0); widely used for thin film deposition - ALD and CVD. The thin films can be grown at room temperature and low pressure by laser CVD .

Uses

In catalysts for olefin polymerization and isomerization; gasoline additive to increase octane number; preparation of chromous oxide, CrO.

Preparation

Chromium hexacarbonyl is prepared by the reaction of anhydrous chromium(III) chloride with carbon monoxide in the presence of a Grignard reagent. A 60% product yield may be obtained at the carbon monoxide pressures of 35 to 70 atm. Other chromium salts may be used with carbon monoxide and Grignard reagent in the preparation. The compound may also be obtained by the reaction of a chromium salt with carbon monoxide in the presence of magnesium in ether or sodium in diglyme.

General Description

White crystalline or granular solid. Sublimes at room temperature. Burns with a luminous flame.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

Chromium hexacarbonyl decomposes violently at 410° F. Chromium hexacarbonyl is decomposed by chlorine and fuming nitric acid. Chromium hexacarbonyl is incompatible with oxidizing agents.

Hazard

Toxic by inhalation and ingestion.

Health Hazard

Chromium hexacarbonyl is a highly toxicsubstance by all routes of exposure. The toxiceffects are similar to those of molybdenumand tungsten carbonyls. The symptoms areheadache, dizziness, nausea, vomiting, andfever. The oral LD50 in mice is 150 mg/kgand in rats 230 mg/kg. The intravenous LD50in mice is 30 mg/kg. As a hexavalent compoundof chromium, it is a carcinogenic substance.

Fire Hazard

Flash point data for Chromium hexacarbonyl are not available; however, Chromium hexacarbonyl is probably combustible.

Potential Exposure

Chromium carbonyl is used as a catalyst for hydrogenation, isomerization, water
gas shift reaction and alkylation of aromatic hydrocarbons; gasoline additive to increase octane number; preparation of chromous oxide, CrO

First aid

Skin Contact: Flood all areas of body that havecontacted the substance with water. Do not wait to removecontaminated clothing; do it under the water stream. Usesoap to help assure removal. Isolate contaminated clothingwhen removed to prevent contact by others. Eye Contact:Remove any contact lenses at once. Immediately flush eyeswell with copious quantities of water or normal saline for atleast 2030 min. Seek medical attention. Inhalation: Leavecontaminated area immediately; breathe fresh air. Properrespiratory protection must be supplied to any rescuers. Ifcoughing, difficult breathing, or any other symptomsdevelop, seek medical attention at once, even if symptomsdevelop many hours after exposure. Ingestion: Contact aphysician, hospital, or poison center at once. If the victim isunconscious or convulsing, do not induce vomiting or giveanything by mouth. Assure that the patient’s airway is openand lay him on his side with his head lower than his bodyand transport immediately to a medical facility. If consciousand not convulsing, give a glass of water to dilute the substance. Vomiting should not be induced without a physician’s advice

storage

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with thischemical you should be trained on its proper handling andstorage. Store in tightly closed containers in a cool, wellventilated area or in a refrigerator. Protect from light. Aregulated, marked area should be established where thischemical is handled, used, or stored in compliance withOSHA Standard 1910.1045

Shipping

UN3466 Metal carbonyls, solid n.o.s. Hazard class 6.1. Technical name required. UN3281 Metal carbonyls, liquid n.o.s. Hazard class 6.1. Technical name required, Potential Inhalation Hazard (Special Provision 5). UN3466 Metal carbonyls, solid n.o.s. Hazard class 6.1. Technical name required.

Purification Methods

Wash the complex with cold EtOH, then Et2O, and allow it to dry in air. Alternatively recrystallise it from dry Et2O. This is best accomplished by placing the hexacarbonyl in a Soxhlet extractor and extracting exhaustively with dry Et2O. Pure Cr(CO)6 is filtered off and dried in air. Completely colourless refracting crystals are obtained by sublimation at 40-50o/<0.5mm in an apparatus where the collecting finger is cooled by Dry Ice and in which there is a wide short bore between the hot and cold sections to prevent clogging by the crystals. Loss of product in the crystallisation and sublimation is slight. It is important not to overdo the drying as the solid is appreciably volatile and TOXIC [vapour pressure is 0.04(8o), 1.0(48o) and 66.5(100o) mm]. Also do not allow the Et2O solutions to stand too long as a brown deposit is formed which is sensitive to light, and to avoid the possibility of violent decomposition. It sinters at 90o, decomposes at 130o, and EXPLODES at 210o. [Owen et al. Inorg Synth III 156 1950, Podall et al. J Am Chem Soc 83 2057 1961.] POISONOUS.

Incompatibilities

Violent reaction on contact with oxidizers. Decomposed by chlorine and fuming nitric acid; sensitive to heat and light (undergoes photochemical decomposition). Many carbonyls react with water, forming toxic and flammable vapors

Waste Disposal

Use a licensed professional waste disposal service to dispose of this material. All federal, state, and local environmental regulations must be observed. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (>=100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal.