10241-05-1

Preparation

Molybdenum pentachloride may be prepared by heating molybdenite in chlorine. Sulfur chloride formed in the reaction is removed by distillation: 2MoS2 + 7Cl2 → 2MoCl5 + 2S2Cl2 Also, the compound may be prepared by the action of chlorine on molybdenum metal at elevated temperatures (500°C): 2Mo + 5Cl2 → 2MoCl5 The pentachloride may be obtained from the tetrachloride, MoCl4. The latter, when heated in a sealed tube sublimes, and upon cooling, disproportionates to MoCl5 and the trichloride, MoCl3: 2MoCl4 → MoCl5 + MoCl3

Air & Water Reactions

MOLYBDENUM(V) CHLORIDE may react with water to produce corrosive hydrochloric acid and toxic fumes.

Reactivity Profile

MOLYBDENUM(V) CHLORIDE is a corrosive, hygroscopic solid, on contact with water or steam MOLYBDENUM(V) CHLORIDE decomposes to form hydrochloric acid. When heated to decomposition MOLYBDENUM(V) CHLORIDE emits toxic fumes of molybdenum chlorides and metallic molybdenum [Lewis, 3rd ed., 1993, p. 892]. Explodes on contact with finely divided sodium [Berry D. H., Chem. Eng. News, 1989, 67(47), p. 2]. Reaction with finely divided sodium sulfide is violent, may lead to autoignition [Kaner, R. B., Nature, 1991, 349, p. 510].

Hazard

Irritant.

Health Hazard

TOXIC; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe injury, burns or death. Contact with molten substance may cause severe burns to skin and eyes. Reaction with water or moist air will release toxic, corrosive or flammable gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Fire Hazard

Combustible material: may burn but does not ignite readily. Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff. When heated, vapors may form explosive mixtures with air: indoors, outdoors and sewers explosion hazards. Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapors may travel to source of ignition and flash back. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water.

Safety Profile

A poison. A corrosive irritant to skin, eyes, and mucous membranes. Reacts with moisture to form hydrochloric acid. When heated to decomposition it emits toxic fumes of Mo and Cl-.

Physical Properties

Greenish-black monoclinic crystals or dark red as liquid or vapor; paramagnetic; hygroscopic; critical temperature 577°C; critical volume 369 cm3/mol; soluble in dry ether, dry alcohol and many other organic solvents; reacts with water.