Entering molybdenum chemistry

Entering molybdenum chemistry - making molybdenum compounds

Compounds commonly used as starting compounds in preparative molybdenum chemistry are molybdenum trioxide, and ammonium and sodium molybdates.

The preparative chemistry of molybdenum is summarised in Fig. 2 starting with molybdenum disulfide, the principal ore of molybdenum. Molybdenum disulfide is chemically unreactive: we enter molybdenum chemistry through molybdenum trioxide, prepared by roasting molybdenum disulfide in air. Reactions of molybdenum trioxide are shown in the figure below.

• Dissolution in aqueous sodium hydroxide or ammonia giving simple molybdate salts and polymolybdates which may be crystallised (see later).
• Calcination of an ammonium molybdate giving a sublimed, pure molybdenum trioxide.
• Reduction with hydrogen to molybdenum metal.
• Reactions with carbon monoxide or carbon and ammonia giving molybdenum carbide and nitride.
• Preparation of molybdenum pentachloride and molybdenum hexacarbonyl. The pentachloride rapidly hydrolyses in ambient air and is too reactive to find wide application. Molybdenum hexacarbonyl has an extensive substitution chemistry.
• Preparation of molybdenum-sulfur compounds by reaction with hydrogen sulfide or organo-sulfur compounds.