Molybdenum and its applications
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.
Preparative chemistry of molybdenum. The highlighted compounds and molybdenum metal are those which find high volume applications
- 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.