heptamolybdate

Heptamolybdate refers to the heptamolybdate( VI) anion, Mo7O24^6−, a discrete polyoxometalate derived from molybdate oxoanions. In aqueous solution it is a stable species under moderately basic conditions and forms salts with common cations, such as sodium, potassium, and ammonium.

Structure and properties: The heptamolybdate anion consists of seven molybdenum centers linked by oxide bridges to form a compact oxide framework. This arrangement makes it a versatile building block in polyoxometalate chemistry and allows various protonation states and interactions in solution. The unit is typically soluble in water and remains stable under conditions that do not strongly reduce Mo(VI) centers.

Preparation and occurrence: Heptamolybdate can be generated by condensation of MoO4^2− units in aqueous solution under controlled pH and ionic strength, often starting from ammonium or sodium molybdate. Through adjustment of concentration, pH, and temperature, the Mo7O24^6− species is stabilized as salts and can be isolated crystallographically or studied in solution.

Reactions and applications: Salts of the heptamolybdate anion serve as convenient sources of molybdenum for the synthesis of larger polyoxometalates and related inorganic frameworks. In research and industry, they are used in catalysis, materials science, and analytical chemistry as building blocks for oxide-based architectures and as reagents in ligand exchange and structural studies.

Safety and handling: As with other inorganic oxide materials, heptamolybdate compounds are generally handled with standard laboratory safety practices. They are not highly volatile and exposure is typically via dust or solution; prolonged exposure or ingestion should be avoided.