Living Reference Work Entry

Encyclopedia of Geochemistry

Part of the series Encyclopedia of Earth Sciences Series pp 1-5

Date: Latest Version

Polyoxometalates and Other Metal-Oxo Clusters in Nature

  • May NymanAffiliated withDepartment of Chemistry, Oregon State University Email author 

Definition

Metal-oxoclusters are broadly defined as polynuclear species (meaning containing two or more metal cations) with ligands of H2O, OH, and O2− and are molecular. Molecular means they have a distinct chemical formula. In the laboratory, they are ideally synthesized in water in a discrete form (meaning all clusters present in the aqueous synthesis solution have the exact same formula and geometry). Solubility of these clusters in water necessitates a negative or positive charge; and the metal-oxo clusters are isolated by crystallization with counterions of the opposite charge. Polyoxometalates, commonly known as POMs, are one subset of metal-oxo clusters. These are discrete polynuclear metal-oxo clusters specifically composed of the early d0 transition metals in their highest oxidation state with no valence electrons. These POM-forming metal cations include V5+, Nb5+,Ta5+, Mo6+, and W6+. POMs are negatively charged and possess predominan ...

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