Polyoxometalates

In chemistry, a polyoxometalate (abbreviated POM) is a polyatomic ion, usually an anion, that consists of three or more transition metal oxyanions linked together by shared oxygen atoms to form a large, closed 3-dimensional framework.

The metal atoms are usually group 5 or group 6 transition metals in their high oxidation states. In this state, their electron configuration is d0 or d1. Examples include vanadium(V), niobium(V), tantalum(V), molybdenum(VI), and tungsten(VI).

The framework of transition metal oxyanions may enclose one or more hetero atoms such as phosphorus or silicon, themselves sharing neighbouring oxygen atoms with the framework. For example, the phosphotungstate anion [PW12O40]3− consists of a framework of twelve octahedral tungsten oxyanions surrounding a central phosphate group.