The vast field of heteropolyanion1 chemistry has historically been centred
around the preparation, structure, properties and analytical chemistry of these
compounds. Only recently has the potential use of heteropolyanions as catalysts slowly
gained recognition, both as Broensted acid and oxidation catalysts.
In this introduction HPAs and polyoxometalates will be briefly discussed:
definition, classification, synthesis, properties and applications.
POMs are well-defined and compact oxygen anion clusters with a charge range of –3 to
–20.2 These discrete molecular-ionic species are mostly represented with the general
formula [MmOy]q− and [XxMmOy]q−, for isopolyanions and heteropolyanions,
respectively. X denotes the heteroatom (a first row transition metal or a main-group
element) at the core of a structure coated with surface metal M or addenda atom and