chemistry

Heteropolymetalate

Heteropolymetalate is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Heteropolymetalate rather than just read about it. In short: The heteropolymetalates are a subset of the polyoxometalates, which consist of three or more transition metal oxyanions linked together by shared oxygen atoms to form a closed 3-dimensional molecular framework. In contrast to isopolymetalates, which contain only one kind of metal atom, the heteropolymetalates contain differing main group oxyanions.

Key takeaways

Heteropolymetalate belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Heteropolymetalate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Heteropolymetalate from memory before moving on to harder problems.

Reference excerpt

The heteropolymetalates are a subset of the polyoxometalates, which consist of three or more transition metal oxyanions linked together by shared oxygen atoms to form a closed 3-dimensional molecular framework. In contrast to isopolymetalates, which contain only one kind of metal atom, the heteropolymetalates contain differing main group oxyanions. The metal atoms are usually group 6 (Mo, W) or less commonly group 5 (V, Nb, Ta) transition metals in their highest oxidation states. They are usually colorless to orange, diamagnetic anions. For most heteropolymetalates the W, Mo, or V, is complemented by main group oxyanions phosphate and silicate. Many exceptions to these general statements exist, and the class of compounds includes hundreds of examples.

Structure Certain structural motifs recur. The Keggin ion for example is common to both molybdates and tungstates with diverse central heteroatoms. The Keggin and Dawson structures have tetrahedrally-coordinated heteroatoms, such as P or Si, and the Anderson structure has an octahedral central atom, such as aluminium.

Three dimensional and rotatable models of these molecular structures can be found on the web-site:" Polyoxometalate structure types: an interactive gallery".

Heteropolyacids Generally, the heteropoly(oxo)metalates are more thermally robust than isopoly(oxo)metalates. This trend reflects the stabilizing influence of the tetrahedral oxyanion that "glues" together the transition metal oxo framework. One reflection of their ruggedness, heteropolymetalates can be isolated in their acid form, whereas homopolymetalates typically cannot. Examples include:

Silicotungstic acid, H4SiW12O40·nH2O Phosphomolybdic acid, H3Mo12PO40·nH2O Phosphotungstic acid, H3W12PO40·nH2O

Isomerism The Keggin structure type has 5 isomers, which are obtained by (conceptually) rotating one or more of the four M3O13 units through 60°.

Lacunary structures The structure of some POMs are derived from a larger POM's structure by removing one or more addenda atoms and their attendant oxide ions, giving a defect structure called a lacunary structure. An example of a compound with a Dawson lacunary structure is As2W15O56. In 2014, vanadate species with similar, selective metal-binding properties were reported. A comparison using three dimensional and interactive models of the trilacunary fragments of the Keggin structure type can be found here.

Uses

This type of acid is a common re-usable acid catalyst in chemical reactions.

The heteropolyacids are widely used as homogeneous and heterogeneous catalysts, particularly those based on the Keggin structure as they can possess qualities such as good thermal stability, high acidity and high oxidising ability. Some examples of catalysis are:

Homogeneous acid catalysis hydrolysis of propene to give propan-2-ol by H3PMo12O40 and H3PW12O40 Prins reaction by H3PW12O40 polymerisation of tetrahydrofuran by H3PW12O40 Heterogeneous acid catalysis dehydration of propan-2-ol to propene and methanol to hydrocarbons by H3PW12O40 reformation of hexane to 2-methylpentane (isohexane) by H3PW12O40 on SiO2 Homogeneous oxidation cyclohexene + H2O2 to adipic acid by the mixed addenda H3PMo6V6O40 ketone by O2 to acid and aldehyde by mixed addenda H5PMo10V2O40 Heteropolyacids have long been used in analysis and histology and are a component of many reagents e.g. the Folin-Ciocalteu reagent, folins phenol reagent used in the Lowry protein assay and EPTA, ethanolic phosphotungstic acid.

See also Polyoxometalate Phosphomolybdic acid Phosphotungstic acid Silicotungstic acid

Citations

References Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5

Illustrations

Worked examples

Example 1 — a first encounter with Heteropolymetalate

Start with the simplest possible case. Write down what Heteropolymetalate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Heteropolymetalate before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Heteropolymetalate ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Heteropolymetalate

In research: Heteropolymetalate appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Heteropolymetalate in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Heteropolymetalate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acid catalysts, Heteropoly acids, so understanding it makes those chapters shorter.
In everyday life: Look for Heteropolymetalate outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Heteropolymetalate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Heteropolymetalate means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Heteropolymetalate out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Heteropolymetalate in simple terms?

Why does Heteropolymetalate matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Heteropolymetalate?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Heteropolymetalate.