chemistry

Praseodymium compounds

Praseodymium compounds 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 Praseodymium compounds rather than just read about it. In short: Praseodymium compounds are compounds formed by the lanthanide metal praseodymium (Pr). In these compounds, praseodymium generally exhibits the +3 oxidation state, such as PrCl3, Pr(NO3)3 and Pr(CH3COO)3.

Key takeaways

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

Reference excerpt

Praseodymium compounds are compounds formed by the lanthanide metal praseodymium (Pr). In these compounds, praseodymium generally exhibits the +3 oxidation state, such as PrCl3, Pr(NO3)3 and Pr(CH3COO)3. However, compounds with praseodymium in the +2 and +4 oxidation states, and unlike other lanthanides, the +5 oxidation state, are also known.

Halides

Praseodymium metal reacts with all the stable halogens to form green trihalides:

2 Pr (s) + 3 F2 (g) → 2 PrF3 (s) 2 Pr (s) + 3 Cl2 (g) → 2 PrCl3 (s) 2 Pr (s) + 3 Br2 (g) → 2 PrBr3 (s) 2 Pr (s) + 3 I2 (g) → 2 PrI3 (s) Praseodymium(III) fluoride is the most stable fluoride of praseodymium. It can be prepared the reaction between praseodymium(III) nitrate and sodium fluoride will produce praseodymium(III) fluoride as a green crystalline solid. Praseodymium(III) chloride is a light green solid that can be prepared by treating praseodymium metal with hydrogen chloride. It is usually purified by vacuum sublimation. It is Lewis acidic, classified as "hard" according to the HSAB concept. Rapid heating of the hydrate may cause small amounts of hydrolysis. PrCl3 forms a stable Lewis acid-base complex K2PrCl5 by reaction with potassium chloride; this compound shows interesting optical and magnetic properties. Praseodymium(III) bromide is the only stable bromide of praseodymium. It adopts the UCl3 crystal structure. The praseodymium ions are 9-coordinate and adopt a tricapped trigonal prismatic geometry. The praseodymium–bromine bond lengths are 3.05 Å and 3.13 Å. Praseodymium(III) iodide can be prepared by heating praseodymium and iodine in an inert atmosphere produces praseodymium(III) iodide, or by heating praseodymium with mercury(II) iodide. It forms orthorhombic crystals which are hygroscopic. It crystallizes in the PuBr3 type with space group Cmcm (No. 63) with a = 4.3281(6) Å, b = 14.003(6) Å and c = 9.988(3) Å. The tetrafluoride, PrF4, is also known, and is produced by reacting a mixture of sodium fluoride and praseodymium(III) fluoride with fluorine gas, producing Na2PrF6, following which sodium fluoride is removed from the reaction mixture with liquid hydrogen fluoride. Additionally, praseodymium forms a bronze diiodide; like the diiodides of lanthanum, cerium, and gadolinium, it is a praseodymium(III) electride compound.

Oxides Praseodymium can form many different oxides, although the only oxides that are stable at room temperature are Pr2O3, Pr6O11 and PrO2. Praseodymium(III) oxide is a green powder that forms hexagonal crystals, and crystallizes in the manganese(III) oxide or bixbyite structure. Praseodymium(IV) oxide can be produced by boiling Pr6O11 in water or acetic acid:

Pr6O11 + 3 H2O → 4 PrO2 + 2 Pr(OH)3 Praseodymium(III,IV) oxide is the most stable form of the praseodymium oxides at ambient temperature and pressure. It is soluble in water and has a cubic fluorite structure. It can be prepared via solid-state methods such as thermolysis, molten salt method, calcination or precipitation.

In addition to Pr6O11, praseodymium also forms a system of oxides at different phases:

Organopraseodymium compounds

Organopraseodymium compounds are compounds with a praseodymium-to-carbon bond. These compounds are very similar to those of the other lanthanides, as they all share an inability to undergo π backbonding. They are thus mostly restricted to the mostly ionic cyclopentadienides (isostructural with those of lanthanum) and the σ-bonded simple alkyls and aryls, some of which may be polymeric. The coordination chemistry of praseodymium is largely that of the large, electropositive Pr3+ ion, and is thus largely similar to those of the other early lanthanides La3+, Ce3+, and Nd3+. For instance, like lanthanum, cerium, and neodymium, praseodymium nitrate forms both the 4:3 and 1:1 complexes with 18-crown-6, whereas the middle lanthanides from promethium to gadolinium can only form the 4:3 complex and the later lanthanides from terbium to lutetium cannot successfully coordinate to all the ligands. Such praseodymium complexes have high but uncertain coordination numbers and poorly defined stereochemistry, with exceptions resulting from exceptionally bulky ligands such as the tricoordinate [Pr{N(SiMe3)2}3]. There are also a few mixed oxides and fluorides involving praseodymium(IV), but it does not have an appreciable coordination chemistry in this oxidation state like its neighbour cerium. However, the first example of a molecular complex of praseodymium(IV) has recently been reported. Like the other organolanthanide compounds, properties of organopraseodymium compounds include:

Organopraseodymium compounds are very air- and water-sensitive and pyrophoric. Chemistry in the 0 oxidation state is far more limited. In fact, their electropositive nature makes their organometallic compounds more likely to be ionic. Organopraseodymium compounds form no stable carbonyls at room temperature; organopraseodymium carbonyl compounds have been observed only in argon matrices, and decompose when heated to 40 K.

σ-Bonded complexes Metal-carbon σ bonds are found in alkyls of praeodymium such as [PrMe6]3− and Pr[CH(SiMe3)2]3.

π-Bonded complexes Cyclopentadienyl complexes, are known for praseodymium. It can be produced by the following reaction scheme:

3 Na[Cp] + PrCl3 → Pr[Cp]3 + 3 NaCl These compounds are of limited use and academic interest.

Applications Praseodymium(III) nitride is used in high-end electric and semiconductor products, and as a raw material to produce phosphor. Also it is used as a magnetic material and sputtering target material. Many praseodymium compounds, such as praseodymium(III) oxalate, are used to colour some glasses and enamels. If mixed with certain other materials, praseodymium(III) oxalate paints glass intense yellow. Praseodymium(III,IV) oxide has a number of potential applications in chemical catalysis, and is often used in conjunction with a promoter such as sodium or gold to improve its catalytic performance. It has a high-K dielectric constant of around 30 and very low leakage currents which have also made it a promising material for many potential applications in nanodevices and microelectronics.

Pictures of praseodymium compounds

References

See also Neodymium compounds Europium compounds

Illustrations

Worked examples

Example 1 — a first encounter with Praseodymium compounds

Start with the simplest possible case. Write down what Praseodymium compounds 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 Praseodymium compounds 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 Praseodymium compounds 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 Praseodymium compounds

In research: Praseodymium compounds 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 Praseodymium compounds 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: Praseodymium compounds is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chemical compounds by element, Praseodymium compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Praseodymium compounds 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 Praseodymium compounds in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Praseodymium compounds 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 Praseodymium compounds out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Praseodymium compounds in simple terms?

Why does Praseodymium compounds 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 Praseodymium compounds?

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 Praseodymium compounds.