chemistry

Tris(ethylenediamine)cobalt(III) chloride

Tris(ethylenediamine)cobalt(III) chloride 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 Tris(ethylenediamine)cobalt(III) chloride rather than just read about it. In short: Tris(ethylenediamine)cobalt(III) chloride is an inorganic compound with the formula [Co(en)3]Cl3 (where "en" is the abbreviation for ethylenediamine). It is the chloride salt of the coordination complex [Co(en)3]3+.

Key takeaways

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Reference excerpt

Tris(ethylenediamine)cobalt(III) chloride is an inorganic compound with the formula [Co(en)3]Cl3 (where "en" is the abbreviation for ethylenediamine). It is the chloride salt of the coordination complex [Co(en)3]3+. This trication was important in the history of coordination chemistry because of its stability and its stereochemistry. Many different salts have been described. The complex was first described by Alfred Werner who isolated this salt as yellow-gold needle-like crystals.

Synthesis and structure The compound is prepared from an aqueous solution of ethylenediamine and virtually any cobalt(II) salt, such as cobalt(II) chloride. The solution is purged with air to oxidize the cobalt(II)-ethylenediamine complexes to cobalt(III). The reaction proceeds in 95% yield, and the trication can be isolated with a variety of anions. A detailed product analysis of a large-scale synthesis revealed that one minor by-product was [Co(en)2Cl(H2NCH2CH2NH3)]Cl3, which contains a rare monodentate ethylenediamine ligand (protonated). The cation [Co(en)3]3+ is octahedral with Co-N distances in the range 1.947–1.981 Å. The N-Co-N angles are 85° within the chelate rings and 90° between nitrogen atoms on adjacent rings.

Stereochemistry

The point group of this complex is D3. The complex can be resolved into enantiomers that are described as Δ and Λ. Usually the resolution entails use of tartrate salts. The optical resolution is a standard component of inorganic synthesis courses. Because of its nonplanarity, the MN2C2 rings can adopt either of two conformations, which are described by the symbols λ and δ. The registry between these ring conformations and the absolute configuration of the metal centers is described by the nomenclature lel (when the en backbone lies parallel with the C3 symmetry axis) or ob (when the en backbone is obverse to this same C3 axis). Thus, the following diastereomeric conformations can be identified: Δ-(lel)3, Δ-(lel)2(ob), Δ-(lel)(ob)2, and Δ-(ob)3. The mirror images of these species of course exist also.

Hydrates Cationic coordination complexes of ammonia and alkyl amines typically crystallize with water in the lattice, and the stoichiometry can depend on the conditions of crystallization and, in the cases of chiral complexes, the optical purity of the cation. Racemic [Co(en)3]Cl3 is most often obtained as the di- or trihydrate. For the optically pure salt (+)-[Co(en)3]Cl3·1.5H2O, (+)-[Co(en)3]Cl3·0.5NaCl·3H2O, and (+)-[Co(en)3]Cl3·H2O are also known.

Related compounds Tris(ethylenediamine)chromium(III) chloride.

References

Illustrations

Worked examples

Example 1 — a first encounter with Tris(ethylenediamine)cobalt(III) chloride

Start with the simplest possible case. Write down what Tris(ethylenediamine)cobalt(III) chloride 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 Tris(ethylenediamine)cobalt(III) chloride 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 Tris(ethylenediamine)cobalt(III) chloride 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 Tris(ethylenediamine)cobalt(III) chloride

In research: Tris(ethylenediamine)cobalt(III) chloride 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 Tris(ethylenediamine)cobalt(III) chloride 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: Tris(ethylenediamine)cobalt(III) chloride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chlorides, Cobalt(III) compounds, Cobalt complexes, so understanding it makes those chapters shorter.
In everyday life: Look for Tris(ethylenediamine)cobalt(III) chloride 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 Tris(ethylenediamine)cobalt(III) chloride in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tris(ethylenediamine)cobalt(III) chloride 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.
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Frequently asked questions

What is Tris(ethylenediamine)cobalt(III) chloride in simple terms?

Why does Tris(ethylenediamine)cobalt(III) chloride 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 Tris(ethylenediamine)cobalt(III) chloride?

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 Tris(ethylenediamine)cobalt(III) chloride.