science

Silanide

Silanide is a science 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 Silanide rather than just read about it. In short: A silanide is a chemical compound containing an anionic silicon(IV) centre, the parent ion being SiH−3. The hydrogen atoms can also be substituted to produce more complex derivative anions such as tris(trimethylsilyl)silanide (hypersilyl), tris(tert-butyl)silanide, tris(pentafluoroethyl)silanide, or triphenylsilanide.

Key takeaways

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

Reference excerpt

A silanide is a chemical compound containing an anionic silicon(IV) centre, the parent ion being SiH−3. The hydrogen atoms can also be substituted to produce more complex derivative anions such as tris(trimethylsilyl)silanide (hypersilyl), tris(tert-butyl)silanide, tris(pentafluoroethyl)silanide, or triphenylsilanide. The simple silanide ion can also be called trihydridosilanide or silyl hydride.

Formation The simplest trihydridosilanides can be produced from a triphenylsilanide in a reaction with hydrogen or PhSiH3 at standard conditions. The triphenylsilanide can be made in a reaction of Ph3SiSiMe3 with the metal tert-butoxy compound. Reacting hydrogen with potassium triphenylsilyl K(Me6TREN)SiPh3 can yield potassium silanide. Other method to form silanides are to heat a heavy metal silicide with hydrogen, or react the dissolved metal with silane. Atomic metals can react directly with silane to yield unstable molecules with HMSiH3 formulae. These can be condensed into a noble gas matrix. With titanium this also yields molecules with hydrogen bridging between silicon and titanium.

Properties The silanide ion has an effective ionic radius of 2.26 Å. In salts at room temperature the ion's orientation is not stable, and it rotates. But at lower temperatures (under 200K) silanide becomes fixed in orientation. The ordered structure forms the β- phase, whereas the higher temperature and more symmetrical disordered structure is called α- phase. The β- phase is about 15% more compact than the α-phase. The silanide ion has C3v symmetry. The silicon to hydrogen bond length is 1.52 Å and the H-Si-H bond angle is 92.2°, not far off a right angle. In a range of compounds, the stretching force constant for the Si-H bond is 1.9 to 2.05 N cm–1, which is much softer than that of silane's 2.77 N cm–1. Silanide salts are very easily damaged by air or water. Heating to under 414K results in the release of hydrogen and the formation of a Zintl-phase MSi. If an alkali silande is rapidly heated to 500K another irreversible reaction occurs:

46KSiH3 → K8Si46 + 38KH + 50H2.

Use Trihydridosilanides have been investigated as hydrogen storage materials. Potassium silanide can reversibly gain or lose hydrogen over several hours at 373K. However this does not work for sodium silanide. The rate of hydrogen exchange may be improved by a catalyst. Unwanted reactions may reduce the number of times this process can happen.

List

Related Under high hydrogen pressure, pentacoordinated and hexacoordinated silicon hydride ions are stabilised including SiH−5 and SiH2−6. More complex derivatives include silanimine -NHSiH3, With a double bond between silicon and the metal a silylene complex is formed. With a triple bond, M≡SiH forms with metals such as molybdenum and tungsten. With less hydrogen, a polyanionic hydride ∞1[(SiH)−] can be formed. General organic compounds are termed silylium ions.

References

Illustrations

Worked examples

Example 1 — a first encounter with Silanide

Start with the simplest possible case. Write down what Silanide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Silanide 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 Silanide 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 Silanide

In research: Silanide appears in science 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 Silanide 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: Silanide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Anions, Silanes, so understanding it makes those chapters shorter.
In everyday life: Look for Silanide 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Silanide in 20 minutes

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

Frequently asked questions

What is Silanide in simple terms?

Why does Silanide matter?

Because it connects several science 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 Silanide?

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 Silanide.