chemistry

Metal amides

Metal amides 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 Metal amides rather than just read about it. In short: Metal amides (systematic name metal azanides) are a class of coordination compounds composed of a metal center with amide ligands of the form NR2−. Amido complexes of the parent amido ligand NH2− are rare compared to complexes with diorganylamido ligand, such as dimethylamido.

Key takeaways

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

Reference excerpt

Metal amides (systematic name metal azanides) are a class of coordination compounds composed of a metal center with amide ligands of the form NR2−. Amido complexes of the parent amido ligand NH2− are rare compared to complexes with diorganylamido ligand, such as dimethylamido. Amide ligands have two electron pairs available for bonding.

Geometry and structure In principle, the M-NX2 group could be pyramidal or planar. The pyramidal geometry is not observed. In many complexes, the amido is a bridging ligand. Some examples have both bridging and terminal amido ligands. Bulky amide ligands have a lesser tendency to bridge. Amide ligands may participate in metal-ligand π-bonding giving a complex with the metal center being co-planar with the nitrogen and substituents. Metal bis(trimethylsilyl)amides form a significant subcategory of metal amide compounds. These compounds tend to be discrete and soluble in organic solvents.

Alkali metal amides

Lithium amides are the most important amides. They are prepared from n-butyllithium and the appropriate amine

R2NH + BuLi → R2NLi + BuH The lithium amides are more common and more soluble than the other alkali metal analogs. Potassium amides are prepared by transmetallation of lithium amides with potassium t-butoxide (see also Schlosser base) or by reaction of the amine with potassium, potassium hydride, n-butylpotassium, or benzylpotassium. The alkali metal amides, MNH2 (M = Li, Na, K) are commercially available. Sodium amide (also known as sodamide) is synthesized from sodium metal and ammonia with ferric nitrate catalyst. The sodium compound is white, but the presence of metallic iron turns the commercial material gray.

2 Na + 2 NH3 → 2 NaNH2 + H2 Lithium diisopropylamide is a popular non-nucleophilic base used in organic synthesis. Unlike many other bases, the steric bulk prevents this base from acting as a nucleophile. It is commercially available, usually as a solution in hexane. It may be readily prepared from n-butyllithium and diisopropylamine.

Main group amido complexes Amido derivatives of main group elements are well developed.

Transition metal complexes Early transition metal amides may be prepared by treating anhydrous metal chloride with alkali amide reagents. In some cases, two equivalents of a secondary amine can be used, one equivalent serving as a base:

MCln + n LiNR2 → M(NR2)n + n LiCl MCln + 2n HNR2 → M(NR2)n + n HNR2·HCl Transition metal amide complexes have been prepared by these methods:

treating a halide complex with an alkali amide deprotonation of a coordinated amine oxidative addition of an amine

Amido-ammine complexes Highly cationic metal ammine complexes such as [Pt(NH3)6]4+ spontaneously convert to the amido derivative:

[Pt(NH3)6]4+ ↔ [Pt(NH3)5(NH2)]3+ + H+ Transition metal amides are intermediates in the base-induced substitution of transition metal ammine complexes. Thus, the Sn1CB mechanism for the displacement of chloride from chloropentamminecobalt chloride by hydroxide proceeds via an amido intermediate:

[Co(NH3)5Cl]2+ + OH− → [Co(NH3)4(NH2)]2+ + H2O + Cl− [Co(NH3)4NH2]2+ + H2O → [Co(NH3)5OH]2+

Illustrations

Worked examples

Example 1 — a first encounter with Metal amides

Start with the simplest possible case. Write down what Metal amides 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 Metal amides 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 Metal amides 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 Metal amides

In research: Metal amides 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 Metal amides 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: Metal amides is common in secondary-school and first-year university syllabi. It links to neighbouring topics Coordination chemistry, Metal amides, so understanding it makes those chapters shorter.
In everyday life: Look for Metal amides 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 Metal amides in 20 minutes

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

Frequently asked questions

What is Metal amides in simple terms?

Why does Metal amides 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 Metal amides?

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 Metal amides.