chemistry

Transition metal carboxamide complex

Transition metal carboxamide complex 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 Transition metal carboxamide complex rather than just read about it. In short: Transition metal carboxamide complexes are coordination complexes containing one or more amide ligands (RC(O)NH2 being the simplest members) bound to a transition metal. Many amides are known, proteins for example.

Key takeaways

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Reference excerpt

Transition metal carboxamide complexes are coordination complexes containing one or more amide ligands (RC(O)NH2 being the simplest members) bound to a transition metal. Many amides are known, proteins for example. Amides are generally at least weakly basic, so the inventory of their coordination complexes is large. Amide complexation is an important structural motif in bioinorganic chemistry. This binding is also relevant to catalysis, since metal-amide complexes are intermediates in the metal-catalyzed hydrolysis of amides to carboxylic acids.

Ligand properties Several principles and trends are illustrated by the case of complexes of dimethylformamide (DMF), a very common amide ligand. Amides bind to metals through oxygen, which is the basic site of amides. Amides are thus L ligands according to the covalent bond classification method, i.e. charge-neutral 2e donors. With respect to HSAB theory, amides are classified as hard ligands. The M-O=C(NH2)H entity is planar in complexes of formamide. Similarly, the M-O=C(NC2)H entity is planar in complexes of DMF. Two geometrically distinct bonding modes are possible depending on the relative positions of the metal ion and the N-substituent on the amide. For simple unidentate amides, like DMF, the M and N are transoid.

Nomenclature Often amide refers to carboxamide, and often amide refers to the anions R2N- and their derivatives. Tetrakis(dimethylamido)titanium (Ti(N(CH3)2)4) illustrates the ambiguity of the terminology.

Homoleptic complexes

Being a compact ligand, DMF forms homoleptic complexes with several metal cations. Some of those characterized by X-ray crystallography are listed below.

[Mn(DMF)6](BPh4)2 [Fe(DMF)6](B(CN)4)2 [Co(DMF)6]I2 [Ni(DMF)6](BPh4)2 [Zn(DMF)6](BPh4)2 [Ru(DMF)6](O3SCF3)2 [Ru(DMF)6](O3SCF3)3 [Cd(DMF)6]B12H12 By contrast with DMF, homoleptic complexes with formamide and methylformamide are rare.

Chelating amide ligands Diacetamide (HN(C(O)CH3)2) and glycinamide (H2NC(O)CH2NH2) are two of many examples of chelating amide ligands. They respectively form the complexes [Co((HN(COCH3)2(SCN)2}} and ([Co(H2NCOCH2NH2)(H2NCH2CH2NH2)2]3+.

Proteins and peptides Some prominent examples of transition metal complexes of carboxamido (deprotonated carboxamide) ligands: bleomycin (Fe), Nickel superoxide dismutase (Ni), and nitrile hydratase (Co).

Reactions The amide ligand in cationic complexes is prone toward hydrolysis:

[Co(NH3)5(OCH(NMe2)]3+ + OH− → [Co(NH3)5(O2CH]2+ + HNMe2 (Me = CH3) The N-H bonds in amide ligands are acidified relative to the free ligand. Consequently, amide complexes are susceptible to deprotonation. This conversion is often accompanied by isomerization to the N-bonded form. This form of linkage isomerism is manifested in glycinamide complexes.

Ureas Urea (O=C(NH2)2) is more basic at oxygen than simple amides owing to the combined pi-donation from the two amino groups. One consequence is that the inventory of urea complexes is large, including many homoleptic derivatives. Urea forms a broader range of complexes, reflected by the existence of [M(urea)6](ClO4)3 (M = Ti, Mn). As for other complexes of carboxamide ligands, the MOC(NH2)2 core of urea is planar with a bent M-O-C angle. Biuret (H2NC(O)N(H)C(O)NH2) is a derivative of urea but with two amido groups. Biuret forms a variety of metal complexes, e.g. [Cu(H2NC(O)NHC(O)NH2)2]2+. In addition to the parent urea and biuret, many derivatives are known where N-H is replaced by alkyl or aryl.

References

Illustrations

Worked examples

Example 1 — a first encounter with Transition metal carboxamide complex

Start with the simplest possible case. Write down what Transition metal carboxamide complex 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 Transition metal carboxamide complex 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 Transition metal carboxamide complex 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 Transition metal carboxamide complex

In research: Transition metal carboxamide complex 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 Transition metal carboxamide complex 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: Transition metal carboxamide complex is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amides, Coordination complexes, Inorganic chemistry, so understanding it makes those chapters shorter.
In everyday life: Look for Transition metal carboxamide complex 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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Frequently asked questions

What is Transition metal carboxamide complex in simple terms?

Why does Transition metal carboxamide complex 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 Transition metal carboxamide complex?

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.

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