chemistry

Metal carbonyl hydride

Metal carbonyl hydride 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 carbonyl hydride rather than just read about it. In short: Metal carbonyl hydrides are complexes of transition metals with carbon monoxide and hydride as ligands. These complexes are useful in organic synthesis as catalysts in homogeneous catalysis, such as hydroformylation.

Key takeaways

Metal carbonyl hydride 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 carbonyl hydride to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Metal carbonyl hydride from memory before moving on to harder problems.

Reference excerpt

Metal carbonyl hydrides are complexes of transition metals with carbon monoxide and hydride as ligands. These complexes are useful in organic synthesis as catalysts in homogeneous catalysis, such as hydroformylation.

Preparation

Walter Hieber et al. prepared the first metal carbonyl hydride in 1931 by the so-called Hieber base reaction of metal carbonyls. In this reaction a hydroxide ion reacts with the carbon monoxide ligand of a metal carbonyl such as iron pentacarbonyl in a nucleophilic attack to form a metallacarboxylic acid. This intermedia releases of carbon dioxide in a second step, giving the iron tetracarbonyl hydride anion. The synthesis of cobalt tetracarbonyl hydride (HCo(CO)4) proceeds in the same way.

Fe(CO)5 + NaOH → Na[Fe(CO)4CO2H] Na[Fe(CO)4CO2H] → Na[HFe(CO)4] + CO2 A further synthetic route is the reaction of the metal carbonyl with hydrogen. The protonation of metal carbonyl anions, e.g. [Co(CO)4]−, leads also to the formation of metal carbonyl hydrides.

Properties

The neutral metal carbonyl hydrides are often volatile and can be quite acidic. The hydrogen atom is directly bounded to the metal. The metal-hydrogen bond length is for cobalt 114 pm, the metal-carbon bond length is for axial ligands 176 and 182 for the equatorial ligands. A direct metal-hydrogen bond was suspected by Hieber for H2Fe(CO)4. A number of metal carbonyl hydrides have been characterized by X-ray crystallography and neutron diffraction. Nuclear magnetic resonance spectroscopy has also proved to be a useful characterization tool.

Applications and occurrence Metal carbonyl hydrides are used as catalysts in the hydroformylation of olefins. The catalyst is usually formed in situ in a reaction of a metal salt precursor with the syngas. The hydroformylation starts with the generation of a coordinatively unsaturated 16-electron metal carbonyl hydride complex like HCo(CO)3 or HRh(CO)(PPh3)2 by dissociation of a ligand. Such complexes bind olefins in a first step via π-complexation, thus beginning the transformation of the alkene to the aldehyde. Iron carbonyl hydrides occur in nature at the active sites of hydrogenase enzymes.

Further reading Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Metal carbonyl hydride

Start with the simplest possible case. Write down what Metal carbonyl hydride 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 carbonyl hydride 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 carbonyl hydride 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 carbonyl hydride

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

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

Frequently asked questions

What is Metal carbonyl hydride in simple terms?

Why does Metal carbonyl hydride 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 carbonyl hydride?

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 carbonyl hydride.