chemistry

Organopalladium chemistry

Organopalladium chemistry 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 Organopalladium chemistry rather than just read about it. In short: Organopalladium chemistry is a branch of organometallic chemistry that deals with organic palladium compounds and their reactions. Palladium is often used as a catalyst in the reduction of alkenes and alkynes with hydrogen.

Key takeaways

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

Reference excerpt

Organopalladium chemistry is a branch of organometallic chemistry that deals with organic palladium compounds and their reactions. Palladium is often used as a catalyst in the reduction of alkenes and alkynes with hydrogen. This process involves the formation of a palladium-carbon covalent bond. Palladium is also prominent in carbon-carbon coupling reactions, as demonstrated in tandem reactions.

Organopalladium chemistry timeline 1873 - A. N. Zaitsev reports reduction of benzophenone over palladium with hydrogen. 1894 - Francis Phillips reports that palladium(II) chloride reduces to palladium metal by contact with ethylene. 1907 - Autoclave technology introduced by Vladimir Ipatieff makes it possible to carry out high pressure hydrogenation. 1956 - In the Wacker process ethylene and oxygen react to acetaldehyde with catalyst PdCl2/CuCl2. During process development, Walter Hafner also identifies the first allylpalladium complex. 1957 - Tetrakis(triphenylphosphine)palladium(0) is reported by Malatesta and Angoletta. 1972 - The Heck reaction is a coupling reaction of a halogenide with an olefin. Pd(0) intermediates are implicated. 1973 - The Trost asymmetric allylic alkylation is a nucleophilic substitution. 1975 - The Sonogashira coupling is a coupling reaction of terminal alkynes with aryl or vinyl halides. 1994 - The Pd-catalyzed Buchwald-Hartwig amination for C-N bond-forming reactions.

Palladium(II)

Alkene complexes Unlike Ni(II), but similar to Pt(II), Pd(II) halides form a variety of alkene complexes. The premier example is dichloro(1,5‐cyclooctadiene)palladium. In this complex, the diene is easily displaced, which makes it a favored precursor to catalysts. In the industrially important Wacker process, ethylene is converted to acetaldehyde via nucleophilic attack of hydroxide on a Pd(II)-ethylene intermediate followed by formation of a vinyl alcohol complex. Fullerene ligands also bind with palladium(II).

Palladium(II) acetate and related compounds are common reagents because the carboxylates are good leaving groups with basic properties. For example palladium trifluoroacetate has been demonstrated to be effective in aromatic decarboxylation:

Allyl complexes The iconic complex in this series is allylpalladium chloride dimer (APC). Allyl compounds with suitable leaving groups react with palladium(II) salts to pi-allyl complexes having hapticity 3. These intermediates too react with nucleophiles for example carbanions derived from malonate esters or with amines in allylic amination as depicted below

Allylpalladium intermediates also feature in the Trost asymmetric allylic alkylation and the Carroll rearrangement and an oxo variation in the Saegusa oxidation.

Palladium-carbon sigma-bonded complexes Various organic groups can bound to palladium and form stable sigma-bonded complexes. The stability of the bonds in terms of bond dissociation energy follows the trend: Pd-Alkynyl > Pd-Vinyl ≈ Pd-Aryl > Pd-Alkyl and the metal-carbon bond length changes in the opposite direction: Pd-Alkynyl < Pd-Vinyl ≈ Pd-Aryl < Pd-Alkyl.

Palladium(0) compounds Zerovalent Pd(0) compounds include tris(dibenzylideneacetone)dipalladium(0) and tetrakis(triphenylphosphine)palladium(0). These complexes react with halocarbon R-X in oxidative addition to R-Pd-X intermediates with covalent Pd-C bonds. This chemistry forms the basis of a large class of organic reactions called coupling reactions (see palladium-catalyzed coupling reactions). An example is the Sonogashira reaction:

Organopalladium(IV) The first organopalladium(IV) compound was described in 1986. This complex is Me3Pd(IV)(I)bpy (bpy = bidentate 2,2'-bipyridine ligand) It was synthesized by oxidative addition of methyl iodide to Me2Pd(II)bpy. Palladium compounds owe their reactivity to the ease of interconversion between Pd(0) and palladium(II) intermediates. There is no conclusive evidence however for the involvement of Pd(II) to Pd(IV) conversions in palladium mediated organometallic reactions. One reaction invoking such mechanism was described in 2000 and concerned a Heck reaction. This reaction was accompanied by a 1,5-hydrogen shift in the presence of amines:

The hydride shift was envisaged as taking place through a Pd(IV) metallacycle:

In related work the intermediate associated with the hydride shift remains Pd(II):

and in other work (a novel synthesis of indoles with two Pd migrations) equilibria are postulated between different palladacycles:

and in certain intramolecular couplings synthetic value was demonstrated regardless of oxidation state:

Illustrations

Worked examples

Example 1 — a first encounter with Organopalladium chemistry

Start with the simplest possible case. Write down what Organopalladium chemistry 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 Organopalladium chemistry 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 Organopalladium chemistry 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 Organopalladium chemistry

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

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Organopalladium chemistry” →

Affiliate

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

How to study Organopalladium chemistry in 20 minutes

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

Frequently asked questions

What is Organopalladium chemistry in simple terms?

Why does Organopalladium chemistry 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 Organopalladium chemistry?

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 Organopalladium chemistry.