PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Organic chemistry → Organometallic Chemistry in Organic Synthesis ↓


Gold and silver catalysis


In the field of organic chemistry, particularly organometallic chemistry, the use of metals as catalysts opens up a world of possibilities for the efficient synthesis of complex organic molecules. Among the many metals used for catalysis, gold and silver have emerged as important players due to their unique properties. One of the most fascinating aspects of gold and silver catalysis is their ability to facilitate the formation of carbon-carbon and carbon-heteroatom bonds, which are fundamental steps in the synthesis of organic molecules ranging from simple pharmaceuticals to complex polymers.

Understanding the basics of metal catalysis

Catalysts are substances that increase the rate of a chemical reaction without expending themselves in the process. In metal catalysis, the metal acts as a platform to bring the reactants together in a favorable orientation, lowering the activation energy needed for the reaction to proceed.

General reaction with a catalyst: A + B → C (uncatalyzed) A + B → [Catalyst] → C (catalyzed)

Why gold and silver?

The use of gold and silver in catalysis can be considered due to their specific properties:

  • Gold: Known for its inertness, gold can effectively stabilize a variety of intermediates without participating in unwanted side reactions. Its ability to activate π-systems makes it invaluable in the electrophilic activation of alkynes and allenes.
  • Silver: Silver is particularly valuable in radical reactions due to its single-electron transfer capabilities. It can facilitate reactions such as coupling, oxidation, and cycloaddition.

The following sections will discuss in depth the unique roles of gold and silver in organic synthesis.

Gold catalysis: A closer look

Gold catalysts have been known since ancient times, but their role in organic synthesis has attracted significant attention only in recent decades. Unlike many transition metals, gold is non-toxic and highly selective, making it a preferred choice for the synthesis of complex molecules.

Mechanism in gold catalysis

A key reaction in gold catalysis is the activation of C–C multiple bonds. This occurs through coordination of the π-bond with the gold(I) catalyst, which makes the bond more electrophilic and susceptible to nucleophilic attack.

HCCCH3 + Au(I) → [HCCCH3–Au]+

In this reaction, the alkene is activated by a gold catalyst, increasing its reactivity towards nucleophilic addition.

Applications of gold catalysis

Gold catalysis has been effectively used in the following syntheses:

  • Hydroamination: Addition of an amine through an unsaturated C-C bond.
  • Hydroalkoxylation: The formation of ethers by the addition of alcohols to alkenes or alkynes catalyzed by gold.
  • Carbocyclization: Formation of cyclic structures using a gold catalyst, important in the synthesis of natural products.

Illustrative examples

An example of a gold-catalyzed reaction is the cyclization of an enyne to form a carbocyclic compound:

RC≡C-CH=CH2 + Au(I) → RC>CH-CH(Au)-CH3

Here, the gold catalyst facilitates cyclization by coordinating with the alkyne, allowing nucleophilic addition of the alkene moiety, resulting in ring closure.

Silver catalysis: An in-depth overview

Like gold, silver also has unique catalytic properties. It is widely used due to its ability to mediate radical and single electron transfer reactions. Silver catalysts find applications in both homogeneous and heterogeneous catalysis.

Mechanism in silver catalysis

Silver catalysis often involves a single electron transfer mechanism. Silver(I) ions can induce radical formation by oxidizing the substrate, and these radicals then participate in various transformations.

RH + Ag(I) → R* + Ag(H)

Radical intermediates like R* are highly reactive and can undergo numerous transformations to form the desired product.

Applications of silver catalysis

Silver catalysis has a wide range of synthetic applications, including:

  • Coupling reactions: Formation of C-C bonds via the coupling of organohalides and organometallics.
  • Oxidative cyclization: Synthesis of cyclic ethers and amines via oxidative pathways.
  • Atom transfer radical cyclization (ATRC): The use of radical pathways to form closed-ring structures.

Illustrative examples

An example of a silver-catalyzed reaction is the radical-mediated cyclization of a haloalkanes:

RX + Ag(I) → R* + Ag(X) R* + Alkene → Cyclized Product

In this mechanism, RX represents the haloalkane, and the silver catalyst promotes the formation of the radical, which subsequently reacts with an alkene to form a cyclized compound.

Comparative analysis and challenges

While both gold and silver offer promising routes to catalysis in organic synthesis, they come with their own challenges. Gold is typically more expensive, making its large-scale use economically challenging. Silver, while more abundant and less expensive, often requires tight control over reaction conditions to prevent undesirable side reactions.

In addition, both metals often require specific ligands or supports to enhance their activity and selectivity. Innovations in ligand design and catalyst fabrication continue to drive this field forward.

Conclusion

Gold and silver catalysis in organometallic chemistry provides powerful tools for the synthesis of complex organic compounds. While each metal offers unique advantages – such as gold's ability to stabilize heavy atoms and silver's efficacy in radical processes – ongoing research and innovation are necessary to overcome current limitations and further expand their applications in organic synthesis.

The future of gold and silver catalysis depends on the development of more efficient, selective, and cost-effective catalysts that can meet the demands of modern synthetic challenges in an environmentally sustainable manner.


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