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 → Inorganic chemistry → Organometallic Chemistry ↓


Metal Carbonyls


In the field of organometallic chemistry, metal carbonyls play an important role due to their unique properties and wide applications. Metal carbonyls are compounds consisting of metal centers bound to carbon monoxide ligands. The fascinating ability of carbon monoxide (CO) to coordinate with metals gives rise to these compounds, leading to fascinating chemical properties and structural diversity.

Structure and bonding in metal carbonyls

Coordination of CO ligands to metal centers occurs primarily through sigma donation from the filled carbon monoxide molecular orbital to the vacant metal orbital, as well as pi-backbonding from the filled metal d orbitals to the vacant antibonding pi* orbital of CO. This double bonding nature provides stability and unique spectroscopic properties to metal carbonyls.

M – C ≡ O

Here, M denotes a metal atom while CO denotes the carbon monoxide ligand. The metal–carbon bond is partially covalent with significant pi-backbonding that weakens the C≡O bond compared to free CO.

Eighteen-electron rule

The 18-electron rule or "effective atomic number" rule is an important concept when considering the stability and formation of metal carbonyls. It suggests that stable transition metal complexes often have 18 valence electrons, achieved through the summation of the metal's d-electrons and the electrons of the surrounding ligands.

  • For example,
    Fe(CO)5
    Iron (Fe) has 8 d-electrons. Each of the five CO ligands donates 2 electrons, giving a total of 10 electrons. This totals 18, which satisfies the rule.

Types of metal carbonyls

Metal carbonyls can be classified based on their oxidation state and coordination number, typically appearing as mononuclear, polynuclear, and mixed-metal complexes.

Mononuclear metal carbonyls

M(CO)N

These contain one metal atom. A classic example of a mononuclear metal carbonyl is 

Ni(CO)4
, where nickel is in the zero oxidation state.

Additional examples include:

Cr(CO)6

Here, chromium is also in the zero oxidation state, surrounded by six CO groups in octahedral geometry.

Polynuclear metal carbonyls

MM(CO)N

These complexes contain multiple metal atoms in a single compound. A notable example is 

Fe2(CO)9
, in which the two iron atoms share a bridging carbonyl ligand.

Fe - Fe
    CO CO CO
    CO - CO

Heteronuclear metal carbonyls

These carbonyls are made from various metals, which show diverse applications in catalysis and materials science. An example of this is 

[FeNi(CO)4]
where iron and nickel are bonded via carbonyl bridges.

Synthesis of metal carbonyls

Several methods are used to synthesize metal carbonyls, often depending on the metal center desired:

Direct feedback

The simplest approach involves the direct reaction of the metal with carbon monoxide under suitable conditions of temperature and pressure:

Ni + 4 CO → Ni(CO)4

The reaction proceeds smoothly at ambient temperature and pressure, demonstrating a direct synthesis route.

Reduction of metal salts

Metal salts are reduced in the presence of carbon monoxide. For example:

VCl3 + 3 CO + Al → V(CO)6 + AlCl3

Ligand substitution

In some reactions, the ligand in the metal complex is replaced by carbon monoxide. An illustrative example is:

MoCl6 + 6 CO → Mo(CO)6 + 6 Cl2

Properties of metal carbonyls

Metal carbonyls are defined by several important physical and chemical properties:

  • Volatility: Many metal carbonyls, such as 
    Ni(CO)4
    , are volatile and can be used in the purification of metals by the Mond process.
  • Solubility: Generally soluble in nonpolar organic solvents.
  • Colour: Varies widely among different compounds, often exhibiting vibrant colours due to metal-ligand interactions.
  • Toxicity: Many metal carbonyls, such as 
    Ni(CO)4
    , are toxic and require careful handling.

Reactions involving metal carbonyls

Metal carbonyls participate in a wide range of reactions due to their structural features and electron-rich nature:

Substitution reactions

Ligand exchange can occur when a CO group is replaced by another ligand, such as a phosphine:

Fe(CO)5 + PPh3 → Fe(CO)4(PPh3) + CO

Oxidative additives

Metal carbonyl complexes can participate in oxidative addition, where a substrate adds to the metal center causing an increase in electron count:

CO2(CO)8 + Cl2 → 2 CO(CO)4(Cl)2

Carbonyl insertion

In this type of reaction, the CO ligand is put into a metal–carbon or metal–hydrogen bond:

LNMR + CO → LNMC(=O)-R

Applications in catalysis

Metal carbonyl complexes are extremely important in industrial and synthetic applications, such as:

Homogeneous catalysis

They serve as catalysts in a variety of organic transformations, including hydroformylation and carbonylation:

R-CH=CH2 + CO + H2 --(Co2(CO)8)--> R-CH2-CH2-CHO

Carbonylation reactions

This process involves the addition of a carbonyl group to a molecule and is widely used in the production of acetic acid and other organic substances:

CH3OH + CO → CH3COOH

Safety and handling

Due to their inherent toxicity and volatility, metal carbonyls require stringent safety protocols:

  • Ventilation: Conduct reactions in well-ventilated areas or fume hoods to avoid inhalation.
  • Protective equipment: Always use gloves and goggles when handling metal carbonyls.
  • Storage: Store in a tightly sealed container in a cool, dry place.

Conclusion

Metal carbonyls emerge as important and fascinating compounds in organometallic chemistry. They embody a symbiotic relationship between carbon monoxide and metals, providing widespread utility in both academic research and industrial applications. Advances in the understanding and manipulation of these compounds continue to push the boundaries of chemistry, making them indispensable tools in the synthesis of complex molecules and catalytic processes.


PHD → 1.2.1


U
username
0%
completed in PHD

← Prev (1.2)
Organometallic Chemistry
Next (1.2.2) →
Metal alkyl and aryl

Comments 



Metal Carbonyls

https://www.chemistryelite.com/phd/1.2.1?ceal=en