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 Hydrides


Metal hydrides are fascinating compounds that form an important part of organometallic chemistry, an interdisciplinary subject that merges principles from inorganic and organic chemistry. Understanding metal hydrides involves delving deeply into the interactions between metal atoms and hydrogen, which result in a vast range of compounds with diverse structures, properties, and applications. Whether you are a student, researcher, or teacher, the study of metal hydrides offers complex challenges and opportunities for discovery.

Introduction to metal hydrides

Metal hydrides are compounds containing metal atoms bonded to hydrogen atoms. They exhibit a variety of structures ranging from simple ionic compounds to more complex covalent networks. The bonding in metal hydrides can be classified mainly into three types depending on the nature of the metal:

  • Ionic or saline hydride
  • Covalent hydrides
  • Interstitial or metallic hydrides

Ionic or saline hydride

Ionic hydrides typically involve alkali and alkaline earth metals. In these compounds, the metal donates electrons to hydrogen, forming an ionic bond. An example of this is sodium hydride, NaH, which is used as a strong base in organic synthesis.

2 Na + H₂ → 2 NaH

Such compounds are usually prepared by reacting the metal with hydrogen gas at high temperatures. They are often white solids and are known for their reactivity, especially with water.

Covalent hydrides

Covalent hydrides involve metals that form covalent bonds with hydrogen. Transition metals often form these compounds. A well-known example is palladium hydride, PdHₓ, which exhibits hydrogen absorption under certain conditions:

P.D. H

This compound plays an important role in catalytic processes, including hydrogenation reactions where hydrogen molecules are added to other compounds.

Interstitial or metallic hydrides

Interstitial hydrides are unique in that they involve transition metals. The hydrogen atoms occupy interstitial spaces or holes in the metal lattice. These compounds exhibit metallic properties such as electrical conductivity. Examples include titanium hydride, TiH₂, and zirconium hydride, ZrH₂.

These compounds are of significant interest in materials science due to their ability to store hydrogen efficiently. This property is particularly interesting for developing hydrogen storage materials, which are important for future energy solutions.

Applications of metal hydrides

The range of applications of metal hydrides is very large, since their properties are so diverse. Important applications include:

Hydrogen storage

The ability of metal hydrides to absorb and release hydrogen makes them ideal candidates for hydrogen storage technology. This is important for applications in fuel cells and other hydrogen-based energy systems.

TiH₂ → Ti + H₂ (on heating)

This reaction exhibits dynamic equilibrium, where the metal hydride releases hydrogen when heated and absorbs it when cooled.

Catalysis

Metal hydrides act as catalysts in a variety of reactions, notably hydrogenation, where unsaturated compounds such as alkenes are converted into saturated compounds using hydrogen.

An example of a catalytic cycle involving a metal hydride:

Rh–H C=C H

This cycle facilitates hydrogenation by reacting a rhodium hydride complex with an alkene, resulting in the formation of an alkene.

Synthesis of metal hydrides

There are several methods for the synthesis of metal hydrides, depending on the metal involved:

Direct combination

Metals react directly with hydrogen gas to form hydrides. This is common for the alkali and alkaline earth metals:

2 Li + H₂ → 2 LiH

Shortage

Some metal hydrides are prepared by reducing metal halides with lithium aluminium hydride (LiAlH₄), which is itself a complex metal hydride.

For example, from titanium chlorine:

TiCl₄ + 4 LiAlH₄ → TiH₄ + 4 LiCl + 4 AlH₃

Role in organometallic chemistry

In organometallic chemistry, metal hydrides serve as key reagents and intermediates. The presence of hydrogen in metal complexes often favorably affects bond energies and reaction pathways, making them indispensable tools in synthesis and catalysis.

For example, in Wilkinson's Catalyst, a rhodium-based metal hydride complex, the hydride ligand helps facilitate the oxidative addition of hydrogen gas:

[Rh(PPh₃)₃Cl] + H₂ → [Rh(H)₂(PPh₃)₃Cl]

Challenges and future outlook

While the potential of metal hydrides is enormous, realizing their practical applications faces challenges. Issues such as stability, economic feasibility, and synthesis conditions remain to be addressed. Researchers are exploring new alloy composition and nanostructured materials to enhance performance characteristics.

As our understanding develops, metal hydrides are expected to play important roles in innovative technologies, especially in renewable energy resources and advanced materials applications.

Conclusion

In conclusion, metal hydrides are a cornerstone of organometallic chemistry, with a broad spectrum of applications ranging from catalysis to hydrogen storage. Their complex structure and properties provide ample opportunities for exploration and innovation.

The future of such studies promises exciting developments that can significantly impact various scientific fields and industries. Continued research on these compounds will undoubtedly lead to new insights and practical applications. This exploration is evidence of the rich potential of chemistry in advancing technology and solving complex scientific challenges.


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Metal Hydrides

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