Inorganic chemistry
Inorganic chemistry deals with
Occurrence
Many inorganic compounds are found in nature as minerals.[2] Soil may contain iron sulfide as pyrite or calcium sulfate as gypsum.[3][4] Inorganic compounds are also found multitasking as biomolecules: as electrolytes (sodium chloride), in energy storage (ATP) or in construction (the polyphosphate backbone in DNA).
Bonding
When one reactant contains hydrogen atoms, a reaction can take place by exchanging protons in
Subdivisions of inorganic chemistry
Subdivisions of inorganic chemistry are numerous, but include:
- organometallic chemistry, compounds with metal-carbon bonds. This area touches on organic synthesis, which employs many organometallic catalysts and reagents.
- metal-metal bonds or bridging ligands.
- bioinorganic chemistry, biomolecules that contain metals. This area touches on medicinal chemistry.
- solid state chemistry, extended (i.e. polymeric) solids exhibiting properties not seen for simple molecules. Many practical themes are associated with these areas, including ceramics.
Industrial inorganic chemistry
Inorganic chemistry is a highly practical area of science. Traditionally, the scale of a nation's economy could be evaluated by their productivity of sulfuric acid.
An important man-made inorganic compound is
Descriptive inorganic chemistry
Descriptive inorganic chemistry focuses on the classification of compounds based on their properties. Partly the classification focuses on the position in the periodic table of the heaviest element (the element with the highest atomic weight) in the compound, partly by grouping compounds by their structural similarities
Coordination compounds
Classical coordination compounds feature metals bound to "lone pairs" of electrons residing on the main group atoms of ligands such as H2O, NH3, Cl−, and CN−. In modern coordination compounds almost all organic and inorganic compounds can be used as ligands. The "metal" usually is a metal from the groups 3–13, as well as the trans-lanthanides and trans-actinides, but from a certain perspective, all chemical compounds can be described as coordination complexes.
The stereochemistry of coordination complexes can be quite rich, as hinted at by Werner's separation of two
- Examples: [Co(THF)2.
Coordination compounds show a rich diversity of structures, varying from tetrahedral for titanium (e.g., TiCl4) to square planar for some nickel complexes to octahedral for coordination complexes of cobalt. A range of transition metals can be found in biologically important compounds, such as iron in hemoglobin.
- Examples: iron pentacarbonyl, titanium tetrachloride, cisplatin
Main group compounds
These species feature elements from
Main group compounds have been known since the beginnings of chemistry, e.g., elemental
- Examples: tetrasulfur tetranitride S4N4, diborane B2H6, silicones, buckminsterfullerene C60.
- Examples: xenon hexafluoride XeF6, xenon trioxide XeO3, and krypton difluoride KrF2
Organometallic compounds
Usually, organometallic compounds are considered to contain the M-C-H group.
Organometallic compounds are mainly considered a special category because organic ligands are often sensitive to hydrolysis or oxidation, necessitating that organometallic chemistry employs more specialized preparative methods than was traditional in Werner-type complexes. Synthetic methodology, especially the ability to manipulate complexes in solvents of low coordinating power, enabled the exploration of very weakly coordinating ligands such as hydrocarbons, H2, and N2. Because the ligands are petrochemicals in some sense, the area of organometallic chemistry has greatly benefited from its relevance to industry.
- Examples: Cyclopentadienyliron dicarbonyl dimer (C5H5)Fe(CO)2CH3, ferrocene Fe(C5H5)2, molybdenum hexacarbonyl Mo(CO)6, triethylborane Et3B, Tris(dibenzylideneacetone)dipalladium(0) Pd2(dba)3)
Cluster compounds
Clusters can be found in all classes of
- Examples: 4Fe-4S
Bioinorganic compounds
By definition, these compounds occur in nature, but the subfield includes anthropogenic species, such as pollutants (e.g.,
- Examples: hemoglobin, methylmercury, carboxypeptidase
Solid state compounds
This important area focuses on structure,[13] bonding, and the physical properties of materials. In practice, solid state inorganic chemistry uses techniques such as crystallography to gain an understanding of the properties that result from collective interactions between the subunits of the solid. Included in solid state chemistry are metals and their alloys or intermetallic derivatives. Related fields are condensed matter physics, mineralogy, and materials science.
- Examples: zeolites, YBa2Cu3O7
Spectroscopy and magnetism
In contrast to most organic compounds, many inorganic compounds are magnetic and/or colored. These properties provide information on the bonding and structure. The magnetism of inorganic compounds can be comlex.For example, most copper(II) compounds are paramagnetic but CuII2(OAc)4(H2O)2 is almost diamagnetic below room temperature. The explanation is due to magnetic coupling between pairs of Cu(II) sites in the acetate.
Qualitative theories
Inorganic chemistry has greatly benefited from qualitative theories. Such theories are easier to learn as they require little background in quantum theory. Within main group compounds,
Molecular symmetry group theory
A construct in chemistry is molecular symmetry, as embodied in Group theory. Inorganic compounds display a particularly diverse symmetries, so it is logical that Group Theory is intimately associated with inorganic chemistry.[14] Group theory]provides the language to describe the shapes of molecules according to their point group symmetry. Group theory also enables factoring and simplification of theoretical calculations.
Spectroscopic features are analyzed and described with respect to the symmetry properties of the, inter alia, vibrational or electronic states. Knowledge of the symmetry properties of the ground and excited states allows one to predict the numbers and intensities of absorptions in vibrational and electronic spectra. A classic application of group theory is the prediction of the number of C-O vibrations in substituted metal carbonyl complexes. The most common applications of symmetry to spectroscopy involve vibrational and electronic spectra.
Group theory highlights commonalities and differences in the bonding of otherwise disparate species. For example, the metal-based orbitals transform identically for
Thermodynamics and inorganic chemistry
An alternative quantitative approach to inorganic chemistry focuses on energies of reactions. This approach is highly traditional and
Mechanistic inorganic chemistry
An important aspect of inorganic chemistry focuses on reaction pathways, i.e. reaction mechanisms.
Main group elements and lanthanides
The mechanisms of main group compounds of groups 13-18 are usually discussed in the context of organic chemistry (organic compounds are main group compounds, after all). Elements heavier than C, N, O, and F often form compounds with more electrons than predicted by the
Transition metal complexes
Transition metal and main group compounds often react differently.
An overarching aspect of mechanistic transition metal chemistry is the kinetic lability of the complex illustrated by the exchange of free and bound water in the prototypical complexes [M(H2O)6]n+:
- [M(H2O)6]n+ + 6 H2O* → [M(H2O*)6]n+ + 6 H2O
- where H2O* denotes isotopically enriched water, e.g., H217O
The rates of water exchange varies by 20 orders of magnitude across the periodic table, with lanthanide complexes at one extreme and Ir(III) species being the slowest.
Redox reactions
Redox reactions are prevalent for the transition elements. Two classes of redox reaction are considered: atom-transfer reactions, such as oxidative addition/reductive elimination, and
- [MnO4]− + [Mn*O4]2− → [MnO4]2− + [Mn*O4]−
Reactions at ligands
Coordinated ligands display reactivity distinct from the free ligands. For example, the acidity of the ammonia ligands in
Characterization of inorganic compounds
Because of the diverse range of elements and the correspondingly diverse properties of the resulting derivatives, inorganic chemistry is closely associated with many methods of analysis. Older methods tended to examine bulk properties such as the electrical conductivity of solutions,
- molecular structures.
- Various forms of spectroscopy:
- Ultraviolet-visible spectroscopy: Historically, this has been an important tool, since many inorganic compounds are strongly colored
- 1H) NMR is also important because the light hydrogen nucleus is not easily detected by X-ray crystallography.
- Infrared spectroscopy: Mostly for absorptions from carbonyl ligands
- Electron nuclear double resonance (ENDOR) spectroscopy
- Mössbauer spectroscopy
- paramagneticmetal centres.
- Electrochemistry: Cyclic voltammetryand related techniques probe the redox characteristics of compounds.
Synthetic inorganic chemistry
Although some inorganic species can be obtained in pure form from nature, most are synthesized in chemical plants and in the laboratory.
Inorganic synthetic methods can be classified roughly according to the volatility or solubility of the component reactants.
See also
References
- ^ "Careers in Chemistry: Inorganic Chemistry". American Chemical Society. Archived from the original on 2012-10-29.
- ISSN 0008-4476.
- ISBN 978-1-4612-7684-5, retrieved 2022-08-21
- S2CID 97227345.
- ISSN 0009-2665.
- S2CID 237588318.
- ISBN 978-90-481-6675-6, retrieved 2022-08-21
- PMID 10788553.
- ISBN 978-3-527-29311-7.
- ISBN 978-0-08-037941-8.
- ISBN 978-3-527-28164-0.
- ISBN 978-0-935702-73-6.
- ^ Wells, A.F. (1984). Structural Inorganic Chemistry. Oxford: Clarendon Press.
- ISBN 978-0-471-51094-9.
- ISBN 978-3-527-28389-7.
- ISBN 978-0-935702-48-4.