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Inorganic chemistry

Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, as there is much overlap in the subdiscipline of organometallic chemistry. It has applications in every aspect of the chemical industry, including catalysis, materials science, pigments, surfactants, coatings, medications, fuels, and agriculture.[1]

The structure of the ionic framework in potassium oxide, K2O

Key concepts

Many inorganic compounds are ionic compounds, consisting of cations and anions joined by ionic bonding.[2] Examples of salts (which are ionic compounds) are magnesium chloride MgCl2, which consists of magnesium cations Mg2+ and chloride anions Cl; or sodium oxide Na2O, which consists of sodium cations Na+ and oxide anions O2−. In any salt, the proportions of the ions are such that the electric charges cancel out, so that the bulk compound is electrically neutral. The ions are described by their oxidation state and their ease of formation can be inferred from the ionization potential (for cations) or from the electron affinity (anions) of the parent elements.

Important classes of inorganic compounds are the oxides, the carbonates, the sulfates, and the halides. Many inorganic compounds are characterized by high melting points. Many inorganic compounds have high melting point and ease of crystallization. Some salts (e.g., NaCl) are very soluble in water, others (e.g., FeS) are not.

The simplest inorganic reaction is double displacement when in mixing of two salts the ions are swapped without a change in oxidation state. In redox reactions one reactant, the oxidant, lowers its oxidation state and another reactant, the reductant, has its oxidation state increased. The net result is an exchange of electrons. Electron exchange can occur indirectly as well, e.g., in batteries, a key concept in electrochemistry.

When one reactant contains hydrogen atoms, a reaction can take place by exchanging protons in acid-base chemistry. In a more general definition, any chemical species capable of binding to electron pairs is called a Lewis acid; conversely any molecule that tends to donate an electron pair is referred to as a Lewis base.[3] As a refinement of acid-base interactions, the HSAB theory takes into account polarizability and size of ions.

Inorganic compounds are found in nature as minerals.[4] Soil may contain iron sulfide as pyrite or calcium sulfate as gypsum.[5][6] Inorganic compounds are also found multitasking as biomolecules: as electrolytes (sodium chloride), in energy storage (ATP) or in construction (the polyphosphate backbone in DNA).

The first important man-made inorganic compound was ammonium nitrate for soil fertilization through the Haber process.[7] Inorganic compounds are synthesized for use as catalysts such as vanadium(V) oxide and titanium(III) chloride, or as reagents in organic chemistry such as lithium aluminium hydride.

Subdivisions of inorganic chemistry are organometallic chemistry, cluster chemistry and bioinorganic chemistry. These fields are active areas of research in inorganic chemistry, aimed toward new catalysts, superconductors, and therapies.

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. The manufacturing of fertilizers, which often begins with the Haber-Bosch process, is another practical application of industrial inorganic chemistry.[8][9]

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

 
EDTA chelates an octahedrally coordinated Co3+ ion in [Co(EDTA)]

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 enantiomers of [Co((OH)2Co(NH3)4)3]6+, an early demonstration that chirality is not inherent to organic compounds. A topical theme within this specialization is supramolecular coordination chemistry.[10]

Main group compounds

 
Tetrasulfur tetranitride, S4N4, is a main group compound that continues to intrigue chemists

These species feature elements from groups I, II, III, IV, V,VI, VII, 0 (excluding hydrogen) of the periodic table. Due to their often similar reactivity, the elements in group 3 (Sc, Y, and La) and group 12 (Zn, Cd, and Hg) are also generally included, and the lanthanides and actinides are sometimes included as well.[11]

Main group compounds have been known since the beginnings of chemistry, e.g., elemental sulfur and the distillable white phosphorus. Experiments on oxygen, O2, by Lavoisier and Priestley not only identified an important diatomic gas, but opened the way for describing compounds and reactions according to stoichiometric ratios. The discovery of a practical synthesis of ammonia using iron catalysts by Carl Bosch and Fritz Haber in the early 1900s deeply impacted mankind, demonstrating the significance of inorganic chemical synthesis. Typical main group compounds are SiO2, SnCl4, and N2O. Many main group compounds can also be classed as "organometallic", as they contain organic groups, e.g., B(CH3)3). Main group compounds also occur in nature, e.g., phosphate in DNA, and therefore may be classed as bioinorganic. Conversely, organic compounds lacking (many) hydrogen ligands can be classed as "inorganic", such as the fullerenes, buckytubes and binary carbon oxides.

Noble gas compounds

Noble gases are elements which have filled valence electron shells in their neutral state, and are thus stable as lone atoms. Historically known as being inert, methods were discovered to react with them. The trend within the group is for the larger elements to be more reactive. Xenon and krypton are more easily ionized, and can combine with extremely electronegative elements to make fluorides and oxides and form solid ionic compounds. Argon, neon, and helium are much less reactive, though in cosmochemistry ArH+ has been observed spectroscopically in interstellar gas. Noble gases can also be trapped in solids while not being directly coordinated in clathrates or in endohedral fullerenes.

Transition metal compounds

Compounds containing metals from group 4 to 11 are considered transition metal compounds. Compounds with a metal from group 3 or 12 are sometimes also incorporated into this group, but also often classified as main group compounds.

Transition metal compounds show a rich coordination chemistry, 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.

Organometallic compounds

 
Organolithium reagents are most often found in polymeric form, such as n-butyllithium shown here

Usually, organometallic compounds are considered to contain the M-C-H group.[12] The metal (M) in these species can either be a main group element or a transition metal. Operationally, the definition of an organometallic compound is more relaxed to include also highly lipophilic complexes such as metal carbonyls and even metal alkoxides.

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.

Cluster compounds

 
Decaborane is a powerfully toxic cluster compound of boron
 
Iron–sulfur clusters are central components of iron–sulfur proteins, essential for human metabolism

Clusters can be found in all classes of chemical compounds. According to the commonly accepted definition, a cluster consists minimally of a triangular set of atoms that are directly bonded to each other. But metal-metal bonded dimetallic complexes are highly relevant to the area. Clusters occur in "pure" inorganic systems, organometallic chemistry, main group chemistry, and bioinorganic chemistry. The distinction between very large clusters and bulk solids is increasingly blurred. This interface is the chemical basis of nanoscience or nanotechnology and specifically arise from the study of quantum size effects in cadmium selenide clusters. Thus, large clusters can be described as an array of bound atoms intermediate in character between a molecule and a solid.

Bioinorganic compounds

 
The octahedral cobalt centre of Vitamin B12

By definition, these compounds occur in nature, but the subfield includes anthropogenic species, such as pollutants (e.g., methylmercury) and drugs (e.g., Cisplatin).[13] The field, which incorporates many aspects of biochemistry, includes many kinds of compounds, e.g., the phosphates in DNA, and also metal complexes containing ligands that range from biological macromolecules, commonly peptides, to ill-defined species such as humic acid, and to water (e.g., coordinated to gadolinium complexes employed for MRI). Traditionally bioinorganic chemistry focuses on electron- and energy-transfer in proteins relevant to respiration. Medicinal inorganic chemistry includes the study of both non-essential and essential elements with applications to diagnosis and therapies.

Solid state compounds

 
YBa2Cu3O7, or YBCO, is a high temperature superconductor able to levitate above a magnet when colder than its critical temperature of about 90 K (−183 °C)

This important area focuses on structure,[14] 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.

Theoretical inorganic chemistry

An alternative perspective on the area of inorganic chemistry begins with the Bohr model of the atom and, using the tools and models of theoretical chemistry and computational chemistry, expands into bonding in simple and then more complicated molecules. Precise quantum mechanical descriptions for multielectron species, the province of inorganic chemistry, is difficult. This challenge has spawned many semi-quantitative or semi-empirical approaches including molecular orbital theory and ligand field theory, In parallel with these theoretical descriptions, approximate methodologies are employed, including density functional theory.

Exceptions to theories, qualitative and quantitative, are extremely important in the development of the field. For example, CuII2(OAc)4(H2O)2 is almost diamagnetic below room temperature whereas crystal field theory predicts that the molecule would have two unpaired electrons. The disagreement between qualitative theory (paramagnetic) and observation (diamagnetic) led to the development of models for magnetic coupling, such as the exchange interaction. These improved models led to the development of new magnetic materials and new technologies.

Qualitative theories

 
Crystal field theory explains why [FeIII(CN)6]3− has only one unpaired electron

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, VSEPR theory powerfully predicts, or at least rationalizes, the structures of main group compounds, such as an explanation for why NH3 is pyramidal whereas ClF3 is T-shaped. For the transition metals, crystal field theory allows one to understand the magnetism of many simple complexes, such as why [FeIII(CN)6]3− has only one unpaired electron, whereas [FeIII(H2O)6]3+ has five. A particularly powerful qualitative approach to assessing the structure and reactivity begins with classifying molecules according to electron counting, focusing on the numbers of valence electrons, usually at the central atom in a molecule.

Molecular symmetry group theory

 

A central construct in inorganic chemistry is the theory of molecular symmetry.[15] Mathematical 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 WF6 and W(CO)6, but the energies and populations of these orbitals differ significantly. A similar relationship exists CO2 and molecular beryllium difluoride.

Thermodynamics and inorganic chemistry

An alternative quantitative approach to inorganic chemistry focuses on energies of reactions. This approach is highly traditional and empirical, but it is also useful. Broad concepts that are couched in thermodynamic terms include redox potential, acidity, phase changes. A classic concept in inorganic thermodynamics is the Born–Haber cycle, which is used for assessing the energies of elementary processes such as electron affinity, some of which cannot be observed directly.

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 octet rule, as explained in the article on hypervalent molecules. The mechanisms of their reactions differ from organic compounds for this reason. Elements lighter than carbon (B, Be, Li) as well as Al and Mg often form electron-deficient structures that are electronically akin to carbocations. Such electron-deficient species tend to react via associative pathways. The chemistry of the lanthanides mirrors many aspects of chemistry seen for aluminium.

Transition metal complexes

Transition metal and main group compounds often react differently.[16] The important role of d-orbitals in bonding strongly influences the pathways and rates of ligand substitution and dissociation. These themes are covered in articles on coordination chemistry and ligand. Both associative and dissociative pathways are observed.

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 electron-transfer. A fundamental redox reaction is "self-exchange", which involves the degenerate reaction between an oxidant and a reductant. For example, permanganate and its one-electron reduced relative manganate exchange one electron:

[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 [Co(NH3)6]3+ is elevated relative to NH3 itself. Alkenes bound to metal cations are reactive toward nucleophiles whereas alkenes normally are not. The large and industrially important area of catalysis hinges on the ability of metals to modify the reactivity of organic ligands. Homogeneous catalysis occurs in solution and heterogeneous catalysis occurs when gaseous or dissolved substrates interact with surfaces of solids. Traditionally homogeneous catalysis is considered part of organometallic chemistry and heterogeneous catalysis is discussed in the context of surface science, a subfield of solid state chemistry. But the basic inorganic chemical principles are the same. Transition metals, almost uniquely, react with small molecules such as CO, H2, O2, and C2H4. The industrial significance of these feedstocks drives the active area of catalysis. Ligands can also undergo ligand transfer reactions such as transmetalation.

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, melting points, solubility, and acidity. With the advent of quantum theory and the corresponding expansion of electronic apparatus, new tools have been introduced to probe the electronic properties of inorganic molecules and solids. Often these measurements provide insights relevant to theoretical models. Commonly encountered techniques are:

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.[17] Soluble inorganic compounds are prepared using methods of organic synthesis. For metal-containing compounds that are reactive toward air, Schlenk line and glove box techniques are followed. Volatile compounds and gases are manipulated in "vacuum manifolds" consisting of glass piping interconnected through valves, the entirety of which can be evacuated to 0.001 mm Hg or less. Compounds are condensed using liquid nitrogen (b.p. 78K) or other cryogens. Solids are typically prepared using tube furnaces, the reactants and products being sealed in containers, often made of fused silica (amorphous SiO2) but sometimes more specialized materials such as welded Ta tubes or Pt "boats". Products and reactants are transported between temperature zones to drive reactions.

See also

References

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inorganic, chemistry, journal, inorganic, chemistry, journal, deals, with, synthesis, behavior, inorganic, organometallic, compounds, this, field, covers, chemical, compounds, that, carbon, based, which, subjects, organic, chemistry, distinction, between, disc. For the journal see Inorganic Chemistry journal Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds This field covers chemical compounds that are not carbon based which are the subjects of organic chemistry The distinction between the two disciplines is far from absolute as there is much overlap in the subdiscipline of organometallic chemistry It has applications in every aspect of the chemical industry including catalysis materials science pigments surfactants coatings medications fuels and agriculture 1 The structure of the ionic framework in potassium oxide K2O Contents 1 Key concepts 1 1 Industrial inorganic chemistry 2 Descriptive inorganic chemistry 2 1 Coordination compounds 2 2 Main group compounds 2 3 Noble gas compounds 2 4 Transition metal compounds 2 5 Organometallic compounds 2 6 Cluster compounds 2 7 Bioinorganic compounds 2 8 Solid state compounds 3 Theoretical inorganic chemistry 3 1 Qualitative theories 3 2 Molecular symmetry group theory 4 Thermodynamics and inorganic chemistry 5 Mechanistic inorganic chemistry 5 1 Main group elements and lanthanides 5 2 Transition metal complexes 5 2 1 Redox reactions 5 2 2 Reactions at ligands 6 Characterization of inorganic compounds 7 Synthetic inorganic chemistry 8 See also 9 ReferencesKey concepts EditMany inorganic compounds are ionic compounds consisting of cations and anions joined by ionic bonding 2 Examples of salts which are ionic compounds are magnesium chloride MgCl2 which consists of magnesium cations Mg2 and chloride anions Cl or sodium oxide Na2O which consists of sodium cations Na and oxide anions O2 In any salt the proportions of the ions are such that the electric charges cancel out so that the bulk compound is electrically neutral The ions are described by their oxidation state and their ease of formation can be inferred from the ionization potential for cations or from the electron affinity anions of the parent elements Important classes of inorganic compounds are the oxides the carbonates the sulfates and the halides Many inorganic compounds are characterized by high melting points Many inorganic compounds have high melting point and ease of crystallization Some salts e g NaCl are very soluble in water others e g FeS are not The simplest inorganic reaction is double displacement when in mixing of two salts the ions are swapped without a change in oxidation state In redox reactions one reactant the oxidant lowers its oxidation state and another reactant the reductant has its oxidation state increased The net result is an exchange of electrons Electron exchange can occur indirectly as well e g in batteries a key concept in electrochemistry When one reactant contains hydrogen atoms a reaction can take place by exchanging protons in acid base chemistry In a more general definition any chemical species capable of binding to electron pairs is called a Lewis acid conversely any molecule that tends to donate an electron pair is referred to as a Lewis base 3 As a refinement of acid base interactions the HSAB theory takes into account polarizability and size of ions Inorganic compounds are found in nature as minerals 4 Soil may contain iron sulfide as pyrite or calcium sulfate as gypsum 5 6 Inorganic compounds are also found multitasking as biomolecules as electrolytes sodium chloride in energy storage ATP or in construction the polyphosphate backbone in DNA The first important man made inorganic compound was ammonium nitrate for soil fertilization through the Haber process 7 Inorganic compounds are synthesized for use as catalysts such as vanadium V oxide and titanium III chloride or as reagents in organic chemistry such as lithium aluminium hydride Subdivisions of inorganic chemistry are organometallic chemistry cluster chemistry and bioinorganic chemistry These fields are active areas of research in inorganic chemistry aimed toward new catalysts superconductors and therapies Industrial inorganic chemistry Edit 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 The manufacturing of fertilizers which often begins with the Haber Bosch process is another practical application of industrial inorganic chemistry 8 9 Descriptive inorganic chemistry EditDescriptive 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 Edit EDTA chelates an octahedrally coordinated Co3 ion in Co EDTA Main article Coordination chemistry 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 enantiomers of Co OH 2Co NH3 4 3 6 an early demonstration that chirality is not inherent to organic compounds A topical theme within this specialization is supramolecular coordination chemistry 10 Examples Co EDTA Co NH3 6 3 TiCl4 THF 2 Main group compounds Edit Tetrasulfur tetranitride S4N4 is a main group compound that continues to intrigue chemists These species feature elements from groups I II III IV V VI VII 0 excluding hydrogen of the periodic table Due to their often similar reactivity the elements in group 3 Sc Y and La and group 12 Zn Cd and Hg are also generally included and the lanthanides and actinides are sometimes included as well 11 Main group compounds have been known since the beginnings of chemistry e g elemental sulfur and the distillable white phosphorus Experiments on oxygen O2 by Lavoisier and Priestley not only identified an important diatomic gas but opened the way for describing compounds and reactions according to stoichiometric ratios The discovery of a practical synthesis of ammonia using iron catalysts by Carl Bosch and Fritz Haber in the early 1900s deeply impacted mankind demonstrating the significance of inorganic chemical synthesis Typical main group compounds are SiO2 SnCl4 and N2O Many main group compounds can also be classed as organometallic as they contain organic groups e g B CH3 3 Main group compounds also occur in nature e g phosphate in DNA and therefore may be classed as bioinorganic Conversely organic compounds lacking many hydrogen ligands can be classed as inorganic such as the fullerenes buckytubes and binary carbon oxides Examples tetrasulfur tetranitride S4N4 diborane B2H6 silicones buckminsterfullerene C60 Noble gas compounds Edit Main article Noble gas compounds Noble gases are elements which have filled valence electron shells in their neutral state and are thus stable as lone atoms Historically known as being inert methods were discovered to react with them The trend within the group is for the larger elements to be more reactive Xenon and krypton are more easily ionized and can combine with extremely electronegative elements to make fluorides and oxides and form solid ionic compounds Argon neon and helium are much less reactive though in cosmochemistry ArH has been observed spectroscopically in interstellar gas Noble gases can also be trapped in solids while not being directly coordinated in clathrates or in endohedral fullerenes Examples xenon hexafluoride XeF6 xenon trioxide XeO3 krypton difluoride KrF2 argon fluorohydride HArFTransition metal compounds Edit Compounds containing metals from group 4 to 11 are considered transition metal compounds Compounds with a metal from group 3 or 12 are sometimes also incorporated into this group but also often classified as main group compounds Transition metal compounds show a rich coordination chemistry 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 cisplatinOrganometallic compounds Edit Organolithium reagents are most often found in polymeric form such as n butyllithium shown here Main article Organometallic chemistry Usually organometallic compounds are considered to contain the M C H group 12 The metal M in these species can either be a main group element or a transition metal Operationally the definition of an organometallic compound is more relaxed to include also highly lipophilic complexes such as metal carbonyls and even metal alkoxides 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 Edit Decaborane is a powerfully toxic cluster compound of boron Iron sulfur clusters are central components of iron sulfur proteins essential for human metabolism Main article Cluster compound Clusters can be found in all classes of chemical compounds According to the commonly accepted definition a cluster consists minimally of a triangular set of atoms that are directly bonded to each other But metal metal bonded dimetallic complexes are highly relevant to the area Clusters occur in pure inorganic systems organometallic chemistry main group chemistry and bioinorganic chemistry The distinction between very large clusters and bulk solids is increasingly blurred This interface is the chemical basis of nanoscience or nanotechnology and specifically arise from the study of quantum size effects in cadmium selenide clusters Thus large clusters can be described as an array of bound atoms intermediate in character between a molecule and a solid Examples Fe3 CO 12 B10H14 Mo6Cl14 2 4Fe 4SBioinorganic compounds Edit The octahedral cobalt centre of Vitamin B12 Main article Bioinorganic chemistry See also Bioorganometallic chemistry By definition these compounds occur in nature but the subfield includes anthropogenic species such as pollutants e g methylmercury and drugs e g Cisplatin 13 The field which incorporates many aspects of biochemistry includes many kinds of compounds e g the phosphates in DNA and also metal complexes containing ligands that range from biological macromolecules commonly peptides to ill defined species such as humic acid and to water e g coordinated to gadolinium complexes employed for MRI Traditionally bioinorganic chemistry focuses on electron and energy transfer in proteins relevant to respiration Medicinal inorganic chemistry includes the study of both non essential and essential elements with applications to diagnosis and therapies Examples hemoglobin methylmercury carboxypeptidaseSolid state compounds Edit Main article solid state chemistry YBa2Cu3O7 or YBCO is a high temperature superconductor able to levitate above a magnet when colder than its critical temperature of about 90 K 183 C This important area focuses on structure 14 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 silicon chips zeolites YBa2Cu3O7Theoretical inorganic chemistry EditAn alternative perspective on the area of inorganic chemistry begins with the Bohr model of the atom and using the tools and models of theoretical chemistry and computational chemistry expands into bonding in simple and then more complicated molecules Precise quantum mechanical descriptions for multielectron species the province of inorganic chemistry is difficult This challenge has spawned many semi quantitative or semi empirical approaches including molecular orbital theory and ligand field theory In parallel with these theoretical descriptions approximate methodologies are employed including density functional theory Exceptions to theories qualitative and quantitative are extremely important in the development of the field For example CuII2 OAc 4 H2O 2 is almost diamagnetic below room temperature whereas crystal field theory predicts that the molecule would have two unpaired electrons The disagreement between qualitative theory paramagnetic and observation diamagnetic led to the development of models for magnetic coupling such as the exchange interaction These improved models led to the development of new magnetic materials and new technologies Qualitative theories Edit Crystal field theory explains why FeIII CN 6 3 has only one unpaired electron 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 VSEPR theory powerfully predicts or at least rationalizes the structures of main group compounds such as an explanation for why NH3 is pyramidal whereas ClF3 is T shaped For the transition metals crystal field theory allows one to understand the magnetism of many simple complexes such as why FeIII CN 6 3 has only one unpaired electron whereas FeIII H2O 6 3 has five A particularly powerful qualitative approach to assessing the structure and reactivity begins with classifying molecules according to electron counting focusing on the numbers of valence electrons usually at the central atom in a molecule Molecular symmetry group theory Edit Nitrogen dioxide NO2 exhibits C2v symmetry A central construct in inorganic chemistry is the theory of molecular symmetry 15 Mathematical 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 WF6 and W CO 6 but the energies and populations of these orbitals differ significantly A similar relationship exists CO2 and molecular beryllium difluoride Thermodynamics and inorganic chemistry EditAn alternative quantitative approach to inorganic chemistry focuses on energies of reactions This approach is highly traditional and empirical but it is also useful Broad concepts that are couched in thermodynamic terms include redox potential acidity phase changes A classic concept in inorganic thermodynamics is the Born Haber cycle which is used for assessing the energies of elementary processes such as electron affinity some of which cannot be observed directly Mechanistic inorganic chemistry EditAn important aspect of inorganic chemistry focuses on reaction pathways i e reaction mechanisms Main group elements and lanthanides Edit 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 octet rule as explained in the article on hypervalent molecules The mechanisms of their reactions differ from organic compounds for this reason Elements lighter than carbon B Be Li as well as Al and Mg often form electron deficient structures that are electronically akin to carbocations Such electron deficient species tend to react via associative pathways The chemistry of the lanthanides mirrors many aspects of chemistry seen for aluminium Transition metal complexes Edit Transition metal and main group compounds often react differently 16 The important role of d orbitals in bonding strongly influences the pathways and rates of ligand substitution and dissociation These themes are covered in articles on coordination chemistry and ligand Both associative and dissociative pathways are observed 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 H217OThe 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 Edit 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 electron transfer A fundamental redox reaction is self exchange which involves the degenerate reaction between an oxidant and a reductant For example permanganate and its one electron reduced relative manganate exchange one electron MnO4 Mn O4 2 MnO4 2 Mn O4 Reactions at ligands Edit Coordinated ligands display reactivity distinct from the free ligands For example the acidity of the ammonia ligands in Co NH3 6 3 is elevated relative to NH3 itself Alkenes bound to metal cations are reactive toward nucleophiles whereas alkenes normally are not The large and industrially important area of catalysis hinges on the ability of metals to modify the reactivity of organic ligands Homogeneous catalysis occurs in solution and heterogeneous catalysis occurs when gaseous or dissolved substrates interact with surfaces of solids Traditionally homogeneous catalysis is considered part of organometallic chemistry and heterogeneous catalysis is discussed in the context of surface science a subfield of solid state chemistry But the basic inorganic chemical principles are the same Transition metals almost uniquely react with small molecules such as CO H2 O2 and C2H4 The industrial significance of these feedstocks drives the active area of catalysis Ligands can also undergo ligand transfer reactions such as transmetalation Characterization of inorganic compounds EditBecause 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 melting points solubility and acidity With the advent of quantum theory and the corresponding expansion of electronic apparatus new tools have been introduced to probe the electronic properties of inorganic molecules and solids Often these measurements provide insights relevant to theoretical models Commonly encountered techniques are X ray crystallography This technique allows for the 3D determination of molecular structures Dual polarisation interferometer This technique measures the conformation and conformational change of molecules Various forms of spectroscopy Ultraviolet visible spectroscopy Historically this has been an important tool since many inorganic compounds are strongly colored NMR spectroscopy Besides 1H and 13C many other NMR active nuclei e g 11B 19F 31P and 195Pt can give important information on compound properties and structure The NMR of paramagnetic species can provide important structural information Proton 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 Mossbauer spectroscopy Electron spin resonance ESR or EPR allows for the measurement of the environment of paramagnetic metal centres Electrochemistry Cyclic voltammetry and related techniques probe the redox characteristics of compounds Synthetic inorganic chemistry EditAlthough 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 17 Soluble inorganic compounds are prepared using methods of organic synthesis For metal containing compounds that are reactive toward air Schlenk line and glove box techniques are followed Volatile compounds and gases are manipulated in vacuum manifolds consisting of glass piping interconnected through valves the entirety of which can be evacuated to 0 001 mm Hg or less Compounds are condensed using liquid nitrogen b p 78K or other cryogens Solids are typically prepared using tube furnaces the reactants and products being sealed in containers often made of fused silica amorphous SiO2 but sometimes more specialized materials such as welded Ta tubes or Pt boats Products and reactants are transported between temperature zones to drive reactions See also EditImportant publications in inorganic chemistryReferences Edit Careers in Chemistry Inorganic Chemistry American Chemical Society Archived from the original on 2012 10 29 Coll Richard K Treagust David F 2003 Investigation of secondary school undergraduate and graduate learners mental models of ionic bonding Journal of Research in Science Teaching 40 5 464 486 Bibcode 2003JRScT 40 464C doi 10 1002 tea 10085 ISSN 0022 4308 Jensen William B 1978 The Lewis acid base definitions a status report Chemical Reviews 78 1 1 22 doi 10 1021 cr60311a002 ISSN 0009 2665 Burns P C 2005 12 01 U6 Minerals and Inorganic Compounds Insights into an Expanded Structural Hierarchy of Crystal Structures The Canadian Mineralogist 43 6 1839 1894 doi 10 2113 gscanmin 43 6 1839 ISSN 0008 4476 Shainberg I Sumner M E Miller W P Farina M P W Pavan M A Fey M V 1989 Lal Rattan Stewart B A eds Use of Gypsum on Soils A Review Soil Restoration New York NY Springer New York vol 17 pp 1 111 doi 10 1007 978 1 4612 3532 3 1 ISBN 978 1 4612 7684 5 retrieved 2022 08 21 Haaijer Suzanne C M Lamers Leon P M Smolders Alfons J P Jetten Mike S M Op den Camp Huub J M 2007 08 14 Iron Sulfide and Pyrite as Potential Electron Donors for Microbial Nitrate Reduction in Freshwater Wetlands Geomicrobiology Journal 24 5 391 401 doi 10 1080 01490450701436489 ISSN 0149 0451 S2CID 97227345 Witschi H 2000 05 01 Fritz Haber 1868 1934 Toxicological Sciences 55 1 1 2 doi 10 1093 toxsci 55 1 1 PMID 10788553 Guo Jianping Chen Ping 2021 Ammonia history in the making Nature Catalysis 4 9 734 735 doi 10 1038 s41929 021 00676 0 ISSN 2520 1158 S2CID 237588318 Leigh G J 2004 Smith Barry E Richards Raymond L Newton William E eds Haber Bosch and Other Industrial Processes Catalysts for Nitrogen Fixation Dordrecht Springer Netherlands pp 33 54 doi 10 1007 978 1 4020 3611 8 2 ISBN 978 90 481 6675 6 retrieved 2022 08 21 Lehn J M 1995 Supramolecular Chemistry Concepts and Perspectives Weinheim VCH ISBN 978 3 527 29311 7 Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann ISBN 978 0 08 037941 8 Elschenbroich C Salzer A 1992 Organometallics A Concise Introduction 2nd ed Weinheim Wiley VCH ISBN 978 3 527 28164 0 S J Lippard J M Berg 1994 Principles of Bioinorganic Chemistry Mill Valley CA University Science Books ISBN 978 0 935702 73 6 Wells A F 1984 Structural Inorganic Chemistry Oxford Clarendon Press Cotton F A 1990 Chemical Applications of Group Theory 3rd ed New York John Wiley amp Sons ISBN 978 0 471 51094 9 R G Wilkins 1991 Kinetics and Mechanism of Reactions of Transition Metal Complexes 2nd ed Wiley VCH ISBN 978 3 527 28389 7 Girolami G S Rauchfuss T B Angelici R J 1999 Synthesis and Technique in Inorganic Chemistry 3rd ed Mill Valley CA University Science Books ISBN 978 0 935702 48 4 At Wikiversity you can learn more and teach others about Inorganic chemistry at the Department of Inorganic chemistry Retrieved from https en wikipedia org w index php title Inorganic chemistry amp oldid 1140743094, wikipedia, wiki, book, books, library,

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