Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term " metalorganic compound " refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry. Organometallic compounds are widely used both stoichiometrically in research and industrial chemical reactions, as well as in the role of catalysts to increase the rates of such reactions e.
Organometallic compounds are distinguished by the prefix "organo-" e. Examples of such organometallic compounds include all Gilman reagents , which contain lithium and copper. Tetracarbonyl nickel , and ferrocene are examples of organometallic compounds containing transition metals. In addition to the traditional metals, lanthanides, actinides, and semimetals, elements such as boron , silicon , arsenic , and selenium are considered to form organometallic compounds, e. Ferrocene is an archetypal organoiron complex.
It is an air-stable, sublimable compound. Cobaltocene is a structural analogue of ferrocene, but is highly reactive toward air. Tris triphenylphosphine rhodium carbonyl hydride is used in the commercial production of many aldehyde-based fragrances. Zeise's salt is an example of a transition metal alkene complex. Trimethylaluminium is an organometallic compound with a bridging methyl group.
Acylsilanes: valuable organosilicon reagents in organic synthesis
It is used in the industrial production of some alcohols. Dimethylzinc has a linear coordination. It is a volatile pyrophoric liquid that is used in the preparation of semiconducting films. Lithium diphenylcuprate bis diethyl etherate is an example of a Gilman reagent , a type of organocopper complex frequently employed in organic synthesis. Adenosylcobalamin is a cofactor required by several crucial enzymatic reactions that take place in the human body.
It is a rare example of a metal cobalt alkyl in biology. Iron 0 pentacarbonyl is a red-orange liquid prepared directly from the union of finely divided iron and carbon monoxide gas under pressure. Technetium[ 99m Tc] sestamibi is used to image the heart muscle in nuclear medicine. Many complexes feature coordination bonds between a metal and organic ligands. The organic ligands often bind the metal through a heteroatom such as oxygen or nitrogen, in which case such compounds are considered coordination compounds. However, if any of the ligands form a direct M-C bond, then complex is usually considered to be organometallic, e.
Furthermore, many lipophilic compounds such as metal acetylacetonates and metal alkoxides are called "metalorganics. A naturally occurring transition metal alkyl complex is methylcobalamin a form of Vitamin B 12 , with a cobalt - methyl bond. This subset of complexes is often discussed within the subfield of bioorganometallic chemistry. The status of compounds in which the canonical anion has a delocalized structure in which the negative charge is shared with an atom more electronegative than carbon, as in enolates , may vary with the nature of the anionic moiety, the metal ion, and possibly the medium; in the absence of direct structural evidence for a carbon—metal bond, such compounds are not considered to be organometallic.
For instance, lithium enolates often contain only Li-O bonds and are not organometallic, while zinc enolates Reformatsky reagents contain both Zn-O and Zn-C bonds, and are organometallic in nature. The metal-carbon bond in organometallic compounds is generally highly covalent.
For highly electropositive elements, such as lithium and sodium, the carbon ligand exhibits carbanionic character, but free carbon-based anions are extremely rare, an example being cyanide. As in other areas of chemistry, electron counting is useful for organizing organometallic chemistry. The electron rule is helpful in predicting the stabilities of metal carbonyls and related compounds. Most organometallic compounds do not however follow the 18e rule. Chemical bonding and reactivity in organometallic compounds is often discussed from the perspective of the isolobal principle.
As well as X-ray diffraction, NMR and infrared spectroscopy are common techniques used to determine structure. The dynamic properties of organometallic compounds is often probed with variable-temperature NMR and chemical kinetics. Early developments in organometallic chemistry include Louis Claude Cadet 's synthesis of methyl arsenic compounds related to cacodyl , William Christopher Zeise 's  platinum-ethylene complex ,  Edward Frankland 's discovery of diethyl- and dimethylzinc , Ludwig Mond 's discovery of Ni CO 4 ,  and Victor Grignard 's organomagnesium compounds.
Though not always acknowledged as an organometallic compound, Prussian blue , a mixed-valence iron-cyanide complex, was first prepared in by paint maker Johann Jacob Diesbach as the first coordination polymer and synthetic material containing a metal-carbon bond. Recognition of organometallic chemistry as a distinct subfield culminated in the Nobel Prizes to Ernst Fischer and Geoffrey Wilkinson for work on metallocenes.
In , Yves Chauvin , Robert H. Grubbs and Richard R. Schrock shared the Nobel Prize for metal-catalyzed olefin metathesis. Organometallic compounds find wide use in commercial reactions, both as homogeneous catalysis and as stoichiometric reagents For instance, organolithium , organomagnesium , and organoaluminium compounds , examples of which are highly basic and highly reducing, are useful stoichiometrically, but also catalyze many polymerization reactions.
Almost all processes involving carbon monoxide rely on catalysts, notable examples being described as carbonylations. Most synthetic aldehydes are produced via hydroformylation. The bulk of the synthetic alcohols, at least those larger than ethanol, are produced by hydrogenation of hydroformylation-derived aldehydes. Similarly, the Wacker process is used in the oxidation of ethylene to acetaldehyde. Almost all industrial processes involving alkene -derived polymers rely on organometallic catalysts.
The world's polyethylene and polypropylene are produced via both heterogeneously via Ziegler—Natta catalysis and homogeneously, e. Most processes involving hydrogen rely on metal-based catalysts. Whereas bulk hydrogenations, e. Many semiconductors are produced from trimethylgallium , trimethylindium , trimethylaluminium , and trimethylantimony.
These volatile compounds are decomposed along with ammonia , arsine , phosphine and related hydrides on a heated substrate via metalorganic vapor phase epitaxy MOVPE process in the production of light-emitting diodes LEDs. The synthesis of many organic molecules are facilitated by organometallic complexes. Sigma-bond metathesis is a synthetic method for forming new carbon-carbon sigma bonds. Sigma-bond metathesis is typically used with early transition-metal complexes that are in their highest oxidation state.
Soil may contain iron sulfide as pyrite or calcium sulfate as gypsum. 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.
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.
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 top 20 inorganic chemicals manufactured in Canada, China, Europe, India, Japan, and the US data :  Aluminium sulfate , Ammonia , Ammonium nitrate , Ammonium sulfate , Carbon black , Chlorine , hydrochloric acid , hydrogen , hydrogen peroxide , nitric acid , nitrogen , oxygen , phosphoric acid , sodium carbonate , sodium chlorate , sodium hydroxide , sodium silicate , sodium sulfate , sulfuric acid , and titanium dioxide.
The manufacturing of fertilizers is another practical application of industrial 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.
When studying inorganic compounds, one often encounters parts of the different classes of inorganic chemistry an organometallic compound is characterized by its coordination chemistry, and may show interesting solid state properties. In modern coordination compounds almost all organic and inorganic compounds can be used as ligands. The "metal" usually is a metal from the groups , as well as the trans - lanthanides and trans - actinides , but from a certain perspective, all chemical compounds can be described as coordination complexes.
A topical theme within this specialization is supramolecular coordination chemistry. 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. Main group compounds have been known since the beginnings of chemistry, e.
Experiments on oxygen, O 2 , 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 s deeply impacted mankind, demonstrating the significance of inorganic chemical synthesis. Main group compounds also occur in nature, e. 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. A range of transition metals can be found in biologically important compounds, such as iron in hemoglobin.
Usually, organometallic compounds are considered to contain the M-C-H group. 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, H 2 , and N 2. Because the ligands are petrochemicals in some sense, the area of organometallic chemistry has greatly benefited from its relevance to industry.
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.
By definition, these compounds occur in nature, but the subfield includes anthropogenic species, such as pollutants e. 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. This important area focuses on structure ,  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.
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 complex 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. The disagreement between qualitative theory paramagnetic and observation diamagnetic led to the development of models for "magnetic coupling. 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 NH 3 is pyramidal whereas ClF 3 is T-shaped. 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.
A central construct in inorganic chemistry is the theory of molecular symmetry.
Silicon Reagents for Organic Synthesis | SpringerLink
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. As an instructional tool, group theory highlights commonalities and differences in the bonding of otherwise disparate species, such as WF 6 and Mo CO 6 or CO 2 and NO 2. 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.
An important and increasingly popular aspect of inorganic chemistry focuses on reaction pathways. The mechanisms of reactions are discussed differently for different classes of compounds. The mechanisms of main group compounds of groups 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. Mechanisms for the reactions of transition metals are discussed differently from main group compounds. These themes are covered in articles on coordination chemistry and ligand. Both associative and dissociative pathways are observed. 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.