A metallocene is a compound typically consisting of two cyclopentadienyl anions (C
5H−
5, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula (C5H5)2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride or vanadocene dichloride. Certain metallocenes and their derivatives exhibit catalytic properties, although metallocenes are rarely used industrially. Cationic group 4 metallocene derivatives related to [Cp2ZrCH3]+ catalyze olefin polymerization.
Annulenes are monocyclic hydrocarbons that contain the maximum number of non-cumulated or conjugated double bonds ('mancude'). They have the general formula CnHn (when n is an even number) or CnHn+1 (when n is an odd number). The IUPAC accepts the use of 'annulene nomenclature' in naming carbocyclic ring systems with 7 or more carbon atoms, using the name '[n]annulene' for the mancude hydrocarbon with n carbon atoms in its ring, though in certain contexts (e.g., discussions of aromaticity for different ring sizes), smaller rings (n = 3 to 6) can also be informally referred to as annulenes. Using this form of nomenclature 1,3,5,7-cyclooctatetraene is [8]annulene and benzene is [6]annulene (and occasionally referred to as just 'annulene').
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy.
Cycloocta-1,5-diene is a cyclic hydrocarbon with the chemical formula C8H12, specifically [−(CH2)2−CH=CH−]2.
In coordination chemistry, hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated. In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity, and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.
Uranocene, U(C8H8)2, is an organouranium compound composed of a uranium atom sandwiched between two cyclooctatetraenide rings. It was one of the first organoactinide compounds to be synthesized. It is a green air-sensitive solid that dissolves in organic solvents. Uranocene, a member of the "actinocenes," a group of metallocenes incorporating elements from the actinide series. It is the most studied bis[8]annulene-metal system, although it has no known practical applications.
Triiron dodecarbonyl is the organoiron compound with the formula Fe3(CO)12. It is a dark green solid that sublimes under vacuum. It is soluble in nonpolar organic solvents to give intensely green solutions. Most low-nuclearity clusters are pale yellow or orange. Hot solutions of Fe3(CO)12 decompose to an iron mirror, which can be pyrophoric in air.The solid decomposes slowly in air, and thus samples are typically stored cold under an inert atmosphere. It is a more reactive source of iron(0) than iron pentacarbonyl.
In organometallic chemistry, a sandwich compound is a chemical compound featuring a metal bound by haptic, covalent bonds to two arene (ring) ligands. The arenes have the formula CnHn, substituted derivatives and heterocyclic derivatives. Because the metal is usually situated between the two rings, it is said to be "sandwiched". A special class of sandwich complexes are the metallocenes.
Organoactinide chemistry is the science exploring the properties, structure, and reactivity of organoactinide compounds, which are organometallic compounds containing a carbon to actinide chemical bond.
Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 is the 2005 version of Nomenclature of Inorganic Chemistry. It is a collection of rules for naming inorganic compounds, as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
Rhodocene is a chemical compound with the formula [Rh(C5H5)2]. Each molecule contains an atom of rhodium bound between two planar aromatic systems of five carbon atoms known as cyclopentadienyl rings in a sandwich arrangement. It is an organometallic compound as it has (haptic) covalent rhodium–carbon bonds. The [Rh(C5H5)2] radical is found above 150 °C (302 °F) or when trapped by cooling to liquid nitrogen temperatures (−196 °C [−321 °F]). At room temperature, pairs of these radicals join via their cyclopentadienyl rings to form a dimer, a yellow solid.
Hexamethylbenzene, also known as mellitene, is a hydrocarbon with the molecular formula C12H18 and the condensed structural formula C6(CH3)6. It is an aromatic compound and a derivative of benzene, where benzene's six hydrogen atoms have each been replaced by a methyl group. In 1929, Kathleen Lonsdale reported the crystal structure of hexamethylbenzene, demonstrating that the central ring is hexagonal and flat and thereby ending an ongoing debate about the physical parameters of the benzene system. This was a historically significant result, both for the field of X-ray crystallography and for understanding aromaticity.
Cyclopentadienyliron dicarbonyl dimer is an organometallic compound with the formula [(η5-C5H5)Fe(CO)2]2, often abbreviated to Cp2Fe2(CO)4, [CpFe(CO)2]2 or even Fp2, with the colloquial name "fip dimer". It is a dark reddish-purple crystalline solid, which is readily soluble in moderately polar organic solvents such as chloroform and pyridine, but less soluble in carbon tetrachloride and carbon disulfide. Cp2Fe2(CO)4 is insoluble in but stable toward water. Cp2Fe2(CO)4 is reasonably stable to storage under air and serves as a convenient starting material for accessing other Fp (CpFe(CO)2) derivatives (described below).
In organometallic chemistry, a transition metal alkene complex is a coordination compound containing one or more alkene ligands. The inventory is large. Such compounds are intermediates in many catalytic reactions that convert alkenes to other organic products.
Neptunocene, Np(C8H8)2, is an organoneptunium compound composed of a neptunium atom sandwiched between two cyclooctatetraenide (COT2-) rings. As a solid it has a dark brown/red colour but it appears yellow when dissolved in chlorocarbons, in which it is sparingly soluble. The compound is quite air-sensitive.
Plutonocene, Pu(C8H8)2, is an organoplutonium compound composed of a plutonium atom sandwiched between two cyclooctatetraenide (COT2-) rings. It is a dark red, very air-sensitive solid that is sparingly soluble in toluene and chlorocarbons. Plutonocene is a member of the actinocene family of metallocenes incorporating actinide elements in the +4 oxidation state.
Metal arene complexes are organometallic compounds of the formula (C6R6)xMLy. Common classes are of the type (C6R6)ML3 and (C6R6)2M. These compounds are reagents in inorganic and organic synthesis. The principles that describe arene complexes extend to related organic ligands such as many heterocycles (e.g. thiophene) and polycyclic aromatic compounds (e.g. naphthalene).
(Cyclooctatetraene)iron tricarbonyl is the organoiron compound with the formula (C8H8)Fe(CO)3. Like other examples of (diene)Fe(CO)3 complexes, it is an orange, diamagnetic solid. Although several isomers are possible, only the η4-C8H8 complex is observed. The complex is an example of a ring-whizzer, since, on the NMR time-scale, the Fe(CO)3 center migrates around the rim of the cyclooctatetraene ligand.
Protactinium compounds are compounds containing the element protactinium. These compounds usually have protactinium in the +5 oxidation state, although these compounds can also exist in the +2, +3 and +4 oxidation states.
A molecular electron-reservoir complex is one of a class of redox-active systems which can store and transfer electrons stoichiometrically or catalytically without decomposition. The concept of electron-reservoir complexes was introduced by the work of French chemist, Didier Astruc. From Astruc's discoveries, a whole family of thermally stable, neutral, 19-electron iron(I) organometallic complexes were isolated and characterized, and found to have applications in redox catalysis and electrocatalysis. The following page is a reflection of the prototypal electron-reservoir complexes discovered by Didier Astruc.
