Fulvenes are the class of hydrocarbon obtained by formally cross-conjugating one ring and methylidene through a common exocyclic double bond. [1] [2]
The name is derived from fulvene, which has one pentagonal ring. Other examples include methylenecyclopropene (triafulvene) and heptafulvene.
Several types of fulvenes are defined. [3] They are:
Fulvenes are readily prepared by the condensation of cyclopentadiene and aldehydes and ketones:
Fulvenes are common ligands and ligand precursors in organometallic chemistry. [8] 2,3,4,5-Tetramethylfulvene, abbreviated Me4Fv, results from the deprotonation of cationic pentamethylcyclopentadienyl complexes. [9] Some Me4Fv complexes are called tuck-in complexes.
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, 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.
An imine is a functional group or organic compound containing a carbon–nitrogen double bond. The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions.
A Schiff base (named after Hugo Schiff) is a compound with the general structure R1R2C=NR' (R' ≠ H). They can be considered a sub-class of imines, being either secondary ketimines or secondary aldimines depending on their structure. The term is often synonymous with azomethine which refers specifically to secondary aldimines (i.e. R-CH=NR' where R' ≠ H).
3-Methylenecyclopropene, also called methylenecyclopropene or triafulvene, is a hydrocarbon with chemical formula C4H4. It is a colourless gas that polymerizes readily as a liquid or in solution but is stable as a gas. This highly strained and reactive molecule was synthesized and characterized for the first time in 1984, and has been the subject of considerable experimental and theoretical interest. It is an example of a cross-conjugated alkene, being composed of cyclopropene with an exocyclic double bond attached.
An alkyne trimerisation reaction is a [2+2+2] cycloaddition reaction in which three alkyne units react to form a benzene ring. The reaction requires a metal catalyst. The process is of historic interest as well as being applicable to organic synthesis. Being a cycloaddition reaction, it has high atom economy. Many variations have been developed including cyclisation of mixtures of alkynes and alkenes as well as alkynes and nitriles.
Cryptands are a family of synthetic bicyclic and polycyclic multidentate ligands for a variety of cations. The Nobel Prize for Chemistry in 1987 was given to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen for their efforts in discovering and determining uses of cryptands and crown ethers, thus launching the now flourishing field of supramolecular chemistry. The term cryptand implies that this ligand binds substrates in a crypt, interring the guest as in a burial. These molecules are three-dimensional analogues of crown ethers but are more selective and strong as complexes for the guest ions. The resulting complexes are lipophilic.
Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry.
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.
The Nazarov cyclization reaction is a chemical reaction used in organic chemistry for the synthesis of cyclopentenones. The reaction is typically divided into classical and modern variants, depending on the reagents and substrates employed. It was originally discovered by Ivan Nikolaevich Nazarov (1906–1957) in 1941 while studying the rearrangements of allyl vinyl ketones.
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.
Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction. This allows spatial information to transfer from one molecule to the target, forming the product as a single enantiomer. The chiral information is most commonly contained in a catalyst and, in this case, the information in a single molecule of catalyst may be transferred to many substrate molecules, amplifying the amount of chiral information present. Similar processes occur in nature, where a chiral molecule like an enzyme can catalyse the introduction of a chiral centre to give a product as a single enantiomer, such as amino acids, that a cell needs to function. By imitating this process, chemists can generate many novel synthetic molecules that interact with biological systems in specific ways, leading to new pharmaceutical agents and agrochemicals. The importance of asymmetric hydrogenation in both academia and industry contributed to two of its pioneers — William Standish Knowles and Ryōji Noyori — being awarded one half of the 2001 Nobel Prize in Chemistry.
In coordination chemistry, a stability constant is an equilibrium constant for the formation of a complex in solution. It is a measure of the strength of the interaction between the reagents that come together to form the complex. There are two main kinds of complex: compounds formed by the interaction of a metal ion with a ligand and supramolecular complexes, such as host–guest complexes and complexes of anions. The stability constant(s) provide(s) the information required to calculate the concentration(s) of the complex(es) in solution. There are many areas of application in chemistry, biology and medicine.
Organoscandium chemistry is an area with organometallic compounds focused on compounds with at least on carbon to scandium chemical bond. The interest in organoscandium compounds is mostly academic but motivated by potential practical applications in catalysis, especially in polymerization. A common precursor is scandium chloride, especially its THF complex.
Oxazoline is a five-membered heterocyclic chemical compound containing one atom each of oxygen and nitrogen. It was likely first synthesized in 1884 but it was not until 5 years later that Siegmund Gabriel correctly assigned the structure. It was named in-line with the Hantzsch–Widman nomenclature and is part of a family of heterocyclic compounds, where it exists between oxazole and oxazolidine in terms of saturation.
Organogold chemistry is the study of compounds containing gold–carbon bonds. They are studied in academic research, but have not received widespread use otherwise. The dominant oxidation states for organogold compounds are I with coordination number 2 and a linear molecular geometry and III with CN = 4 and a square planar molecular geometry. The first organogold compound discovered was gold(I) carbide Au2C2, which was first prepared in 1900.
In organometallic chemistry, a tuck-in complex usually refers to derivatives of Cp* ligands wherein a methyl group is deprotonated and the resulting methylene attaches to the metal. The C5–CH2–M angle is acute. The term "tucked in" was coined to describe derivatives of organotungsten complexes. Although most "tucked-in" complexes are derived from Cp* ligands, other pi-bonded rings undergo similar reactions.
A transition metal fullerene complex is a coordination complex wherein fullerene serves as a ligand. Fullerenes are typically spheroidal carbon compounds, the most prevalent being buckminsterfullerene, C60.
Parisa Mehrkhodavandi is a Canadian chemist and Professor of Chemistry at the University of British Columbia (UBC). Her research focuses on the design of new catalysts that can effect polymerization of sustainably sourced or biodegradable polymers.
The parent metallacyclobenzene has the formula LnM(CH)5. They can be viewed as derivatives of benzene wherein a CH center has been replaced by a transition metal complex. Most metallabenzenes do not feature the M(CH)5 ring itself, but, instead, some of the H atoms are replaced by other substituents.
Transition metal isocyanide complexes are coordination compounds containing isocyanide ligands. Because isocyanide are relatively basic, but also good pi-acceptors, a wide range of complexes are known. Some isocyanide complexes are used in medical imaging.
