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Bis(pinacolato)diboron
Bis(pinacolato)diboron is a covalent compound containing two boron atoms and two pinacolato ligands. It has the formula CH3)4C2O2Bsub>2; the pinacol groups are sometimes abbreviated as "pin", so the structure is sometimes represented as B2pin2. It is a colourless solid that is soluble in organic solvents. It is a commercially available reagent for making pinacol boronic esters for organic synthesis. Unlike some other diboron compounds, B2pin2 is not moisture-sensitive and can be handled in air. Preparation and structure This compound may be prepared by treating tetrakis(dimethylamino)diboron with pinacol Pinacol is a white solid organic compound. It is a diol that has hydroxyl groups (-OH) on vicinal carbon atoms. Preparation It may be produced by the pinacol coupling reaction from acetone: Reactions As a vicinal-diol, it can rearrange t ... in acidic conditions. The B-B bond length is 1.711(6) Å. Dehydrogenation of pinacolborane provides an alternative route: :2(CH ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinacol Boronic Ester
A boronic acid is an organic compound related to boric acid () in which one of the three hydroxyl groups () is replaced by an alkyl or aryl group (represented by R in the general formula ). As a compound containing a carbon–boron bond, members of this class thus belong to the larger class of organoboranes. Boronic acids act as Lewis acids. Their unique feature is that they are capable of forming reversible covalent complexes with sugars, amino acids, hydroxamic acids, etc. (molecules with vicinal, (1,2) or occasionally (1,3) substituted Lewis base donors ( alcohol, amine, carboxylate)). The p''K''a of a boronic acid is ~9, but they can form tetrahedral boronate complexes with p''K''a ~7. They are occasionally used in the area of molecular recognition to bind to saccharides for fluorescent detection or selective transport of saccharides across membranes. Boronic acids are used extensively in organic chemistry as chemical building blocks and intermediates predominantly in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinacol
Pinacol is a white solid organic compound. It is a diol that has hydroxyl groups (-OH) on vicinal carbon atoms. Preparation It may be produced by the pinacol coupling reaction from acetone: Reactions As a vicinal-diol, it can rearrange to pinacolone by the pinacol rearrangement, e.g. by heating with sulfuric acid: Pinacol can be used with borane and boron trichloride to produce useful synthetic intermediates such as pinacolborane, bis(pinacolato)diboron,{{OrgSynth , collvol = 10 , collvolpages = 115 , year = 2004 , prep = v77p0176 , title = Bis(pinacolato)diboron , author1 = Tatsuo Ishiyama, author2= Miki Murata, author3=Taka-aki Ahiko, author4-link= Norio Miyaura, author4=Norio Miyaura and pinacolchloroborane. See also * Semipinacol rearrangement The semipinacol rearrangement is a rearrangement reaction in organic chemistry involving a heterosubstituted alcohol of the type R1R2(HO)C–C(X)R3R4. The hetero substituent can be a halogen (Cl, Br, I), a tosylate, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoboron Compounds
Organoborane or organoboron compounds are chemical compounds of boron and carbon that are organic derivatives of BH3, for example trialkyl boranes. Organoboron chemistry or organoborane chemistry is the chemistry of these compounds. Organoboron compounds are important reagents in organic chemistry enabling many chemical transformations, the most important one called hydroboration. Reactions of organoborates and boranes involve the transfer of a nucleophilic group attached to boron to an electrophilic center either inter- or intramolecularly. α,β-Unsaturated borates, as well as borates with a leaving group at the α position, are highly susceptible to intramolecular 1,2-migration of a group from boron to the electrophilic α position. Oxidation or protonolysis of the resulting organoboranes may generate a variety of organic products, including alcohols, carbonyl compounds, alkenes, and halides. Properties of the B-C bond The C-B bond has low polarity (the difference in electron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Covalent Compound
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding. Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. The term ''covalent bond'' dates from 1939. The prefix ''co-'' means ''jointly, associated in action, partnered to a lesser degree, '' etc.; thus a "co-valent bond", in essence, means that the atoms share " valence", such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boron
Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has three valence electrons for forming covalent bonds, resulting in many compounds such as boric acid, the mineral borax, sodium borate, and the ultra-hard crystals of boron carbide and boron nitride. Boron is synthesized entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, so it is a low-abundance element in the Solar System and in the Crust (geology), Earth's crust. It constitutes about 0.001 percent by weight of Earth's crust. It is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. These are mined industrially as evaporites, such as borax and kernite. The largest known deposits are in Turkey, the largest producer of boron minerals. Elemental b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: ''total synthesis'', ''semisynthesis'', and ''methodology''. Total synthesis A total synthesis is the complete chemical synthesis of complex organic molecules from simple, commercially available petrochemical or natural precursors. Total synthesis may be accomplished either via a linear or convergent approach. In a ''linear'' synthesis—often adequate for simple structures—several steps are performed one after another until the molecule is complete; the chemical compounds made in each step are called synthetic intermediates. Most often, each step in a synthesis refers to a separate rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinacolborane
Pinacolborane is the borane Trihydridoboron, also known as borane or borine, is an unstable and highly reactive molecule with the chemical formula . The preparation of borane carbonyl, BH3(CO), played an important role in exploring the chemistry of boranes, as it indicated ... with the formula (CH3)4C2O2BH. Often pinacolborane is abbreviated HBpin. It features a boron hydride functional group incorporated in a five-membered C2O2B ring. Like related boron alkoxides, pinacolborane is monomeric. It is a colorless liquid. It features a reactive B-H functional group. Use in organic synthesis In the presence of catalysts, pinacolborane hydroborates alkenes and, less rapidly, alkynes. Pinacolborane also affects catalyst-free hydroboration of aldehydes, ketones, and carboxylic acids. Pinacolborane is used in borylation, a form of C-H activation. Dehydrogenation of pinacolborane affords dipinacolatodiborane (B2pin2): :2{{nbsp(CH3)4C2O2BH → (CH3)4C2O2B-BO2C2(CH3)4 + H2 Related ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organorhodium Chemistry
Organorhodium chemistry is the chemistry of organometallic compounds containing a rhodium-carbon chemical bond, and the study of rhodium and rhodium compounds as catalysts in organic reactions. Stable organorhodium compounds and transient organorhodium intermediates are used as catalyst such as in olefin hydroformylation, olefin hydrogenation, olefin isomerization and the Monsanto process Classification based on principal oxidation states Organometallic rhodium compounds share many characteristics with those of iridium, but less so with cobalt. Rhodium can exist in oxidation states of -III to +V, but rhodium(I) and rhodium(III) are the more common. Rhodium(I) compounds (d8 configuration) usually occur with square planar or trigonal bipyramidal geometries, while rhodium (III) compounds (d6 configuration) typically have an octahedral geometry. Rhodium(0) Rhodium(0) complexes are binary carbonyls, the principal examples being tetrarhodium dodecacarbonyl, Rh4(CO)12, and hexadecacarbony ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoiridium Compound
Organoiridium chemistry is the chemistry of organometallic compounds containing an iridium-carbon chemical bond. Organoiridium compounds are relevant to many important processes including olefin hydrogenation and the industrial synthesis of acetic acid. They are also of great academic interest because of the diversity of the reactions and their relevance to the synthesis of fine chemicals. Classification based on principal oxidation states Organoiridium compounds share many characteristics with those of rhodium, but less so with cobalt. Iridium can exist in oxidation states of -III to +V, but iridium(I) and iridium(III) are the more common. iridium(I) compounds (d8 configuration) usually occur with square planar or trigonal bipyramidal geometries, whereas iridium(III) compounds (d6 configuration) typically have an octahedral geometry. Iridium(0) Iridium(0) complexes are binary carbonyls, the principal member being tetrairidium dodecacarbonyl, Ir4(CO)12. Unlike the relate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition Metal Boryl Complex
In chemistry, a transition metal boryl complex is a molecular species with a formally anionic boron center coordinated to a transition metal. They have the formula LnM-BR2 or LnM-(BR2LB) (L = ligand, R = H, organic substituent, LB = Lewis base). One example is (C5Me5)Mn(CO)2(BH2PMe3) (Me = methyl). Such compounds, especially those derived from catecholborane and the related pinacolborane, are intermediates in transition metal-catalyzed borylation reactions. Synthesis Oxidative addition is the main route to metal boryl complexes. Both B-H and B-B bonds add to low-valent metal complexes. For example, catecholborane oxidatively adds to Pt(0) to give the boryl hydride. :C6H4O2BH + Pt(PR3)2 → C6H4O2B Pt(PR3)2H Addition of diboron tetrafluoride to Vaska's complex Vaska's complex is the trivial name for the chemical compound ''trans''-carbonylchlorobis(triphenylphosphine)iridium(I), which has the formula IrCl(CO) (C6H5)3sub>2. This square planar diamagnetic organometallic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
