Request PDF on ResearchGate | Carboranes and Metallacarboranes | IntroductionCarborane Structures and Skeletal Electron NumbersLocalized Bond . Most of the carborane derivatives of the icosahedral (C2B10) or small cage ( C2B4) systems are formed, by varying the groups on the cage carbons. This is. The general formula of carboranes is represented by C2BnHn + 2, in which n is an derivatives called metallacarboranes, some of which show catalytic activity.
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Carboraneany member of a class of organometallic compounds containing carbon Cboron Band hydrogen H. The first carboranes were produced in the s, but the results were not declassified and published until — Since then, many thousands of carboranes have been prepared, and they have been combined with transition metals to yield derivatives called metallacarboranes, some of which show catalytic activity.
The carboranes have polyhedral molecular structures based on networks of boron and carbon atoms, in which the carbon atoms occupy adjacent positions.
As a result, the structures of carboranes and their derivatives are similar to those of the isoelectronic possessing the same number of electrons polyhedral boranes, and, like the boranes, they involve metallacarvoranes bonds as well as ordinary two-centre bonds.
Their most significant structural feature is the covalent bonding of carbon simultaneously to five or six other atoms. In addition, the nomenclature of carboranes employs the same structural prefixes closo – arachno – etc. The numbering of the atoms in carborane compounds begins with the apex atom of lowest coordination i. The best-studied carborane is ortho metallacarborans, C 2 B 10 H 12made by reaction of acetylene with decaborane in the presence of diethyl sulfide.
Its molecular structure resembles an icosahedron with the 10 boron atoms and two adjacent metalllacarboranes atoms forming the apices.
Carboranes are generally prepared by reaction of acetylene or acetylene derivatives with boron hydrides. The first three carboranes—trigonal bipyramidal 1,5-C 2 B 3 H 5 ; the 1,2- and 1,6- isomers of octahedral C 2 B 4 H 6 ; and pentagonal pyramidal 2,4-C 2 B 5 H 7 —that were produced in the s were generated in low yield by the reaction of pentaborane 9 with acetylene in a silent electric discharge.
The three isomeric icosahedral closo -carboranes of formula C 2 B 10 H 12 are unusual both in their ease of preparation and their stability in air. Not only has their chemistry been the most extensively studied of all carboranes, but their discovery ushered in the rapid snd of the field.
Although their systematic International Union of Pure and Applied Chemistry IUPAC name is closo -dicarbadodecaborane 12the three isomers are often simply called ortho – meta metallacarbornes, and para -carborane. The most common carborane, the ortho -isomer, metallacarborxnes been available in multikilogram quantities since the early s and is best prepared by the reaction of acetylene, C 2 H 2with decaborane 14 in the presence of a Lewis base such as diethyl sulfide, C 2 H 5 2 S.
Numerous derivatives of icosahedral closo -carboranes, especially of 1,2-C 2 B 10 H 12have been prepared by replacement of hydrogen atoms by other groups. Despite their stability toward heat and reagents, the American chemist M. Greenwood, and their colleagues. We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind. Your contribution may be further edited by our staff, and its publication is subject to our final approval.
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Our editors will review what you’ve submitted, and if it meets our criteria, we’ll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Learn More in these related Britannica articles: The most commonly encountered carborane cluster is icosahedral dicarbaborane C 2 B 10 H Depending on the location of the carbon atoms in the boron cage, dicarbaboranes are classified into three isomers: Carbon Cnonmetallic chemical element in Group 14 IVa of the periodic table.
Although widely distributed in nature, carbon is not particularly plentiful—it makes up only about 0. In the isotope carbon was selected to…. Hydrogen Ha colourless, odourless, tasteless, flammable metallacarbofanes substance that is the simplest member of the family of chemical elements.
The hydrogen atom has a nucleus consisting of a proton bearing one unit of positive electrical charge; an electron, bearing one unit of negative electrical charge, is also associated with…. Metalany of a class of substances characterized by high electrical and thermal conductivity as well as by malleability, ductility, and high reflectivity of light. Approximately three-quarters of all known chemical elements are metals.
Boraneany of a homologous series of inorganic compounds of boron and hydrogen or their derivatives. The boron hydrides were first systematically…. Help us improve this article! Contact our editors with your feedback. Introduction Structure and bonding of carboranes Reactions and synthesis of carboranes. You may find it helpful to search within the site to see how similar or related subjects are covered. Any text you add should be original, not copied from other sources.
Carboranes And Metallacarboranes: Advances And New Perspectives |
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