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Carborane
Carboranes are electron-delocalized (non-classically bonded) clusters composed of boron, carbon and hydrogen atoms.Grimes, R. N., ''Carboranes 3rd Ed.'', Elsevier, Amsterdam and New York (2016), . Like many of the related boron hydrides, these clusters are polyhedra or fragments of polyhedra. Carboranes are one class of heteroboranes. In terms of scope, carboranes can have as few as 5 and as many as 14 atoms in the cage framework. The majority have two cage carbon atoms. The corresponding C-alkyl and B-alkyl analogues are also known in a few cases. Structure and bonding Carboranes and boranes adopt 3-dimensional cage (cluster) geometries in sharp contrast to typical organic compounds. Cages are compatible with sigma—delocalized bonding, whereas hydrocarbons are typically chains or rings. Like for other electron-delocalized polyhedral clusters, the electronic structure of these cluster compounds can be described by the Wade–Mingos rules. Like the related boron hydrides, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ortho-carborane
Ortho-carborane is the organoboron compound with the formula C2B10H12. The prefix ''ortho'' is derived from ortho. It is the most prominent carborane. This derivative has been considered for a wide range of applications from heat-resistant polymers to medical applications. It is a colorless solid that melts, without decomposition, at 320 °C. Structure The cluster has C2v symmetry. Preparation Ortho-carborane is prepared by the addition of acetylenes to decaborane(14). Modern syntheses involve two stages, the first involving generation of an adduct of decaborane: :B10H14 + 2 SEt2 → B10H12(SEt2)2 + H2 In the second stage, the alkyne is installed as the source of two carbon vertices: :B10H12(SEt2)2 + C2H2 → C2B10H12 + 2 SEt2 + H2 Substituted acetylenes can be employed more conveniently than acetylene gas. For example bis(acetoxymethyl)acetylene adds to the decarborane readily. :B10H12(SEt2)2 + C2(CH2O2CCH3)2 → C2B10H10(CH2O2CCH3)2 + 2 SEt2 + H2 The organic subs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superacid
In chemistry, a superacid (according to the classical definition) is an acid with an acidity greater than that of 100% pure sulfuric acid (), which has a Hammett acidity function (''H''0) of −12. According to the modern definition, a superacid is a medium in which the chemical potential of the proton is higher than in pure sulfuric acid. Commercially available superacids include trifluoromethanesulfonic acid (), also known as triflic acid, and fluorosulfuric acid (), both of which are about a thousand times stronger (i.e. have more negative ''H''0 values) than sulfuric acid. Most strong superacids are prepared by the combination of a strong Lewis acid and a strong Brønsted acid. A strong superacid of this kind is fluoroantimonic acid. Another group of superacids, the carborane acid group, contains some of the strongest known acids. Finally, when treated with anhydrous acid, zeolites (microporous aluminosilicate minerals) will contain superacidic sites within their pores. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of an ...—its atom making four electrons available to form covalent bond, covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three Isotopes of carbon, isotopes occur naturally, Carbon-12, C and Carbon-13, C being stable, while Carbon-14, C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the Timeline of chemical element discoveries#Ancient discoveries, few elements known since antiquity. Carbon is the 15th Abundance of elements in Earth's crust, most abundant element in the Earth's crust, and the Abundance of the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dicarbollide
In organometallic chemistry, a dicarbollide is an anion of the formula 2B9H11sup>2-. Various isomers exist, but most common is 1,2-dicarbollide derived from ortho-carborane. These dianions function as ligands, related to the cyclopentadienyl anion. Substituted dicarbollides are also known such as 2B9H10(pyridine)sup>− (pyridine bonded to B) and 2R2B9H9sup>2- (R groups bonded to carbon). Synthesis of dicarbollides Dicarbollides are obtained by base-degradation of 12-vertex dicarboranes. This degradation of the ortho derivative has been most heavily studied. The conversion is conducted in two-steps, first "deboronation" and second deprotonation: :C2B10H12 + NaOEt + 2 EtOH → Na+C2B9H12− + H2 + B(OEt)3 :Na+C2B9H12− + NaH → Na2C2B9H11 + H2 The dianion derived from ortho-carborane, 2B9H11sup>2- is a nido cluster. The nomenclature rules call the high coordination number vertex as 1. Thus the nido cluster with two adjacent carbon centers on the rim is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boron Hydrides
Boranes is the name given to compounds with the formula BxHy and related anions. Many such boranes are known. Most common are those with 1 to 12 boron atoms. Although they have few practical applications, the boranes exhibit structures and bonding that differs strongly from the patterns seen in hydrocarbons. Hybrids of boranes and hydrocarbons, the carboranes are also well developed. History The development of the chemistry of boranes led to innovations in synthetic methods as well as structure and bonding. First, new synthetic techniques were required to handle diborane and many of its derivatives, which are both pyrophoric and volatile. Alfred Stock invented the glass vacuum line for this purpose. The structure of diborane was correctly predicted in 1943 many years after its discovery. The structures of the boron hydride clusters were determined beginning in 1948 with the characterization of decaborane. William Lipscomb was awarded the Nobel prize in Chemistry in 1976 for th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heteroborane
Heteroboranes are classes of boranes, at least one boron atom is replaced by another element. Like many of the related boranes, these clusters are polyhedra and are similarly classified as ''closo-, nido-, arachno-, hypho-,'' according to the so-called electron count. ''Closo-'' represents a complete polyhedron, while ''nido-'', ''arachno-'' and ''hypho-'' stand for polyhedrons that are missing one, two and three vertices. Structurally, various heteroboranes can be derived from the icosahedral (''I''h) B12H122– via formal replacement of its BH fragments with isoelectronic CH+, P+ or S2+ fragments, e.g. ''closo''-1-CB11H12–, ''closo''-1,2-C2B10H12, ''closo''-1,2-P2B10H10 or ''closo''-1-SB11H11. See also * Carborane * Azaborane Azaborane usually refers a boranes, borane Cluster chemistry, cluster where BH vertices are replaced by N or NR (R = H, organic substituent). Like many of the related boranes, these clusters are polyhedra and can be classified as ''closo-'', ''nid . ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyhedral Skeletal Electron Pair Theory
In chemistry the polyhedral skeletal electron pair theory (PSEPT) provides electron counting rules useful for predicting the structures of clusters such as borane and carborane clusters. The electron counting rules were originally formulated by Kenneth Wade, and were further developed by others including Michael Mingos; they are sometimes known as Wade's rules or the Wade–Mingos rules. The rules are based on a molecular orbital treatment of the bonding. These notes contained original material that served as the basis of the sections on the 4''n'', 5''n'', and 6''n'' rules. These rules have been extended and unified in the form of the Jemmis ''mno'' rules. Predicting structures of cluster compounds Different rules (4''n'', 5''n'', or 6''n'') are invoked depending on the number of electrons per vertex. The 4''n'' rules are reasonably accurate in predicting the structures of clusters having about 4 electrons per vertex, as is the case for many boranes and carboranes. For such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decaborane
Decaborane, also called decaborane(14), is the borane with the chemical formula B10 H14. This white crystalline compound is one of the principal boron hydride clusters, both as a reference structure and as a precursor to other boron hydrides. It is toxic and volatile, with a foul odor. Handling, properties and structure The physical characteristics of decaborane(14) resemble those of naphthalene and anthracene, all three of which are volatile colorless solids. Sublimation is the common method of purification. Decaborane is highly flammable, but, like other boron hydrides, it burns with a bright green flame. It is not sensitive to moist air, although it hydrolyzes in boiling water, releasing hydrogen and giving a solution of boric acid. It is soluble in cold water as well as a variety of non-polar and moderately polar solvents. In decaborane, the B10 framework resembles an incomplete octadecahedron. Each boron has one "radial" hydride, and four boron atoms near the open part of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Closo Cluster
In chemistry the polyhedral skeletal electron pair theory (PSEPT) provides electron counting rules useful for predicting the structures of cluster compound, clusters such as borane and carborane clusters. The electron counting rules were originally formulated by Kenneth Wade, and were further developed by others including Michael Mingos; they are sometimes known as Wade's rules or the Wade–Mingos rules. The rules are based on a molecular orbital treatment of the bonding. These notes contained original material that served as the basis of the sections on the 4''n'', 5''n'', and 6''n'' rules. These rules have been extended and unified in the form of the Jemmis mno rules, Jemmis ''mno'' rules. Predicting structures of cluster compounds Different rules (4''n'', 5''n'', or 6''n'') are invoked depending on the number of electrons per vertex. The 4''n'' rules are reasonably accurate in predicting the structures of clusters having about 4 electrons per vertex, as is the case for many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weakly Coordinating Anion
Anions that interact weakly with cations are termed non-coordinating anions, although a more accurate term is weakly coordinating anion. Non-coordinating anions are useful in studying the reactivity of electrophilic cations. They are commonly found as counterions for cationic metal complexes with an 18-Electron rule, unsaturated coordination sphere. These special anions are essential components of Homogeneous catalysis, homogeneous Ziegler–Natta catalyst, alkene polymerisation catalysts, where the active catalyst is a coordinatively unsaturated, cationic transition metal complex. For example, they are employed as counterions for the electron counting, 14 valence electron cations [(C5H5)2ZrR]+ (R = methyl or a growing polyethylene chain). Complexes derived from non-coordinating anions have been used to catalyze hydrogenation, hydrosilylation, oligomerization, and the living polymerization of alkenes. The popularization of non-coordinating anions has contributed to increased underst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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