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Boranes
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 t ... [...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 suc ... [...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 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 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 boron is a meta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Lipscomb
William Nunn Lipscomb Jr. (December 9, 1919April 14, 2011) was a Nobel Prize-winning American inorganic and organic chemist working in nuclear magnetic resonance, theoretical chemistry, boron chemistry, and biochemistry. Biography Overview Lipscomb was born in Cleveland, Ohio. His family moved to Lexington, Kentucky in 1920, and he lived there until he received his Bachelor of Science degree in Chemistry at the University of Kentucky in 1941. He went on to earn his Doctor of Philosophy degree in Chemistry from the California Institute of Technology (Caltech) in 1946. From 1946 to 1959 he taught at the University of Minnesota. From 1959 to 1990 he was a professor of chemistry at Harvard University, where he was a professor emeritus since 1990. Lipscomb was married to the former Mary Adele Sargent from 1944 to 1983. They had three children, one of whom lived only a few hours. He married Jean Evans in 1983. They had one adopted daughter. Lipscomb resided in Cambridge, Massach ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetraborane
Tetraborane (systematically named ''arachno''-tetraborane(10)) was the first boron hydride compound to be classified by Stock and Messenez in 1912 and was first isolated by Alfred Stock. It has a relatively low boiling point at 18 °C and is a gas at room temperature. Tetraborane gas is foul smelling and toxic. History The class of boranes was elucidated using X-ray diffraction analysis by Lipscomb et al. in the 1950s. The X-ray data indicated two-electron multicenter bonds. Later, analysis based on high-resolution X-ray data was performed to analyze the charge density. Structure Like other boranes, the structure of tetraborane involves multicenter bonding, with hydrogen bridges or protonated double bonds. According to its formula, B4H10, it is classified as an ''arachno''-cluster and has a butterfly geometry, which can be rationalized by Wade's rules. Each boron is ''sp3'' hybridized, and “the configuration of the three hydrogens surrounding borons B1 and B3 is appro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentaborane(11)
Pentaborane(11) is inorganic compound with the chemical formula B5H11. It is an obscure boron hydride cluster, especially relative to the heavily studied pentaborane(9) (B5H9). With two more hydrogen atoms than ''nido''-pentaborane(9), pentaborane(11) is classified as an ''arachno''- cluster. Synthesis Like many boron hydride clusters, pentaborane(11) was originally obtained from the pyrolysis of diborane. A more systematic synthesis entails treatment of 4H9sup>− with boron tribromide Boron tribromide, BBr3, is a colorless, fuming liquid compound containing boron and bromine. Commercial samples usually are amber to red/brown, due to weak bromine contamination. It is decomposed by water and alcohols. Chemical properties Boron .... The Lewis acid abstracts hydride to give unstable B4H8, the precursor to B5H11: : 4H9sup>− + BBr3 → B4H8 + HBBr3− :2 B4H8 → B5H11 + "B3H5" References {{Hydrides by group Boranes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diborane
Diborane(6), generally known as diborane, is the chemical compound with the formula B2H6. It is a toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Diborane is a key boron compound with a variety of applications. It has attracted wide attention for its electronic structure. Several of its derivatives are useful reagents. Structure and bonding The structure of diborane has D2h symmetry. Four hydrides are terminal, while two bridge between the boron centers. The lengths of the B–Hbridge bonds and the B–Hterminal bonds are 1.33 and 1.19 Å respectively. This difference in bond lengths reflects the difference in their strengths, the B–Hbridge bonds being relatively weaker. The weakness of the B–Hbridge compared to B–Hterminal bonds is indicated by their vibrational signatures in the infrared spectrum, being ≈2100 and 2500 cm−1 respectively. The model determined by molecular orbital theory describes the bonds between boron and the termina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decaborane(14)-from-xtal-view-1-tilt-3D-bs-17
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 ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dodecaborate
The dodecaborate(12) anion, 12H12sup>2−, is a borane with an icosahedral arrangement of 12 boron atoms, with each boron atom being attached to a hydrogen atom. Its symmetry is classified by the molecular point group Ih. Synthesis and reactions The existence of the dodecaborate(12) anion, 12H12sup>2−, was predicted by H. C. Longuet-Higgins and M. de V. Roberts in 1955. Hawthorne and Pitochelli first made it 5 years later, by the reaction of 2-iododecaborane with triethylamine in benzene solution at 80 °C. It is more conveniently prepared in two steps from sodium borohydride. First the borohydride is converted into a triborate anion using the etherate of boron trifluoride: : 5 NaBH4 + BF3 → 2 NaB3H8 + 3 NaF + 2 H2 Pyrolysis of the triborate gives the twelve-boron cluster as the sodium salt. A variety of other synthetic methods have been published. Salts of the dodecaborate ion are stable in air and do not react with hot aqueous sodium hydroxide or hydrochloric acid ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentaborane(9)
Pentaborane(9) is an inorganic compound with the formula B5H9. It is one of the most common boron hydride clusters, although it is a highly reactive compound. Because of its high reactivity toward oxygen, it was once evaluated as rocket or jet fuel. Like many of the smaller boron hydrides, pentaborane is colourless, diamagnetic, and volatile. It is related to pentaborane(11) (B5H11). Structure, synthesis, properties Its structure is that of five atoms of boron arranged in a square pyramid. Each boron has a terminal hydride ligand and four hydrides span the edges of the base of the pyramid. It is classified as a nido cage. It was first prepared by Alfred Stock by pyrolysis of diborane at about 200 °C. An improved synthesis starts from salts of octahydrotriborate (B3H8−), which is converted to the bromide B3H7Br− using HBr. Pyrolysis of this bromide gives pentaborane. :5 B3H7Br− → 3 B5H9 + 5 Br− + 4 H2 In the U.S., pentaborane was produced on a commerci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentaborane(9)
Pentaborane(9) is an inorganic compound with the formula B5H9. It is one of the most common boron hydride clusters, although it is a highly reactive compound. Because of its high reactivity toward oxygen, it was once evaluated as rocket or jet fuel. Like many of the smaller boron hydrides, pentaborane is colourless, diamagnetic, and volatile. It is related to pentaborane(11) (B5H11). Structure, synthesis, properties Its structure is that of five atoms of boron arranged in a square pyramid. Each boron has a terminal hydride ligand and four hydrides span the edges of the base of the pyramid. It is classified as a nido cage. It was first prepared by Alfred Stock by pyrolysis of diborane at about 200 °C. An improved synthesis starts from salts of octahydrotriborate (B3H8−), which is converted to the bromide B3H7Br− using HBr. Pyrolysis of this bromide gives pentaborane. :5 B3H7Br− → 3 B5H9 + 5 Br− + 4 H2 In the U.S., pentaborane was produced on a commerci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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