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As anticipated by its hydride clusters, boron forms a variety of stable compounds with formal oxidation state less than three. B 2 F 4 and B 4 Cl 4 are well characterized. [6] Ball-and-stick model of superconductor magnesium diboride. Boron atoms lie in hexagonal aromatic graphite-like layers, with a charge of −1 on each boron atom.
The bridging boron site is tetrahedrally coordinated by four boron atoms. Those atoms are another boron atom in the counter bridge site and three equatorial boron atoms of one of three B 12 icosahedra. The yttrium sites have partial occupancies of ca. 60–70%, and the YB 25 formula merely reflects the average atomic ratio [B]/[Y] = 25.
Ball-and-stick model of superconductor magnesium diboride. Boron atoms lie in hexagonal aromatic graphite-like layers, with a charge of −1 on each boron atom. Magnesium(II) ions lie between layers. Binary metal-boron compounds, the metal borides, contain only boron and a metal. They are metallic, very hard, with high melting points.
The boron atoms lie on each vertex of the octahedron and are sp hybridized. [11] One sp-hybrid radiates away from the structure forming the bond with the hydrogen atom. The other sp-hybrid radiates into the center of the structure forming a large bonding molecular orbital at the center of the cluster.
One boron atom, on the other hand, is vacant and possesses a free binding site (cf. Figures 1 and 4). [ 1 ] [ 2 ] Depending on the nature of the substituents, this fragmentation can either occur directly by CID of the precursor [B 12 X 12 ] 2– , or by fragmentation of a so-called anionic ion pair M + [B 12 X 12 ] 2– , which loses the ...
The boron atom in BH 3 has 6 valence electrons. Consequently, it is a strong Lewis acid and reacts with any Lewis base ('L' in equation below) to form an adduct: [8] BH 3 + L → L—BH 3. in which the base donates its lone pair, forming a dative covalent bond. Such compounds are thermodynamically stable, but may be easily oxidised in air.
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Amorphous powder boron and polycrystalline β-rhombohedral boron are the most common forms. The latter allotrope is a very hard [ n 1 ] grey material, about ten percent lighter than aluminium and with a melting point (2080 °C) several hundred degrees higher than that of steel.