Octadecaborane
Chemical compound
From Wikipedia, the free encyclopedia
Octadecaborane is an inorganic compound, a boron hydride cluster with chemical formula B18H22. It is a colorless flammable solid, like many higher boron hydrides. Although the compound has no practical applications, its structure is of theoretical and pedagogical interest.
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| Names | |
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| Other names
octadecaborane; octadecaboron doicosahydride; octodecaborane; n-Octadecaborane; i-Octadecaborane | |
| Identifiers | |
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3D model (JSmol) |
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| ECHA InfoCard | 100.224.871 |
| EC Number |
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CompTox Dashboard (EPA) |
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| Properties | |
| B18H22 | |
| Molar mass | 216.77 g/mol |
| Appearance | White to off white powder |
| Density | 1.012 g/cm3 |
| Melting point | 180 and 129 °C (356 and 264 °F; 453 and 402 K) n-B18H22 and i-B18H22 respectively |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis
It is formed by oxidative degradation of B20H182− or by oxidative coupling of B9H12−.
Structure
Two isomers are known of octadecaborane, providing the first example of isomers in a boron-hydride cluster. The clusters are also of interest because the boron centers shared between the two subunits have an unusually high number of B-B interactions. The isomers consists of two B9H11 polyhedral subunits, each having a decaborane-like form, joined at a B–B edge.[1][2] These two boron atoms are each coordinated to six others; this compound was the first one found to have such a high number of borons coordinated around a single boron center.[3] There are two different geometric isomers of this compound, differing in the orientation of the two edge-fused polyhedra to each other.[1][2] This compound was the first borane found to have multiple isomeric forms.[4] Among the geometric isomers, one with chirality was the first borane to be resolved into its separate enantiomers, and was only the second chiral borane known at that time.[5]