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3D model (JSmol)
ECHA InfoCard 100.038.447
Molar mass 65.14 g·mol−1
Melting point −123 °C (−189 °F; 150 K)
Boiling point 63 °C (145 °F; 336 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

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.[1]


Like many boron hydride clusters, pentaborane(11) was originally obtained from the pyrolysis of diborane. A more systematic synthesis entails treatment of [B4H9] with boron tribromide. The Lewis acid abstracts hydride to give unstable B4H8, the precursor to B5H11:[2]

[B4H9] + BBr3 → B4H8 + HBBr3
2 B4H8 → B5H11 + "B3H5"


  1. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  2. ^ Toft, Mark A.; Leach, J. B.; Himpsl, Francis L.; Shore, Sheldon G. (1982). "New, Systematic Syntheses of Boron Hydrides via Hydride ion Abstraction Reactions: Preparation of B2H6, B4H10, B5H11, and B10H14". Inorganic Chemistry. 21: 1952–7. doi:10.1021/ic00135a048.CS1 maint: uses authors parameter (link)