Advanced Topic 635 of 1102 Inorganic Chemistry
Boranes
Electron-deficient boron-hydrogen compounds such as diborane with three-center bonds.
In-depth explanation of Boranes
Boranes are compounds of boron and hydrogen, such as diborane, B2H6, and pentaborane, B5H9, and they are electron deficient. Diborane has two bridging hydrogen atoms that hold the boron atoms together through three-centre two-electron bonds. The cage structures of larger boranes are described by Wade's rules, which relate the number of skeletal electron pairs to the cluster shape. Boranes are flammable and toxic, and diborane ignites spontaneously in air. They are important in organic synthesis, especially hydroboration, and William Lipscomb won a Nobel Prize for his work on their bonding.
Going deeper: Boranes
Key ideas: Boron hydrides such as B2H6 (diborane) and B4H10 follow BnHn+4 or BnHn+6. Diborane has two bridging three-center two-electron bonds (banana bonds) between the B atoms, and four terminal B-H bonds. It is prepared from NaBH4 with I2 or BF3 with LiAlH4. B2H6 hydrolyzes to boric acid and H2, and ignites in air. Hydroboration adds B-H across alkenes to give anti-Markovnikov alcohols.
Common mistakes and connections: Students draw diborane like ethane, with a B-B bond; it has none. It has 12 valence electrons, which cannot cover 8 two-center bonds, hence bridges. Terminal and bridging B-H lengths differ. The bridge bonds link to molecular orbital theory and Wade rules for clusters. Related to organic hydroboration-oxidation.
Visualization of Boranes
Bond lengths in diborane B2H6: the bridging B-H-B three-centre bonds are longer than the terminal B-H bonds, reflecting electron deficiency. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Diborane, B2H6, burns spontaneously in air to give boron oxide and water.
Frequently asked questions about Boranes
What is Boranes?
Electron-deficient boron-hydrogen compounds such as diborane with three-center bonds.
Is Boranes a beginner, intermediate or advanced topic?
Boranes is a advanced topic in Inorganic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Boranes?
Study these earlier topics in Inorganic Chemistry first: Magnesium Chemistry, Boron Family, Borax.
What comes after Boranes?
The next topics in Inorganic Chemistry are Aluminium Chemistry and Alums.
Can I practise Boranes with quizzes?
Yes. The interactive lesson includes a self-check question on Boranes, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Boranes fits in Inorganic Chemistry
Boranes is topic 20 of 113 in Inorganic Chemistry.