India-Japan Seminar On Computational Materials Science, October 1998, Bangalore

Bulletin of Materials Science

, Volume 22, Issue 5, pp 863-867

First online:

The ubiquitous icosahedral B12 in boron chemistry

  • E D JemmisAffiliated withSchool of Chemistry, University of Hyderabad
  • , M M BalakrishnarajanAffiliated withSchool of Chemistry, University of Hyderabad

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Though boranes exhibit a wide variety of polyhedral structures, all the three polymorphs of elemental boron essentially contain icosahedral B12 units as the predominant building block in their unit cell. Theoretical and experimental studies on boranes show that the icosahedral arrangement leads to most stable boranes and borane anions. This paper attempts to explain the phenomenal stability associated with the icosahedral B12 structure. Using fragment molecular orbital theory, the remarkable stability of B12H 12 2− amongcloso boranes are explained. The preferential selection icosahedral B12 unit by elemental boron is explained by improvising a contrived B84 sub-unit of the β-rhombohedron, the most stable polymorph. This also leads to a novel covalent way of stuffing fullerenes with icosahedral symmetry.


Boron polyhedralcloso borane dianions icosahedral B12 β-rhombohedral polymorph orbital compatibility