Computational Studies: Boranes

Abstract

Computational studies on boranes, in recent years, are summarized with the special emphasis on the macropolyhedral boranes. Computational studies to understand the energetics, geometry, aromaticity, and reactivity of boranes and substituted boranes are reviewed. There is a recent interest in macropolyhedral boranes because of their uses in boron neutron capture therapy (BNCT) of cancer, ionic liquids, weakly coordinating ions, and materials chemistry. The mno rule, which is the electronic counting rule for the macropolyhedral boranes, is explained. Even though the electron counting rule explains the electronic structure of macropolyhedra, it cannot explain the relative stability of isomers since different structures are possible with the same electron count. There have been many computational studies to explain the relative stability of various structural patterns in macropolyhedral boranes. We have used the concept of orbital compatibility to explain the relative energies of different macropolyhedral structural patterns. Computations on the closo ‐ closo macropolyhedral boranes show that a large polyhedral borane prefers to condense with a smaller polyhedron owing orbital compatibility. Even though only a few closo ‐ closo macropolyhedral structures have been synthesized experimentally, calculations suggest optimism for the synthesis of many condensation products. A brief discussion about the use of the computational methods for the rearrangement of the B 20 H 16 skeleton reacting with ligands is also provided.