Analysis of Why Boron Avoids sp2 Hybridization and Classical Structures in the BnHn+2 Series

Authors

  • Edison Osorio,

    1. Departamento de Química, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. República 252, Santiago (Chile)
    2. Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322 (USA)
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  • Dr. Jared K. Olson,

    1. Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322 (USA)
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  • Prof. William Tiznado,

    Corresponding author
    1. Departamento de Química, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. República 252, Santiago (Chile)
    • Departamento de Química, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. República 252, Santiago (Chile)
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  • Prof. Alexander I. Boldyrev

    Corresponding author
    1. Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322 (USA)
    • Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322 (USA)
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Abstract

We performed global minimum searches for the BnHn+2 (n=2-5) series and found that classical structures composed of 2c–2e B[BOND]H and B[BOND]B bonds become progressively less stable along the series. Relative energies increase from 2.9 kcal mol−1 in B2H4 to 62.3 kcal mol−1 in B5H7. We believe this occurs because boron atoms in the studied molecules are trying to avoid sp2 hybridization and trigonal structure at the boron atoms, as in that case one 2p-AO is empty, which is highly unfavorable. This affinity of boron to have some electron density on all 2p-AOs and avoiding having one 2p-AO empty is a main reason why classical structures are not the most stable configurations and why multicenter bonding is so important for the studied boron–hydride clusters as well as for pure boron clusters and boron compounds in general.

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