Bonding in clusters. Part 3. Protonation of nido-pentaborane(9), nido-hexaborane(10), and closo-hexaborate(6)(2–)

Abstract

The bonding and structures of B₅H₉, B₆H₁₀, and B₆H₆^2– and the protonated species B₅H₁₀⁺, B₆H₁₁⁺, B₆H₇^–, and B₆H₈ are analysed with MNDO, Gaussian-80, and self-consistent charge calculations. The known isomer of B₆H₁₀ is shown to be more stable than other isomers for which metalloborane analogues are known. The bonding in B₅H₁₀⁺ can be regarded as a B₅H₈⁺⋯ H₂ complex but B₆H₁₁⁺ prefers a structure with six B–H terminal and five B–H–B bridged bonds. Protonation of B₆H₆^2– gives a face-capped B₆H₇^– structure. Diprotonation of B₆H₆^2– produces a molecule in which the B₆ octahedral skeleton is entirely disrupted and the molecule is predicted to be highly unstable. Attention is drawn to some of the observed differences in the chemistries of related borane, metalloborane, and metallo-clusters.