Reactions of Carbaalanes with HBF₄ and HCl:  A μ₃-Bridging Fluorine Atom in (AlEt)₇(CCHPh)₂(CCH₂Ph)₃(μ₃-F) versus a Terminal Chlorine Atom in (AlMe)₇(AlCl)(CCH₂Ph)₅H

The carbaalane cluster (AlEt)₇(CCHC₆H₅)₂(CCH₂C₆H₅)₃H (2) reacted with HBF₄·OEt₂ to yield the fluorine derivative (AlEt)₇(CCHC₆H₅)₂(CCH₂C₆H₅)₃(μ₃-F) (4) by the replacement of its bridging hydrogen atom and the cleavage of a B−F bond. The fluorine atom bridges three aluminum atoms with the Al−F distances in a narrow range between 1.97 and 2.00 Å. A similar reaction was observed with the arachno-carbaalane (AlMe)₈(CCH₂C₆H₅)₅H (1). However, an impure product was isolated which could not be purified by repeated recrystallization. In contrast, use of HCl instead of HBF₄·OEt₂ as a proton donor did not result in substitution of the bridging hydrogen atom of 1, but a methyl group at the bottom of the cluster was replaced by release of methane. The compound (AlMe)₇(AlCl)(CCH₂C₆H₅)₅(μ-H) (6), which possesses a terminally bonded chlorine atom, was formed.