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Abstract

Reduction of nido-5,6-C₂B₈H₁₂ with sodium tetrahydroborate in ethanolic sodium hydroxide as a new method for preparing arachno-6,9-C₂B₈H₁₄ is reported. Electrophilic halogenation of 6,9-C₂B₈H₁₄ occurs at the B₍₁₎ site to give a series of 1-X-6,9-C₂B₈H₁₃ (X = Cl, Br, and I) derivatives. Stereoselective addition of hydrogen halides to the B₍₅₎-C₍₆₎ bond in the [6,9-C₂B₈H₁₀]^2- anion results in the formation of 5-X-6,9-C₂B₈H₁₃ (X = F, Cl, Br, I and 5'-0-6,9-C₂B₈H₁₃) compounds. Constitution of all compounds isolated is suggested on the basis of their ¹H and ¹¹B NMR data and the effects of halogen substituents on the ¹¹B NMR shielding of individual cage boron atoms are discussed in terms of Δδ and k₂ values.