Halogenation and μH Tautomerism of 7-Benzyl-7,8-dicarba-nido-undecaborate(−1) Anion

Abstract

Deboration of 1-PhCH₂-1,2-C₂B₁₀H₁₁ by heating in ethanolic potassium hydroxide afforded Me₄N⁺ [7-PhCH₂-7,8-C₂B₉H₁₁]⁻ which was treated with excess halosuccinimide (NCS, NBS) in acetonitrile or with elemental iodine or bromine in methanol to obtain Me₄N⁺ [7-PhCH₂-9,11-X₂-7,8-C₂B₉H₉]⁻ (X = Cl, Br, I). The reaction of 1-PhCH₂-1,2-C₂B₁₀H₁₁ with an equimolar amount of iodine gave a mixture of Me₄N⁺·[7-PhCH₂-11-I-7,8-C₂B₉H₁₀]^- and Me₄N⁺[7-C₆H₅CH₂-9-I-7,8-C₂B₉H₁₀]⁻ at a ratio 1:1.8 due to steric effect of the benzyl substituent. The ¹¹B chemical shifts of each μ-H tautomer of Me₄N⁺ [7-PhCH₂-9,11-X₂-7,8-C₂B₉H₉]⁻ (X = H, F, Cl, Br, I) were calculated at the DFT level of theory, and their contributions to the average ¹¹B NMR spectrum and the corresponding tautomeric equilibrium constants were determined.