Diverse chemistry of the dianion [closo-B9H9]2−: synthesis and reactivity of its mono-anionic derivative [arachno-B9H12-4,8-Cl2]−

Abstract

Attempted protonation of the dianion [closo-B₉H₉]²⁻ under moisture-free conditions did not afford its mono-protonated form [closo-B₉H₁₀]⁻. The reaction of the former closo-borate with CH₃COOH in dichloromethane yielded a monoanionic product [B₂O(MeCO₂)₅]⁻. The treatment of [closo-B₉H₉]²⁻ with HCl in dichloromethane afforded its arachno-derivative [arachno-B₉H₁₂-4,8-Cl₂]⁻ in a high yield. The experimental solution and quantum-chemically calculated ¹¹B and ¹H NMR spectra of the latter monoanion were found to be in a good agreement; its structure in the solid state was studied by the single crystal X-ray diffraction experiment for the crystal (PPh₄)[arachno-B₉H₁₂-4,8-Cl₂]·0.04HCl. The reaction of [arachno-B₉H₁₂-4,8-Cl₂]⁻ with liquid ammonia caused its quantitative conversion into the parent [closo-B₉H₉]²⁻.