The [3,3′-Co(1,2-C2B9H11)2]− anion as a platform for new materials: synthesis of its functionalized monosubstituted derivatives incorporating synthons for conducting organic polymers

Abstract

[3,3′-Co(8-C₅H₁₀O-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] (2) was synthesized by reaction of the caesium salt of [Co(C₂B₉H₁₁)₂]⁻ with dimethyl sulfate in the presence of sulfuric acid as catalyst and tetrahydropyrane as solvent; the zwitterionic compound (2) yielded [3,3′-Co(8-C₄H₄N-(CH₂)₅-O-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (6), [3,3′-Co(8-C₈H₆N-(CH₂)₅-O-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (7), and [3,3′-Co(8-C₁₂H₈N-(CH₂)₅-O-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (8) through the nucleophilic addition of potassium pyrrolyl, indolyl and carbazolyl, respectively. The nucleophilic addition of the same salts on [3,3′-Co(8-C₄H₈O₂-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] (1) yielded, respectively, [3,3′-Co(8-C₄H₄N-(CH₂)₂-O-(CH₂)₂-O-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (3), [3,3′-Co(8-C₈H₆N-(CH₂)₂-O-(CH₂)₂-O-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (4), and [3,3′-Co(8-C₁₂H₈N-(CH₂)₂-O-(CH₂)₂-O-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (5). All these products were isolated, purified and characterized by means of ¹H, ¹H{¹¹B}, ¹¹B, ¹¹B{¹H} and ¹³C{¹H}-NMR and IR spectroscopies, MS MALDI-TOF spectrometry and elemental analysis. The behavior of the exo-cluster chain has been proven to be, in solution, very similar irrespective of the nucleophilic agent introduced into the molecule. The X-ray diffraction study of the potassium salt of 3 has proven the evidence of B–H⋯K⁺ interactions in solid state. The ¹H{¹¹B}-NMR spectra recorded in the range between 37 °C and −58 °C have proven the presence of the three intramolecular B–H⋯K⁺ interactions in solution. The possible role of [Co(C₂B₉H₁₁)₂]⁻ as a doping agent in conducting organic polymers is also discussed.