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キーワード:
Tetracyanoborates; Crystal structure; Vibrational spectroscopy; Thermal stability
要旨:
Treatment of an aqueous solution of Na[B(CN)4] with an acidic cation exchange resin leads to a solution of the strong tetracyanoboronic acid. Evaporation of the solution at room temperature yields colourless single crystals of [H5O2][B(CN)4] (P ͞4n2, a=9.5830(2)Å, c=14.25440(3)Å, Z=1). Further drying of [H5O2][B(CN)4] (mp. 115 °C) in vacuum at 50 °C gives polycrystalline [H3O][B(CN)4] (P63mc, a=8.704(1)Å, c=6.152(1)Å, Z=2), which is thermally stable up to 145 °C. The anhydrous polycrystalline acid H[B(CN)4] is formed quantitatively by reacting Me3SiNCB(CN)3 with gaseous HCl. This acid starts to decompose at 190 °C with loss of HCN. All three acids were further characterized by vibrational spectroscopy, and elemental analysis.
