Die Tetracyanoborate M[B(CN)4], M = [Bu4N]+, Ag+, K+

The Tetracyanoborates MB(CN)₄], M = Bu₄N]⁺, Ag⁺, K⁺ The tetracyanoborate anion is prepared for the first time as the tetrabutylammonium salt by the reaction of NBu₄]BX and BX₃ (X = Br, Cl) in toluene with KCN. After purification and recrystallization of the product from CHCl₃ colorless and needle size single crystals of Bu₄N]B(CN)₄] are formed. After metathesis with AgNO₃ the silver salt and subsequently with KBr the potassium salt is prepared. The three salts are characterized by single crystal X‐ray diffraction (AgB(CN)₄] P 43m, a = 5.732(1) Å, V = 188.3 ų, Z = 1, R₁ = 0.75%; KB(CN)₄] I4₁/a, a = 6.976(1), c = 14.210(3) Å, V = 691.5 ų, Z = 4, R₁ = 1.90%; Bu₄N]B(CN)₄] Pnna, a = 17.765(3), b = 11.650(2), c = 11.454(2) Å, V = 2370.5 ų, Z = 4, R₁ = 6.09%) and by NMR‐, IR‐, Raman‐ as well by UV‐spectroscopy.