The tetracyanoborates M[B(CN)(4)], M = [Bu4N](+), Ag+, K+

The tetracyanoborate anion is prepared for the first time as the tetrabutyl ammonium salt by the reaction of [NBu4]BX and BX3 (X = Br, Cl) in toluene w ith 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 p otassium salt is prepared. The three salts are characterized by single crys tal X-ray diffraction (Ag[B(CN)(4)] P (4) over bar 3m, a = 5.732(1) Angstro m, V = 188.3 Angstrom(3), Z = 1, R-1 = 0.75%; K[B(CN)(4)] I4(1)/a. a = 6.97 6(1), c = 14.210(3) Angstrom, V = 691.5 Angstrom(3), Z = 4, R-1 = 1.90%; [B u4N][B(CN)(4)] Pnna, a = 17.765(3), b = 11.650(2), c = 11.454(2) Angstrom, V = 2370.5 Angstrom(3), Z = 4, R-1 = 6.09%) and by NMR-, IR-, Raman- as wel l by UV-spectroscopy.