SYNTHESIS, CRYSTAL-STRUCTURE, AND SOLID-S TATE MAS-NMR SPECTROSCOPIC INVESTIGATION OF K5H(CN2)(3)

Single phase K5H(CN2)(3) was synthesized by reaction of KHCN2 with met allic potassium in liquid ammonia or by reaction of KNH2 with melamine C3N3(NH2)(3) at 320 degrees C, respectively. The crystal structure wa s determined from X-ray powder and single crystal data: K5H(CN)(3), sp ace group Im3m, a = 795.68(7) pm, Z = 2, R1 = 0.025, wR2 = 0.0438. In the solid K5H(CN2)(3) contains K+ and CN22-, the anions exhibit D-infi nity h symmetry. According to H-1 and C-13 Solid State MAS-NMR investi gations, temperature dependent impedance spectroscopy, and FTIR spectr oscopy the protons are only loosely bound to the CN22- ions. The proto n conductivity shows a sharp increase above 70 degrees C.