PREPARATION AND CRYSTAL-STRUCTURE OF POTASSIUM IRON HYDROGEN PHOSPHATE, KFE3(HPO4)(2)(H2PO4)(6)CENTER-DOT-4H(2)O

Single crystals of potassium iron hydrogen phosphate, KFe3(HPO4)(2)(H2 PO4)(6).4H(2)O, were prepared hydrothermally by heating a mixture of F e2O3, H3PO4 and K2CO3 with a small amount of water. It crystallizes mo noclinic, space group C2/c (N degrees 15 Int. Tab.) with Z = 4 and a = 1701(2), b = 960.4(5), c = 1750(1) pm, beta = 90.88(7)degrees. The cr ystal structure was solved by using 1716 unique reflections F-0>4 sigm a(F-0) with a final wR2 value of 0.126 (SHELXL-93). The main feature o f the crystal structure are layers formed by PO4-tetrahedra around the FeO6-octahedra parallel to (001). K+ and H2O molecules connect these layers. Effective Coordination Numbers (ECoN), Mean Fictive Ionic Radi i (MEFIR), Charge Distribution (CHARDI) and the Madelung Part of Latti ce Energy (MAPLE) are calculated for the title compound. The existence of hydrogen bonds is confirmed by these calculations.