Synthesis and crystal structure of KLa[C(CN)(3)](4)center dot H2O containing a shielded potassium ion

KLa[C(CN)(3)](4)-H2O was crystallized from an aqueous solution containing La(NO3)(3)-6H(2)O and K[C(CN)(3)]. The crystal structure was solved and refined from X-ray single crystal data (P4/n, Z = 2, a = b = 12.379(1) angstrom, c = 6.5695(8) angstrom, V = 1006.7(2) angstrom(3)). Solid KLa[C(CN)(3)](4)-H2O forms a framework structure with bridging tricyanomethanide ions, each of them connecting two La3+ ions and one K+ ion. Potassium is apparently situated in a tetrahedral environment with four K-N distances of 2.741(3) angstrom, shielded by four other tricyanomethanide ions. Each La3+ has a square antiprismatic coordination of nitrogen atoms from eight [C(CN)(3)](-) ions, and this antiprism is mono-capped by one water molecule.