Synthesis and characterization of alkali-metal tin(II) phosphates: and K_2SnP_2O_7

摘要

Two new alkali-metal tin(II) phosphates - Na_(10)Sn_31(HPO_4)_6(P_2O_7)_6(PO_4)_(12) (1) and K_2SnP_2O_7 (2) - were synthesized by high-temperature reactions and structurally characterized by single-crystal X-ray diffraction. Na_(10)Sn_(31)HPO_4)_6(P_2O_7)_6(PO_4)_(12) crystallized in the noncentrosym-metric space group P-62c (No. 190) with a = 9.6445(1) A, b = 9.6445(1) A, c =34.059(6) A, V= 2743.6(7) A~3 and Z=1. K_2SnP_2O_7 crystallized in the monoclinic space group P2_1 with a = 9.856(3) A, b = 6.7244(1) A, c = 12.225(3) A, beta = 108.240(5)deg, V = 769. 5(3) A~3 and Z = 4. Both structures exhibit a novel open-framework structure. The crystal structure of 1 contains SnO_3 and SnO_4 polyhedra sharing corners with [HPO_4]~(2-), [PO_4]~(3-) and [P_2O_7]~(4-) groups, which form tunnels of six rings filled with Na~+ cations and parallel to the c-axis, which are connected via O-Sn-O bridges to form a three-dimensional open framework. The crystal structure of 2 contains SnO_4 seesaw polyhedra sharing corners with diphosphate groups to form a three-dimensional [SnP_2O_7]~(2-) framework that exhibits a tunnel structure of 10- and 12-membered rings expanding along [011] and [100] with four arrays of K~+ cations located in channels of the framework