Synthesis and characterization of alkali-metal tin(II) phosphates: Na 10Sn 31(HPO 4) 6(P 2O 7) 6(PO 4) 12 and K 2SnP 2O 7

Abstract

Two new alkali-metal tin(II) phosphates – Na 10Sn 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 10Sn 31(HPO 4) 6(P 2O 7) 6(PO 4) 12 crystallized in the noncentrosymmetric space group P-62 c (No. 190) with a = 9.6445(1) Å, b = 9.6445(1) Å, c = 34.059(6) Å, V = 2743.6(7) Å 3 and Z = 1. K 2SnP 2O 7 crystallized in the monoclinic space group P2 1/ n with a = 9.856(3) Å, b = 6.7244(1) Å, c = 12.225(3) Å, β = 108.240(5)°, V = 769. 5(3) Å 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.