Dimere und polymere Pnictidostannat(IV)-Anionen -Darstellung und Kristallstrukturen von Na2K3[SnP3], Na2Cs3[SnP3] und Na2K3[SnBi3] / Dimeric and Polymeric Pnictidostannate(IV) Anions -Preparation and Crystal Structures of Na2K3[SnP3], Na2Cs3[SnP3] and Na2K3[SnBi3]

The metallic lustrous compounds Na [SnP ], Na Cs [SnP ], and Na [SnBi ] were prepared from melts of mixtures of the elements. The isotypic compounds Na [SnP ] and Na Cs [SnP ] crystallize in the orthorhombic system, space group Cmca (No 64), Z = 8, with lattice constants a = 1996.1 (4)/2047.9(4) pm, b = 669.5(1)/686.5(2) pm, c = 1494.5(2)/1617.8(3) pm. The structure is characterized by dimeric units [Sn ] of edge-sharing [SnP ] tetrahe­dra, which are coordinated by the alkali cations. Na [SnBi ] crystallizes in the orthorhombic system, space group Ibca (No 73), Z = 8, with lattice constants a = 718.2(1) pm , b -1692.6(2) pm, c = 2159.5(2) pm. In the anionic partial structure [SnBi ] tetrahedra are connected via common corners to infinite [SnBi Zweier single chains. The sodium and potassium cat­ ions separate the chains from each other. Neglecting the distortions caused by covalent bonding and different radii both structure types can be classified as superstructure defect variants of the Li Bi structure. Different orderings in the occupation of the tetrahedral voids lead to the variants in the anionic assemblies.