Pnictogenidostannates(IV) with discrete tetrahedral anions:: New representatives (E1)4(E2)2[Sn(E15)4] (with E1=Na, K; E2=Ca, Sr, Ba; E15=P, As, Sb, Bi) of the Na6[ZnO4] type and the superstructure variant of K4Sr2[SnAs4]

The silvery to dark metallic lustrous compounds (E1)(4)(E2)(2)[Sn(E15)(4)] (E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) were prepared from melts of stoichiometric mixtures of the elements. They crystallize in the Na-6[ZnO4]-type structure (hexagonal, space group: P6(3)mc, Z = 2; Na4Ca2[SnP4]: a = 938.94(7), c = 710.09(8) pm; K4Sr2-2[SnAs4]: a = 1045.0(2), c = 767.0(1) pm; K4Ba2[SnP4]: a = 1029.1(6), c = 780.2(4) pm; K4Ba2[SnAs4]: a = 1051.3(1), c = 795.79(7) pm; K4Ba2[SnSb4]: a = 1116.9(2), c = 829.2(1) pm; K4Ba2[SnBi4]: a = 1139.5(2), c = 832.0(2) pm). The anionic partial structure consists of tetrahedra [Sn(E15)(4)](8-) orientated all in the same direction along [001]. In the cationic partial structure one of the two cation positions is occupied statistically by alkali and alkaline earth metal atoms. Up to now only for K4Sr2[SnAs4] a second modification could be isolated, forming a superstructure type with three times the unit cell volume (hexagonal, space group: P6(3)cm, Z = 6; a = 1801.3(2), c = 767.00(9) pm) and an ordered cationic partial structure.