K5[InSe4] and K12[InS4]2(S): New Alkali Chalcogenido Indates with [InQ4]5–ortho Anions

Abstract

The new chalcogenido ortho indates(III) K5[InSe4] and K12[InS4]2(S) were synthesized from melts of the elements (Se) [or with S/In2S3 as chalcogen source] at maximum temperatures of 700/800 °C. The two potassium salts, which were characterized by means of X‐ray single crystal structure analysis, contain isolated tetrahedral ortho anions [InQ4]5–. K5[InSe4] crystallizes in a new structure type [monoclinic, space group C2/c, a = 2014.2(2), b = 1553.1(2), c = 1661.1(2) pm, β = 94.716(2)°, Z = 16, R1 = 0.0317]. The complex structure contains two crystallographically different [InSe4]5– tetrahedra [d(In···Se) = 254.3–263.6 pm], which are arranged into 44 [In(1), A] and 32.4.3.4 [In(2), B] nets. These nets are |:ABA'B':| stacked along the a axis. The 11 crystallographically independent K+ ions are coordinated by four (1×), five (3×) and six (7×) selenido anions [d(K–Se) = 309–415 pm]. The crystal structure and the calculated electronic structure of the pure ortho indate K5[InSe4] are compared with the known “double salts” K9[InSe4]2(Se) and K9[InSe4](Se2)(Se), which exhibit selenide (and diselenide) anions in addition to the ortho metallate. Similarly, the new sulfido indate K11[InS4]2(S) contains sulfide anions besides the indate tetrahedra. In the chiral structure (K6[InTe4](Cl)‐type, hexagonal, space group P63mc, a = 1026.22(10), c = 752.34(7) pm, Z = 2, R1 = 0.0332) layers of similarly oriented [InS4] tetrahedra [d(In···Se) = 246.6/248.1 pm] are hexagonally |:AB:| stacked along one threefold axis. The additional sulfide anions are centered in K+ octahedra. In contrast to the isotypic chloride, only every second polyhedron within the columns of face‐sharing K6 octahedra is statistically occupied by a sulfide ion. Both of the two different K positions exhibit a sixfold coordination by sulfide anions, with K–S distances between 307.1 and 382.1 pm. In the two title compounds, each of the [InQ4] tetrahedra is overall enclosed by 18 potassium cations. The crystal chemistry of the new indates is discussed and compared with that of the (yet comparatively low number) of alkali chalcogenido metallates(III) of Fe, Al and Ga containing isolated metallate tetrahedra.