K${}_7$In${}_4$As${}_6$ and K${}_3$InAs${}_2$ - two more Zintl phases showing the rich variety of In-As polyanion structures

Binary phases of triel (Tr) and pentel (Pn) elements (III-V semiconductors) represent a unique compound class due to their tunable intrinsic band gap in dependency of the element combination. We report here on two new compounds in the ternary system K-In-As. In K${}_3$InAs${}_2$ the edge-sharing tetrahedral InAs${}_4$ units are connected via opposed edges of the tetrahedra forming linear [InAs${}_2$]${}^{3-}$ chains and are thus iso(valence)- electronic with SiS${}_2$. In K${}_7$In${}_4$As${}_6$, the InAs${}_4$ tetrahedra are connected via neighboring edges of the tetrahedra forming zig-zag chains. These chains are linked in two directions through dimeric [As${}_3$In - InAs${}_3$] units. Both reported Zintl phases extend the number of structures that possess the same In-As ratio. In K${}_3$InAs${}_2$ a one-dimensional polyanion in contrast to known Na${}_3$InAs${}_2$ comprising a three-dimensional polyanion structure is found. K${}_7$In${}_4$As${}_6$ forms together with the known phases K${}_2$In${}_2$As${}_3$ and K${}_3$In${}_2$As${}_3$ a series of Zintl phases with the ratio In : As=2 : 3. Even though the three phases differ only slightly in their valence electron concentration (VEC) of the polyanion, the VECs have a strong influence on the structures. Syntheses, crystal structures and the electronic band structures are reported. The compounds are discussed in the context of the Zintl concept. (© 2023 The Authors. Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbH)