New Layered Materials in the K–In–Ge–As System: K8In8Ge5As17and K5In5Ge5As14

Synthesis and Characterization of Cs5In3As4 with a Structure of Two Coexisting “Polymorphic” Forms of Different Dimensionality

“…The shortest bonds are around indium atoms bonded to four arsenic atoms, i.e., In1, In4, and In5, and range from 2.661(2)−2.774(2) Å. They are quite typical for In−As distances and compare well with similar distances observed in K 8 In 8 Ge 5 As 17 (2.591(9)−2.784(8) Å), K 4 In 4 As 6 (2.611(1)−2.793(1) Å), and Na 3 InAs 2 (2.671(2)−2.774(2) Å) . In the second category fall the distances around indium atoms bonded to three arsenic and one indium atoms, i.e., In2 and In3, with distances from 2.719(2) to 2.829(2) Å.…”

Quaternary Arsenides ACdGeAs2 (A = K, Rb) Built of Ethane-Like Ge2As6 Units

“…In fact, reversing the roles of the Ge and As atoms as formally cationic and anionic species, respectively, would only exacerbate deviations of the bond valence sums from expected values. The ethane-like Ge 2 As 6 unit is unusual but has been previously observed in GeAs, 24 A 3 Ge 2 As 4 (A = Ca, Sr), 10 K 5 In 5 Ge 5 As 14 , 17 and K 8 In 8 Ge 5 As 17 . 17 , which contain formally low oxidation states for M and thus the presence of M−M bonds within these anions, 1,29−37 but they remain relatively rare compared to chalcogenide polyanions such as P 2 S 6 4− .…”

“…The ethane-like Ge 2 As 6 unit is unusual but has been previously observed in GeAs, 24 A 3 Ge 2 As 4 (A = Ca, Sr), 10 K 5 In 5 Ge 5 As 14 , 17 and K 8 In 8 Ge 5 As 17 . 17 , which contain formally low oxidation states for M and thus the presence of M−M bonds within these anions, 1,29−37 but they remain relatively rare compared to chalcogenide polyanions such as P 2 S 6 4− . 8 The structure of ACdGeAs 2 bears a cursory resemblance to those of K 5 In 5 Ge 5 As 14 and K 8 In 8 Ge 5 As 17 , only to the extent that the latter also consist of layers, but has a much more complicated connectivity of Ge 2 As 6 units, which suffer from partial disordering of Ge and In atoms.…”

“…8 The structure of ACdGeAs 2 bears a cursory resemblance to those of K 5 In 5 Ge 5 As 14 and K 8 In 8 Ge 5 As 17 , only to the extent that the latter also consist of layers, but has a much more complicated connectivity of Ge 2 As 6 units, which suffer from partial disordering of Ge and In atoms. 17 The binary arsenide GeAs consists of neutral layers held together by van der Waals forces and is built up of edgesharing octahedra filled by Ge 2 dumbbells, which can be contrasted with the anionic [CdGeAs 2 ] − layers built up of edgesharing octahedra and tetrahedra in ACdGeAs 2 (Figure S3 in Supporting Information). A better comparison is to Sr 3 Ge 2 As 4 (or Ca 3 Ge 2 As 4 ), 10 for which the arrangement of Ge 2 As 6 units occurring in isolated chains is more easily related to those present in the layers in ACdGeAs 2 (Figure 3).…”

“…The arsenides A CdGeAs 2 ( A = K, Rb) are the first examples of quaternary phases in the A –Cd–Ge–As systems. Previously reported quaternary arsenides A – M –Ge–As ( A = alkali metal, M = any other metal) are Na 4.3 Eu 1.7 GeAs 4 , K 5 In 5 Ge 5 As 14 , K 8 In 8 Ge 5 As 17 , and NaZn 1.5 Ge 0.5 As 2 . Known ternary arsenide phases in the related A –Cd–As, A –Ge–As, and Cd–Ge–As systems include KCdAs, K 4 CdAs 2 , A Cd 4 As 3 ( A = K, Rb), Rb 2 Cd 5 As 4 , K 2 GeAs 2 , and CdGeAs 2 , all of which have structures built from Cd- or Ge-centered tetrahedra and contain only heteroatomic bonds, as can be predicted by their adherence to charge-balanced formulations involving normal oxidation states ( A + , Cd 2+ , Ge 4+ , and As 3– ).…”