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

Abstract

Exploratory synthesis in the K–In–Ge–As system has yielded the unusual layered compounds K8In8Ge5As17(1) and K5In5Ge5As14(2), both of which contain In–Ge–As layers with interleaved potassium ions, Ge–Ge bonds, InAs4tetrahedra, As–As bonds, and rows of Ge2As6dimers. Compound 1 has As3groups, while compound 2 has infinite As ribbons on both faces of each layer. Unlike compound 1, compound 2 has substitutional defects where indium partially occupies each of the three independent germanium sites in the ratio of 1:5 for In:Ge. This partial occupancy makes 2 an electron-precise compound. The Ge(In)–Ge(In) bond of 2 is longer than the Ge–Ge bond of 1, and this bond lengthening effect was confirmed by performing DFT-MO calculations on the model compounds H3Ge–GeH3and H3Ge–InH−3. Possible implications of electron imprecise formulas determined by X-ray crystal structure determinations are discussed. Compound 1: space groupP21/cwitha=18.394 (8) Å,b=19.087 (7) Å,c=25.360 (3) Å,β=105.71 (2)°,V=8571 (4) Å3, andDcalcd=4.45g/cm3forZ=4. Refinement on 4455 reflections yieldedR(Rw)=6.8%(7.8%). Compound 2: space groupC2/mwitha=40.00 (1) Å,b=3.925 (2) Å,c=10.299 (3),β=99.97 (2)°,V=1592 (1) Å3, andDcalcd= 4.55g/cm3forZ=8. Refinement on 1206 reflections yieldedR(Rw)=5.6% (5.7%).