title: Synthesis, crystal structures, and optical properties of two new layered quaternary tantalum thiophosphates and the thermal conversion of Cs4Ta4P4S24 into Cs2Ta2P2S12.
abstract: The reaction of Ta with an in situ formed polythiophosphate melt of Cs2S3, P2S5, and S yields the two new quaternary tantalum thiophosphates Cs2Ta2P2S12 (I) and Cs4Ta4P4S24 (II). Both compounds were obtained with the same stoichiometric ratio but at different reaction temperatures. Compound I was prepared at 873 K and crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 8.862(2) A, b = 12.500(3) A, c = 17.408(4) A, beta = 99.23(3) degrees, and Z = 4. Compound II was prepared at 773 K and crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 14.298(3) A, b = 17.730(4) A, c = 16.058(3) A, beta = 106.19(3) degrees, and Z = 4. The two structures are closely related and exhibit two-dimensional anionic layers consisting of dimeric [Ta2S11] units which are linked by two tetradentate and two tridentate [PS4] tetrahedra. The significant difference between these two compounds is the orientation of the [Ta2S11] units in infinite [Ta2S4(PS4)]x chains which are subunits of both structures. The specific orientation of the [Ta2S11] blocks in compound I leads to the formation of one cavity in the 2(infinity)[Ta2P2S12]2- layers, whereas in compound II two types of cavities are observed in the 2(infinity)[Ta4P4S24]4- layers. The Cs+ ions are located between the layers above and below the cavities. The compounds were characterized with infrared spectroscopy in the MIR region, Raman spectroscopy, and UV/Vis diffuse reflectance spectroscopy. When Cs4Ta4P4S24 (II) is heated at the synthesis temperature of compound I it is fully converted into compound I.
authors.affiliation: Institut für Anorganische Chemie, Universität Kiel, Olshausenstr. 40, D-24098 Kiel, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Gutzmann
authors.forename: Christian
authors.initials: C
authors.lastname: Näther
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bensch