Synthesis, Crystal Structures, and Optical Properties of Two New Layered Quaternary Tantalum Thiophosphates and the Thermal Conversion of Cs₄Ta₄P₄S₂₄ into Cs₂Ta₂P₂S₁₂

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 P21/c (No. 14) with a = 8.862(2) Å, b = 12.500(3) Å, c = 17.408(4) Å, β = 99.23(3)°, and Z = 4. Compound II was prepared at 773 K and crystallizes in the monoclinic space group P21/n (No. 14) with a = 14.298(3) Å, b = 17.730(4) Å, c = 16.058(3) Å, β = 106.19(3)°, 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∞[Ta2P2S12]2- layers, whereas in compound II two types of cavities are observed in the 2∞[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.将金属钽（Ta）与原位生成的由三硫化二铯（Cs₂S₃）、五硫化二磷（P₂S₅）和单质硫（S）组成的多硫代磷酸盐熔融体系反应，得到两种新型钽基硫代磷酸四元化合物：Cs₂Ta₂P₂S₁₂（记为I）与Cs₄Ta₄P₄S₂₄（记为II）。两种化合物的化学计量比一致，但合成反应温度不同。化合物I在873 K下合成，结晶于单斜晶系空间群P2₁/c（编号14），晶胞参数为a = 8.862(2) 埃，b = 12.500(3) 埃，c = 17.408(4) 埃，β = 99.23(3)°，Z=4。化合物II在773 K下合成，同样结晶于单斜晶系空间群P2₁/n（编号14），晶胞参数为a = 14.298(3) 埃，b = 17.730(4) 埃，c = 16.058(3) 埃，β = 106.19(3)°，Z=4。两种化合物的晶体结构密切相关，均呈现由二聚体[Ta₂S₁₁]单元构成的二维阴离子层；该二聚体单元通过2个四齿和2个三齿的[PS₄]四面体相互连接。二者的显著差异在于，作为两种结构亚单元的无限长[Ta₂S₄(PS₄)]ₓ链中，[Ta₂S₁₁]单元的排布取向不同。化合物I中[Ta₂S₁₁]结构基元的特定取向，使得其二维无限层状阴离子2∞[Ta₂P₂S₁₂]²⁻中仅存在1类空腔；而化合物II的二维无限层状阴离子2∞[Ta₄P₄S₂₄]⁴⁻中则存在2类空腔。铯阳离子（Cs⁺）填充于空腔上下两侧的阴离子层之间。通过中红外（MIR）光谱、拉曼光谱以及紫外-可见漫反射光谱对两种化合物进行了表征。当将化合物II置于化合物I的合成温度下加热时，可完全转化为化合物I。