Arsenic-Containing Chalcophosphate Molecular Anions

We report five new discrete molecular arsenic-based chalcophosphates, K7As3(P2Se6)4 (1), K6As2(P2Se6)3 (2), Cs6As2(P2Se6)3 (3), and Cs5As(P2Q6)2 [Q = Se (4a) and S (4b)]. Each of the compounds contains unique complex anions comprised of common building blocks that have condensed to produce these anions. Phosphorus forms well-known [P2Q6]4− moieties in all of the compounds that are bridged by arsenic trigonal pyramids in 1 and 2 and distorted octahedra in 3, 4a, and 4b. Although 2 and 3 have the same molecular formula, the structural difference between the two salts is attributed to the size of the alkali metal. The influence of flux basicity also seems to play a role in the formation of the molecular anion in 4a and 4b, which has been observed with other trivalent main-group elements at the octahedral position but only with the highly basic cesium alkali metal as the counterion. All structures were determined by single-crystal X-ray diffraction and are discussed along with phase-purity powder X-ray diffraction, thermal analyses, electronic absorption, and Raman spectroscopy.

本工作报道了5种新型离散分子型砷基硫代磷酸盐（arsenic-based chalcophosphates）：K7As3(P2Se6)4（1）、K6As2(P2Se6)3（2）、Cs6As2(P2Se6)3（3）及Cs5As(P2Q6)2[Q=Se（4a）、S（4b）]。所有目标化合物均含有独特的复合阴离子，该类阴离子由常见结构基元经缩合过程生成。在所有化合物中，磷元素均形成广为已知的[P2Q6]4−结构单元；在1和2中，该结构单元由砷三角锥结构桥联，而在3、4a与4b中则由畸变八面体结构桥联。尽管化合物2与3具有相同的分子式，但二者作为盐类的结构差异可归因于碱金属阳离子的尺寸差异。助熔剂碱度对4a与4b中分子阴离子的形成亦存在重要影响；该现象此前已在其他占据八面体位点的三价主族元素体系中被观测到，但仅在以高碱度铯作为抗衡阳离子的体系中得以实现。所有化合物的晶体结构均通过单晶X射线衍射（single-crystal X-ray diffraction）确定，同时结合相纯粉末X射线衍射、热分析、电子吸收光谱及拉曼光谱对其进行了表征与讨论。