Thiele Günther, Donsbach Carsten, Nußbruch Isabell, Dehnen Stefanie
Department of Chemistry, University of California, Berkeley.
Fachbereich Chemie, Philipps-Universität Marburg and Wissenschaftliches Zentrum für Materialwissenschaften.
J Vis Exp. 2016 Dec 29(118):54789. doi: 10.3791/54789.
The phases of "PbCh2" (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica glass ampules). Reduction of such phases by elemental alkaline metals in amines affords crystalline chalcogenidoplumbate(II) salts comprised of [PbTe3] or [Pb2Ch3] anions, depending upon which sequestering agent for the cations is present: crown ethers, like 18-crown-6, or cryptands, like [2.2.2]crypt. Reactions of solutions of such anions with transition-metal compounds yield (poly-)chalcogenide anions or transition-metal chalcogenide clusters, including one with a µ-PbSe ligand (i.e., the heaviest-known CO homolog). In contrast, the solid-state synthesis of a phase of the nominal composition "K2PbSe2" by successive reactions of the elements and by the subsequent solvothermal treatment in amines yields the first non-oxide/halide inorganic lead(IV) compound: a salt of the ortho-selenidoplumbate(IV) anion [PbSe4]. This was unexpected due to the redox potentials of Pb(IV) and Se(-II). Such methods can further be applied to other elemental combinations, leading to the formation of solutions with binary [HgTe2] or [BiSe3] anions, or to large-scale syntheses of K2Hg2Se3 or K3BiSe3 via the solid-state route. All compounds are characterized by single-crystal X-ray diffraction and elemental analysis; solutions of plumbate salts can be investigated by Pb and Se or Te NMR techniques. Quantum chemical calculations using density functional theory methods enable energy comparisons. They further allow for insights into the electronic configuration and thus, the bonding situation. Molecular Rh-containing Chevrel-type compounds were found to exhibit delocalized mixed valence, whereas similar telluridopalladate anions are electron-precise; the cluster with the µ-PbSe ligand is energetically favored over a hypothetical CO analog, in line with the unsuccessful attempt at its synthesis. The stability of formal Pb(IV) within the [PbSe4] anion is mainly due to a suitable stabilization within the crystal lattice.
“PbCh₂”（Ch = Se、Te）相是通过固态合成法得到的（即通过在惰性条件下于石英玻璃安瓿中熔融各元素）。在胺类溶剂中用碱金属单质还原此类相可得到由[PbTe₃]或[Pb₂Ch₃]阴离子组成的结晶硫属铅酸盐（II）盐，这取决于存在哪种阳离子螯合剂：冠醚，如18 - 冠 - 6，或穴醚，如[2.2.2]穴醚。此类阴离子溶液与过渡金属化合物的反应会生成（多）硫属阴离子或过渡金属硫属化物簇，其中包括一个带有μ - PbSe配体的簇（即已知最重的一氧化碳同系物）。相比之下，通过元素的连续反应以及随后在胺类溶剂中的溶剂热处理，固态合成标称组成为“K₂PbSe₂”的相，得到了首个非氧化物/卤化物无机铅（IV）化合物：原硒酸铅（IV）阴离子[PbSe₄]的盐。鉴于Pb（IV）和Se（ - II）的氧化还原电位，这一结果出人意料。此类方法可进一步应用于其他元素组合，从而形成含有二元[HgTe₂]或[BiSe₃]阴离子的溶液，或通过固态路线大规模合成K₂Hg₂Se₃或K₃BiSe₃。所有化合物均通过单晶X射线衍射和元素分析进行表征；铅酸盐溶液可用Pb和Se或Te的核磁共振技术进行研究。使用密度泛函理论方法进行的量子化学计算能够进行能量比较。它们还能深入了解电子构型，进而了解键合情况。发现含Rh分子的 Chevrel型化合物表现出离域混合价态，而类似的碲钯酸盐阴离子则是电子精确的；带有μ - PbSe配体的簇在能量上比假设的一氧化碳类似物更有利，这与合成该类似物的尝试未成功一致。[PbSe₄]阴离子中正式的Pb（IV）的稳定性主要归因于晶格内的适当稳定作用。
