title: Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV).
abstract: 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]2-or [Pb2Ch3]2-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]4-. 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]2-or [BiSe3]3-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 by205Pb and77Se or127Te 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]4-anion is mainly due to a suitable stabilization within the crystal lattice.
authors.affiliation: Department of Chemistry, University of California, Berkeley.
authors.forename: Günther
authors.initials: G
authors.lastname: Thiele
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg and Wissenschaftliches Zentrum für Materialwissenschaften.
authors.forename: Carsten
authors.initials: C
authors.lastname: Donsbach
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg and Wissenschaftliches Zentrum für Materialwissenschaften.
authors.forename: Isabell
authors.initials: I
authors.lastname: Nußbruch
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg and Wissenschaftliches Zentrum für Materialwissenschaften; dehnen@chemie.uni-marburg.de.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Dehnen
mesh_terms: D018360:Crystallography, X-Ray; D004583:Electrons; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D060327:Solid-Phase Synthesis Techniques; D014961:X-Ray Diffraction
chemical_list: D008024:Ligands