Smallest molecular chalcogenidometalate anions of the heaviest metals: syntheses, structures, and their interconversion

Ionic liquid cations as methylation agent for extremely weak chalcogenido metalate nucleophiles

Selective in situ methylation of terminal chalcogenide ligands of molecular chalcogenido metalate anions in ionothermal reactions with alkylimidazolium-based ionic liquids yields a series of organo-functionalized chalcogenido metalate compounds. We present the syntheses and crystal structures of (C₄C₁C₁Im)_4+x [Sn₁₀S₁₆O₄(SMe)₄][An] _x (1a-1f), (dmmpH)₆[Mn₄Sn₄Se₁₃(SeMe)₄] (2), and (C _n C₁Im)₆[Hg₆Te₁₀(TeMe)₂] (3a, 3b). The methylation was confirmed by Raman spectroscopy, and the optical absorption properties of the methylated compounds were determined and compared to purely inorganic analogs.

Syntheses and properties of selenido mercurates with [HgSe2]2−anions in diverse chemical environments

Four new cesium selenido mercurates, synthesized aminothermally in 1,2-diaminoethane (en), show a diversity of complex crystal structures and a close relationship of the latter with their optical band gap.

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

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 by ²⁰⁵Pb and ⁷⁷Se or ¹²⁷Te 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.

Crystalline chalcogenido metalates – synthetic approaches for materials synthesis and transformation

The formation and transformation of crystalline chalcogenido metalates in ionic liquids as solvents is discussed as a new synthetic approach for the generation of novel materials. A comparison to conventional solvothermal reactions, classical high-temperature syntheses and chemical solution based approaches in common is discussed.