The Hydronaphthalide Monoanion: Isolation of the "red transient" Birch Intermediate from liquid Ammonia.

Birch reactions employing alkali metals in ammonia have been a well-established method for the reduction and functionalisation of aromatic compounds for nearly 100 years. Speculations regarding intermediates in the reaction pathway have been discussed since the beginning. We hereby report the isolation of NMe4(HNaph) (1), a kinetically trapped intermediate of the Birch reaction of naphthalene and sodium in liquid ammonia. 1 has been fully characterised and has been shown to continue to react to 1,2/1,4-dihydronaphthalene - the Birch product of the reduction of naphthalene. The reactivity of 1 was investigated towards activity as an electron and hydride transfer agent with both, elements and small organic molecules. 1 demonstrates a tamed reduction potential which allows for controlled reactions such as the selective formation of hexasulphide and hexaselenide anions.

Optical and Electrical Properties of A3[VS4] (A = Na, K) Synthesized via a Straightforward and Scalable Solid-State Method.

Two literature-known sulfido vanadates, Na3[VS4] and K3[VS4], were obtained through a straightforward and scalable synthetic method. Highly crystalline powders of both compounds were obtained from the homogeneous molten phases of starting materials via a─comparably rapid─solid-state technique. Low-temperature structure determination, ambient temperature powder diffraction, and solid-state NMR spectroscopy verify previous structural reports and indicate purity of the obtained samples. Both compounds show semiconductivity with the optical band gap values in the range of 2.1 to 2.3 eV. Experimental values of the ionic conductivity and dielectric constants are σ = 2.41·10-5 mS·cm-1, k = 76.52 and σ = 1.36·10-4 mS·cm-1, k = 103.67 at ambient temperature for Na3[VS4] and K3[VS4], respectively. It is demonstrated that Na3[VS4] depicts second-order nonlinear optical properties, i.e., second harmonic generation over a broad wavelength spectrum. The results introduce new aspects of sulfido vanadates as multifunctional candidates for potential optical and electrical applications.

Low-Cost, Multifunctional, and Sustainable Sodium Sulfido Ferrate(II).

We introduce Na2[Fe3S4], comprising anionic layers, synthesized by a simple and straightforward solid-state method based on the fusion of binary sulfides of abundant sodium and iron. The structure crystallizes in a trigonal lattice with honeycomb cavities, as well as 25% of statistical iron vacancies in the crystal structure. The compound depicts high dielectric constants from 998 to 1850 at a frequency of 1 kHz depending on the sintering temperature, comparable with benchmark dielectric materials. According to the complex electrochemical impedance results, the compound depicts an electrical conductivity at ambient temperature. Optical investigations reveal a band gap of 1.64 eV, which is in agreement with an electronic band gap of 1.63 eV computed by density functional theory calculations. Magnetometry results reveal an antiferromagnetic behavior with a transition at 120 K. These findings introduce Na2[Fe3S4] as a sustainable multifunctional material with potential for a variety of electronic and magnetic applications.

Unravelling the Role of the Pentafluoroorthotellurate Group as a Ligand in Nickel Chemistry.

The pentafluoroorthotellurate group (teflate, OTeF5 ) is able to form species, for which only the fluoride analogues are known. Despite nickel fluorides being widely investigated, nickel teflates have remained elusive for decades. By reaction of [NiCl4 ]2- and neat ClOTeF5 , we have synthesized the homoleptic [Ni(OTeF5 )4 ]2- anion, which presents a distorted tetrahedral structure, unlike the polymeric [NiF4 ]2- . This high-spin complex has allowed the study of the electronic properties of the teflate group, which can be classified as a weak/medium-field ligand, and therefore behaves as the fluoride analogue also in ligand-field terms. The teflate ligands in [NEt4 ]2 [Ni(OTeF5 )4 ] are easily substituted, as shown by the formation of [Ni(NCMe)6 ][OTeF5 ]2 by dissolving it in acetonitrile. Nevertheless, careful reactions with other conventional ligands have enabled the crystallization of nickel teflate complexes with different coordination geometries, i.e. [NEt4 ]2 [trans-Ni(OEt2 )2 (OTeF5 )4 ] or [NEt4 ][Ni(bpyMe2 )(OTeF5 )3 ].

Ino-Chloridolithates from Ionothermal Synthesis.

Anionic lithium-containing species were predicted to impact ionic liquid-based electrochemical applications but have hitherto never been isolated from ionic liquid systems. Here, we report the first representatives of this class of compounds, ino-chloridolithates, comprising [LiCl2]- and [Li2Cl3]- polyanions from ionothermal reactions. Such compounds are obtained at moderate temperatures with imidazolium-based ionic liquids and LiCl. The addition of an auxiliary ammonium salt enhances the lattice energy to yield an ammonium lithate in good yields, which enables extensive investigations including solid-state nuclear magnetic resonance, infrared, and Raman spectroscopy. The structural motifs of ino-lithates are related to ino-silicates, as 1D-extended anionic substructures are formed. Despite this analogy, according to density functional theory calculations with periodic boundary conditions, no evidence of covalent bonding in the anionic moieties is found-indicating packing effects to be the main cause for the formation. Based on an in-depth analysis of the different synthetic parameters, this class of compounds is discussed as an intermediate in ionic liquid applications and could serve as a model system for electrochemical lithium-based systems.

K2Hg2Te3: Straightforward and Large-Scale Mercury-Flux Synthesis of a Small-Band-Gap Photoconducting Material.

K2Hg2Te3 was synthesized via a mercury-flux synthesis pathway. Single-crystal and powder X-ray diffraction reveal the compound to be isostructural to its lighter congener K2Hg2Se3, yet exhibiting enhanced photoconductivity and electrical conductivity of (several) orders of magnitude and a decreased thermal conductivity and band gap. In this report, we elaborate on the synthesis and properties of the novel ternary compound.

A Very Strong Methylation Agent: [Me2 Cl][Al(OTeF5 )4 ].

A new chloronium-containing salt, [Me2 Cl][Al(OTeF5 )4 ], was synthesized on multigram scale by means of a simple one-pot procedure. The isolated product can be handled at room temperature and used as a strong electrophilic methylation agent. This is demonstrated by the methylation of the very weak bases P(CF3 )3 , PF3 , MeI, and MeBr.

Stable Alkali-Metal Complexes of Hybrid Disila-Crown Ethers.

The complexation ability of hybrid disilane and ethylene containing crown ether ring systems was analyzed using 1,2-disila[12]crown-4 (1), 1,2-disila[15]crown-5 (2), 1,2-disila[18]crown-6 (3), and 1,2,7,8-tetrasila[12]crown-4 (7). Alkali-metal complexes (Li(+), Na(+), K(+)) were obtained and analyzed via X-ray diffraction. The complex stability of [Li(1,2-disila[12]crown-4)](+) and [Li(1,2,7,8-tetrasila[12]crown-4)](+) was determined, in relation to the lithium complex of [12]crown-4, by density functional theory (DFT) calculations employing the BP86/def2-TZVP level of theory. In solution, the exchange of lithium cations between pure [12]crown-4 and hybrid [12]crown-4 is on even terms, as has been shown from the relative binding affinity of compounds 1 and 7 by means of dynamic proton nuclear magnetic resonance (NMR) spectroscopy.

Mercurates from a Revised Ionothermal Synthesis Route: The Pseudo-Flux Approach.

K2Hg6Se7, Na2Hg3S2.51Se1.49, K2Hg3S1.03Se2.97, and K2Hg3S2.69Se1.31 were prepared by ionothermal treatment of K2Hg2Se3, Na2HgSe2, and K2Hg3Se4, respectively, in a nonclassical hydrosulfide ionic liquid (EMIm)(SH). In contrast to their lighter congeners, the title compounds could so far not be synthesized by inorganic polychalcogenide salt flux techniques. The applied method hence mimics polychalcogenide flux conditions, while operating at much lower temperatures below the decomposition temperature of the ionic liquid. It might thus be viewed as a pseudo-flux approach.

Molecular CHEVREL-like clusters [(RhPPh3)6(µ3-Se)8] and [Pd6(µ3-Te)8](4-).

[(RhPPh3)6(µ3-Se)8]·0.5en (1; en = ethane-1,2-diamine), obtained by the reaction of [Pb2Se3](2-) anions with [Rh(PPh3)3Cl] in en, represents the first compound comprising a molecular [Rh6] octahedron with all faces capped by Se atoms. Analogous treatment of [Pb2Te3](2-) with [Pd(PPh3)2Cl2] yielded [Li4(en)10][Pd6(µ3-Te)8] (2), the first compound exhibiting a molecular, chalcogen-capped [Pd6] aggregate. Besides syntheses and structures of the title compounds, we report quantum-chemical calculations to understand the electronic properties of these molecular CHEVREL-like complexes.

{µ-PbSe}: a heavy CO homologue as an unexpected ligand.

Reactions of [K(18-crown-6)]2 [Pb2 Se3 ] and [K([2.2.2]crypt)]2 [Pb2 Se3 ] with [Rh(PPh3 )3 Cl] in en (ethane-1,2-diamine) afforded ionic compounds with [Rh3 (PPh3 )6 (µ3 -Se)2 ](-) and [Rh3 (CN)2 (PPh3 )4 (µ3 -Se)2 (µ-PbSe)](3-) anions, respectively. The latter contains a PbSe ligand, a rather uncommon homologue of CO that acts as a µ-bridge between two Rh atoms. Quantum chemical calculations yield a significantly higher bond energy for PbSe than for CO, since the size of the ligand orbitals better matches the comparably rigid Rh-Se-Rh angles and the resulting Rh⋅⋅⋅Rh distance. To rationalize the bent coordination of the ligand, orbitals with significant ligand contributions and their dependence on the bonding angle were investigated in detail.

K(4)[PbSe(4)]⋠en⋠NH(3) : a non-oxide, non-halide inorganic lead(IV) compound.

The first inorganic lead(IV) compound without oxygen, nitrogen or halogen ligands attached to the lead atom was obtained as the potassium salt of the tetraselenidoplumbate(IV) anion [Pb(IV) Se4 ](4-) . It is stable under inert conditions which may enable the transfer of the chemistry of chalcogenidogermanate(IV) or chalcogenidostannate(IV) materials, to the lead homologues.

Heterobimetallic chalcogenidometallate strands: synthesis, structure, magnetism, and conductivity.

Two salts with one-dimensional, SiS(2)-type telluridostannate chain anions {[MSnTe(4)](2-)}(n), Rb(2)[HgSnTe(4)] (2) and (NMe(4))(2)[MnSnTe(4)] (3), were prepared by the reactions of [SnTe](4-) anions with Hg(2+) or Mn(2+) ions in solution. We present the crystal structures of 2 and 3, as well as the magnetic properties of the previously reported Cs(+) analogue Cs(2)[MnSnTe(4)] (1).

3D-printed equipment to decouple (powder) X-ray diffraction sample preparation and measurement.

An alternative storage method to separate sample preparation from single-crystal and powder X-ray diffraction measurements at home source diffractometers is described. For single crystals, a setup is presented which allows storage of preselected crystals under cryogenic and ambient temperatures. For powders, a disposable sample holder is introduced. The method is suitable for the storage of air- and moisture-sensitive samples. Equipment made of biodegradable polylactic acid is produced by 3D printing and can be adapted to individual needs. As 3D printers are widely available at research institutions nowadays, models of the presented equipment are provided for the reader to allow easy reproduction.

Large-scale synthesis of mixed valence K3[Fe2S4] with high dielectric and ferrimagnetic characteristics.

High yields of phase-pure K3[Fe2S4] are obtained using a fast, straight-forward, and efficient synthetic technique starting from the binary precursors K2S and FeS, and elemental sulphur. The compound indicates soft ferrimagnetic characteristics with magnetization of 15.23 A m2 kg-1 at 300 K due to the mixed valence of FeII/FeIII. Sintering at different temperatures allows the manipulation of the microstructure as well as the ratio of grains to grain boundaries. This results in a variation of dielectric and impedance properties. Samples sintered at 923 K demonstrate a dielectric constant (κ) of around 1750 at 1 kHz, which lies within the range of well-known high-κ dielectric materials, and an ionic conductivity of 4 × 10-2 mS cm-1 at room temperature. The compound has an optical band gap of around 2.0 eV, in agreement with tailored quantum chemical calculations. These results highlight its potential as a material comprising non-toxic and abundant elements for electronic and magnetic applications.

Remarkable Infrared Nonlinear Optical, Dielectric, and Strong Diamagnetic Characteristics of Semiconducting K3[BiS3].

The ternary sulfido bismuthate K3[BiS3] is synthesized in quantitative yields. The material exhibits nonlinear optical properties with strong second harmonic generation properties at arbitrary wavelengths in the infrared spectral range and a notable laser-induced damage threshold of 5.22 GW cm-2 for pulsed laser radiation at a wavelength of 1040 nm, a pulse duration of 180 fs, and a repetition rate of 12.5 kHz. K3[BiS3] indicates semiconductivity with a direct optical band gap of 2.51 eV. Dielectric and impedance characterizations demonstrate κ values in the range of 6-13 at 1 kHz and a high electrical resistivity. A strong diamagnetic behavior with a susceptibility of -2.73 × 10-4 m3 kg-1 at room temperature is observed. These results suggest it is a promising nonlinear optical candidate for the infrared region. The synergic physical characteristics of K3[BiS3] provide insight into the correlation of optical, electrical, and magnetic properties.

Excavating hidden adsorption sites in metal-organic frameworks using rational defect engineering.

Metal-organic frameworks are known to contain defects within their crystalline structures. Successful engineering of these defects can lead to modifications in material properties that can potentially improve the performance of many existing frameworks. Herein, we report the high-throughput computational screening of a large experimental metal-organic framework database to identify 13 frameworks that show significantly improved methane storage capacities with linker vacancy defects. The candidates are first identified by focusing on structures with methane-inaccessible pores blocked away from the main adsorption channels. Then, organic linkers of the candidate structures are judiciously replaced with appropriate modulators to emulate the presence of linker vacancies, resulting in the integration and utilization of the previously inaccessible pores. Grand canonical Monte Carlo simulations of defective candidate frameworks show significant enhancements in methane storage capacities, highlighting that rational defect engineering can be an effective method to significantly improve the performance of the existing metal-organic frameworks.

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.

Synthesis and coordination ability of a partially silicon based crown ether.

The first hybrid crown ether with two adjacent disilane fragments was synthesized through reaction of O(Si2Me4Cl)2 (3) with O(C2H4OH)2. By means of DFT calculations, the complexation ability of 1,2,4,5-tetrasila[12]crown-4 (7) towards Li+ was determined to be considerably higher compared to [12]crown-4.