Crystalline chalcogenidometalate-based compounds from uncommon reaction media

Chalcogenides are one of the most versatile inorganic materials families, further subdivided into a large variety of specific groups of compounds, ranging from neat binary or multinary solids and nanoparticles of the same formal compositions, both in crystalline or non-crystalline form, to complicated open-framework structures and cluster compounds, also including organ(ometall)ic derivates of the latter. The large variety regarding both the compositions and the structures is associated with an enormous variety of properties, ranging from simple or high-tech pigments through a multitude of opto-electronic devices and electrolytes to materials for ion separation or high-sophisticated catalysts. Naturally, this also goes hand in hand with a corrosponding breadth of synthesis strategies. Traditionally, chalcogenides have been accessed via high-temperature methods, which continuously have been replaced by lower-temperature approaches for economical and ecological reasons. Moreover, more recent methods also showed that new types of chalcogenide materials can be obtained under such milder conditions that are not accessible via traditional routes. To shed light onto one of the numerous families of chalcogenides, this feature article summarizes current achievements in the generation of multinary chalcogenidometallate-based clusters and networks via non-classical routes, using ionic liquids, surfactants, or hydrazine as reaction media at moderately elevated termperature.

Crystal structure of μ3-tetrathioantimonato-tris[(cyclam)zinc(II)] tetrathioantimonate acetonitrile disolvate dihydrate showing Zn disorder over the cyclam ring planes (cyclam = 1,4,8,11-tetraazacyclotetradecane)

In the crystal structure of the title compound, [Zn(cyclam)]²⁺ cations and SbS₄^3– anions are present, which are linked to aceto­nitrile and water solvate mol­ecules via inter­molecular hydrogen bonding.

Reaction of Zn(ClO₄)₂·6H₂O with cyclam (cyclam = 1,4,8,11-tetra­aza­cyclo­tetra­decane, C₁₀H₂₄N₄) and Na₃SbS₄ in an aceto­nitrile/water mixture led to the formation of crystals of the title compound, [Zn₃(SbS₄)(C₁₀H₂₄N₄)₃](SbS₄)·2CH₃CN·2H₂O or [(Zn-cyclam)₃(SbS₄)₂](H₂O)₂(aceto­nitrile)₂. The set-up of the crystal structure is similar to that of [(Zn-cyclam)₃(SbS₄)₂]^.8H₂O reported recently [Danker et al. (2021 ▸). Dalton Trans. 50, 18107–18117]. The crystal structure of the title compound consists of three crystallographically independent Zn^II cations (each disordered around centers of inversion), three centrosymmetric cyclam ligands, one SbS₄^3– anion, one water and one aceto­nitrile mol­ecule occupying general positions. The aceto­nitrile mol­ecule is equally disordered over two sets of sites. Each Zn²⁺ cation is bound to four nitro­gen atoms of a cyclam ligand and one sulfur atom of the SbS₄^3– anion within a distorted square-pyramidal coordination. The cation disorder of the [Zn(cyclam)]²⁺ complexes is discussed in detail and is also observed in other compounds, where identical ligands are located above and below the [Zn(cyclam)]²⁺ plane. In the title compound, the building units are arranged in layers parallel to the bc plane forming pores in which the aceto­nitrile solvate mol­ecules are located. Inter­molecular C—H⋯S hydrogen bonding links these units to the SbS₄^3– anions. Between the layers, additional water solvate mol­ecules are present that act as acceptor and donor groups for inter­molecular N—H⋯O and O—H⋯S hydrogen bonding.

Pseudohalogen Chemistry in Ionic Liquids with Non-innocent Cations and Anions

Within the second funding period of the SPP 1708 "Material Synthesis near Room Temperature",which started in 2017, we were able to synthesize novel anionic species utilizing Ionic Liquids (ILs) both, as reaction media and reactant. ILs, bearing the decomposable and non-innocent methyl carbonate anion [CO3 Me]- , served as starting material and enabled facile access to pseudohalide salts by reaction with Me3 Si-X (X=CN, N3 , OCN, SCN). Starting with the synthesized Room temperature Ionic Liquid (RT-IL) [nBu3 MeN][B(OMe)3 (CN)], we were able to crystallize the double salt [nBu3 MeN]2 [B(OMe)3 (CN)](CN). Furthermore, we studied the reaction of [WCC]SCN and [WCC]CN (WCC=weakly coordinating cation) with their corresponding protic acids HX (X=SCN, CN), which resulted in formation of [H(NCS)2 ]- and the temperature labile solvate anions [CN(HCN)n ]- (n=2, 3). In addition, the highly labile anionic HCN solvates were obtained from [PPN]X ([PPN]=μ-nitridobis(triphenylphosphonium), X=N3 , OCN, SCN and OCP) and HCN. Crystals of [PPN][X(HCN)3 ] (X=N3 , OCN) and [PPN][SCN(HCN)2 ] were obtained when the crystallization was carried out at low temperatures. Interestingly, reaction of [PPN]OCP with HCN was noticed, which led to the formation of [P(CN)2 ]- , crystallizing as HCN disolvate [PPN][P(CN⋅HCN)2 ]. Furthermore, we were able to isolate the novel cyanido(halido) silicate dianions of the type [SiCl0.78 (CN)5.22 ]2- and [SiF(CN)5 ]2- and the hexa-substituted [Si(CN)6 ]2- by temperature controlled halide/cyanide exchange reactions. By facile neutralization reactions with the non-innocent cation of [Et3 HN]2 [Si(CN)6 ] with MOH (M=Li, K), Li2 [Si(CN)6 ] ⋅ 2 H2 O and K2 [Si(CN)6 ] were obtained, which form three dimensional coordination polymers. From salt metathesis processes of M2 [Si(CN)6 ] with different imidazolium bromides, we were able to isolate new imidazolium salts and the ionic liquid [BMIm]2 [Si(CN)6 ]. When reacting [Mes(nBu)Im]2 [Si(CN)6 ] with an excess of the strong Lewis acid B(C6 F5 )3 , the voluminous adduct anion {Si[CN⋅B(C6 F5 )3 ]6 }2- was obtained.

Synthesis of nickel/gallium nanoalloys using a dual-source approach in 1-alkyl-3-methylimidazole ionic liquids

NiGa is a catalyst for the semihydrogenation of alkynes. Here we show the influence of different dispersion times before microwave-induced decomposition of the precursors on the phase purity, as well as the influence of the time of microwave-induced decomposition on the crystallinity of the NiGa nanoparticles. Microwave-induced co-decomposition of all-hydrocarbon precursors [Ni(COD)2] (COD = 1,5-cyclooctadiene) and GaCp* (Cp* = pentamethylcyclopentadienyl) in the ionic liquid [BMIm][NTf2] selectively yields small intermetallic Ni/Ga nanocrystals of 5 ± 1 nm as derived from transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and supported by energy-dispersive X-ray spectrometry (EDX), selected-area energy diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). NiGa@[BMIm][NTf2] catalyze the semihydrogenation of 4-octyne to 4-octene with 100% selectivity towards (E)-4-octene over five runs, but with poor conversion values. IL-free, precipitated NiGa nanoparticles achieve conversion values of over 90% and selectivity of 100% towards alkene over three runs.