A convenient approach for a controlled and high-yield synthesis of copper-deficient Cu 3−x P (0.1 < x < 0.7) is reported that makes use of ionic liquids with highly nucleophilic "naked" halide anions. Halide anions drastically enhance the reactivity of the white phosphorus precursor and kinetically disfavour the formation of phosphorus-rich side products. Cu 3−x P shows a high degree of tolerance for cation vacancies without mayor structural reorganisation, as evidenced by X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy. Measurements of the electric properties reveal that Cu 3−x P is a bad metallic p-type conductor. The resistivity is composition-dependent and displays a distinct anomaly from a phase transition, leading to the discovery and structural characterisation of two hitherto unknown low temperature polymorphs. Electrochemical evaluation of copper-deficient Cu 3−x P as anode material for lithium ion batteries reveals a drastic change in the cycling mechanism leading to an increase of the initial capacities by about 70 %. This work gives a comprehensive insight into the chemical and structural features of copper-deficient Cu 3−x P and should lead to an improved understanding of its properties, not only for battery applications.

Ionic liquids (ILs) have been proven to be valuable reaction media for the synthesis of inorganic materials among an abundance of other applications in different fields of chemistry. Up to now, the syntheses have remained mostly “black boxes”; and researchers have to resort to trial-and-error in order to establish a new synthetic route to a specific compound. This review comprises decisive reaction parameters and techniques for the directed synthesis of polyions of heavy main-group elements (fourth period and beyond) in ILs. Several families of compounds are presented ranging from polyhalides over carbonyl complexes and selenidostannates to homo and heteropolycations.

Polycrystalline Cu3-xP was successfully synthesized in different ionic liquids comprising imidazolium and phosphonium cations. The reaction of elemental copper and red phosphorus in trihexyltetradecylphosphonium chloride at 200 °C led to single-phase Cu3-xP (x = 0.05) within 24 h with a quantitative yield (99%). Liquid-state nuclear magnetic resonance spectroscopy of the ionic liquids revealed degeneration of the imidazolium cations under the synthesis conditions, while phosphonium cations remain stable. The solid products were characterized with X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, solid-state nuclear magnetic resonance spectroscopy, and elemental analysis. A reinvestigation of the electronic transport properties of Cu2.95(4)P showed metallic behavior for the bulk material. The formation of CuP2 during the synthesis of phosphorus-rich Cu3-xP (x ≥ 0.1) was observed.

We present the syntheses, crystal structures, and properties of five metal-rich salts containing the Bi-10(4+) pentagonal antiprism with an endohedral palladium or, for the first time, platinum atom. Tetragonal [Pt@Bi-10](AlBr4)(4) [P4(2)/n at 296(1) K; Pstyled-content style "text-decoration:overline"4/styled-content at 150(2) K] was obtained by reacting platinum, bismuth, and bismuth tribromide in [BMIm]Br4.1AlBr(3) at 140 degrees C (BMIm = 1-butyl-3-methylimidazolium). Monoclinic [Pt@Bi-10](AlBr4)(2)(Al2Br7)(2) [P2(1)/n] occurs as by-product. The two corresponding palladium compounds result from the dissolution of Bi16PdCl22 in [BMIm]Br4.1AlBr(3). [Pd@Bi-10](AlBr4)(4) [P4(2)/n] adopts a disordered structure homeotypic to its platinum analog. [Pd@Bi-10](AlBr4)(2)(Al2Br7)(2) [P2(1)/n] is isostructural to [Pt@Bi-10](AlBr4)(2)(Al2Br7)(2). In all structures, the [M@Bi-10](4+) cations are well separated by the bromido-aluminate anions with inter-cluster BiBi distances longer than 520 pm. This is not the case in [Pd@Bi-10][Bi2Sn6Cl22], which crystallized from a tin-containing melt of the metals and BiCl3. In its monoclinic structure [P2(1)/c], the cluster cations are arranged in chains along [001] with an inter-cluster distance of only 357 pm. Despite further structural evidence, DFT-based quantum chemical analysis gave no hint on inter-cluster bonding. According to the calculated band structure as well as resistivity and magnetic susceptibility measurements, the black compound is a diamagnetic semiconductor

Mixtures of the phosphorus(III) halides PX3 (X = Cl, Br, I) and the ionic liquids [HMIm][X] (X = Cl, Br, I; HMIm = 1‐hexyl‐3‐methylimidazolium) were studied by nuclear magnetic resonance and Raman spectroscopy. The chloride PCl3 was found to be stable in all mixtures, whereas PBr3 and PI3 can undergo halide exchange depending on the anion of the utilized ionic liquid. The exchange occurs immediately after mixing the compounds at room temperature. In contrast to previous observations made in conventional solvents, intermediate mixed phosphorus halides have not been observed in ionic liquids, indicating a rapid exchange under the applied conditions. Compared to the chemical shifts observed in nuclear magnetic resonance spectra of pure PX3 liquids, the signal of PCl3 is strongly shifted upfield in [HMIm][Cl] indicating strong interaction between the phosphorus halide and the surrounding ionic liquid.

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PX compounds (X=Cl, Br, I) in imidazolium halide ionic liquids combine with the anion Z (Z=Cl, Br, I) of the solvent to form [PX Z] complex anions. These anions have a sawhorse shape in which the lone pair of the phosphorus atom fills the third equatorial position of the pseudotrigonal bipyramid. Theoretical results show that this association remains incomplete due to strong hydrogen bonding with the cations of the ionic liquid, which competes with the phosphorus trihalide for interaction with the Z anion. Temperature-dependent P NMR experiments indicated that the P-Z binding is weaker at higher temperature. Both theory and experiment evidence dynamic exchange of the halide anions at the phosphorus atom, together with continuous switching of the ligands at the phosphorus atom between equatorial and axial positions. Detailed knowledge of the mechanism of the spontaneous exchange of halogen atoms at phosphorus trihalides suggests a way to design novel, highly conducting ionic-liquid mixtures.

In order to explore if and how salts comprising polycations and salts comprising polyanions might interact, the [AlBr ] salt of the [Pt@Bi ] cluster cation was added to the reaction mixture for the synthesis of the supersphere cluster anion [Ge Sn Se ] from Cs [Ge Se ]⋅H O and SnCl ⋅5 H O under ionothermal conditions at 120 °C. Indeed, the reaction yields two new compounds, depending on the cation of the used ionic liquid. Apparently, the polycation is not retained under the given conditions, but it acts as a reductant affording Sn . In a (C C C im) -based ionic liquid mixture, a unique supertetrahedral anion is obtained that embeds a Cs cation, 0D-{[Cs@Sn (Ge Se ) ] }, while (C C im) cations stabilize an unprecedented ternary layered anion, 2D-{[Sn (Ge Se )] }. Test reactions with common sources of Sn did not afford the new compounds, indicating the necessity of an in situ reduction, for which the polycation seems appropriate.