Alexander Weiz

Resource-Efficient High-Yield Ionothermal Synthesis of Microcrystalline Cu3–xP

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.

“Naked” S2O72– ions – the serendipitous formation of the disulfates [HPy]2[S2O7] and [bmim][HPy][S2O7] (HPy = pyridinium; bmim = 1-Butyl-3-methylimidazolium)

Abstract [bmim][HPy][S2O7] [monoclinic, P21/n, Z = 4, a = 825.78(2), b = 1545.30(3), c = 1410.80(3) pm, β = 104.726(1)°, V = 1741.16(7) Å3] was obtained as a side product in the reaction of GeCl4, oleum (65% SO3), and the pyridine (Py) complex Py·SO3 in the ionic liquid 1-butyl-3-methylimidazolium hydrogensulfate, [bmim][HSO4], at 50 °C. Charge compensation of the disulfate ion is achieved by the counterions pyridinium, [HPy]+, and 1-butyl-3-methylimidazolium, [bmim]+. The crystal structure shows alternating layers of [bmim]+ cations on one hand and [HPy]+ cations and disulfate anions on the other hand. Pyridinium disulfate, [HPy]2[S2O7] [orthorhombic, P212121, Z = 4, a = 801.35(1), b = 1257.62(2), c = 1357.22(3) pm, V = 1367.80(4) Å3] was formed unexpectedly in the reaction of Eu2O3 and Py·SO3 in pyridine. The crystal structure exhibits a layer-like arrangement of disulfate and pyridinium moieties in the ab plane. In both compounds, the disulfate groups are essentially uncoordinated allowing for a detailed inspection of “naked” S2O72– ions.