On Copper(I) Fluorides, the Cuprophilic Interaction, the Preparation of Copper Nitride at Room Temperature, and the Formation Mechanism at Elevated Temperatures

Abstract

Our attempts to synthesize the hitherto unknown binary copper(I) fluoride have led to first successes and a serendipitious result: By conproportionation of elemental copper and copper(II) fluoride in anhydrous liquid ammonia, two copper(I) fluorides were obtained as simple NH3 complexes. One of them presents an example of ligand-unsupported "cuprophilic" interactions in an infinite [Cu2 (NH3 )4 ](2+) chain with alternating Cu-Cu distances. We discovered that both copper(I) fluorides can easily be converted into Cu3 N at room temperature, just by applying a vacuum. Additionally, we investigated the formation mechanism of the classical synthesis route of Cu3 N that starts with CuF2 and flowing NH3 in the temperature range between ambient and 290 °C by means of thermal analysis and in situ neutron diffraction. The reaction proceeds at elevated temperatures through the formation of a blue and amorphous ammoniate Cu(NH3 )2 F2 , the reformation of CuF2 , and finally the redox reaction to form Cu3 N.

Evolutionary Algorithm‐Based Crystal Structure Prediction for Copper(I) Fluoride

“…Other Z4 structures that are not illustrated here are available as Supporting Information in CIF format. One of the predicted Z4 structures, Z4 g ( P 2 1 / c ), looks similar to the distorted MnP structure also investigated in a previous study on hypothetical CuF structures . Also, structures Z4 a ( Pnma ), Z4 d ( P 2 1 ), Z4 g ( P 2 1 / c ), and Z4 k ( P ) seem to have a very similar framework, however the energy difference between Z4 a and Z4 k is 4.1 kJ mol −1 per CuF unit (Table ).…”

“…The USPEX simulation for Z= 2 also produced the distorted wurtzite structure, discovered in a previous study to be a low‐energy structure (Figure b) . Compared to the previous PBE0/TZVP results, we found that taking dispersion interactions into account clearly changes the energetics of the distorted wurtzite structure.…”

“…Even the lowest‐energy structures found here do not appear to be stable with respect to disproportionation to CuF 2 and Cu metal at ambient pressure. The disproportionation reaction 2 CuF( Z 3 a )→CuF 2 +Cu is exoenergetic by −37 kJ mol −1 , whereas previous studies reported −34 kJ mol −1 and −49 kJ mol −1 . We also investigated the disproportionation reaction at 10 GPa pressure, where the reaction is also exoenergetic by −39 kJ mol −1 .…”

Synthesis of Metastable Co4N, Co3N, Co2N, and CoO0.74N0.24 from a Single Azide Precursor and Intermediates in CoBr2 Ammonolysis

“…In the DSC curve two endothermal signals at 178.9 °C (onset) and 268.4 °C (onset) are obtained. In contrast to the reported tensiometric decomposition measurements on [Co(NH 3 ) 6 ]Br 2 and the thermal decomposition of [Fe(NH 3 ) 6 ]Cl 2 and Cu(NH 3 ) 2 F 2 , we observed no formation of a monoammoniate; however, for [Fe(NH 3 ) 6 ]Br 2 also no formation of a monoammoniate was found . A synthesis of Co 3 N starting from Co(NH 3 ) 2 Br 2 is equally possible.…”

Cuprophilic Interactions in and between Molecular Entities

“…and Kraus et al. reported the characterization of [{Cu(NH 3 ) 2 } 2 ] 2+ stabilized in supramolecular frameworks with the empirical formulae [{Cu(NH 3 ) 2 } 2 ][H 2 THPE] 2 ⋅ 3.25 H 2 O ( 120 ) (H 2 THPE: tris(hydroxyphenyl)ethane anions), and {[Cu(NH 3 ) 3 ] 2 [Cu 2 (NH 3 ) 4 ]}F 4 ⋅ 4 NH 3 ( 121 ), respectively. Compound 120 was prepared from the reaction of Cu(OH) 2 and H 3 THPE in the presence of aqueous NH 3 , whereas 121 was obtained from the reaction of CuF 2 and Cu with the addition of liquid NH 3 .…”