Über Metallazide und Silbersalze in flüssigem Ammoniak

Nitrides have various interesting properties and application possibilities, e.g. as ceramic materials. Normally, their syntheses are carried out under high temperatures and/or high pressures. It is possible to synthesize metal nitrides at clearly milder conditions by thermal decomposition of the corresponding metal azides. The aim of this work was, beside the synthesis and characterization of yet unknown metal azides from liquid ammonia, their thermal decomposition to nitridic compounds. The ammine complexes of silver azide could be isolated and were analyzed by single X-ray diffraction. The tri- as well as the tetraammine complex of binary silver azide, [Ag(NH3)3]N3 and [Ag(NH3)4]N3·NH3, were synthesized in liquid ammonia at −36 °C and −70 °C, respectively. The tetraammine silver(I) azide, [Ag2(NH3)4](N3)2, consisting of two [Ag(NH3)2]+ units, is accessible from liquid ammonia in presence of water. From the reaction of sodium azide with NH3 the compound [Na(NH3)5]N3 could be obtained and was investigated through X-ray diffraction. The redox reaction of silver azide with elementary manganese or zinc provided the corresponding bivalent metal azides in liquid ammonia. From the solutions their hexaammine complexes could be isolated. By warming these to room temperature, the corresponding diammine compounds are generated, which could be investigated and characterized by X-ray powder diffraction as well as IR spectroscopy. In case of the colorless Mn(N3)2(NH3)2 it was possible to obtain manganese nitride, MnN, by thermal decomposition at 230 °C. From the redox reactions of silver azide with rare-earth metals in liquid ammonia numerous ammine complexes of the bi- and trivalent lanthanoids could be isolated and investigated by X-ray diffraction on single crystals. Thereby either octa- or nonaammine complexes with various amount of ammonia were obtained. The thermal decomposition of the bivalent europium and ytterbium azides with one ammonia molecule of crystallization to the corresponding nitride was investigated. The nitrides were analyzed by X-ray powder diffraction as well as transmission electron microscopy. Reactions performed in bomb tubes at room temperature, higher pressure and the presence of water resulted in various azide compounds which could be isolated and were investigated by single crystal X-ray diffraction. The compounds [Ln2(μ-NH2)3(NH3)11](N3)3 and [Ln2(μ-NH2)3(NH3)10](N3)3 are only formed when traces of moisture are present. Additionally, crystals of the oxygen containing compounds [Ln4(μ4-O)(μ-NH2)6-x(μ-N3)x(NH3)12](N3)4 (Ln = La, Pr, Nd; x = 0-1) as well as the neodymium compound [Nd6(μ6-O)(μ3-OH)8(N3)3(NH3)18](N3)5 could be isolated. Their formation can be explained by deprotonation of water, which is a weak acid in liquid ammonia. First reactions of silver azide with uranium(IV) halides gave promising results. From the reaction of UCl4 with silver azide in liquid ammonia, an ammine complex of uranium could be isolated in which chloride anions as well as azido and nitrido ligands are present. The syntheses of the triammine silver(I) salts with the anions Cl– and PF6− were successfully performed in liquid ammonia at −36 °C. In the structure of [Ag(NH3)3]Cl short Ag···Ag distances could be observed, which indicate argentophilic interactions. From the reactions of the silver compounds AgSCN and AgCF3COO with liquid ammonia at −36 °C the ammine complexes Ag2(μ-SCN)2(NH3)4 and [Ag(NH3)4][Ag(NH3)3](CF3COO)2 were obtained. The latter contained the unusual tetraammine silver(I) cation, which could also be isolated in the form of an ammine complex of the binary silver azide. The ammonolysis of Na2PtF6 by liquid ammonia was investigated. Thereby, crystals of the compound [Na(NH3)3]2[PtF6] were isolated and investigated by X-ray diffraction. The cation of this compound with its unusual coordination of the sodium atom was obtained for the first time. Warming to room temperature leads to phase-pure Na2PtF6. The crystal structure of the long-known compound [Co(NH3)6][Co(CO)4]2 could be determined. Attempts to synthesize binary CuF by decomposition of its ammine complex by magnesium perchlorate failed. Instead, the formation of copper nitride, Cu3N, at room temperature and ambient pressure was observed.