Synthese und Charakterisierung von Verbindungen mit neuen, binären Zintl-Anionen sowie intermetalloiden, heterometallischen Clustern

Ausgehend von Vorarbeiten zu Polybismutiden und den dabei gesammelten präparativen und konzeptionellen Erfahrungen wurde mit dieser Doktorarbeit ein Beitrag zu verschiedenen Bereichen der Zintl-Chemie geleistet. Dies betrifft sowohl die Erweiterung der Reihe der intermetalloiden Cluster mit Lanthano...

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Bibliographic Details
Main Author: Eulenstein, Armin Rainer
Contributors: Dehnen, Stefanie (Prof. Dr.) (Thesis advisor)
Format: Dataset Doctoral Thesis
Published: Philipps-Universität Marburg 2019
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This doctoral thesis covers several aspects of Zintl-chemistry. This concerns the extension of the series of intermetalloid Ln-clusters onto the related actinoids, the synthesis of a compound containing a novel, oblate Zn/Bi-cluster with an metalloid Zn-core and one with a never observed intermetalloid arsenide as well as the phase-pure preparation of a new compound in the K-Ge-As-system. By supervision of students in their respective bachelor and master programs two more so far unprecedented heterometallic clusters and one binary Zintl-Anion were characterized and investigated further. The reactions of U- and Th-complexes with the salt [K(crypt-222)]₂(GaBi₃)·en or the slightly more reduced solid K₅Ga₂Bi₄ led to the isolation of two novel, isostructural [An@Bi₁₂]-clusters in their corresponding compounds. The extraordinary bonding features in these compounds were examined using magnetization measurements and quantum chemical calculations. These measurements and the use of quantum theory led to a model for the electronic situation as well as the structural composition of these clusters. By reacting K₅Ga₂Bi₄ with diphenyl zinc, a compound with the unique heterometallic cluster-Anion [K₂Zn₂₀Bi₁₆]⁶⁻ was isolated. Its core consists of a {Zn₁₂}-fragment, which represents the biggest metalloid agglomeration of Zn-atoms in a molecular compound to date. By employing extensive quantum chemical studies the extraordinary bonding features were elucidated and the metalloid character of the involved Zn-atoms confirmed. Further reactions of K₅Ga₂Bi₄ with transition metal complexes done by Shangxin Wei led to the synthesis of compounds with two new clusters, (Ga₂Bi₁₆)⁴⁻ and [{{Ru(cod)}₂Bi₉}₂]⁴⁻ respectively. Both are related to published clusters, (Ga₂Bi₁₆)⁴⁻ being isoelectronic to the known (Ge₄Bi₁₄)⁴⁻-ion and the cluster-dimer [{{Ru(cod)}₂Bi₉}₂]⁴⁻ can be described as the product of oxidative coupling of two [{Ru(cod)}₂Bi₉]³⁻ units. These examples expand the spectrum of known binary Zintl ions and heterometallic clusters by adding one new representative to each field. By extracting ternary solid mixtures with KAs, K and Nb from high temperature syntheses, a new compound with the intermetalloid cluster [Nb@As₁₁]q⁻ was prepared. It contains a cage of three As zigzag-chains which are fused together at the ends of each and encase the endohedral Nb-Atom. Despite extensive experimental as well as quantum chemical studies it was not possible to elucidate the presence of just two counter ions in the compound while the intuitive assignment of the cluster charge would be –4 thus requiring four counter ions. Temporarily, the low cluster charge was founded upon an unusual protonation pattern of the cluster in the compound, which was confirmed by infrared-spectroscopy and a mass spectrum of a solution of the crystals. However, the DFT-calculations are not able to reproduce this situation which is why this study is not yet completed. By exploratory high temperature syntheses in the system K-Ge-As a new compound of the composition K₂Ge₃As₃ was found and using a purification method, a protocol for phase pure synthesis could be established. Besides experimental determination of composition and structure of the compound, material properties were thoroughly investigated. The substance is a semiconductor with a relatively small band gap of 1.4 eV and a mixed ionic/electronic conductivity behavior. The extraordinary, thread-like appearance of the single crystalline substance was related to its crystal structure which contains a one-dimensional anionic substructure. By using ultrasound treatment, the crystalline fibers could be spliced into single strands with around 0.5 nm in diameter. With this work the spectrum of known species in the K-Ge-As-System was expanded by one representative and the foundation for further investigations in this compound class was established. A unique, heterometallic cluster [(PbxBi₈-x){Mn(hmds)}₂]²⁻ was obtained after reactions using the metal complex [Mn(hmds)₂]. The cluster is similar to [(SnxSb₈-x){Mn(hmds)}₂]²⁻ prepared earlier by Dr. Gunnar Werncke. In difference to this one, in the compound first prepared by Andreas Schmidt containing a ternary Pb/Bi/Mn cluster shell two cluster units are in close proximity to each other. However, the distance is rather long for a covalent bond, therefore additional spectroscopic investigations and quantum theory should be employed in the future in order to establish a model explaining the short distance between the two clusters in the solid.