Synthese und Charakterisierung von kleinen, konzeptionell einfachen Actinoid-Verbindungen
Zusammenfassung der Projektergebnisse
The synthesis and characterization of compounds of two main research areas was undertaken namely the characterization of (i) novel actinide (uranium and thorium) complexes and (ii) small molecule, non-metal compounds. All of the compounds that are reported here were investigated since they were expected to show either unusual structures or properties. In addition, most of the compounds investigated were experimentally challenging. The synthesis of many related complexes to those reported here is a future direction for this work, since it will build up a library of data which will be useful in order to interpret vibrational spectra more accurately, or for comparison with computational results. However, the goal of this work was not to prepare many examples of the same class of compounds, but to prepare the first examples of novel classes of uranium or actinide compounds. A particularly important area of this research was the synthesis of uranium azides, dinitramides and related complexes, since few nitrogen-rich ligands have been coordinated to uranium, yet the synthesis of new precursors for the synthesis of new uranium-nitrides is a topic of particular interest in current uranium research. The synthesis of UO2(N(NO2)2)2L2 and [UO2(N(CN)2)2L2]2 were the first uranium dinitramide and dicyanamide complexes to be structurally characterized and the related azide complex UO2(N3)2L2 was the first structurally characterized neutral U(VI)-azide to be reported (L = OP(NMe2)3). Furthermore, we were able to report on the first structurally characterized uranium complex which shows coordination of a triazolate ligand via one of the triazolate ring nitrogen atoms. In addition, although it has not been described in this work, further work in this area allowed us to coordinate a tetrazolate ligand to uranium via one of the ring nitrogen atoms for the first time and structurally characterize the resulting complex using single crystal X-ray diffraction. In the non-metal chemistry section, we wanted to improve on our previous investigations since we now have much better access to the appropriate equipment and as a result we have been able to establish the existence or non-existence of compounds that we had investigated many years ago, albeit not to the desired standard. The difficulties in working with the non-metal compounds described in this work is that without the very best access to analytical and preparative equipment, the compounds cannot be correctly investigated. The non-metal compounds which are described in this work are fundamentally simple ones, however, they are of interest for a variety of reasons such as new (i) preparation of examples of unstable bond types (S-----I interactions), (ii) the pseudohalogen principle (CS2N3- chemistry and the X-I-N3- anions), as well as (iii) the first recent structural characterization of simple and well-known but toxic halogen cyanides (BrCN, ICN), (iv) the influence of the presence of the halogen in XCN (X = Cl, Br, I) on the structure of the adducts formed with the Lewis acid SbF5, and (v) the ‚I+’ donor properties of the homopolyatomic [I3]+ cation towards stronger Lewis nitrile bases such as CH3CN.
