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Synthesis and Characterization of Polydentate C3 Symmetric Ligand Systems in Metal Coordination

dc.contributor.advisorStalke, Dietmar Prof. Dr.
dc.contributor.authorStollberg, Peter
dc.publisherNiedersächsische Staats- und Universitätsbibliothek Göttingende
dc.titleSynthesis and Characterization of Polydentate C3 Symmetric Ligand Systems in Metal Coordinationde
dc.contributor.refereeStalke, Dietmar Prof. Dr.
dc.description.abstractengTripodal ligand systems are of key interest in the synthesis of new and promising metal complexes since their tridentate coordination sphere can be used to generate a multitude of different bonding motifs with a suitable metal centre. The high flexibility of the ligand bearing multiple coordination sites allows the formation of mono- and dimeric, as well as mono- and multidentate metal complexes. In particular, the possibility to maintain the C3 symmetry of the ligand systems in the resulting metal complex allows the formation of compounds with interesting catalytic properties. The C3 symmetric metal complex should provide a better stereoselectivity than a comparable bidentate system because of a higher number of homotopic bonding points. In order to explore the different possible coordination motifs and to get a deeper understanding of the reactivity and synthetic approach towards these types of tripodal metal complexes two classes of ligand systems were used in this work, the iminophosphoranes and 1,2,3-triacolylidenes. For the iminophosphoranes two different ligands have been synthesized via the Staudinger reaction from an organoazide (1,1,1-tris(azidomethyl)ethane) as starting material. These ligands were subjected to a multitude of reactions with multiple metal salts in order to explore the selectivity towards different metal centres and subsequently form new metal complexes which could be fully characterized and analysed by the use of x-ray diffraction. With that approach two new complexes bearing a germanium atom and a zinc atom could be generated and their coordination sphere analysed. Furthermore, the transfer of the C3 symmetry from the precursors could be achieved. In the second part of the work the same organoazide (1,1,1-tris(azidomethyl)ethane) was used to form the 1,2,3-triacolylidenes ligand systems by employing the 1,3-dipolar-[3+2]-cycloaddition reaction also known as copper catalysed click-chemistry. With this approach eight ligands with different residues at the triazolic rings could be synthesized which show different properties in regards to their reactivity towards suitable metal bearing substrates. In order to build new metal complexes these ligands needed to be activated by the introduction of an additional methyl group via the use of a methylation reaction. The resulting compounds were used in a deprotonation and metal coordination reaction in the presence of silver oxide to form in situ a mesoionic carbene while a simultaneous coordination with the silver atom took place. These silver metal complexes were then subjected to a transmetallation reaction with pre-coordinated metal atoms from the coinage metal group like gold and copper as well as known catalytic active metals like palladium and nickel. This approach facilitated the formation of four new metal complexes which differ by their coordination pattern between monomeric (copper-, palladium- and nickel-complex) and dimeric (gold-complex) structures and their number of coordinated metal atoms. These compounds have been either analysed by x-ray diffraction or high resolution mass spectrometry in order to fully elucidate their respective coordination
dc.contributor.coRefereeSchneider, Sven Prof. Dr.
dc.contributor.thirdRefereeDiederichsen, Ulf Prof. Dr.
dc.contributor.thirdRefereeSindlinger, Christian Dr.
dc.contributor.thirdRefereeThomas, Franziska Dr.
dc.contributor.thirdRefereeSowa, Heidrun Prof. Dr.
dc.subject.engstructure analysisde
dc.subject.engC3 symmetryde
dc.subject.engmesoionic carbenede
dc.subject.engmetal coordinationde
dc.subject.engmultidentate ligandde
dc.subject.engtripodal ligandde
dc.affiliation.instituteFakultät für Chemiede
dc.subject.gokfullChemie  (PPN62138352X)de

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