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Ammonia stabilized Carbanions

dc.contributor.advisorStalke, Dietmar Prof. Dr.
dc.contributor.authorMichel, Reent
dc.publisherNiedersächsische Staats- und Universitätsbibliothek Göttingende
dc.titleAmmonia stabilized Carbanionsde
dc.contributor.refereeStalke, Dietmar Prof. Dr.
dc.description.abstractengThis thesis examines the solvation of alkali metal cyclopentadienyl derivatives (Cp, CpMe, Cp*, indenyl, fluorenyl) in liquid ammonia as well as in solutions of ammonia in polar aprotic solvents. The degree of solvation has been determined by single crystal X-Ray diffraction. Liquid ammonia is a very potent solvent for organometallic compounds due the small size, aprotic character, and strong electron donating properties. The liquid window, ranging from -77°C to -33°C, is challenging to handle and therfore ammonia plays a minor role in organometallic synthesis. Ammonia dissolves a range of salts and small molecules, which are both characteristics of alkali metal cyclopentadienyl derivatives and making them ideal target compounds to investigate ammonias beneficial solvation properties. Salts of alkali metals and the respective carbanion have either been dissolved in liquid ammionia and ammonia containing solutions or created in situ. The solutions have been stored for crystallization at various temperatures ranging from -87°C to -16°C. The crystals very highly sensitive to temperature and moisture. New methods in crystal selection and preparation were developed to accomodate the challenging requirements. The research shows a very efffective solvation of lithium cyclopentadienyl compounds. In most cases the lithium cation is totally detached from the anion. Solvent separated ion pairs (SSIP) are formed with a [Li(NH3)3]+ cation and a naked anion. Sodium cycopentadienyl compounds form piano stool complexes with Cp, CpMe, and Cp*. SSIPs are formed with indenyl and fluorenyl. Potassium, rubidium, and caesium form ammonia solvated linear coordination polymers with Cp and CpMe. Indenyl and fluorenyl form 2-dimensional layers with the higher alkali metal cations with exception of indenylpotassium. Two factors have been identified to determine the degree of solvation. With increasing cationic radius, the metal ion is increasingly attracted to the pi-system of the anion and the degree of solvations decreases. NH3-pi hydrogen bonding plays the major role in the formation of highly solvated litihum and sodium compounds. The smaller the cation radius, the higher is the impact of hydrogen bonding in the formation of SSIPs and contact ion pairs (CIP). Ammonia has proven to be an effective solvent for the target compounds. Especially the high degree of solvation of the lithium and sodium compounds show the potential of ammonia as solvent or additive to enhance reactivity since a high degree of solvation offers easier pathways for
dc.contributor.coRefereeMeyer, Franc Prof. Dr.
dc.contributor.thirdRefereeKoszinowski, Konrad Prof. Dr.
dc.contributor.thirdRefereeAlcarazo, Manuel Prof. Dr.
dc.contributor.thirdRefereeWaitz, Thomas Prof. Dr.
dc.contributor.thirdRefereeSowa, Heidrun Dr.
dc.subject.enghydrogen bondingde
dc.subject.engalkali metalsde
dc.subject.engaromatic carbanionsde
dc.subject.engcrystal engineeringde
dc.affiliation.instituteFakultät für Chemiede
dc.subject.gokfullChemie  (PPN62138352X)de

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