Untersuchungen zur Darstellung und Anwendung neuer Bispidin-Übergangsmetallverbindungen

Das Ziel dieser Arbeit waren Untersuchungen zum Einfluß von gezielten strukturellen Veränderungen an molekularen Katalysatoren auf die Reaktivität und Selektivität von homogenen katalytischen Reaktionen. Aufgrund ihrer speziellen strukturellen Eigenschaften und ihrer Starrheit haben Bispidine und ihre Übergangsmetallkomplexe interessante Eigenschaften in katalytischen Reaktionen. Auf der Basis konkreter Konzepte zur Synthese neuer Liganden wurden chirale Bispidine synthetisiert und deren Eigenschaften ausführlich untersucht. So konnte durch gezieltes Liganddesign in den Liganden L4 und L5 eine Versteifung der Koordinationsumgebung entsprechender FeII-Koordinationsverbindungen erreicht werden. Die damit einhergehende Erhöhung der Epoxidierungsaktivität ist durch zusätzliche Rigidität der Liganden und damit positivere FeIII/FeII Reduktionspotentiale verursacht. Durch die Synthese eines neuen chiralen, tricyclischen Bispidingerüstes gelang die Aufhebung der Spiegelsymmetrie in den Bispidinen. Die Eigenschaften der resultierenden Liganden L7-L9 wurden ausführlich untersucht. So gelang auch die Darstellung optisch reiner CuII-Koordinationsverbindungen mit chiralen, tricyclischen Bispidinderivaten. Weiterhin wird ein Konzept zur Anwendung von chiralen, optisch reinen Naturstoffen in der Bispidin-synthese vorgestellt, mit Hilfe dessen die modulare Synthese tetra- und pentadentater chiraler Liganden möglich ist. Die Ausweitung der Koordinationschemie der Bispidine auf Ruthenium erbrachte neue Einblicke in die Reaktivität und Stereoselektivität der Epoxidierungskatalyse im Vergleich zu Eisen. Desweiteren stellte sich die Verbindung [(L1)RuII(OH2)](ClO4)2 als hoch aktiver Sulfoxidationskatalysator heraus

Digitalización, catalogación y transcripción de obras compuestas por ocho grandes artistas costeños destacados en la segunda mitad del siglo XX presentes en el Archivo sonoro Antonio Cuéllar

El trabajo Digitalización, catalogación y transcripción de obras compuestas por ocho grandes artistas costeños destacados en la segunda mitad del siglo XX presentes en el Archivo sonoro Antonio Cuéllar, fue realizado en el Centro de documentación de las Artes Gabriel Esquinas de la Facultad de Artes ASAB de la Universidad Distrital Francisco José de Caldas. Este trabajo aporta la digitalización sonora y de imagen de 314 piezas musicales de siete artistas que hicieron parte de la agrupación Los Corraleros de Majagual: Alfredo Gutiérrez (n. 1943), Calixto Ochoa (n. 1934-2015), Aníbal Velásquez (n. 1936), Lisandro Meza (n. 1939), Eliseo Herrera (n. 1925-2016), Cesar Castro (n. 1937), y Lucho Argaín (n. 1927-2002), además del saxofonista y clarinetista Clímaco Sarmiento (n. 1916- 1986). Adicionalmente, el trabajo suministra información relacionada con cada una de las piezas digitalizadas, como de sus compositores e intérpretes, la cual permite ampliar el catalogo pre-existente. Finalmente incluye la transcripción musical de cuatro solos de viento que por su lenguaje improvisatorio tienen gran valor para el estudio de estas músicas.The Digitalisation, cataloguing and transcription of works composed by eight prolific artists from the Carribean Coast, prominent in the late twentieth Century and present in the Antonio Cuellar Sound Archives (Archivo Sonoro Antonio Cuellar), was realised in the Gabriel Esquinas Documentation Center (Centro de Documentación de las Artes Gabriel Esquinas) in the Universidad Distrital Francisco José de Caldas Faculty of Arts (ASAB). This work offers the sound and image digitalisation of three hundred fourteen musical works of seven artists that were part of the group Los Corraleros de Majagual: Alfredo Gutiérrez, Calixto Ochoa, Aníbal Velásquez, Lisandro Meza, Eliseo Herrera, Cesar Castro, y Lucho Argaín, in addition to the saxophone and clarinet player Clímaco Sarmiento. Information about the composers and musicians of each of the digitalised pieces is also provided with the aim to widen the pre-existing catalogue. Finally, a musical transcription of four wind solos has been included which, due to is improvisatory language, is of great value in the study of these genres

Synthesis and Structural Characterization of Tetraalkylammonium Salts of the Weakly Coordinating Anion [Al(OTeF5)4]–

The weakly coordinating properties of the [Al(OTeF5)4]– anion were studied by the synthesis and characterization of its tetraalkylammonium salts [NAlk4][Al(OTeF5)4] [Alk4 = –(CH3)4, –(C2H5)4, –(C2H5)3CH3, –(C3H7)4, –(C4H9)4]. The one‐pot synthesis includes formation of the Brønsted acid in 1,2–difluorobenzene, H[Al(OTeF5)4](solv.), and its reaction with [NAlk4]Cl [Alk4 = –(CH3)4, –(C2H5)4, –(C2H5)3CH3, –(C3H7)4, –(C4H9)4] to the corresponding salts. Single crystals were obtained for [N(C4H9)4][Al(OTeF5)4] and characterized by X‐ray diffraction analysis

Insights on the Lewis Superacid Al(OTeF5)3: Solvent Adducts, Characterization and Properties

Preparation and characterization of the dimeric Lewis superacid [Al(OTeF5)3]2 and various solvent adducts is presented. The latter range from thermally stable adducts to highly reactive, weakly bound species. DFT calculations on the ligand affinity of these Lewis acids were performed in order to rank their remaining Lewis acidity. An experimental proof of the Lewis acidity is provided by the reaction of solvent‐adducts of Al(OTeF5)3 with [PPh4][SbF6] and OPEt3, respectively. Furthermore, their reactivity towards chloride and pentafluoroorthotellurate salts as well as (CH3)3SiCl and (CH3)3SiF is shown. This includes the formation of the dianion [Al(OTeF5)5]2−

[P4H]+[Al(OTeF5)4]−: protonation of white phosphorus with the Brønsted superacid H[Al(OTeF5)4](solv)

A sustainable transformation of white phosphorus (P4) into chemicals of higher value is one of the key aspects in modern phosphorus research. Even though the chemistry of P4 has been investigated for many decades, its chemical reactivity towards the simplest electrophile, the proton, is still virtually unknown. Based on quantum-chemical predictions, we report for the first time the successful protonation of P4 by the Brønsted acid H[Al(OTeF5)4](solv). Our spectroscopic results are in agreement with acid-mediated activation of P4 under protonation of an edge of the P4-tetrahedron and formation of a three-center two-electron P–H–P bond. These investigations are of fundamental interest as they permit the activation of P4 with the simplest electrophile as a new prototype reaction for this molecule

Formation of Peroxynitrite, [O−N−O−O]−, via a Cascade of Reactions between Ozonide and Ammonia

We report on an unexpected reaction between ammonia and potassium ozonide dissolved in liq. NH3 resulting in the formation of peroxynitrite, [ONOO]−, which exclusively happens in the presence of a specific partially fluorinated aniline-based ammonium cation. High-resolution structural data of the peroxynitrite anion in cis-conformation have been obtained. We further studied this molecule anion by single crystal Raman spectroscopy. The cis and trans isomers of peroxynitrite were analysed computationally with respect to their relative energies, the cis-trans transition barrier and their decomposition pathways to the nitrate anion. By experimentally examining cations decorated with fluorine ligands to different degrees, we demonstrate that fluorine specific interactions play a crucial role in the unexpected formation of peroxynitrite and as a conspicuously structure directing factor for the underlying crystalline solid phases, exhibiting distinct micro-separations of fluorine and hydrogen enriched regions

A Highly Sterically Encumbered Boron Lewis Acid Enabled by a Organotellurium-based Ligand

Lewis acidic boron compounds are ubiquitous in chemistry due to their numerous applications, yet tuning and optimizing their properties towards different purposes is still a challenging field of research. In this work, the boron Lewis acid B[OTeF3(C6F5)2]3 was synthesized by reaction of the teflate derivative HOTeF3(C6F5)2 with BCl3 or BCl3·SMe2. This new compound presents a remarkably high thermal stability up to 300 °C, as well as one of the most sterically encumbered boron centres known in the literature. Theoretical and experimental methods revealed that B[OTeF3(C6F5)2]3 exhibits a comparable Lewis acidity to that of the well-known B(C6F5)3 and around 85% of the Lewis acidity of the related B(OTeF5)3. The affinity of B[OTeF3(C6F5)2]3 towards pyridine was accessed by Isothermal Titration Calorimetry (ITC) and compared to that of B(OTeF5)3 and B(C6F5)3. The ligand-transfer reactivity of this new boron compound towards different fluorides was demonstrated by the formation of an anionic Au(III) complex and a hypervalent iodine(III) species

Fluorinated Dialkyl Chloronium Salts: Synthesis and Reactivity for Fluoroalkylation and Hydride Abstraction

A new concept for the synthesis of dialkyl chloronium cations [R‒Cl‒R]+ is described (R = CH3, CH2CF3), that allows the formation of fluorinated derivatives. By utilizing the xenonium salt [XeOTeF5][M(OTeF5)n] (M = Sb, n = 6; M = Al, n = 4) chlorine atoms of chloroalkanes or the deactivated chlorofluoroalkane CH2ClCF3 are oxidized and removed as ClOTeF5 leading to the isolation of the corresponding chloronium salt. Since the resulting highly electrophilic cation [Cl(CH2CF3)2]+ is able to alkylate weak nucleophiles, this compound can be utilized for the introduction of a fluorinated alkyl group to those. In addition, the fluorinated alkyl chloronium cation displays a high hydride ion affinity, enabling the activation of linear hydrocarbons by hydride abstraction even at low temperatures ultimately leading to the formation of branched carbocations

[Xe(OTeF5)(pyF)]+: a strong oxidizing xenonium(ii) teflate cation with N-donor bases

Herein we report on the formation of the adduct salts [Xe(OTeF5)(pyF)][Al(OTeF5)4] (pyF = C5F5N, C5H3F2N) by abstraction of an –OTeF5 group from Xe(OTeF5)2 with the Lewis superacid Al(OTeF5)3 and subsequent adduct formation of the generated [XeOTeF5]+ cation with fluorinated pyridines. These salts represent the first xenonium cations with the weakly coordinating [Al(OTeF5)4]− anion. The strong oxidizing property of these compounds is further assessed

Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine

The adsorption of organic micropollutants onto activated carbon is a favourable solution for the treatment of drinking water and wastewater. However, these adsorption processes are not sufficiently understood to allow for the appropriate prediction of removal processes. In this study, thermogravimetric analysis, alongside evolved gas analysis, is proposed for the characterisation of micropollutants adsorbed on activated carbon. Varying amounts of carbamazepine were adsorbed onto three different activated carbons, which were subsequently dried, and their thermal decomposition mechanisms examined. The discovery of 55 different pyrolysis products allowed differentiations to be made between specific adsorption sites and conditions. However, the same adsorption mechanisms were found for all samples, which were enhanced by inorganic constituents and oxygen containing surface groups. Furthermore, increasing the loadings led to the evolution of more hydrated decomposition products, whilst parts of the carbamazepine molecules were also integrated into the carbon structure. It was also found that the chemical composition, especially the degree of dehydration of the activated carbon, plays an important role in the adsorption of carbamazepine. Hence, it is thought that the adsorption sites may have a higher adsorption energy for specific adsorbates, when the activated carbon can then potentially increase its degree of graphitisation.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli