Universität Bonn


AC Kolloquium - M. Sc. Leonard R. Maurer
15.06.2023 ab 17:15 Uhr

Universität Bonn - "About Silenylidenes & Metalloplumbylenes: Unusual low-valent Tetrel Compounds from a Theoretical Perspective"⠀ In the last decades, great progress was made to obtain compounds with heavier low-valent tetrels Si – Pb that offer fascinating properties and reactivity. To stabilize the reactive cores, N-heterocyclic carbenes as well as transition metals can be employed and allow the isolation of molecules like iminosilenylidenes and tetrylidyne complexes. Quantum chemistry is a very useful tool here, enabling the chemist to gaze beyond the limitations of the experiment, study the bond situation or make predictions of further reactivity for molecules not (yet) isolated. Such an investigation for heavier group 10 tetrylidyne complexes suggests considerably bent metallotetrylene isomers for Sn and Pb with an unexpected σ(M→E) donation motif, and will be presented in this lecture.

GDCh Kolloquium - Professor Dr. Jieping Zhu
20.06.2023 von 17:00 bis 18:00

Catalytic Enantioselective Pictet-Spengler Reaction of Ketones: Development and Applications in the Total Synthesis of Indole Alkaloids The asymmetric Pictect-Spengler reaction (PSR) between tryptamine and aldehydes is now well-developed. Conversely, catalytic enantioselective PSR of ketone is essentially unexploited. In this presentation, we will present our work on the catalytic enantioselective PSR of tryptamine with 1,2-diones, α-ketoesters and α-ketoamide for the synthesis of enantioenriched 1,1-Disubstituted tetrahydro-β-carboline (THBC) and their application in the total synthesis of monoterpene indole alkaloids.

AC Kolloquium - Prof. Dr. Rainer Niewa
22.06.2023 ab 17:15 Uhr

Universität Stuttgart - "Main Group Nitrides and Intermediates in Synthesis from Ammonia and Alkali Metal Melts"⠀ Crystal growth of new chemical compounds as well as functional materials often proceeds from solvents and fluxes. This presentation discusses products and chemistry of crystal growth of main group element nitrides from ammonia and molten alkali metal as two prominent approaches. The ammonothermal synthesis typically uses ammonobasic or ammonoacidic mineralizers in supercritical ammonia at elevated temperatures and pressures, and has been shown to be able to grow a wide range of interesting materials such as AlN crystals and free-standing GaN wafers. The latter have proven to be ideal substrates for manufacturing blue and white LEDs with superior performance. However, the crystal growth mechanism in the ammonothermal synthesis in terms of the involved solute species was poorly understood, although the chemical processes during dissolution of the starting material, [...]

AC Kolloquium - M. Sc. Tatjana Terschüren
29.06.2023 ab 17:15 Uhr

Universität Bonn - "Chemistry of rigid, planar and bent bis-NHCs annulated to 1,4-dihydro-1,4-diphosphinines" Despite the first 1,4-diphosphinine was published in 1976, isolated tricyclic imidazole-based dithione and -selone derivatives were synthesised only recently. They readily undergo reactions with nucleophiles as well as [4+2]-cycloadditions, while only their 1,4-dihydro-1,4-diphosphinine precursors have been converted into planar P-bridged bis(N-heterocyclic) carbenes (bis-NHCs). The latter were investigated regarding their reactivity towards transition metal complexes and, hence, represent interesting tetratopic ligands. Herein, the synthesis of new rigid, bent bis-NHCs is presented. Their reactivity towards metal complexes and main group element halides will be discussed and compared to that of already established bis-NHCs, including some surprises.

GDCh Kolloquium - Junge Forscher stellen sich vor
04.07.2023 von 16:00 bis 21:00

Stefan Flesch Photolytical formation of a nitrido-iron(V) complex tracked by ultrafast mid-IR spectroscopy Hagen Neugebauer Toward reliable quantum chemical modeling of homogeneous 3d transition metal electrocatalysis Lea Schmidt Mixed-metal monophosphate tungsten bronzes containing divalent transition metal ions (M<sup>2</sup>: Fe, Co, Ni) and tungsten(VI) Houchao Xu The Mysterious Case of Sodorifen Biosynthesis Anschliessend BBQ

AC Kolloquium - Prof. Dr. Moumita Majumdar
06.07.2023 ab 17:15 Uhr

Indian Institute of Science Education and Research (IISER) - "Designing Cationic Main-Group Compounds: New Feats in the Field of Lewis Acid Catalysis”⠀ We have been interested in main-group compounds having positive charges on their reactive sites that shows implications in Lewis-acid catalysis. We have been engaged in utilizing Ge(II) di- and mono-cations as ligands towards Au(I) for Lewis-acid catalysis and in cooperative catalysis respectively. In 2021, we have reported the stabilization of the fugitive Sb(I) cation which is the isoelectronic analogue of carbones. The rich electronics available at the Sb(I) cation leading to its coordination towards transition metal ions and the unusual reactivity with main-group compounds will be discussed. Our group is currently focussed on the stabilization of Sb(III) and Bi(III) polycations within redox-active ligand frameworks. The unique electronic features of these highly charged compounds and their implications will be discussed. [...]

AC Kolloquium - Prof. Dr. Takahiro Sasamori
13.07.2023 ab 17:15 Uhr

Universität Tsukuba - "Chemistry of Hetarenes Including Heavier Main Group Elements”⠀ In contrast to the wealth of physical functionality of benzene, chemically it is generally inert due to considerable aromatic stabilization energy. However, replacing a C-H moiety of benzene with a heavier main-group moiety significantly affects the physical and chemical properties of the cyclic-π-conjugated systems. Therefore, we are interested in the replacement of C–H moieties with moieties that contain heavier group 14 elements (E–R; E = Si, Ge, Sn, or Pb; R = organic substituent) in order to control the physical and chemical properties. Since Sekiguchi et al. have reported the synthesis of the first stable 1,2-disilabenzenes by the reaction of the stable disilyne, the chemistry of 1,2-dimetallabenzenes have been developed. We have also reported the synthesis of the stable 1,2- and 1,4-digermabenzenes by the analogous reactions, i. e., the reaction of the diaryldigermyne with alkynes.[...]

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