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Introduction
Additional affiliations
September 2012 - March 2016
Position
- PhD Student
Description
- DOSY External Calibration Curve Molecular Weight Determination
Publications
Publications (19)
Alkali metal 1,1,1,3,3,3-hexamethyldisilazide (MHMDSs) are one of the most utilised weakly nucleophilic Brønsted bases in synthetic chemistry and especially in natural product synthesis. Like lithium organics, they aggregate depending on the employed donor solvents. Thus, they show different reactivity and selectivity as a function of their aggrega...
Invited for the cover of this issue are D. Stalke and R. Neufeld from the University of Göttingen. The image symbolizes for the authors′ navigation to the solution structure of the turbo-Hauser base, TMPMgCl⋅LiCl. Read the full text of the article at 10.1002/chem.201601494.
Grignard reagents that are at the simplest level described as "RMgX" (where R is an organic substituent and X a halide) are one of the most widely utilized classes of synthetic reagents. Lately especially Grignard reagents with amido ligands of the type R1R2NMgX, so called Hauser bases, and their Turbo analogue R1R2NMgX•LiCl play an outranging role...
Lithium diisopropyl amide (LDA) is a very prominent reagent that plays a key role in organic synthesis, serving as a base par excellence for a broad range of deprotonation reactions. However, the state of aggregation in solution in the absence of donor bases was unclear. In this paper we solved this problem by employing DOSY NMR experiments based o...
Determination of the aggregation and solvation numbers of organometallic complexes is an important task to get better insight in reaction mechanisms. Thus knowing which aggregates are formed during a reaction is of high interest to develop better selectivity and higher yields. Diffusion-ordered spectroscopy (DOSY), which separates NMR signals accor...
Lithium borates like LiBOB and LiDFOB are often used as additives in lithium-ion battery electrolytes (LIBs). Unfortunately, they react with alcohols, whereby water is released as a byproduct.
As a result, Karl Fischer (KF) titrations in alcoholic KF reagents provide wrong results, which are highly overdetermined.
Herein, we show how alcohol-free...
Many samples, like lithium-ion battery (LiB) electrolytes or those with additives, undergo side reactions with alcohols in common KF reagents. This leads to an increase in drift, and delayed or no titration endpoint, rendering incorrect water content results. It can even make water determination impossible.
New Hydranal alcohol-free reagents suppr...
To help users solve their critical Karl Fischer titration challenges, Cosimo and I have compiled the most frequently asked advanced technical questions and arranged them into categories for quick reference.
Boosted by LiCl addition, the turbo-Hauser base, TMPMgCl⋅LiCl, contains a trigonal coordinated magnesium atom providing outstanding reactivity and selectivity. ECC DOSY NMR spectroscopy confirms the structure in solution. More information can be found in the Communication by D. Stalke and R. Neufeld (DOI: 10.1002/chem.201601494).
Turbo-Hauser bases are very useful and highly reactive organometallic reagents in synthesis. Especially TMPMgCl*LiCl 1 (TMP = 2,2,6,6-tetramethylpiperidide) is an excellent base for converting a wide range of (hetero)aromatic substrates into highly functionalized compounds with a broad application in organic synthesis. The knowledge of its structur...
New external calibration curves (ECCs) for the estimation of aggregation states of small molecules in solution via DOSY NMR spectroscopy for a range of different common NMR solvents (DMSO-d6, C6D12, C6D6, CDCl3 and CD2Cl2) are introduced and applied. ECCs are of avail to estimate molecular weights (MWs) from diffusion coefficients of previously unk...
Lithiumdiisopropylamid (LDA) ist ein überaus wichtiges Reagens und nimmt vor allem in der organischen Synthesechemie eine Schlüsselrolle bei einer Vielzahl von Deprotonierungsreaktionen ein. Trotzdem ist seine Aggregation, und damit die Gestalt der reaktiven Spezies in nichtdonierenden Lösungsmitteln, bislang noch ungeklärt. Hier lösen wir dieses P...
Cr(I)Cl is a very unstable species. The present work describes the stabilization of Cr(I)Cl in the low-coordinate environment of cyclic alkyl(amino) carbene ligands and its synthetic application to yield an unprecedented cationic complex with a two-coordinate Cr(I). One electron reduction of (cAAC)2CrCl2 (1) with equivalent amounts of KC8 results i...
Cyclic alkyl(amino) carbene stabilized two- and three-coordinate Fe(I) complexes, (cAAC)2FeCl (2) and [(cAAC)2Fe][B(C6F5)4] (3) respectively, were prepared and thoroughly studied by a bouquet of analytical techniques as well as theoretical calculations. SQUID data and Mössbauer spectroscopy reveal the +1oxidation state and S = 3/2 spin ground state...
Four at one stroke: A quadruple domino carbopalladation reaction gives access to highly substituted dibenzopentafulvalenes and the complete pentafulvalene backbone is constructed in only one synthetic step. Structural and electronic properties have been evaluated by X-ray crystallography and cyclovoltammetry.
Vier auf einen Schlag: Eine vierfache Domino‐Carbopalladierungssequenz macht hochsubstituierte Dibenzopentafulvalene zugänglich, wobei das Pentafulvalengerüst in einem Syntheseschritt aufgebaut wird. Strukturelle und elektronische Eigenschaften wurden mittels Röntgenkristallographie und Cyclovoltammetrie untersucht.
Quadratisch, praktisch, gut! Die Ammine [Li(NH3)4][Ind] und [Na(NH3)4][Ind] (Ind=Indenid) enthalten vom Ammoniak vierfach koordinierte Kationen. Während das erste die erwartete tetraedrische Koordination aufweist, ist das zweite quadratisch-planar koordiniert. Das solvensgetrennte Ionenpaar bildet eine gewellte Schichtstruktur aus abwechselnden Na(...
It's hip to be a square! The ammines [Li(NH(3) )(4) ][Ind] and [Na(NH(3) )(4) ][Ind] both contain a cation coordinated by four ammonia molecules. Whereas the first shows the anticipated tetrahedral coordination, in the second the metal coordination is unexpectedly square-planar. The solvent-separated ion pair forms a rippled layer structure of alte...
A flexible and robust method for the assembly of (1-->6)-linked C-glycosidic disaccharides is presented. The key reaction is a Pd-catalyzed coupling of 1-iodo- or 1-triflato-glycals with alkynyl glycosides. Reinstallation of the native hydroxyl group pattern is achieved after selective hydrogenation of the triple bond using Raney-nickel. Epoxidatio...
