Roman Neufeld

Electronic Structure and Slow Magnetic Relaxation of Low-Coordinate Cyclic Alkyl(amino) Carbene Stabilized Iron(I) Complexes

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. Magnetic susceptibility and Mössbauer spectroscopy reveal the +1 oxidation state and S = 3/2 spin ground state of iron in both compounds. 2 and 3 show slow magnetic relaxation typical for single molecule magnets under an applied direct current magnetic field. The high-frequency EPR measurements confirm the S = 3/2 ground state with a large, positive zero-field splitting (∼20.4 cm(-1)) and reveal easy plane anisotropy for compound 2. CASSCF/CASPT2/RASSI-SO ab initio calculations using the MOLCAS program package support the experimental results.

A Pd-catalyzed approach to (1-->6)-linked C-glycosides.

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. Epoxidation with DMDO and reductive epoxide opening gives access to either the alpha- or the beta-derivative, depending on the hydride source.

The Donor-Base-Free Aggregation of Lithium Diisopropyl Amide in Hydrocarbons Revealed by a DOSY Method†

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 on a newly elaborated external calibration curve (ECC) approach with normalized diffusion coefficients.

New External Calibration Curves (ECCs) for the Estimation of Molecular Weights in Various Common NMR Solvents

New external calibration curves (ECCs) for the estimation of aggregation states of small molecules in solution by DOSY NMR spectroscopy for a range of different common NMR solvents ([D6 ]DMSO, C6 D12 , C6 D6 , CDCl3 , and CD2 Cl2 ) are introduced and applied. ECCs are of avail to estimate molecular weights (MWs) from diffusion coefficients of previously unknown aggregates. This enables a straightforward and elaborate examination of (de)aggregation phenomena in solution.

The Layered Structure of [Na(NH3)4][Indenide] Containing a Square‐Planar Na(NH3)4+ Cation

Its 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 alternating planar Na(NH(3))(4)(+) cations and indenyl carbanions that is attributed to NH(3) ⋅⋅⋅π hydrogen bonds.

Solution Structure of Turbo-Hauser Base TMPMgCl⋅LiCl in [D8]THF

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 structure in solution is of essential importance to understand the extraordinary reactivity and selectivity. However, very little is known about the aggregation of this prominent reagent in solution. Herein, we present the THF-solution structure of 1 by employing our newly elaborated DOSY NMR method based on external calibration curves (ECC) with normalized diffusion coefficients.