Hans-Jörg Deiseroth

Atomistic Characterisation of Li+ Mobility and Conductivity in Li7−xPS6−xIx Argyrodites from Molecular Dynamics Simulations, Solid‐State NMR, and Impedance Spectroscopy

The atomistic mechanisms of Li(+) ion mobility/conductivity in Li(7-x)PS(6-x)I(x) argyrodites are explored from both experimental and theoretical viewpoints. Ionic conductivity in the title compound is associated with a solid-solid phase transition, which was characterised by low-temperature differential scanning calorimetry, (7)Li and (127)I NMR investigations, impedance measurements and molecular dynamics simulations. The NMR signals of both isotopes are dominated by anisotropic interactions at low temperatures. A significant narrowing of the NMR signal indicates a motional averaging of the anisotropic interactions above 177+/-2 K. The activation energy to ionic conductivity was assessed from both impedance spectroscopy and molecular dynamics simulations. The latter revealed that a series of interstitial sites become accessible to the Li(+) ions, whilst the remaining ions stay at their respective sites in the argyrodite lattice. The interstitial positions each correspond to the centres of tetrahedra of S/I atoms, and differ only in terms of their common corners, edges, or faces with adjacent PS(4) tetrahedra. From connectivity analyses and free-energy rankings, a specific tetrahedron is identified as the key restriction to ionic conductivity, and is clearly differentiated from local mobility, which follows a different mechanism with much lower activation energy. Interpolation of the lattice parameters as derived from X-ray diffraction experiments indicates a homogeneity range for Li(7-x)PS(6-x)I(x) with 0.97 < or = x < or = 1.00. Within this range, molecular dynamics simulations predict Li(+) conductivity at ambient conditions to vary considerably.

Zincation of primary amines: synthesis and structures of dimeric alkylzinc amides

Abstract The zincation of triisopropylsilylamine with dimethyl- and diethylzinc yields dimeric methylzinc (1) and ethylzinc triisopropylsilylamide (2). Complex 1 crystallizes in the monoclinic space group P21/n, 2 in P21/c. The reaction of dimethylzinc with adamantylamine gives [(THF)ZnMe][(AdNH2)ZnMe][μ-N(H)Ad]2 (3) which crystallizes in the monoclinic space group P21/n. All these compounds have central Zn2N2 cycles. Contrary to 1 and 2 with triply coordinated metal centers, the zinc atoms in 3 show a distorted tetrahedral coordination sphere due to the contact to the neutral coligands THF and adamantylamine.

Lithium Argyrodites with Phosphorus and Arsenic: Order and Disorder of Lithium Atoms, Crystal Chemistry, and Phase Transitions

Crystal chemical data of high- (HT) and low-temperature (LT) modifications of lithium argyrodites with the compositions Li(7)PCh(6) (Ch=S, Se), Li(6)PCh(5)X (X=Cl, Br, I), Li(6)AsS(5)Br, and Li(6)AsCh(5)I (Ch=S, Se) based on single-crystal, powder X-ray (113 K<T<503 K) and neutron measurements (5 K<T<293 K) are presented. In the HT modifications, the Li atoms are strongly disordered over a fraction of the available tetrahedral holes, whereas in the LT modifications they occupy ordered crystallographic positions with a pronounced site preference that is analysed on a crystal chemical basis. The Ch/X partial structures remain nearly unchanged upon the reversible phase transitions. Crystal chemical and crystallographic relations between HT and LT modifications based on the Frank-Kasper model of tetrahedral close packing are discussed. X-ray single-crystal data for HT-Li(6)PS(5)I show the electron density of the disordered Li to be smeared out over an extended region preferably inside face-sharing double tetrahedra. A series of temperature-dependent powder neutron data for Li(6)PS(5)I gives clear evidence for an HT/LT phase transition at approximately 175 K with an ordering of the Li atoms in different polyhedra with coordination numbers between three and four.

Ag6GeS4X2 (X: Cl, Br) : surprisingly no filled laves phases but the first representatives of a new structure type

Abstract The two new deeply coloured, air stable, isotypic compounds Ag6GeS4X2 (X: Cl, Br) were obtained in the course of a series of experiments to prepare new “non-metallic filled Laves phases (= argyrodites)”. Although the chemical compositions of the new compounds are in accordance with the desired rare type of doubly halide (X) substituted argyrodites Ag6GeS4X2, their crystal structures are not of the argyrodite type. Instead they are the first members of the new family of “non-metallic filled NaHg2 phases”, i.e. the partial structure of the non-metal atoms S and X (Cl, Br) corresponds to the arrangement of Na and Hg atoms in NaHg2 (= X2S4) with Ge located in tetrahedral holes exclusively and Ag located in tetrahedral as well as octahedral holes. The lattice constants of the new phases are (both space group Pnma, Z = 4): Ag6GeS4Cl2 (a = 643.0(1) pm, b = 761.0(2) pm, c = 2266.0(5) pm), Ag6GeS4Br2 (a = 654.0(1) pm, b = 772.7(2) pm, c = 2289.9(5) pm). High temperature X-ray powder studies show an irreversible loss of halogen resulting in inhomogeneous decomposition products with argyrodite structure.

Synthesis of 6-amino-3,4-dihydroisoquinolinium derivatives by ring-opening reactions of acridizinium ions.

The reaction of the 9-fluoroacridizinium (9-fluorobenzo[b]quinolizinium) or the 9-aminoacridizinium (9-aminobenzo[b]quinolizinium) ion with primary alkyl amines gives with high diastereoselectivity 6-amino-3,4-dihydroisoquinolinium derivatives as main products, which exhibit pronounced absorption and fluorescence properties. It is proposed that the reaction proceeds via a nucleophilic ring-opening followed by an aza Diels-Alder reaction.

Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

Summary A one-pot transformation, which involves the reaction of ketones with aldehydes in the presence of metal halides to furnish tetrahydro-2H-pyran-2,4-diols in a highly diastereoselective manner, is investigated thoroughly by experiments and computations. The reaction was also successfully implemented on a flow micro reactor system.

A supramolecular ladder motif in 2-(2,2,6,6-tetramethylpiperidin-1-yloxy)propane-1,3-diol

An O—H⋯O hydrogen-bonded step-ladder motif was observed in the crystal structure of the title compound, C12H25NO3. The ladder arrangement is typical of 1,2- and 1,3-diols with a synclinal orientation of the diol functionality.

Unusual ladder-like supramolecular arrangement by cooperative effect of bifurcated O–H⋯O hydrogen bonding in crystals of racemic 4-ferrocenylbutan-1,2-diol

A new short synthetic approach to 4-ferrocenebutan-1,2-diol (15) is described. In solution, both intra- and intermolecular hydrogen bonding are observed, the solid state structure is characterised by intermolecular hydrogen bonding only. In the solid state, the bifurcated cooperative hydrogen bonding not only leads to a dimeric structure but on a supramolecular level gives rise to a secondary duplex staircase ladder.