Das Pyren und der Einfluß von Substitution oder Komplexie-rung auf seine Geometrie und Packung im kristallinen Zustand

The crystal structures of pyrene and substituted and complexed derivatives of pyrene have been investigated by X-ray and neutron diffraction. The geometry of the pyrene skeleton has been determined experimentally with high accuracy and calculated by quantum chemical methods. In the cases reported in the literature and cited here the pyrene skeleton has the molecular symmetry mmm or mm2 with values for the bond lengths of the six symmetrically independent bondsa, b, c, d, e, f differing significantly in the limits of error. Mean values of a number of experimental and theoretical bond lengths are given and can be considered as standard values for the mm2 symmetric pyrene skeleton. In the case of substitution of the pyrene in 3-position with a polar heterocyclic molecule of the azomethine-imine type the mm2 symmetry vanishes, a C–H ... N intramolecular hydrogen bond arises and the directly neighbouring pyrene units are not packed parallel with their planes to each other, but they are considerably tilted. Relatively narrow intermolekular C-C contacts, 3.314 and 3.368 Å, have been observed. The conclusion is drawn that the asymmetry of the pyrene molecule and a tilt of directly neighbouring pyrene units in the crystal packing can be induced by substitution e. g. with suitable polar heterocycles.

Juli 1985.     

The Molecular and Crystal Structure of p-methyl-phenyl-glyoxyacid-p-chloranilide

Using X-ray crystal structure analysis of the title compound the positions of all the atoms (including all H atoms) in the monoclinic unit cell with the parameters a = 13.90₀ Å, b = 5.13₈ Å, c = 17.95₆ Å and β = 91.05° and the space group P 2₁/n were localized. The existence of an intramolecular N—H(N)…︁ O(1)-bridge was inferred, whose H-bridge acceptor predominantly is the π-electron density of the carbonyl group. At the same time the H(N) atom participates in the intermolecular bridge N H(N)…︁ O′(1) to the symmetry-equivalent neighbouring molecule. H-bridge-like interactions of the two phenyl hydrogen atoms H(6) and H(15) to the carbonyl oxygen O(2) have also been inferred from the torsion angles.     

Minimalistic Ditopic Ligands: An α‐S,N‐Donor‐Substituted Alkyne as Effective Intermetallic Conjugation Linker

The capability of donor‐substituted alkynes to link different metal ions in a side‐on carbon donor‐chelate coordination mode is extended from the donor centers S and P to the second period element N. The complex [Tp′W(CO)₂{η²‐C₂(S)(NHBn)}] (Tp′=hydrido‐tris(3,5‐dimethylpyrazolyl)borate, Bn=benzyl) bearing a terminal sulfur atom and a secondary amine substituent is accessible by a metal‐template synthesis. Subsequent deprotonation allowed the formation of remarkably stable heterobimetallic complexes with the [(η⁵‐C₅H₅)Ru(PPh₃)] and the [Ir(ppy)₂] moiety. Electrochemical and spectroscopic investigations (cyclic voltammetry, IR, UV/Vis, luminescence, EPR), as well as DFT calculations, and X‐ray structure determinations of the W–Ru complex in two oxidation states reveal a strong metal–metal coupling but also a limited delocalization of excited states.     

Zur Chemie des Dimesityleisens. I. Trimesitylferrate und Komplexbildung mit P-Donoren

Dimesityl Iron Chemistry. I. Trimesityl Iron Compounds and Complexes with P-Donors Concerned with the formation of FeMes₂ the compounds LiFeMes₃(dx)₄ and Mg[FeMes₃]₂(thf)_5.75 were synthesized. Phosphines, aminophosphines, and phosphites react with FeMes₂ forming complexes FeMes₂L and FeMes₂L₂, respectively. Magnetic and thermal behaviour are reported.     

Zur Kenntnis des Bisphenyl-bis(dipyridyl)chrom(II) und des Lithium-tetraphenylochromat(II)

On bisphenyl-bis(dipyridyl) chromium(II) and lithium tetraphenylo chromate(II) By reaction of Ph₂CHCrCl₂ · 2 THF with two moles of phenyl lithium Ph₂CHCrPh₂ is obtained in solution. With this solution we prepared the new Cr(II) compounds CrPh₂ · 2 bipy and Li₂Ph₄ · 4 THF by addition of 2,2′-bipyridine and two moles of further phenyl lithium, respectively. During this reactions the diphenylmethyl group is cleaved under reduction of Cr(III) to Cr(II). Li₂CrPh₄ · 4 THF is an example of a new group of high spin organochromates(II).     

Incompressible quantum liquids and new conservation laws

In this Letter, we investigate a class of Hamiltonians which, in addition to the usual center-of-mass momentum conservation, also have center-of-mass position conservation. We find that, regardless of the particle statistics, the energy spectrum is at least q-fold degenerate when the filling factor is p/q, where and are coprime integers. Interestingly, the simplest Hamiltonian respecting this type of symmetry encapsulates two prominent examples of novel states of matter, namely, the fractional quantum Hall liquid and the quantum dimer liquid. We discuss the relevance of this class of Hamiltonian to the search for featureless Mott insulators.     

A new copper acetate-bis(oxazoline)-catalyzed, enantioselective Henry reaction

A highly enantioselective, nitroaldol reaction catalyzed by a chiral Cu(II) bis(oxazoline) complex has been developed. The reaction scope includes both aromatic and aliphatic aldehydes (15 examples) affording products in good yields and enantioselectivities (87-94% ee). An X-ray structure of the catalyst has been provided along with a rationalization of the sense of asymmetric induction.