Abstract Monomerie diiodides of 2,4,6-tri(tert-butyl)phenyl = (s-Mes), 2,4,6-triisopropylphenyl = (Trip)-and 2,4-di-tert-butyl-6-methylphenyl = (DBMP)-gallium and -indium were prepared by the reaction of the lithiated aryls with MI3 (M = Ga, In) in hexane/Et2O. s-MesInI2 (1), s-Mes2InI (2), s-MesGaI2 (3), s-Mes2GaI (4), Trip2InI (5) and (DBMP)2InI (6) were obtained and characterized by their mass and NMR spectra (1H, 13C), and/or by elemental analyses. An X-ray crystal structure analysis was carried out for 1.
Abstract Depending on the solvent and the bulkiness of the substituents, Iithiated aminofluorosilanes are dimers, monomers, or LiF-adducts of iminosilanes. In the crystal structure of the dimeric lithium derivative of di-tert-butyl(rm-butylamino)fluorosilane, each lithium atom is coordinated by one fluorine and two nitrogen atoms. LiF-elimination leads - if sterically possible - to dimerisation. The limits of dimerisation are reached with the dimer diisopropyl(tri-tert-butylphenyI- imino)silane, for which the crystal structure analysis shows severe steric distortions. Fluorine- chlorine-cxchange occurs in reactions of lithiated (tri-tert-butylphenylimino)fluorosilanes with Me3SiCl. Iminosilanes are obtained by thermal LiCl-elimination from the resulting salts.
AbstractThe crystallographic characterization of the following three calcium channel antagonists is reported here: 2,6-dimethyl-3,5-dicarbamoyl-4-[2-nitro]-1,4-dihydropyridine (
The arrangement of hydroxyl groups in the benzene ring has a significant effect on the propensity of dihydroxybenzoic acids (diOHBAs) to form different solid phases when crystallized from solution. All six diOHBAs were categorized into distinctive groups according to the solid phases obtained when crystallized from selected solvents. A combined study using crystal structure and molecule electrostatic potential surface analysis, as well as an exploration of molecular association in solution using spectroscopic methods and molecular dynamics simulations were used to determine the possible mechanism of how the location of the phenolic hydroxyl groups affect the diversity of solid phases formed by the diOHBAs. The crystal structure analysis showed that classical carboxylic acid homodimers and ring-like hydrogen bond motifs consisting of six diOHBA molecules are prominently present in almost all analyzed crystal structures. Both experimental spectroscopic investigations and molecular dynamics simulations indicated that the extent of intramolecular bonding between carboxyl and hydroxyl groups in solution has the most significant impact on the solid phases formed by the diOHBAs. Additionally, the extent of hydrogen bonding with solvent molecules and the mean lifetime of solute–solvent associates formed by diOHBAs and 2-propanol were also investigated.
Equilibrium Structure, Stabilized Transition State, or Disorder in the Crystal? Studies of the Antiaromatic Systems Tetra-tert-butyl-s-indacene and Tetra-tert-butylcyclobutadiene by Low-Temperature Crystal Structure Analysis