C-c bond formation through oxidatively induced elimination of platinum complexes--a novel approach towards conjugated macrocycles

A novel and effective method for the synthesis of conjugated macrocycles is described. By the self-assembly of conveniently accessible building blocks to a metalla-macrocycle, and subsequent C-C bond formation through elimination of transition metal units, the strained cyclodimeric terthiophene-diyne 4 -as a precursor for cyclo[8]thiophene 5- was synthesized in a good overall yield.     

Coincidence of the molecular organization of beta-substituted oligothiophenes in two-dimensional layers and three-dimensional crystals

The molecular arrangements of three different alkyl-substituted oligothiophenes both in two-dimensional adsorbed layers at a substrate interface and in bulk three-dimensional crystals were studied. Scanning tunneling microscopy (STM) was used to investigate the ordering of the conjugated oligomers in two-dimensional layers adsorbed on graphite. These data were compared with the X-ray structure determinations of single crystals revealing the arrangement in the three-dimensional bulk material. Quaterthiophenes 1 and 2, bearing dodecyl and hexyl side chains, respectively, exhibit a lamella-type stacking of the conjugated backbone concomitant with an interlocking of the alkyl side chains both on the surface and in the crystal. In contrast, the arrangement of propyl-substituted quaterthiophene 3 is rather "herringbone-like" due to the reduced interactions of the shorter alkyl side chains. In all three cases, evidently, the two-dimensional ordering at the graphite surface is coincident with the molecular packing in one cross-section of the three-dimensional crystal.     

Beiträge zur Chemie der Halogensilan-Addukte. XVII. Darstellung,Kristall- und Molekülstruktur von (2, 2′ -Bipyridin)- trichloro (trichlorosiloxy)- silicium,Cl3SiOSiCl3. bipy

Contributions to the Chemistry of Halosilane Adducts. XVII. Preparation, Crystal and Molecular Structure of (2, 2′ -Bipyridine) - trichloro - (trichlorosiloxy) -silicon, Cl₃SiOSiCl₃. bipy 1 is obtained by the reaction of Cl₃SiOSiCl₃ and bipy. It crystallizes orthorhombic in the space group Pca2₁ (Z = 4). 1 contains a tetracoordinated and a hexacoordinated Si atom. The plain defined by coordinated bipy also contains the SiOSi group. The SiOSi bonding angle (152.8°) is larger than that of Cl₃SiOSiCl₃ (146°). The SiCl bonds are about 8% longer than the tetrahedral SiCl bonds. The two SiO bond lengths are different (1.684; 1.554 Å). The SiN distances (average 1.967 Å) as well as the other bond distances correspond to values found for related compounds. Configuration, SiOSi bond angle and other structural features are due to steric requirements. 1 represents the structure of least steric hindrance. The same structure is found in solution (¹H-NMR). The results confirm that sterically more demanding ligands preferentially occupy the positions vertical to the plain of bipy (phen) in octahedral bip(phen) complexes of Si, hereby minimizing steric repulsions among each other(trans positions) and by CH groups of bipy(phen) exerted on ligands in he plain of bipy(phen).     

Copper(II) complexes with the N,N,O-tridentate ligand 6-amino-5-formyl-1,3-dimethyluracilato-(N6)-benzoylhydrazone: synthesis, spectral and XRD studies

From reactions between different Cu(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone (H₂BEZDO) in alcohol, six new copper complexes with simplified formulas [Cu(HBEZDO)(H₂O)(MeOH)]NO₃ (1), [CuCl(HBEZDO)(DMF)] (2), [CuBr(HBEZDO)]·2H₂O (3), CuBr(HBEZDO) (4), Cu(ClO₄)(HBEZDO)·H₂O (5), and Cu(SO₄)_1/2(HBEZDO)·1 H₂O (6) were isolated. The structures of compounds 1, 2 and 3 have been established by means of XRD diffraction methods. In the three compounds, the Schiff base acts as a tridentate monodeprotonated ligand through the N(6), N(51) and O(52) atoms, making two five- and six-membered chelate rings. In the structure of 1 and 2, the solvent molecules are coordinated giving square-based pyramidal environments, with the basal plane completed by a MeOH (1) or Cl (2) and the apical positions occupied by the oxygen atom of a water (1) or a DMF molecule (2). The molecular unit of the complex [CuBr(HBEZDO)]·2H₂O (3) is defined by a square-plane containing the three donor atoms of the organic ligand and a bromide ligand (Cu–Br 2.384 Å), but there is a stronger tetragonally elongated pyramidal geometry around the metal, the apical position of the polyhedron being occupied by a weakly bound-to-copper bromine atom (3.086 Å) of a neighbouring molecule. This fact gives the appearance of an apparent dimer with very asymmetric bromine bridges, in which there are no exchange interactions between metal centres. Also, infrared, magnetic and EPR data of the isolated complexes are reported.     

An alkyl–palladium(II) complex with a bidentate phosphine ligand: [1,3‐bis(di­phenyl­phosphino)­propane‐P,P′]­dimethyl­palladium(II) toluene hemi­solvate

In the title compound, [Pd(CH₃)₂(C₂₇H₂₆P₂)]·0.5C₇H₈, the Pd atom is at the centre of an approximately square‐planar arrangement of two P atoms and two methyl groups. The P—Pd—P angle [93.19 (3)°] is significantly larger than that in the corresponding dichloride complex [Pd(dppp)Cl₂]. The toluene mol­ecule is disordered across an inversion centre.