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Halide Complexes (halide + complex)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Iminohydroxamato Early and Late Transition Metal Halide Complexes , New Precatalysts for Aluminoxane-Cocatalyzed Olefin Insertion Polymerization

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2004
Alexander Krajete
Abstract We report on new families of non-metallocene metal precatalysts for olefin polymerization with titanium, zirconium, vanadium and nickel as the active metal sites. The novel ligand design concept is based on iminohydroxamic acids and their derivatives as the principal chelating units. Various anionic and neutral [N,O] and [N,N] ligand systems are easily accessible by a modular synthetic sequence of imidoyl chlorides with substituted hydroxylamines or hydrazines, respectively. Steric protection of the metal coordination site, a necessary requirement for suppression of chain termination pathways of non-metallocene catalysts, is brought about by bulky aryl substituents on the imino nitrogen atoms. Crystal structures of some of the hydroxamato ligands reveal interesting intermolecular hydrogen-bridged structures, whereas in the solid-state structure of one titanium precatalyst a five-membered chelate was observed, in line with the design principle of these systems. Preliminary ethylene polymerization studies with methylaluminoxane-activated metal complexes (M = Ti, Zr, V, Ni) show that the most active systems are [N,O]NiBr2 catalysts containing neutral O -alkyl iminohydroxamate ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Theoretical Study of Mixed MLaX4 (M: Na, K, Cs; X: F, Cl, Br, I) Rare Earth/Alkali Metal Halide Complexes

CHEMINFORM, Issue 16 2003
Cornelis Petrus Groen
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr3

JOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2008
Liubov V. Stepakova
Abstract Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching CuIIX modes in the equatorial plane, were found in the ranges 247,288 cm,1 for X = Cl, and 173,189 cm,1 for X = Br, while the low-wavenumber stretching modes for the weaker axial CuX interactions varied considerably. The tetrahedral coordination for Cs2CuCl4 and Cs2CuBr4 leads to somewhat lower CuX symmetric stretching wavenumbers, 295 and 173 cm,1, respectively. The assignments of the copper,ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged CuX stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn,Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer-sphere cations. Force constant ratios for terminal and bridging metal,halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M2X6 species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr3 (K2Cu2Br6), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu2Br6]2, complexes held together by weak axial CuBr interactions. Copyright © 2007 John Wiley & Sons, Ltd. [source]

The Stereospecific Ligand Exchange at a Pseudo-Benzylic T -4 Iridium Centre in Planar-Chiral Cycloiridium (,6 -Arene)tricarbonylchromium Complexes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 41 2009
Jean-Pierre Djukic Dr.
Abstract The stereospecificity of ligand exchange at the IrIII centre of a cycloiridium arenetricarbonylchromium complex has been established experimentally by various analytical methods as well as by X-ray diffraction structural analysis and computational investigations. Two new cases of phenyl and methyl iridium(III) complexes have been prepared by reaction of (,)-chlorido{2-[(tricarbonyl)(,6 -phenylene-,C1,)chromium(0)]pyridine-,N}(pentamethylcyclopentadienyl)iridium(III) with PhMgBr and MeMgBr. The determining influence of electrostatic repulsion has been established by means of density functional theory at the Becke,Perdew/TZP(ZORA) level by using, among other means, energy partitioning analysis. It is also shown that the Cr(CO)3 fragment is likely to ease the ionic cleavage of the IrCl bond in chlorido cycloiridium tricarbonylchromium complexes in a way similar to that already established for the solvolysis of benzyl halide complexes, that is, through a direct interaction of the Cr0 centre with the cationic IrIII centre. [source]