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Ligand Environment (ligand + environment)

Distribution by Scientific Domains

Chemistry	83%

Selected Abstracts

Titelbild: Templated Ligand Environments for the Selective Incorporation of Different Metals into DNA (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 52 2009
52/2009)
DNA kann als Templat für die Bildung unterschiedlicher Ligandenumgebungen fungieren, die selektiv für ihre bindenden Metalle sind. H. F. Sleiman et,al. schildern in ihrer Zuschrift auf S.,10,103,ff., wie das Einbringen eines Metallzentrums in eine nichtkorrekte Umgebung in einer "Fehlerprüfung" resultiert: Das Metallzentrum kann spontan seinen Redoxzustand anpassen, ein anderes labiles Metallzentrum unter Bildung eines stabileren Komplexes verdrängen oder das Koordinationszentrum reorganisieren, um zu einem günstigeren Komplex zu gelangen. [source]

Templated Ligand Environments for the Selective Incorporation of Different Metals into DNA,

ANGEWANDTE CHEMIE, Issue 52 2009
Hua Yang
Wie es ihm gefällt: DNA wirkt als Templat für die Bildung von Bis(terpyridin)-, Bis(phenanthrolin)- und Terpyridin:Phenanthrolin-Ligandenumgebungen, die sehr selektiv für FeII, CuI bzw. CuII sind und hochstabile Metall-DNA-Komplexe bilden (siehe Bild). Wird ein Metallion in die ,falsche" Umgebung eingebracht, kann es spontan seinen Redoxzustand anpassen, durch ein anderes Metall ersetzt werden oder das Koordinationszentrum unter Bildung eines günstigeren Komplexes reorganisieren. [source]

Reactivity of InCp* Towards Transition Metal Carbonyl Clusters: Synthesis and Structural Characterization of the Rh6(CO)16,x(InCp*)x Mixed-Metal Cluster Compounds, x = 1,2

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2007
Elena V. Grachova
Abstract With [Rh6(CO)15(InCp*)], the first example of a transition metal carbonyl cluster with a coordinated InCp* (Cp* = C5Me5) fragment in the ligand environment is reported. This cluster with direct Rh,In bonds forms in the reaction of the hexanuclear carbonyl rhodium cluster Rh6(CO)15(NCMe) with InCp* under mild conditions. This is characterized by means of IR and NMR spectroscopy and crystal structure analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Synthesis and Structure of Trialkyltantalum Complexes Stabilized by Aminopyridinato Ligands

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2006
Awal Noor
Abstract (4-Methylpyridin-2-yl)(trimethylsilyl)amine (1), (6-methylpyridin-2-yl)(trimethylsilyl)amine (2), and (2,6-diisopropylphenyl)(pyridin-2-yl)amine (3) were deprotonated and used as ligands to synthesize trialkyltantalum complexes. The reaction of 2 equiv. of 1 or 2 with pentabenzyltantalum afforded tribenzyltantalum(V) complexes by toluene elimination. Analogous reaction using 3 failed. Lithiation of 3 followed by the reaction with tribenzyltantalum dichloride gave rise to the corresponding tribenzyl complex. Other alkyltantalum complexes stabilized by this ligand environment can be prepared by treating tantalum pentachloride with 2 equiv. oflithiated 3 to form a bis(aminopyridinato)tantalum trichloride. The reaction of this trichloride with 3 equiv. of alkyllithium compounds like methyllithium affords the corresponding trialkyltantalum complexes. X-ray diffraction studies of four of the synthesized complexes were carried out. They adopt two different coordination environments, either slightly distorted capped octahedrons (sterically less demanding aminopyridinato ligands) or pentagonal bipyramids (bulkier aminopyridinato ligands). The alkyl species were surprisingly stable at elevated temperatures and no formation of mixed alkyl/alkylidene complexes was observed. Alkyl cation formation and the behaviour of a selection of these compounds in olefin polymerization were explored. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Long-lived layered silicates-immobilized 2,6-bis(imino)pyridyl iron (II) catalysts for hybrid polyethylene nanocomposites by in situ polymerization: Effect of aryl ligand and silicate modification

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2009
Giuseppe Leone
Abstract Heterogeneous-layered silicate-immobilized 2,6-bis(imino)pyridyl iron (II) dichloride/MMAO catalysts, in which the active polymerization species are intercalated within sodium- and organomodified-layered silicate galleries, were prepared for producing hybrid exfoliated polyethylene (PE) nanocomposites by means of in situ polymerization. The inorganic filler was first treated with modified-methylaluminoxane (MMAO) to produce a supported cocatalyst: MMAO reacts with silicates replacing most of the organic surfactant, thus modifying the original crystallographic clay order. MMAO anchored to the nanoclay was able to activate polymerization iron complexes initiating the polymer growth directly from the filler lamellae interlayer. The polymerization mechanism taking place in between the montmorillonite lamellae separates the layers, thus promoting deagglomeration and effective clay dispersion. Transmission electron microscopy revealed that in situ polymerization by catalytically active iron complexes intercalated within the lower organomodified clay led to fine dispersion and high exfoliation extent. The intercalated clay catalysts displayed a longer polymerization life-time and brought about ethylene polymerization more efficiently than analogous homogeneous systems. PEs having higher molecular masses were obtained. These benefits resulted to be dependent more on the filler nature than on the ligand environment around the iron metal center and the experimental synthetic route. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 548,564, 2009 [source]

PM3-compatible zinc parameters optimized for metalloenzyme active sites

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2004
Edward N. Brothers
Abstract Recent studies have shown that semiempirical methods (e.g., PM3 and AM1) for zinc-containing compounds are unreliable for modeling structures containing zinc ions with ligand environments similar to those observed in zinc metalloenzymes. To correct these deficiencies a reparameterization of zinc at the PM3 level was undertaken. In this effort we included frequency corrected B3LYP/6-311G* zinc metalloenzyme ligand environments along with previously utilized experimental data. Average errors for the heats of formation have been reduced from 46.9 kcal/mol (PM3) to 14.2 kcal/mol for this new parameter set, termed ZnB for "Zinc, Biological." In addition, the new parameter sets predict geometries for the Bacillus fragilis active site model and other zinc metalloenzyme mimics that are qualitatively in agreement with high-level ab initio results, something existing parameter sets failed to do. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1677,1692, 2004 [source]