ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe role of torsional isomers planarly chiral nonbridged bis(indenyl)metal type complexes in stereoselective propene polymerizationGerhard Erker, Michael Aulbach, Markus Knickmeier, Doris Wingbermuehle, Carl Krueger, Matthias Nolte, and Stefan WernerCite this: J. Am. Chem. Soc. 1993, 115, 11, 4590–4601Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June...

Type I interferons (IFNs) are helical cytokines that have diverse biological activities despite the fact they appear to interact with same receptor system. To achieve a better understanding of structural basis for different α and β IFNs, we determined crystal structure glycosylated human IFN-β at 2.2-Å resolution by molecular replacement. The molecule adopts fold similar previously structures murine IFN-α 2b but displays several distinct features. Like , contains zinc-binding site interface...

A set of parameters has been derived for a global optical potential from elastic \ensuremath{\alpha}-nucleus scattering with energies higher than 80 MeV. The geometry and energy dependence by Put Paans was adopted. model predictions were tested data as well inelastic scattering.

The α1β1 integrin is a major cell surface receptor for collagen. Ligand binding mediated, in part, through ∼200 amino acid inserted ‘I’‐domain contained the extracellular part of α chain. Integrin I‐domains contain divalent cation (MIDAS) site and require cations to interact with ligands. We have determined crystal structure recombinant I‐domain from rat at 2.2 Å resolution absence cations. α1 adopts dinucleotide fold that characteristic all structures been solved date has very similar...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of ansa-metallocenes by intramolecular photochemical [2 + 2] cycloaddition bis(alkenylcyclopentadienyl)zirconium complexesGerhard Erker, Stephan Wilker, Carl Krueger, and Matthias NolteCite this: Organometallics 1993, 12, 6, 2140–2151Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural characterization of the acetylide bridge in dinuclear (.mu.-C.tplbond.CSiMe3)-Al/Al and -Al/Zr complexesGerhard Erker, Markus Albrecht, Carl Krueger, Matthias Nolte, Stefan WernerCite this: Organometallics 1993, 12, 4979–4986Publication Date (Print):December 1, 1993Publication History Published online1 May 2002Published inissue 1 December...

A general theoretical description of polarization transfer processes in multi-spin systems containing dipole as well quadrupole spins is formulated on the background Liouville–von Neumann equation. The density operator formalism used to describe evolution an arbitrary spin system due quadrupole, Zeeman and dipole–dipole interactions. This approach applied interpret previously published 1H–14N cross-relaxation NMR experiments for measuring 14N coupling constants paranitrotoluene (PNT)...

The levels of 74Kr were identified to a tentative 20+ level in the reaction 58Ni(19F, p2n gamma ) by using neutron multiplicity filter. moment inertia yrast cascade exhibits first high-spin double discontinuity such light nuclei, above 10+ and 14+. Both discontinuities are interpreted as arising from crossing rotation aligned bands.

A Simple Synthesis of Dimetallic Zirconium/Aluminium Compounds Containing Planar‐Tetracoordinate Carbon (η 2 ‐Alkyne)(trimethylphosphane)zirconium complexes [alkyne = cyclohexyne ( 3a ) or diphenylacetylene 3b )] react with diisobutylaluminium hydride at room temperature by PMe 3 cleavage and addition HAl(isobutyl) to the in situ‐generated ‐alkyne)ZrCp intermediate give dimetallic Zr,Al compounds 4 . These thermodynamically stable contain a planar‐tetracoordinate carbon center whose...

Bis(isopropylcyclopentadienyl)zirconiumdichloride (1) was synthesized by the reaction of isopropylcyclopentadienyl lithium with 1/2 molar equivalent zirconiumtetrachloride and then crystallized from methylenechloride. Complex 1 crystallizes in space group C2/c cell parameters a = 24.492(3)A, b 13.525(1)Å, c 22.894(3)Å, β 117.90(1)°, Z 16, R 0.046, w 0.057. There are three independent molecular entities asymmetric unit. These represent torsional isomers differing relative positions isopropyl...

How many metal atoms can coordinate to a CC unit? The answer for Co–Al clusters 1 (R = Me) and 2 Et), the first η-η2:η2-bridged dialumin-ioethene clusters, is “four”. complexes are formed in about 30% yield on treatment of [Cp+(η2-ethene)2Co] (Cp+ C5Me5, C5Me4Et) with AlEt2H.

Monoazadiene Complexes of Electron‐Deficient Transition Metals, I. – Zirconocene(1‐aza‐1,3‐diene) Complexes: Synthesis, Structure and Reactions [1] The reduction Cp 2 ZrCl in THF by Mg the presence 1‐aza‐1,3‐dienes 2a–d generates orange air‐sensitive zirconocene( s ‐ cis ‐1‐aza‐1,3‐diene) complexes 3a–d . 1 H‐and 13 C‐NMR spectral data indicate that bonding heterodiene ligand has σ ,π1‐metallacyclopentene rather than η 4 ‐1‐aza‐1,3‐diene character. No evidence for s‐trans 1‐heterodiene...

Abstract (η 4 ‐Butadiene)zirconocene adds one equivalent of benzonitrile to form the five‐membered azazirconacyclopentene derivative 7 , which contains an NH group in ring and a vinyl substituent at α‐carbon center. The reaction with additional furnishes chiral nine‐membered metallacycle ( magnified image ) 12 may be isomerized thermo‐dynamically favored tautomer 13 ). Gibbs activation energy enantiomerization trans ‐cycloalkene‐like is Δ G # (323 K) = 15.5 ± 0.3 kcal mol ‐1 . analogous...

Is the question of catalytically active species for Sharpless epoxidations again open? The results NMR spectroscopy and X-ray structural analysis on inactive (tartrato)zirconocene dimers show how complicated situation can be. Simple stereochemical changes variation substituents in crystal solution result these complexes forming either ten-membered dimetallacycles (type A) or dimetallatricycles B). E = CO2CHMe2, CO2Me.

2,5‐Hexanedione ( 1 ) was converted into the bis(fulvene) 2 , which then treated with molar equiv. of ethereal meth‐yllithium to give novel annulated C ‐bridged dilithium bis(cyclopentadienide) 5 . Reagent MCl 4 (M = Ti, Zr) yield ansa‐metallo‐cene dichlorides 6a and 6b respectively. The homogeneous /methylalumoxane Ziegler‐type systems were employed in propene polymerization reactions.

Abstract Colourless single crystals of three piperazine (Pip) complexes divalent mercury with ‐CF 3 and SCN ‐ as the ligands have been obtained from aqueous ethanolic solution respective components Hg(CF ) 2 , Hg(SCN) piperazine. The crystal structures were determined by X‐ray diffraction: ( 1 [monoclinic, C2/c, Z = 4, a 891.2(1), b 1649.8(2), c 777.7(1) pm, β 101.27(2)°, R (all) 0.0413], tetragonal, P4 /ncm, 840.8(1), 1511.0(1) 0.0479], (Hg(SCN) [triclinic, ${\rm P}{\bar 1}$ 1, 590.6(1),...