Search results for "COPPER"

1,3-Dipolar cycloaddition of diaryldiazomethanes across N-ethoxy-carbonyl-N-(2,2,2-trichloroethylidene)amine and reactivity of the resulting 2-azabut…

2016

Abstract 1,3-dipolar cycloaddition of diaryldiazomethanes Ar2C N2 across Cl3C–CH N–CO2Et 1 yields Δ3-1,2,4-triazolines 2. Thermolysis of 2 leads, via transient azomethine ylides 3, to diaryldichloroazabutadienes [Ar(Ar')C N–CH CCl2] 4. Treatment of 4a (Ar = Ar' = C6H5) and 4c (Ar = Ar' = p-ClC6H4) with NaSR in DMF yields 2-azabutadienes [Ar2C N–C(H) C(SR)2] 5. In contrast, nucleophilic attack of NaStBu on 4 affords azadienic dithioethers [Ar2C N–C(StBu) C(H)(StBu)] (7a Ar = C6H5; 7b Ar' = p-ClC6H4). The reaction of 4a with NaSEt conducted in neat EtSH produces [Ph2C N–C(H)(SEt)–CCl2H] 8, which after dehydrochloration by NaOMe and subsequent addition of NaSEt is converted to [Ph2C N–C(SEt) C…

Stereoselective syntheses of piperidinones and their modification by organometallic coupling reactions

2007

Dehydropiperidinones stereoselectively obtained from N-arabinosyl imines were iodinated at the enaminone structure. Knochel iodine-magnesium exchange afforded Grignard compounds of these piperidinone derivatives which reacted, either directly or after transmetalation to zinc or copper intermediates, with alkyl-, aryl- or acylhalides to give correspondingly substituted piperidinones. Stereoselective conjugate allyl cuprate addition to a thus obtained 5-allyl dehydropiperidinone and ring-closing metathesis of the product gave a hydroquinolinone containing three stereogenic centers.

Adhesion trends and growth mode of ultra-thin copper films on MgO

2004

Ab initio simulations are performed for Cu atoms adsorbed on the perfect MgO(001) substrate, with an ordered metal coverage varied from 1 monolayer (ML), i.e. almost single atoms, up t o1M L. As trong dependence of the adhesion energy and the sub-monolayer film distance from the substrate on the surface coverage and adsorbate positions (Mg 2+ or O 2− )i s discussed. The nature of interfacial bonding at all coverages is physisorption .W hen increasing Cu atomic fraction, a decrease of the substrate-induced polarization of adatoms accompanied by an increase of both in-plane metallic bonding and the interfacial distance has been found. Combining results of ab initio calculations with thermodyn…

Characterization of Pumice-Supported Ag–Pd and Cu–Pd Bimetallic Catalysts by X-Ray Photoelectron Spectroscopy and X-Ray Diffraction

1999

Bimetallic Ag–Pd and Cu–Pd catalysts supported on pumice have been prepared in order to be used in the selective hydrogenation of dienes. The catalysts were obtained by the classical impregnation method and in the case of the Cu–Pd system also by organometallic precursors. They were analysed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS allowed us to determine the surface distribution and chemical state of the two elements; XRD yielded the lattice parameters and allowed us to establish the possible formation of alloys. The two bimetallic systems behave differently. In the case of the Ag-Pd catalysts, Pd particles covered by silver atoms along with highly dispers…

Motional Resistance Evaluation of the Quartz Crystal Microbalance to Study the Formation of a Passive Layer in the Interfacial Region of a Copper|Dil…

2015

A hyphenated technique based on vis–NIR spectroscopy and electrochemical quartz crystal microbalance with motional resistance monitoring was employed to investigate the dissolution of copper in acid media. Changes in motional resistance, current, mass, and absorbance during copper dissolution allow the evolution of the interfacial region of copper|diluted sulfuric solution to be understood. In particular, motional resistance is presented in this work as a useful tool to observe the evolution of the passive layer at the interface. During the forced copper electrodissolution in sulfuric solution, SO4(2–) favors the formation of soluble [Cu(H2O)6]2+. On the contrary, OH– involves the formation…

Ab initio modeling of copper adhesion on regular BaTiO3(001) surfaces

2005

Ab initio calculations have been performed for copper adsorption on a regular, defect-free TiO"2- and BaO-terminated (001) surfaces of a cubic BaTiO"3, using a posteriori HF-CC method as implemented into the CRYSTAL-03 computer code. To clarify the nature of the interfacial bonding, we use slab models of the Cu/BaTiO"3(001) interfaces with different one-side substrate coverages, varied from 1/8 monolayer (ML) up to 1/2 ML, over both TiO"2- and BaO-terminated surfaces. TiO"2 termination has been found to be energetically more favorable for the adsorption of copper atoms. In agreement with previous experimental and theoretical data, our calculations indicate essential contribution of atomic p…

Evolution of Copper Contents from Colostrum to Transitional Human Milk

2002

Unique direct synthesis of cyanide-bridged Fe2Cu2 molecular squares by destruction of sodium nitroprusside

2009

Abstract The one-pot reaction of copper powder, sodium nitroprusside, ammonium thiocyanate and 2,2′-bipyridine (bpy) in acetonitrile solution at ambient conditions of air and water yields the novel heterometallic [Fe2Cu2(bpy)6(μ-CN)4(NCS)2]2[Fe(CN)5(NO)](NCS)2·5H2O complex 1, which has been structurally and magnetically characterized. The most prominent feature of this complex is the unique tetranuclear Fe 2 II Cu 2 II squares comprised [Cu(bpy)NCS]+ and [Fe(bpy)2]2+ corners with CN edges. The Cu⋯Cu and Fe⋯Fe separations are ∼6.72 and ∼7.73 A, respectively. The variable-temperature magnetic susceptibility study revealed that a very weak antiferromagnetic coupling is active between Cu(II) ce…

Die selektive invers-voltammetrische Bestimmung des Antimons in salzsauren Lösungen nach Lösungswechsel in einer einfachen Durchflußzelle

1987

The selective invers-voltammetric determination of antimony in a simple flow-through cell in hydrochloric acid solutions is described. After double medium exchange for post-electrolysis and inverse-voltammetric determination, the determination of antimony is possible in the presence of a large excess of copper, bismuth and other elements. The limit of determination is 0.2–0.3 ppb Sb, the reproducibility 1.5% (10 ppb Sb).

Synthesis, crystal structure and magnetic properties of [Cr2Cu2(bpy)4(ox)5]·2H2O. An oxalato-bridged heterometallic tetramer

2003

A new heterometallic tetramer of formula [Cr2Cu 2(bpy)4(ox)5]·2H2O (1) (bpy=2,2′-bipyridine; ox=oxalate dianion) has been prepared and characterised by single-crystal X-ray diffraction, magnetic susceptibility measurements and ESR spectroscopy. The tetranuclear unit in 1 can be viewed as the combination of two terminal [Cr(bpy)2(ox)]- units with a central oxalato-bridged copper(II) dimer. The chromium ions are in a distorted octahedral environment with metal-ligand distances ranging from 1.944(4) to 2.064(5) A. The copper(II) centres lie in an axially distorted octahedron. The axial positions are occupied by one oxygen atom belonging to the central bridging oxalate anion [O(9)-Cu(1): 2.245(…