Chemistry

Distribution by Scientific Domains
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  • Selected Abstracts


    Electrochemical Phenomena in the Nanoworld/Molecular Devices and Machines/Surface Science/Spectroscopic Advances/Chemistry at a Historic Crossroads

    CHEMPHYSCHEM, Issue 1 2009
    Christian Amatore Prof. Dr.
    First page of article [source]


    BRASSICALES , AN ORDER OF PLANTS CHARACTERISED BY SHARED CHEMISTRY

    CURTIS'S BOTANICAL MAGAZINE, Issue 3 2010
    Michael F. Fay
    Among the many advances in our understanding of angiosperm relationships in recent decades due to the advent of DNA sequence data is the confirmation that all plants (apart from Drypetes) that produce mustard oil precursors are related to each other and should be treated as one order, Brassicales. Due to the lack of obvious shared morphological characters, this is one of the more unexpected of these advances. Here we give the background to this development and introduce the families in Brassicales, including Tropaeolaceae, the subject of this issue. [source]


    THE IMPACT OF SOLUBLE SALTS ON THE DETERIORATION OF PHARAONIC AND COPTIC WALL PAINTINGS AT AL QURNA, EGYPT: MINERALOGY AND CHEMISTRY*

    ARCHAEOMETRY, Issue 2 2009
    A. M. A. MOUSSA
    The wall paintings of Al Qurna in Egypt were studied by means of XRD and ICP,AES in order to determine their mineralogical and chemical composition, and to evaluate the impact of soluble salts on their deterioration, including the identification of the building materials and pigments used. Soluble salts analysis showed that NaCl is the most common soluble salt in the bedrock, ground water and surface water samples. The building materials are affected by the ground water, while the wall paintings in the area are affected by the Upper Egypt climatic conditions, which were studied in order to detect their role in the deterioration cycle in the area. [source]


    THE HISTORY OF THE BROOKHAVEN NATIONAL LABORATORY PROJECT IN ARCHAEOLOGICAL CHEMISTRY, AND APPLYING NUCLEAR METHODS TO THE FINE ARTS

    ARCHAEOMETRY, Issue 2 2007
    G. HARBOTTLE
    This paper traces the events leading up to the formation of a project in 1954, in the Chemistry Department at Brookhaven National Laboratory, dedicated to the application of those new developments that were rapidly transforming postwar nuclear science to the parallel humanistic disciplines of archaeology and the fine arts. The further evolution of this effort involved the enlightened support of the Department of Energy (then AEC and ERDA) coupled with the lively interests of the archaeological, fine-arts and art-historical communities, their professional academics and the many graduate and undergraduate students who participated in the Brookhaven project. But more than new scientific methodologies, concepts and instrumentation were deployed. What developed was a large-scale, truly interdisciplinary effort, where scholars of the humanities and sciences worked side by side in a remarkable way, each led by the other, to the mutual benefit and increase of their knowledge and understanding. A paradigm of co-operation between arts and sciences was initiated: this paper presents a record of the process and its outcome, a novel blending of science and humanism that is very much taken for granted by research workers today. [source]


    THE PETROGRAPHY AND CHEMISTRY OF THIN-WALLED WARE FROM AN HELLENISTIC, ROMAN SITE AT SEGESTA (SICILY),

    ARCHAEOMETRY, Issue 3 2003
    G. Montana
    Samples of Roman thin-walled ware from Segesta (northwestern Sicily), dating back to the early Imperial period, were studied by optical microscopy (OM) and Neutron Activation Analysis (NAA). Up to now, this class of Roman fine tableware has only occasionally been evaluated archaeometrically. Nevertheless, numerous production centres are believed to have been simultaneously active in the western Mediterranean area. Petrographic and chemical data seem to be in agreement with the archaeological hypothesis of local manufacture in Segesta for most of the analysed samples, through a comparison with kiln wasters and local raw materials. The effectiveness of thin-section petrography for determining the provenance of such a tiny tempered class of pottery and the integrated use of two different grouping procedures (petrography and chemistry) were also tested. [source]


    CHINESE JOURNAL OF CHEMISTRY: Instructions for Authors

    CHINESE JOURNAL OF CHEMISTRY, Issue 3 2000
    Article first published online: 27 AUG 2010
    First page of article [source]


    Merging Organic and Polymer Chemistries to Create Glycomaterials for Glycomics Applications

    MACROMOLECULAR BIOSCIENCE, Issue 8 2006
    Graldine Coullerez
    Abstract Summary: Oligosaccharides at cell surfaces are known to play a critical role in many biological processes such as biorecognition, interactions between cells and with artificial surfaces, immune response, infection and inflammation. In order to facilitate studies of the role of sugars, an increasing number of novel tools are becoming available. New synthetic strategies now provide much more efficient access to complex carbohydrates or glycoconjugates. Branched carbohydrates and hybrids of carbohydrates conjugated to polymers have been prepared using solution and/or solid-phase synthesis and advanced methods of polymerization. These materials are essential for the development of methodologies to study and map the molecular structure-function relationship at interfaces. This article highlights recent advances in the synthesis of carbohydrates and polymer hybrids mimicking the properties and functionalities of the natural oligosaccharides, as well as selected applications in biology, biotechnology and diagnostics. [source]


    Current Awareness in Contrast Media and Molecular Imaging

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2010
    Article first published online: 20 APR 2010
    In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source]


    Current Awareness in Contrast Media and Molecular Imaging

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2010
    Article first published online: 22 FEB 2010
    In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source]


    Current Awareness in Contrast Media and Molecular Imaging

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2008
    Article first published online: 11 MAR 200
    In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source]


    Current Awareness in Contrast Media and Molecular Imaging

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2006
    Article first published online: 8 DEC 200
    In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source]


    Current Awareness in Contrast Media and Molecular Imaging

    CONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2006
    Article first published online: 10 OCT 200
    In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source]


    Physics, Chemistry and Applications of the AC Diaphragm Discharge and Related Discharges in Electrolyte Solutions

    CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-2 2007
    A. I. Maximov
    Abstract Three types of the underwater discharges produced by means of AC voltage sources (500-2000 V, 0.05-1 A) were investigated. Dynamic volt-ampere characteristics and radiation intensity of these discharges were measured. It was observed the optical afterglow time up to 0.1-0.2 s. The information about their chemical action was got by stimulation of the oxidation of the organic and inorganic substances. It was found that the treatment of the cellulose and the flax by means of the underwater discharges results in the change of their molecular mass, lignin contain and surface concentration of the oxygen containing functional groups. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Recent Updates of Chemically Modified Electrodes in Analytical Chemistry

    ELECTROANALYSIS, Issue 13 2003
    Jyh-Myng Zen
    Abstract This review article updates recent developments in chemically modified electrodes (CMEs) towards analytical applications for the year of 2000,2002 with 179 references. The broad topics are subdivided into four main categories: i) physisorption/chemisorption, ii) covalently linked, iii) homogenous (uniform) multilayer and iv) heterogeneous (non-uniform) multilayer CMEs. The criteria for the preparation of CMEs in elecrocatalytic systems are clearly described in Section 1. Some of the encouraging results related to Au-nanoparticles for DNA detection and new ceramic carbon, carbon nanotubes, copper-plated screen-printed and Nafion/lead ruthenate pyrochlore CMEs for catalytic application were especially discussed in this review. [source]


    Book Review: Eectrokinetec Phenomena: Principles and Applications in Analytical Chemistry and Microchip Technology.

    ELECTROPHORESIS, Issue 6 2004
    A. Guttman (Eds.), By A.S. Rathore
    No abstracts. [source]


    Field assessments in conjunction with whole effluent toxicity testing

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2000
    Thomas W. La Point
    Abstract Whole effluent toxicity (WET) tests are widely used to assess potential effects of wastewater discharges on aquatic life. This paper represents a summary of chapters in a 1996 Society of Environmental Toxicology and Chemistry,sponsored workshop and a literature review concerning linkages between WET testing and associated field biomonitoring. Most published studies thus far focus primarily on benthic macroinvertebrates and on effluent-dominated stream systems in which effluents demonstrate little or no significant acute toxicity. Fewer studies examine WET test predictability in other aquatic ecosystems (e.g., wetlands, estuaries, large rivers) or deal with instream biota such as fish and primary producers. Published results indicate that standards for the usual WET freshwater test species, Ceriodaphnia dubia and Pimephales promelas, may not always protect most of the species inhabiting a receiving stream. Although WET tests are useful in predicting aquatic individual responses, they are not meant to directly measure natural population or community responses. Further, they do not address bioconcentration or bioaccumulation of hydrophobic compounds; do not assess eutrophication effects in receiving systems; and lastly, do not reflect genotoxic effects or function to test for endocrine-disrupting chemicals. Consequently, a more direct evaluation of ecosystem health, using bioassessment techniques, may be needed to properly evaluate aquatic systems affected by wastewater discharges. [source]


    Norbornene Bidentate Ligands: Coordination Chemistry and Enantioselective Catalytic Applications

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2010
    Fernando Fernndez
    Abstract N - and P-donor derivatives have been prepared by functionalization of a readily available norbornene precursor. Palladium catalytic systems containing these new ligands were applied in allylic substitution, and yielded high activities and excellent enantioselectivities for the allylic alkylation and amination reactions (ee up to 97,%). A full coordination analysis of the catalytic precursors including modelling studies was also carried out. [source]


    Synthesis and Characterisation of a New Cu(O2CNAllyl2)2 Carbamato Complex and an Unusual Polymeric CuI Complex [CuI4Cl4(NHAllyl2)4]n: New Insights into Metal Carbamato Chemistry

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2009
    Alberto Albinati
    Abstract Transition-metal N,N -dialkylcarbamato complexes represent an interesting class of compounds that can be conveniently used as precursors for the controlled formation of inorganic compounds, typically oxides. They can also be used as convenient precursors for chemical grafting of metal oxides on oxide surfaces as well as for the synthesis of inorganic,organic hybrid materials. In this last case, the presence of double bonds on the complex would enable its covalent embedding into a polymer matrix through reaction with suitable monomers. To this aim, we addressed the synthesis of an allyl-functionalised copper carbamato complex. During the synthesis of the N,N -diallylcarbamato complex Cu(O2CNAllyl2)2 (Cu1), the formation of the crystalline and unusual polymeric CuI complex [CuI4Cl4(NHAllyl2)4]n (Cu2) was observed. The new compound was characterised by X-ray single crystal diffraction and FTIR, 1H and 13C NMR spectroscopic analysis. In an attempt to investigate the redox mechanism and the equilibria leading to the formation of the observed unusual CuI polymeric complex, gas chromatography coupled with mass spectrometry (GC,MS) experiments were carried out, which allowed us to identify 3,4-dimethylpyrrole as the oxidation product of the reaction, leading to the reduction of CuII to CuI.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    New Insights into the Chemistry of the Antineoplastic Lanthanum Complex Tris(1,10-phenanthroline)tris(thiocyanato-,N)lanthanum(III) (KP772) and Its Interaction with Biomolecules

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2009
    Florian Biba
    Abstract The lanthanide complex tris(1,10-phenanthroline)tris(thiocyanato-,N)lanthanum(III) [La(phen)3(NCS)3] (KP772) is a promising anticancer drug candidate, capable of overcoming resistance of tumors to established chemotherapeutics. The compound was characterized by elemental analysis, IR, 1H NMR spectroscopy, TG/DTA measurements, mass spectrometry and X-ray diffraction analysis. The results indicate that KP772 is a neutral, nine-coordinate complex. In addition the behavior in water, important for the application as a chemotherapeutic drug, and the binding to biomolecules was investigated by capillary electrophoresis and ICP-MS.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Strong Evidence for an Unprecedented Borderline Case of Dissociation and Cycloaddition in Open-Shell 1,3-Dipole Chemistry: Transient Nitrilium Phosphane-Ylide Complex Radical Cations

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009
    Holger Helten
    Abstract The reaction of 3-ferrocenyl-substituted 2H -azaphosphirene complexes 1a,c in the presence of substoichiometric amounts of ferrocenium hexafluorophosphate yields 3,5-diferrocenyl-substituted 2H -1,4,2-diazaphosphole complexes 3a,c and difluoro(organo)phosphane complexes 4a,c. The reaction of 1a,c and [FcH]PF6 with cyanoferrocene yields 3a,c in a straightforward way. The molecular structures of 3a,c were unambiguously identified by multinuclear NMR spectroscopic experiments, mass spectrometry, and single-crystal X-ray diffraction studies. DFT calculations on model complexes 1d,m and 3d,m reveal a close similarity of Mo and W complexes (vs. Cr) and a strong influence of the ferrocenyl substituent on the geometry, spin, and charge distribution of reactive intermediates and the reaction course. Strong support for the assumption of a dissociation,cycloaddition reaction sequence leading to 3 and thus a surprising "cannibalistic" reaction was obtained.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Oxido Pincer Ligands , Exploring the Coordination Chemistry of Bis(hydroxymethyl)pyridine Ligands for the Late Transition Metals

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2009
    Axel Klein
    Abstract Coordination of the 2,6-bis(hydroxymethyl)pyridine-based oxido pincer ligands RR,pydimH2 [R = R, = H (pydimH2); R = R, = Me (pydipH2); R = 2-tolyl, R, = Me (pydotH2)] towards late transition metals CoII, NiII, CuII, ZnII, PdII and PtII allows the formation of molecular species (complexes), which exhibit three main structural motifs in the solid state. The two main species are pentacoordinate [(RR,pydimH2)MCl2] and hexacoordinate [(RR,pydimH2)2M]X2, both of which are stable in solution and can be interconverted by changing the solvent polarity. The disproportionation equilibrium [(RR,pydimH2)MCl2] [rlhar2] [(RR,pydimH2)2M]2+ + [MCl4]2, was studied by optical spectroscopy. The chiral ligand pydotH2 allows the formation of chiral complexes. In the square-planar complexes [(pydimH2)2MCl2] (M = PdII or PtII) the oxido donor functions of the ligands do not take part in the coordination.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Influence of Surface Chemistry on Dehydrogenation in Carbon Cryogel Ammonia Borane Nanocomposites

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2009
    Saghar Sepehri
    Abstract This paper reports the synthesis and characterization of boron- and nitrogen-modified carbon cryogel (CC) ammonia borane (AB) nanocomposites (BNCC-AB) for hydrogen storage. Resorcinol,formaldehyde (RF) derived CCs were modified by homogeneous dispersion of AB in RF hydrogel prior to pyrolysis. Nanocomposites were fabricated by immersing CC in the AB solution. Nitrogen sorption analysis, X-ray photoelectron spectroscopy, and differential scanning calorimetry at multiple heating rates were used to study the structure and dehydrogenation properties of the nanocomposites. The results demonstrated lower dehydrogenation temperatures and reduced activation energies for AB when confined inside pores of B- and N-modified CCs relative to AB when confined in the unmodified CC with the same pore size.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Pyrazole and Pyrazolyl Complexes of cis -Bis(2,2,-bipyridine)chlororuthenium(II): Synthesis, Structural and Electronic Characterization, and Acid-Base Chemistry

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2009
    Hershel Jude
    Abstract Complexes of the type cis -[Ru(bpy)2(Cl)(L)]+ [bpy = 2,2,-bipyridine; with L = pyrazole (1H), 4-methylpyrazole (2H), and 3,5-dimethylpyrazole (3H)] were synthesized and isolated as hexafluorophosphate salts. The molecular structures of these new complexes were fully characterized by 1H NMR spectroscopy and ESI mass spectrometry, and the crystal structure of 3HPF6 was determined by X-ray crystallography. Compound 3HPF6 (C25H24ClF6N6PRu) crystallizes in the monoclinic space group P21/n with a = 12.102(2) , b = 16.826(3) , c = 13.016(2) , , = 92.606(2), V = 2647.6(8) 3, and Z = 4. The crystal structure of 3H reveals the formation of an intramolecular hydrogen bond (2.562 ) between the pyrazole N(2),H site and the chloride ligand. The redox and electronic absorption properties of 1H, 2H, and 3H, as well as their deprotonated counterparts [L = pyrazolate (1), 4-methylpyrazolate (2), and 3,5-dimethylpyrazolate (3)], were investigated by cyclic voltammetry and UV/Vis spectroscopy. For detailed analysis of the electronic nature of this series of pyrazolyl ligands, the results are discussed along with other relevant cis -[Ru(bpy)2(X)(Y)]n+ complexes. From spectrophotometric pH titrations, the basicity associated with the coordinated pyrazole/pyrazolate couple in water was found in all three cases to be unusually high, partly owing to the N,HCl hydrogen bond that stabilizes the protonated, azole state. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Gas-Phase Chemistry of Vanadium Oxide Cluster Cations VmOn+ (m = 1,4; n = 1,10) with Water and Molecular Oxygen

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2008
    Sandra Feyel
    Abstract Bare vanadium oxide cluster cations VmOn+ (m = 1,4; n =1,10) generated by electrospray ionization are investigated with respect to their reactivity toward water and molecular oxygen by using mass spectrometric techniques. Besides ion hydration, the ion/molecule reactions of VmOn+ with oxygen-labeled water (H218O) also lead to 16O/18O exchange reactions of the vanadium oxide clusters cations. Although the probability of degenerate 16O/18O exchange between VmOn+ and water is fairly high for the cluster cations with a medium valence state of vanadium, oxygen-atom exchange reactions between VmOn+ and 18O2 can only be accomplished by VO+, V3O6+, and V4O8+. Particularly interesting is the fact that not only oxygen atoms from vanadyl units are exchanged in the cluster cations, but bridging oxygen atoms are also most likely involved in the processes. Other reaction channels for the interaction of VmOn+ cluster cations with molecular oxygen are reported as well, such as oxidative degradation of the low-valent cluster cations upon collision with O2 and formation of association complexes for the high-valent cluster cations. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


    Studies on Nickel(II) Complexes with Amide-Based Ligands: Syntheses, Structures, Electrochemistry and Oxidation Chemistry

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008
    Jyoti Singh
    Abstract The present work discusses the nickel chemistry in a set of amide-based open-chain ligands with subtle differences in the backbone or terminal amine substituents. The ligands coordinate to the Ni2+ ion through the Namide and Namine atoms maintaining a square-planar geometry. Absorption spectra and NMR studies reveal that the solid-state square-planar geometry is retained in solution. The electrochemical results suggest that the NiIII/NiII redox couple primarily depends on the N4 donors, which is composed of two Namide and twoNamine atoms and not on the peripheral substituents. All four ligands with variable backbone and substituents are equally competent in stabilizing the NiIII state. On the basis of electrochemical findings, chemical oxidations were carried out, and they reveal generation of the NiIII state in two cases, whereas decomposition was observed in others. Preliminary alkene epoxidation reactions suggest that the present nickel complexes transiently stabilize the higher oxidation state of the nickel ion that possibly participates in the oxidation of the substrates.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


    Synthesis and Reactions of Polynuclear Polyhydrido Rare Earth Metal Complexes Containing "(C5Me4SiMe3)LnH2" Units: A New Frontier in Rare Earth Metal Hydride Chemistry

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007
    Zhaomin Hou
    Abstract A series of tetranuclear octahydrido rare earth metal complexes of general formula [(C5Me4SiMe3)Ln(,-H)2]4(THF)n (Ln = Sc, Y, Gd, Dy, Ho, Er, Tm, Lu; n = 0, 1, or 2) that contain C5Me4SiMe3 as an ancillary ligand have been prepared and structurally characterized. These hydride clusters are soluble in common organic solvents such as THF, toluene, and hexane, and maintain their tetranuclear framework in solution. Such polynuclear polyhydrido complexes exhibit extremely high and unique reactivity toward a variety of unsaturated substrates including CO, CO2, and nitriles. The reaction of these neutral polyhydrides with one equivalent of [Ph3C][B(C6F5)4] affords the corresponding cationic hydride clusters [(C5Me4SiMe3)4Ln4H7(THF)n][B(C6F5)4], which can act as catalysts for the syndiospecific polymerization of styrene and regio- and stereospecific cis -1,4-polymerization of 1,3-cyclohexadiene. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


    Bis(phosphinimino)methanides as Ligands in Divalent Samarium Chemistry: Synthesis, Structures and Catalysis

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2007
    Michal Wiecko
    Abstract The reaction of K{CH(PPh2NSiMe3)2} with samarium diiodide in a 1:1 molar ratio in thf affords the corresponding divalent samarium complex [{(Me3SiNPPh2)2CH}Sm(,-I)(thf)]2 (1), whereas treatment of K{CH(PPh2NSiMe3)2} with samarium diiodide in a 2:1 molar ratio in thf gives the homoleptic complex [{(Me3SiNPPh2)2CH}2Sm] (2). When 1 is treated with KNPh2 in toluene in a 2:1 molar ratio the mixed dimeric compound [({(Me3SiNPPh2)CH}2Sm)2(,-I)(,-NPh2)] (3) is obtained. The single-crystal X-ray structures of all these complexes have been determined. [{(Me3SiNPPh2)2CH}Sm(,-I)(thf)]2 has also been successfully used as a catalyst for the polymerization of ,-caprolactone. Good activities and molecular masses are observed with this catalyst.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


    Coordination Chemistry of 3-Mercapto-2-(mercaptomethyl)propanoic Acid (Dihydroasparagusic Acid) with Iron and Nickel

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006
    Phillip I. Volkers
    Abstract The first transition-metal complexes bearing the natural product dihydroasparagusic acid, (HSCH2)2CHCO2H, as a ligand are reported. Various coordination modes and nuclearities are demonstrated for the chelating ligand by a series of iron and nickel complexes. Fe2[(SCH2)2CHCO2H](CO)6 retains carbonyl substitution reactivity typical of Fe2(SR)2(CO)6 complexes, yet carboxy coordination to FeI was unobserved. Coupling of the carboxylic acid with amines yields the corresponding amides Fe2[(SCH2)2CHC(O)NHR](CO)6 (R = Et, gly,O,tBu). Fe2[(SCH2)2CHCO2H](CO)4(PMe3)2 catalyzes H2 production, but no better than unfunctionalized alkyl dithiolate analogs. Reactions of the ligand with NiCl2(dppe) afforded mono-, di-, and trinuclear complexes. Noteworthy is Ni3[(SCH2)2CHCO2]2(dppe)2, which features an octahedrally coordinated NiII center linked to a pair of square-planar NiII centers. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


    New Polar Pyrazolylborate Ligands and Their Basic Zinc Complex Chemistry

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006
    Cristina Prez Olmo
    Abstract By refinement of Trofimenko's procedures, four new tris(pyrazolyl)borate (Tp) ligands bearing pyridyl and carboxamide substituents at the 3-positions of the pyrazole rings, were obtained. Two of them were identified by structure determinations of their potassium salts. Their coordinative properties were explored by preparing Tp*Zn-X complexes, with X = Cl, Br, I, NO3, OAc, phenolate, thiophenolate and diorganophosphate, including the cationic complexes [Tp*ZnL]+ with L = methanol and pyrazole. From the spectra and structure determinations of these complexes it has become evident that the polar Tp* ligands favor coordination numbers higher than four for zinc, either by inducing bidentate coordination of the coligands X and L, using the carboxamide oxygen atoms for coordination, or by linking two Tp*Zn-X units through the pyridyl nitrogen atoms. As a result, the structural chemistry of these complexes is quite varied, and includes coordination dimers and polymers.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


    N -Methylation Effects on the Coordination Chemistry of Cyclic Triamines with Divalent Transition Metals and Their CoII Dioxygen Carriers

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006
    Silvia Del Piero
    Abstract The thermodynamics of complex formation of CoII and CdII ions with the triaza macrocyclic ligand 1,4,7-triazacyclononane (tacn) and its N -methylated derivative 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3tacn) has been studied in dimethyl sulfoxide (DMSO) at 298.1 K and in an ionic medium (0.1 M Et4NClO4) by means of potentiometric, UV/Vis, calorimetric and FT-IR techniques. The results are discussed by taking into account electronic and steric effects as well as solvation of the species concerned. Computational methods based on density functional theory (DFT) have been used to obtain structural information about the ligands and their complexes in order to provide further, independent insights into the effect of N -methylation on the coordination affinity of the ligands towards the metal ions. The computational suggestions are of great help to correlate steric effects and thermodynamic results. The kinetics of dioxygen uptake for the formation of the Co(tacn)2O2 superoxo adduct has also been studied by means of UV/Vis measurements. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]