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1

Digitale Medien

Synthesis of Homo- and Hetero-Bimetallic Complexes Containing the Ni(C6F5)2 Moiety - Crystal Structure of [(C6F5)2Ni(μ-SPh)2Pd(dppe)] (1998)

Sánchez, Gregorio ; Momblona, Francisca ; Sánchez, Mateo ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1199-1204

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ISSN: 1434-1948

Schlagwort(e): Organometallic compounds ; Nickel complexes ; Crystal structures ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The compound cis-[Ni(C6F5)2(PhCN)2] has been used as the starting material for the preparation of the bimetallic complexes [(C6F5)2Ni(μ-X)2Ni(C6F5)2]2- (X = SCN, OCN, N3), [(C6F5)2Ni(μ-SCN)2Pd(C6F5)2]2-, [(C6F5)2Ni(μ-NCS)2Pd-(dppe)] [dppe = 1,2-bis(diphenylphosphanyl)ethane], and the trimetallic[(C6F5)2Ni(μ-NCS)2Pd(μ-SCN)2Ni(C6F5)2]2-. The mononuclear compounds [(C6F5)2NiLX] (L = PPh3, P(C6H4MeO-p)3; X = SCN, OCN) are obtained by reaction between [(C6F5)2Ni(&μ-X)2Ni-(C6F5)2]2- and L. The treatment of cis-[Ni(C6F5)2(PhCN)2] with [M(SAr)2(dppe)] leads to the formation of the arylthiolate complexes [(C6F5)2Ni(μ-SAr)2M(dppe)] (Ar = Ph, C6H4Me-p, C6H4NO2-p; M = Ni, Pd, Pt). The X-ray diffraction study of [(C6F5)2Ni(μ-SPh)2Pd(dppe)] shows that both metal atoms, Ni and Pd, are coordinated in a slightly distorted square-planar geometry and the μ-thiolato groups are in the syn conformation.

Materialart: Digitale Medien

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2

Digitale Medien

λ5-Phosphetes, Benzo-λ5-Phosphetes, Naphtho-λ5-Phosphetes: Four-π-, Eight-π-, and Twelve-π-Electron SystemsDedicated to Professor Manfred Regitz on the occasion of his 60th birthday (1996)

Heim, Udo ; Pritzkow, Hans ; Fleischer, Ulrich ; [weitere]

Weinheim : Wiley-Blackwell

Chemistry - A European Journal 2 (1996), S. 68-74

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ISSN: 0947-6539

Schlagwort(e): ab initio calculations ; cyclic ylides ; heterocycles ; phosphorus ylides ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A number of possible strategies for the preparation of λ5-phosphetes were tested as follows: cyclopropenium 6 was treated with the lithium salt of diphenylphosphine to give phosphinocyclopropene 7, but 7 did not undergo ring expansion upon photolysis or thermolysis. P-chloro-C—trimethylsilyl-substituted ylide 8b reacted with two equivalents of dimethyl acetylenedicarboxylate to afford phosphinine 13 via a transient λ5-phosphete 12. Addition of aluminum trichloride to P-halogenated ylides 17a-b led to dihydrophosphetium salts 19a-b, which, upon treatment with pyridine, isomerized into the 1, 2-dihydrophosphet-2-ium salts 20a-b. Hydrolysis of derivatives 20a-b cleanly afforded phosphoniums 21 a-b, which reacted with NaN(SiMe3)2 to give rise to the corresponding λ5-phosphetes 22a-b. The benzo-λ5-phosphete 22a underwent ring expansion reactions with dimethyl acetylenedicarboxylate and acetonitrile, leading to benzo-λ5-phosphinine and benzo-1, 4λ5-azaphosphinine in good yields. Derivative 22b was characterized by X-ray crystal structure analysis. Ab initio SCF calculations, IGLO-13C chemical shifts and Δχ for various benzannulated derivatives and phosphorus heterocycles are presented.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/chem.19960020113

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3

Digitale Medien

Equilibria Between Gas and Liquid Phases for Concentrated Aqueous Solutions of Nitric Acid (1999)

Balbaud, Fanny ; Sanchez, Gérard ; Santarini, Gérard ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 277-285

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ISSN: 1434-1948

Schlagwort(e): Nitric acid ; Nitrogen oxides ; Electrochemistry ; Thermodynamics ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Calculated diagrams, representing chemical and electrochemical properties of concentrated aqueous nitric acid mixtures, have been drawn for temperatures of 25 °C and 100 °C using vapor pressures and thermochemical data of related gaseous species. Electrochemical measurements have permitted the establishment of an experimental potential scale (referenced to the saturated mercurous sulfate electrode at 25 °C) incorporated in the diagram at 100 °C. These measurements also allowed the determination of the Gibbs free energy of formation of dissolved nitrous acid for various nitric acid solutions at 100 °C, leading to a value of ΔGf(HNO2) = -36.31 kJ mol-1, for the whole nitric acid concentration range.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

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4

Digitale Medien

Structural Analyses of Borane and Chloroborane Adducts of 1,3,5-Dithiaza-, -Dioxaza-, -Thiadiaza-, and -Triazacyclohexanes and Their Rearrangement Products, Boracyclohexanes (1999)

Flores-Parra, Angelina ; Sánchez-Ruíz, Sonia A. ; Guadarrama-Pérez, Carlos

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2063-2068

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ISSN: 1434-1948

Schlagwort(e): Borane adducts ; Triazacyclohexanes ; Thiadiazacyclohexanes ; Dioxazacyclohexanes ; Boracyclohexanes ; Rearrangements ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Structural and conformational studies performed by 1H-, 11B-, 13C-, two-dimensional, and variable-temperature NMR spectroscopy of borane and chloroborane adducts of 1,3,5-heterocyclohexanes and their rearrangement products, boracyclohexanes, are reported. N-Methyl derivatives gave equatorial N-borane adducts whereas the N-isopropyl derivatives produced the axial borane compounds. Rearrangement reactions of the adducts gave the first examples of chloroboracyclohexanes bearing boron and nitrogen atoms as stable stereogenic centers. BClH2 and BCl2H adducts were found to be more stable towards ring rearrangement than the corresponding N-BH3 analogs.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

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5

Digitale Medien

BHδ--δ+HC Interactions in N-Borane and N-Chloroborane Adducts Derived from 1,3,5-Heterocyclohexanes (1999)

Flores-Parra, Angelina ; Sánchez-Ruiz, Sonia A. ; Guadarrama, Carlos ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2069-2073

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ISSN: 1434-1948

Schlagwort(e): Hydridic-protic hydrogen interactions ; Amine boranes ; 1,3,5-Heterocyclohexanes ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The molecular structures of 5-methyl-1,3-dithia-5-aziniumcyclohexane iodide, 5-chloroborane-5-methyl-1,3-dithia-5-azacyclohexane, 3,5-bis(borane)-3,5-dimethyl-1-thia-3,5-diazacyclohexane, and 1-borane-1,3,5-trimethyl-1,3,5-triazacyclohexane were determined by X-ray diffraction studies. Interactions between hydridic and protic hydrogen atoms are present when the distances between hydridic and protic hydrogen atoms are shorter than 265 pm and angles for B-N-C bonds are smaller than 107.6(3)°. These interactions explain the conformation of the borane adducts in the solid state.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

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6

Digitale Medien

New Di- and Trinuclear Complexes with Pyrazolato Bridges. Crystal Structures of [{(C6F5)2Pd(μ-pz)(μ-Cl)}2Pd]2- and [(C6F5)2Pd(μ-pz)2Pd(η3-C4H7)] (pz = pyrazolate) (2000)

Ruiz, José ; Florenciano, Félix ; Sánchez, Miguel A. ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 943-949

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ISSN: 1434-1948

Schlagwort(e): Pyrazolate complexes ; Palladium ; Platinum ; N ligands ; Bridging ligands ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Trinuclear complexes containing pyrazolate bridging ligands of the type [NBu4]2[{(C6F5)2 M(μ-pz)(μ-X)}2M′] (M, M′= Pd or Pt; X = Cl, OH, or pz) (Hpz = pyrazole) have been prepared using [NBu4][M(C6F5)2(acac)] (acac = acetylacetonate) or [NBu4]2[M2(C6F5)4(μ-OH)2] and [M′Cl2(Hpz)2] or [M′(Hpz)4]2+ as starting materials. Asymmetric homo- and heterobimetallic complexes of the types [NBu4][R2M(μ-pz)2Pd(η3-allyl)] and [R2M(μ-pz)2M′L2] (allyl = C3H5 or C4H7; L2 = 2 PEt3 or bipy; R = C6F5 or C6Cl5; M, M′ = Pd or Pt) have been obtained starting from [NBu4][MR2(pzHpz)] and [Pd(η3-allyl)(acac)] or [M′L2Cl2], respectively. The identity of the new complexes has been established by NMR (1H, 19F and 31P) spectroscopy. The crystal structure of [{(C6F5)2Pd(μ-pz)(μ-Cl)}2Pd]2- has an inversion centre, with a bent appearance of the Pd3(μ-pz)2(μ-Cl)2 moiety. The crystal structure of [(C6F5)2Pd(μ-pz)2Pd(η3-C4H7)] has also been determined by single-crystal X-ray diffraction, where a boat conformation of the central “Pd2N4” six-membered rings is observed.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

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7

Digitale Medien

Cathodic Reactions Involved in Corrosion Processes Occurring in Concentrated Nitric Acid at 100 °C (2000)

Balbaud, Fanny ; Sanchez, Gérard ; Santarini, Gérard ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 665-674

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ISSN: 1434-1948

Schlagwort(e): Autocatalysis ; Cyclic voltammetry ; Nitric acid ; Nitrogen oxides ; Reduction mechanism ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: In order to explain and analyze the corrosion process of AISI 304 L stainless steel in the presence of nitric acid condensates, the reduction mechanism of nitric acid was studied on a platinum electrode in various nitric acid solutions (4 mol·L-1, 8 mol·L-1 and 12 mol·L-1) at 100 °C. Classical electrochemical techniques were used: cyclic voltammetry, chronoamperometry on a stationary electrode as well as on a rotating disk electrode. A reduction mechanism is proposed; this mechanism is autocatalytic and involves a charge-transfer step and a heterogeneous chemical reaction which regenerates the electroactive species at the electrode surface. The electroactive species is assumed to be nitrous acid which is a soluble species. The other compounds involved in the reduction mechanism are NO and NO2, which are supposed to be adsorbed. The nitric acid concentration influences the major product of the reduction process: NO for concentrations lower than 8 mol·L-1 and NO2 for higher concentrations.

Zusätzliches Material: 19 Ill.

Materialart: Digitale Medien

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8

Digitale Medien

Homogeneous and Supported Copper Complexes of Cyclic and Open-Chain Polynitrogenated Ligands as Catalysts of Cyclopropanation Reactions (1999)

Adrián, F. ; Burguete, M. I. ; Fraile, J. M. ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2347-2354

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ISSN: 1434-1948

Schlagwort(e): Cyclopropanation ; Copper ; N ligands ; Macrocycles ; Supported catalysts ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: CuI and CuII complexes of cyclic and open-chain polyaza compounds have been tested as catalysts in the benchmark cyclopropanation reaction of styrene with ethyl diazoacetate. In general, only small amounts of copper are needed to promote the reaction. The catalytic activity depends on the structure of the ligand, e.g. amine-amides are more efficient than polyamines, and on the oxidation state of copper, CuII being more active than CuI. Given that CuI is the active species, these changes of behavior must be related to the stabilities of the complexes. The nature of the counterion also has a noticeable influence on the catalytic activity, the role of which is discussed. XAS measurements suggest the formation of oligomeric species. Some of the chiral ligands lead to small enantiomeric excesses. Open-chain ligands can easily be supported on organic polymers and their complexes can be used as catalysts. Furthermore, cyclic and acyclic complexes can be supported on clays by cation exchange and the solids obtained tend to promote the reaction with a decrease in the trans/cis ratio.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

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9

Digitale Medien

Reactions of Cadmium(II) Acetate with Acetoacetanilide and Methylacetoacetate Thiosemicarbazones: A Cyclization Process Leading to a Pyrazolone - The Molecular and Crystal Structures of the Free Ligands and the Complex [CdL2Py] (HL = 2-[Amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolone, Py = Pyridine) (2000)

Casas, José S. ; Castaño, María V. ; Castellano, Eduardo E. ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 83-89

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ISSN: 1434-1948

Schlagwort(e): Cadmium(II) pyrazolonates ; Thiosemicarbazones ; Cyclizations ; 2-[Amino(thioxo)methyl]-3-pyrazolone ; 1H-, 13C-, 113Cd-NMR spectra ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Acetoacetanilide- and methylacetoacetate thiosemicarbazones (HTSC1 and HTSC2, respectively) react with cadmium(II) acetate in methanol, giving complexes containing the ligand 2-[amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolonate (L-). An X-ray diffraction study of the structures of HTSC1, HTSC2, HL, and [CdL2Py], identified the main structural changes in the cyclization process. Additionally, the coordination of the metal in the complexes [CdL(AcO)] · 2 MeOH and [CdL2] · 3 H2O was analyzed using IR spectroscopy in the solid state and 1H-, 13C-, and 113Cd-NMR spectroscopy in solution. On reaction with aqueous trifluoroacetic acid, both complexes releases the free pyrazolone, which can be easily isolated.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

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10

Digitale Medien

Hydrolysis and Condensation Reactions of Transition Metal Alkoxides: Calorimetric Study and Evaluation of the Extent of Reaction (1998)

Blanchard, Juliette ; In, Martin ; Schaudel, Barbara ; [weitere]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1115-1127

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ISSN: 1434-1948

Schlagwort(e): Sol-gel process ; Polymers, inorganic ; Transition metal alkoxides ; 17O-NMR spectroscopy ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The behavior of titanium and zirconium alkoxides towards complexation and water addition is analyzed through water titration and calorimetric experiments. A simple model is presented, which allows evaluation of the mean hydrolysis and condensation constants, Kh and Kc, of both pure and complexed transition metal alkoxides in the sol state, through the analysis of consumed water versus initial hydrolysis ratio curves. These constants allow comparison of the extents of the hydrolysis and condensation reactions for sols obtained from several alkoxide precursors. The complexation ratio only affects the condensation constant Kc, whereas the hydrolysis constant Kh remains unchanged. Analysis of the Kh/Kc ratios has shown that in the sol state, silanol Si-OH groups are more stable than the Ti-OH or Zr-OH groups. Moreover, this study has shown that the proton concentration not only affects the kinetics, but also the final composition of the system. Calorimetric studies of the complexation and hydrolysis/condensation reactions have highlighted the role of coordination unsaturation of the transition metal alkoxides in the exothermicity of these reactions, clearly demonstrating that coordination unsaturation is the driving force behind the reactivity of these alkoxides towards nucleophilic species (e.g. water, complexing ligands, polar solvents).

Materialart: Digitale Medien

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