Untersuchungen an oxidischen Katalysatoren. XLII. Redoxverhalten des Nickels in NiNa?Y-Zeolithen 4. Einfluß der Zusammensetzung auf die Reduzierbarkeit von Nickel in NiNa?Y-Zeolithen

Studies on Oxide Catalysts. XLii. Redox Behaviour of Nickel in Zeolites NiNa? Y. 4. Influence of Composition on the Reducibility of Nickel in Zeolites NiNa? Y By chemical analysis (reaction with K₂Cr₂O₇) and ESCA investigations we determined the degree of reduction in reduced samples NiNa-Y as function of the mole ratio SiO₂/Al₂O₃ (module), of the Ni²⁺ degree of exchange and the kind of the second cations. (NH₄₊, Ca²+, Co²+, and Nd³+) in the temperature region of 620–770 K. The degree of nickel reduction increases with increasing module, decreasing degree of exchange and decreasing number of Brönsted acidic centres. This behaviour is caused by the influence of the interaction between cations Ni²⁺ and zeolite lattice on the reduction equilibrium.     

Untersuchungen an oxidischen Katalysatoren. XXXIV. Redoxverhalten des Nickels in NiNaY-Zeolithen 1. Reduzierbarkeit und Reoxydierbarkeit von Nickel in NiNaY-Zeolithen

Studies on Oxide Catalysts. XXXIV. Redoxbehaviour of Nickel in Zeolite NiNaY. 1. Reducibility and Reoxidizability of Nickel in Zeolites NiNaY The properties of metallic nickel in reduced (470–870 K) and reoxidized (470, 670 K) samples were studied by chemical analysis (reaction with K₂Cr₂O₇) and spectroscopic methods (FMR, IR after CO adsorption, UV/VIS). The reduction of Ni²⁺ cations from oxidic clusters proceeds in an onestep reaction. Contrary to this, isolated Ni²⁺ cations are reduced stepwise to Ni⁺ cations and subsequently to metallic nickel. The reduction degree depends in characteristic manner on the reduction temperature. Metallic nickel which was reduced at temperatures < 620 K, can be completely reoxidized at 470 K. Higher temperatures result in metallic aggregations which are not completely reoxidized even at 670 K.     

Charakterisierung und katalytische Aktivität von Ni2+-ausgetauschten X- und Y-Zeolithen. II. Die Reduzierbarkeit des Ni2+ durch niedere Olefine und die Dimerisierungsaktivität der Ni2+-ausgetauschten Zeolithe

Characterization and Catalytic Activity of Ni²⁺ -X and -Y Zeolites. II. Reducibility of Ni²⁺ by Low Olefines and the Dimerization Activity of the Ni²⁺ -Zeolites The reducibility of Ni²⁺ in X and Y zeolites by hydrogen, but-1-ene, propene, and ethene is compared. The degree of reduction was determined after isothermal reduction and reoxidation by the TPR method. At 673 K on X zeolites the reducibility decreases in the order: H₂ > but-1-ene, propene > ethene. On Y zeolites an inversion takes place: but-1-ene, propene > H₂, ethene. The mechanism of reduction by olefins should be determined by an intermediate splitting off of a hydride ion as a reducing species. Such a mechanism explains the higher degree of reduction in the more acid Y zeolites. Assuming low valent nickel as an active center in ethen dimerization the induction period results from the reduction of Ni²⁺ ions.     

Penicillamin-Komplexe des Nickels,Chroms und Molybdäns — Strukturelle Besonderheiten und biologische/medizinische Relevanz

Penicillamine Complexes of Nickel, Chromium, and Molybdenum — Structural Particularity and Biological/Medical Relevance The compounds Tl₂[Ni^II(H₂O)₆][Ni^II(D-pen)(L-pen)]₂[Ni^II(SCN)₂(H₂O)₄] 1 , Tl[Ni^II(D-pen)₂H] · H₂O 2 , Tl[Cr^III(D-pen)₂] 3 , and Na₂[MoO₄(pen)₂] · 3 CH₃OH · 3 H₂O 4 have been prepared by the reaction of nickel nitrate (for 1 ), nickel acetate (for 2 ), potassium chromate (for 3 ), and sodium molybdate (for 4 ) with D- and D, L-penicillamine, respectively. They were characterized by single-crystal X-ray structure analysis and other physical methods. Whereas penicillamine acts as a bidentate (N, S)-ligand in 1 and 2 , Cr^III (in 3 ), and Mo^V (in 4 ) are coordinated to the three ligand atoms N, O, and S. The presence of three different types of Ni^II-complexes a cationic, a neutral, and an anionic one in 1 is remarkable. For crystal data see Inhaltsübersicht.     

Controlled Synthesis of Heterotrimetallic Single‐Chain Magnets from Anisotropic High‐Spin 3 d–4 f Nodes and Paramagnetic Spacers

By using the node‐and‐spacer approach in suitable solvents, four new heterotrimetallic 1D chain‐like compounds (that is, containing 3d–3d′–4f metal ions), {[Ni(L)Ln(NO₃)₂(H₂O)Fe(Tp*)(CN)₃] ? 2 CH₃CN ? CH₃OH}_n (H₂L=N,N′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane, Tp*=hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; Ln=Gd ( 1 ), Dy ( 2 ), Tb ( 3 ), Nd ( 4 )), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide‐ and phenolate‐bridged heterotrimetallic chain, with a {? Fe? C?N? Ni(? O? Ln)? N?C? }_n repeat unit. Within these chains, each [(Tp*)Fe(CN)₃]^? entity binds to the Ni^II ion of the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit is linked to two [(Tp*)Fe(CN)₃]^? ions through the Ni^II ion in a trans mode. In the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit, the Ni^II and Ln^III ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1 – 4 are rare examples of 1D cyanide‐ and phenolate‐bridged 3d–3d′–4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe^III and Ni^II ions through a cyanide bridge and between neighboring Ni^II and Ln^III (except for Nd^III) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single‐chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d–4f heterotrimetallic single‐chain magnets.     

Komplexe des vierwertigen Nickels mit o-Methylbenzamidoxim

Zusammenfassung Der Komplex des Ni²⁺ mit o-Methylbenzamidoxim (oMB), [Ni(oMB)₂], wurde mit H₂O₂ in Anwesenheit von Cu²⁺ oder unter Luftdurchblasen in alkalischer Lösung mit O₂ zu [Ni(oMB)₄] oxydiert. Die Ligandenzahl und die Bildungskonstante sindn=4 und lgK=7,33. Die Vierwertigkeit des Nickels wurde analytisch nachgewiesen. Die Oxydation verändert dasoMB nicht, wie aus dem IR-Spektrum ersichtlich ist. Die Geschwindigkeitskonstante istk=36,3 l/mol^–1 sec^–1 und entspricht einer bimolekularen Reaktion.

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Complexes of quadrivalent Ni with o-methylbenzamide oxime

The complex of Ni²⁺ with o-methylbenzamide oxime [Ni(oMB)₂] was oxidized to [Ni(oMB)₄] with H₂O₂ in the presence of Cu²⁺ or with O₂ by air-blowing in alkaline solution. The ligand number and the formation constant aren=4 and lgK=7.33, resp. It was proved analytically that nickel is 4-valent. The IR-spectra showed that the oxidation does not attackoMB. The speed constant isk=36.3 l/mole^–1 sec^–1, corresponding to a bimolecular reaction.

     

Analyse von Gemischen aus metallischem Nickel und Oxidhydraten des II- und h?herwertigen Nickels

Zusammenfassung Laugefeuchte Gemische aus metallischem Nickel und dessen Hydroxiden bzw. Oxidhydraten verschiedener Wertigkeitsstufen können in Proben von 50–200 mg bezüglich Zusammensetzung und effektiver Wertigkeit nach folgendem Schema analysiert werden:Reduktion der Probe mit alkalischer Arsenat(III)-Lösung, Umsatz des entstandenen Arsenats(V) mit KJ zu photometrisch bestimmbarem elementarem Jod, Extraktion der im Rückstand enthaltenen Nickelverbindungen mit verd. H₂SO₄, Auflösung des metallischen Nickels in H₂SO₄ + H₂O₂ und photometrische Bestimmung der Ni²⁺-Lösungen als ÄDTA-Komplex. Die effektive Wertigkeit der Nickelverbindungen kann auf ±0,02 Wertigkeitseinheiten genau ermittelt werden. Die Ergebnisse stimmen gut mit elektrochemisch erhaltenen Werten überein.Beachtet werden muß ein starker Phototropieeffekt der zu photometrierenden Jodlösung. Ein 380facher Überschuß an As(III) stört die As(V)-Bestimmung nicht.

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Analysis of mixtures of metallic nickel and oxide-hydrates of bivalent and higher-valency nickel

Mixtures consisting of metallic nickel and the hydroxides or oxide-hydrates in various valency stages moistened with alkali in samples of 50 to 200 mg can be analysed by the following scheme: Reduction of the sample with alkaline As(III) solution, reaction of As(V) with KI setting free elementary, photometrically determinable iodine, extraction of the Ni-compounds present in the residue with dilute H₂SO₄, dissolution of the metallic M in H₂SO₄ + H₂O₂, and photometric determination of the Ni²⁺ solutions as EDTA complex.In this manner the effective valency of the Ni-compounds can be determined within ± 0.02 valency units, The results agree well with those obtained electrochemically.The iodine solution from which the extinction has to be measured photometrically shows a strong phototropic effect.An excess of 380 parts of As(III) does not interfere with the As(V) determination.

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Auszugsweise vorgetragen auf der Hauptversammlung der Gesellschaft Deutscher Chemiker, 13. bis 18. September 1971 in Karlsruhe [6].

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Dem Vorstand der VARTA AGdanke ich für die freundliche Genehmigung zur Publikation. Besonderer Dank gebührt Fräulein H. Slomp, die alle Arbeiten durchgeführt und durch ihre Fähigkeit zu beobachten und zu kombinieren wesentlich zur Lösung des Problems beigetragen hat.     

EPR Studies of Photoreduction of Ni/TiO2 Catalysts

Irradiations of Ni/TiO₂ catalyst by UV in hydrogen at 77 K produced not only Ni⁺ ions on the catalyst surface, but also Ni³⁺ and Ti³⁺ species in bulk or near the interface between nickel and titania. These photo-generated species were detected and characterized by low temperature electron paramagnetic resonance (EPR) spectroscopy. Relative spin concentrations of the photogenerated paramagnetic species (Niⁿ⁺ and Ti³⁺) varied with the nickel content in titania. A high nickel content in the sample resulted in a high peak intensity ratio of Niⁿ⁺ to Ti³⁺. It was found that the photoinduced self-redox reaction of Ni²⁺ ions to form Ni⁺ and Ni³⁺ ions has a priority over the photoreduction of Ti⁴⁺ to Ti³⁺ ions. The characteristic EPR spectrum of the Ni³⁺ (3d⁷) ions with g₁ = 2.268, g₂ = 2.237, and g₃ = 2.045 indicates that the Ni³⁺ ions are most likely located in the substitutional sites of TiO₂, possibly near the surface rutile phase. The Ni⁺ species (3d⁹) with g₄ = 2.130 and g₁ = 2.063 are on the surface of TiO₂. Both Ni⁺ and Ni³⁺ ions are quite stable in hydrogen. The Ni³⁺ ions seem to be responsible for anchoring the nickel ions onto titania and stablizing the Ni⁺ species on the surface. The Ni⁺ ions are thus free from oxygen poisoning and still show a high activity toward olefin oligomerization.     

Electron impact ionization of ethylene–methanol heteroclusters: Stable configurations and mechanisms in intracluster ion–molecule reactions

Reactions that proceed within mixed ethylene–methanol cluster ions were studied using an electron impact time-of-flight mass spectrometer. The ion abundance ratio, [(C₂H₄)_n(CH₃OH)_mH⁺]/[(C₂H₄)_n(CH₃OH)_m⁺], shows a propensity to increase as the ethylene/methanol mixing ratio increases, indicating that the proton is preferentially bound to a methanol molecule in the heterocluster ions. The results from isotope-labelling experiments indicate that the effective formation of a protonated heterocluster is responsible for ethylene molecules in the clusters. The observed (C₂H₄)_n(CH₃OH)_m⁺ and (C₂H₄)_n(CH₃OH)_m–1CH₃O⁺ ions are interpreted as a consequence of the ion–neutral complex and intracluster ion–molecule reaction, respectively. Experimental evidence for the stable configurations of heterocluster species is found from the distinct abundance distributions of these ions and also from the observation of fragment peaks in the mass spectra. Investigations on the relative cluster ion distribution under various conditions suggest that (C₂H₄)_n(CH₃OH)_mH⁺ ions with n + m ≤ 3 have particularly stable structures. The result is understood on the basis of ion–molecule condensation reactions, leading to the formation of fragment ions, $ {\rm CH}_2=\!=\mathop {\rm O}\limits^ + {\rm CH}_3 $ and (CH₃OH)H₃O⁺, and the effective stabilization by a polar molecule. The reaction energies of proposed mechanisms are presented for (C₂H₄)_n(CH₃OH)_mH⁺(n + m ≤ 3) using semi-empirical molecular orbital calculations.     

Synthesis of magnetic nickel spinel ferrite nanospheres by a reverse emulsion-assisted hydrothermal process

Nickel ferrite nanospheres were successfully synthesized by a reverse emulsion-assisted hydrothermal method. The reverse emulsion was composed of water, cetyltrimethyl ammonium bromide, polyoxyethylene(10)nonyl phenyl ether, iso-amyl alcohol and hexane. During the hydrothermal process, β-FeO(OH) and Ni_0.75Fe_0.25(CO₃)_0.125(OH)₂·0.38H₂O (INCHH) nanorods formed first and then transformed into nickel spinel ferrite nanospheres. The phase transformation mechanism is proposed based on the results of X-ray powder diffraction, transmission electron microscopy and energy-dispersive X-ray spectroscopy, etc. Nickel ferrite may form at the end of the INCHH nanorods or from the solution accompanied by the dissolution of β-FeO(OH) and INCHH nanorods. The X-ray photoelectron spectroscopy analysis shows that a few Fe³⁺ ions have been reduced to Fe²⁺ ions during the formation of nickel ferrite. The maximum magnetization of the nickel ferrite nanospheres obtained after hydrothermal reaction for 30 h is 55.01 emu/g, which is close to that of bulk NiFe₂O₄.     

pH‐Dependent Proton Conducting Behavior in a Metal–Organic Framework Material

A porous metal–organic framework (MOF), [Ni₂(dobdc)(H₂O)₂]?6 H₂O (Ni₂(dobdc) or Ni‐MOF‐74; dobdc^4?=2,5‐dioxido‐1,4‐benzenedicarboxylate) with hexagonal channels was synthesized using a microwave‐assisted solvothermal reaction. Soaking Ni₂(dobdc) in sulfuric acid solutions at different pH values afforded new proton‐conducting frameworks, H⁺@Ni₂(dobdc). At pH 1.8, the acidified MOF shows proton conductivity of 2.2×10^?2 S cm^?1 at 80 °C and 95 % relative humidity (RH), approaching the highest values reported for MOFs. Proton conduction occurs via the Grotthuss mechanism with a significantly low activation energy as compared to other proton‐conducting MOFs. Protonated water clusters within the pores of H⁺@Ni₂(dobdc) play an important role in the conduction process.     

Effect of the support and the reduction temperature on the formation of metallic nickel phase in Ni/silica gel precursors of vegetable oil hydrogenation catalysts

Ni/SiO₂ materials with identical composition (SiO₂/Ni = 1.0) have been synthesized by precipitation of Ni(NO₃)₂ · 6H₂O solution with Na₂CO₃ solution on the silica gel, obtained at three different pH values. The present investigation was undertaken in an endeavor to study the effects of the silica gel support type and the reduction temperature on the formation and dispersion of the metallic nickel phase in the reduced Ni/SiO₂ precursors of the vegetable oil hydrogenation catalyst. The physicochemical characterization of the unreduced and reduced precursors has been accomplished appropriately by powder X-ray diffraction, infrared spectroscopy, temperature programmed reduction and H₂-chemisorption techniques. It can be stated that the texture peculiarities of the silica gels used as supports influence on the crystalline state and distribution of the deposited Ni-containing phases during the preparation of the precursors, on the reduction temperature of the investigated solids as well as on the bulk size and surface dispersion of the arising metallic nickel particles. It was shown that two types of Ni²⁺-species are formed during the synthesis procedure, namely basic nickel carbonate-like and Ni-phyllosilicate with different extent of presence, location and strength of interaction. The different location of these species is supposed to result in various strength of Ni-O and Ni-O-Si interaction, thus determining the overall reducibility of the precursors. It was specified that the Ni²⁺-species are strongly bonded to the surface of the silica gel obtained at neutral pH value and weakly bonded to the surface of those prepared in acidic and alkaline conditions. It was established that the precursor, derivates from the silica gel obtained at alkaline conditions, demonstrates both significant reduction of the Ni2+ ions at 430°C and finely dispersed metallic nickel particles on its surface. High dispersion of the metallic nickel might be the crucial reason for achieving of high activity in the vegetable oil hydrogenation.     

Hydrothermal synthesis and structural characterization of three inorganic–organic composite sandwich-type phosphotungstates

Three inorganic–organic composite sandwich-type phosphotungstates [Ni(tepa)(H₂O)]₄H₂[Ni₄(H₂O)₂(α-B-PW₉O₃₄)₂]·8H₂O (1), (enH₂)₃[Ni₂(H₂O)₁₀][Ni₄(H₂O)₂(α-B-PW₉O₃₄)₂]·en·8H₂O (2) and (enH₂)₁₀[Mn₄(H₂O)₂(α-B-PW₉O₃₄)₂]₂·20H₂O (3) (tepa=tetraethylenepentamine and en=ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW₉O₃₄]⁹⁻ with Ni²⁺ or Mn²⁺ ions in the presence of tepa or en and structurally characterized by IR spectra, elemental analysis, thermogravimetric analysis and variable temperature magnetic susceptibility. X-ray crystallographic analyses indicate that they all contain the classical tetra-M sandwiched polyoxoanions [M₄(H₂O)₂(α-B-PW₉O₃₄)₂]¹⁰⁻ (M=Ni²⁺ or Mn²⁺) and nickel-organoamine cations or organoamine cations work as the charge balance ions. The tetra-M clusters in 1, 2 and 3 exhibit the familiar structural type of a β-junction at the sites of metal incorporation. The study of magnetic property of 1 is indicative of a typical ferromagnetic coupling between Ni²⁺ cations.     

Untersuchungen an Nickeloxid-Mischkatalysatoren. I. Strukturelle Eigenschaften von NiO/SiO2-Katalysatoren

Studies on Nickel Oxide Mixed Catalysts. I. Structural Properties of NiO/SiO₂ Catalysts Structural properties of NiO/SiO₂ catalysts prepared by precipitation-deposition and impregnation have been investigated. A nickel-layer-silicate like structure is formed only in the precipitated catalysts showed infrared spectroscopic measurements. After thermal treatment at 723 K by means of magnetic measurements and reflectance spectroscopy besides Ni²⁺ ions in octahedral environment tetrahedral coordinated Ni²⁺ions were found. The part of tetrahedral coordinated Ni²⁺ ions is independent of the NiO-content up to 40 mole % NiO. Nickel oxide is formed above a content of 40 mole %. In the case of the impregnated catalysts nickel oxide cluster are formed on the surface after annealing at 723 K.     

Interaction of the Ni<Superscript>2+</Superscript> ion with citric acid in an aqueous solution

The formation of nickel citrate complexes was studied at ionic strength values of 0.1 and 0.3 mol/l (Et₄NCl) and 298.15 K by potentiometric titration. The NiCit^?, NiHCit, and NiH₂Cit⁺ complexes were formed in a Ni²⁺ ion-citric acid (H₃Cit) system. The thermodynamic formation constants of the nickel(II) citrate complexes were calculated in an aqueous solution at \(I = 0:\log \beta _{NiCit^ - }^0 \) = 6.86 ± 0.12 (Ni²⁺ + Cit^3? ai NiCit^?), logK ₁ ⁰ = 4.18 ± 0.10 (Ni²⁺ + HCit^2? ai NiHCit), and logK ₂ ⁰ = 2.24 ± 0.11 (Ni²⁺ + H₂Cit^? ai NiH₂Cit⁺). The spectral properties of the Ni²⁺-H₃Cit system were studied by spectrometry. The conditions of calorimetric determination of the thermal effects of formation of the nickel citrate complexes in an aqueous solution were optimized on the basis of the calculated stability constants of the Ni(II) complexes with H₃Cit.     

Magnetocaloric Properties of Heterometallic 3d–Gd Complexes Based on the [Gd(oda)3]3− Metalloligand

A series of heterometallic 3d–Gd³⁺ complexes based on a lanthanide metalloligand, [M(H₂O)₆][Gd(oda)₃] ? 3 H₂O [M=Cr³⁺ ( 1‐Cr )] (H₂oda=2,2′‐oxydiacetic acid), [M(H₂O)₆][MGd(oda)₃]₂ ? 3 H₂O [M=Mn²⁺ ( 2‐Mn ), Fe²⁺ ( 2‐Fe ) and Co²⁺ ( 2‐Co )], and [M₃Gd₂(oda)₆(H₂O)₆] ? 12 H₂O [M=Ni²⁺ ( 3‐Ni ), Cu²⁺ ( 3‐Cu ), and Zn²⁺ ( 3‐Zn )], are reported. Magnetic and heat‐capacity studies revealed a significant impact on the magnetocaloric effect depending on the anisotropy of the 3d transition metal ions, as confirmed by comparison of the observed maximum values of ?ΔS_m between complexes 2‐Co and 1‐Cr . In these two complexes, the 3d metal ions have the same spin (S=3/2 for Co²⁺ and Cr³⁺ ions), and the theoretical calculation suggested a larger ?ΔS_m value for 2‐Co (47.8 J K^?1 kg^?1) than 1‐Cr (37.5 J K^?1 kg^?1); however, the significant anisotropy of Co²⁺ ions in 2‐Co , which can result in smaller effective spins, gives a smaller value of ?ΔS_m for 2‐Co (32.2 J K^?1 kg^?1) than for 1‐Cr (35.4 J K^?1 kg^?1) at ΔH=9 T.     

Kinetics of Stripping Ni(II) from the Ni‐BTMPPA Complex/BTMPPA/Kerosene System by Sulfate‐Acetato Solution

The kinetics of stripping of Ni²⁺ from a Ni‐BTMPPA complex, dissolved in a kerosene solution of BTMPPA (H₂A₂, Cyanex 272), by acidic sulfate‐acetato solution, was studied using the single (falling) drop technique and flux (F) method of data treatment. The empirical flux equation at 303 K is F_b (kmol/m²s) = 10^?4.35 [Ni²⁺] (1+10^?3.42 [H⁺]^?1)^?1 ([H₂A₂]_(o)^0.5+2.50 [H₂A₂]_(o))^?1 (1+6[SO₄^2?]) (1+3.20 [Ac^?]). Activation energy (E_a), entropy change in activation (ΔS^±), and enthalpy change in activation (ΔH^±) were measured under different experimental conditions. Based on the empirical flux equation, E_a and ΔS^±, the mechanism of Ni²⁺ stripping is provided. In a low [H⁺] region, the stripping reaction steps appear as [NiA⁺] → Ni²⁺ + A^? and [Ni(HA₂)₂]_(int) → [NiHA₂]⁺_(int) + HA_2(int)^? in lower and higher concentration regions of free BTMPPA, respectively, provided [SO₄^2?] and [Ac^?] are kept low. However, at higher [H⁺] concentrations, the stripping is under diffusion control. With increasing [SO₄^2?] and [Ac^?], the enhancement of the rate is attributed to the attack of the Ni(II) complex by SO₄^2? or HSO₄^? and Ac^? to form NiSO₄ or NiHSO₄⁺ and NiAc⁺ complexes. Negative ΔS^± values indicate that the rate‐determining stripping reaction steps occur via an substitution nucleophilic, bimolecular (S_N2) mechanism.     

Theoretical and Experimental Study of Complex Ions from Reactions of Al+ (Cu+) with Amine Molecules

The gas phase reactions of metal ions (Al⁺, Cu⁺) with amine molecules [CH₃NH₂=MA, (CH₃)₂NH=DMA] were investigated using a laser ablation‐molecular beam method. The directly associated product complex ions,Al⁺‐MA and Al⁺‐DMA, and the dehydrogenation product ions, Cu⁺(CH₂NH) and Cu⁺(C₂H₅N), as well as hydrated ion Cu⁺(NC₂H₅·H₂O), have been obtained and recorded from the reactions of the metal ions and organic amine molecules, and density functional theory (B3LYP) calculations have been performed to reveal the optimized geometry, energetics, and reaction mechanism of the title reactions with basis set 6‐311+G(d,p) adopted.     

Conformational Effects of [Ni2(μ‐ArS)2] Cores on Their Electrocatalytic Activity

Two nickel complexes supported by tridentate NS₂ ligands, [Ni₂(κ‐N,S,S,S′‐N^Ph{CH₂(MeC₆H₂R′)S}₂)₂] ( 1 ; R′=3,5‐(CF₃)₂C₆H₃) and [Ni₂(κ‐N,S,S,S′‐N^iBu{CH₂C₆H₄S}₂)₂] ( 2 ), were prepared as bioinspired models of the active site of [NiFe] hydrogenases. The solid‐state structure of 1 reveals that the [Ni₂(μ‐ArS)₂] core is bent, with the planes of the nickel centers at a hinge angle of 81.3(5)°, whereas 2 shows a coplanar arrangement between both nickel(II) ions in the dimeric structure. Complex 1 electrocatalyzes proton reduction from CF₃COOH at ?1.93 (overpotential of 1.04 V, with i_cat/i_p≈21.8) and ?1.47 V (overpotential of 580 mV, with i_cat/i_p≈5.9) versus the ferrocene/ferrocenium redox couple. The electrochemical behavior of 1 relative to that of 2 may be related to the bent [Ni₂(μ‐ArS)₂] core, which allows proximity of the two Ni???Ni centers at 2.730(8) Å; thus possibly favoring H⁺ reduction. In contrast, the planar [Ni₂(μ‐ArS)₂] core of 2 results in a Ni???Ni distance of 3.364(4) Å and is unstable in the presence of acid.     

Charakterisierung und katalytische Aktivität von Ni2+-ausgetauschten X- und Y-Zeolithen. I. TPR-Untersuchungen an NiNaX- und NiNaY-Zeolithen

Charaterization and Catalytic Activity of Ni²⁺ Exchanged X and Y Zeolites. I. TPR Studies on NiNaX and NiNaY Zeolites . The structure of TPR spectra of NiNaX and NaNiY zeolites variously exchanged is determined by the location of the cations. In case of X zeolites a peak appears with a maximum at 750–800 K (reduction on S_II and S_I, positions) and for higher exchange degrees an additional one at about 1000 K (reduction on S_I positions). Three ranges of reduction may be separated in case of Y zeolites (reduction on S_II, S_I′, and S_I). With increasing Si/Al ratios the maximum of the hightemperature peak is shifted to higher temperatures. The reduction at temperatures up to 800 K resulted in higher reduction degrees for X reolites while the overall reduction up to high temperatures led to higher reduction degrees for Y zeolites. The kinetic analysis by means of two different methods yielded the following activation energies: (85 ± 10) or (86 ± 2) kJ/mole, respectively, for the low-temperature peak, and (223 ± 12) or (214 ± 2) kJ/mole, respectively, for the high-temperature peak.