AQUEOUS EQUILIBRIA OF COPPER(II)- AND NICKEL(II)-POLYGLYCINE COMPLEXES

Abstract

Magnetic susceptibility measurements, new potentiometric data, optical spectra, and a new statistical method of calculation are combined in the formulation of an equilibrium scheme defining the dilute solution interactions of nickel(II) and copper(II) ions with diglycine, triglycine, and tetraglycine as a function of pH. At low pH appreciable concentrations of a previously unreported complex, MHL²⁺ (HL =polyglycine ligands) are shown to be present in all nickel(II)-polyglycine systems and in the copper(II)-triglycine system. This new protonated species is assigned a structure in which the metal ion is coordinated to the terminal carboxylate and to the adjacent peptide carbonyl oxygen with the proton residing on the terminal amino group. As the pH is raised in the 1:1 systems, MH_?1L, MH_?2L^? and MH_{_3}L^2- are formed in succession depending on the number of peptide linkages in the ligands, HL. The concentration of the monodeprotonated intermediate species NiH_?1L never exceeds 10% of the total metal ion concentration in the triglycine case and is always less than 0.5% when tetraglycine is the ligand. The dideprotonated intermediate NiH_?2L- reaches a maximum of 38% of the total metal concentration in the 1:1 Ni-tetraglycine system. An explanation is presented for this negative deviation from the predictions based on statistical grounds. Complete species distribution diagrams which include the new protonated complexes are presented and are employed to explain the differences in the interactions of copper(II) and nickel(II) ions with polyglycine ligands. Probable coordinate bonding sites suggested for the complexes formed in solution are inferred on the basis of stoichiometry, relative stabilities, and available microscopic information.     

Theoretical analysis of dissociative adsorption of H2O on Ni(100)

In conclusion, let us note the principal results of the calculation.

Metal complexes with chloride and triazole‐based ligands: investigation of a well‐resolved up–up–down–down (uudd) cyclic water tetramer and X—H...Cl (X = O and C) hydrogen‐bonding interactions

The crystal structure of the title complex, trans‐dichloridotetrakis[1‐phenyl‐3‐(1H‐1,2,4‐triazol‐1‐yl‐κN⁴)propan‐1‐one]copper(II) hexahydrate, [CuCl₂(C₁₁H₁₁N₃O)₄]·6H₂O, is isomorphous with that of the corresponding nickel and cobalt compounds. The complex has crystallographic inversion symmetry with the Cu^II atom on an inversion centre. Each Cu^II atom is six‐coordinated by one N atom from each of the four 1‐phenyl‐3‐(1H‐1,2,4‐triazol‐1‐yl)propan‐1‐one ligands in the equatorial plane and by two chloride ligands in axial positions. The structure includes a centrosymmetric irregular up–up–down–down (uudd) water tetramer cluster and O—H...Cl hydrogen bonds. Intermolecular C—H...Cl hydrogen bonds exist between adjacent molecules, resulting in a three‐dimensional supramolecular network.     

Etude des complexes sulfosalicylate de cuivre(III), nickel(II), cobalt(II) et uranyle(II) a l'aide d'une resine echangeuse de cations: Study of the sulphosalicylate complexes ofcopper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.

Study of the sulphosalicylate complexes of copper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.The conditional stability constants of the 1:1 complexes of the sulphosalicylate ions (L^3-) with copper(II), nickel(II), cobalt(II) and uranyl ions have been determined in a sodium perchlorate solution (0.1 M) and at various pH values by a cation-exchange method based on Schubert's procedure. The limits of application of the method are discussed. The variation with pH of the conditional stability constants can be explained by the existence of the complexes: CuH₂L, CuHL, CuL^-; NiH₂L⁺, NiHL, NiL^-; CoHL, CoL^-; UO₂H₂L⁺, UO₂HL, UO₂L^-, UO₂LOH^2-. The stability constants of these complexes are reported. Distribution diagrams of the various complexes of each element with pH and total concentration of sulphosalicylate parameters are given.     

Unified reciprocity of dithiophosphate by dichalcogenophosph(in)ate ligands on copper hydride nanoclusters via ligand exchange reaction

A structural study of ligand exchange on chalcogen‐passivated copper nanoclusters is far less developed. Herein, we report the synthesis of polyhydrido copper nanoclusters [Cu₂₀H₁₁{Se₂P(O ⁱBu)₂}₉] ( 2 ) passivated by Se‐donor ligands via ligand replacement reaction on [Cu₂₀H₁₁{S₂P(O ⁱPr)₂}₉] ( 1 ) with NH₄[Se₂P(O ⁱBu)₂]. In parallel to the synthesis of 2 , cluster [Cu₂₀H₁₁{S₂P(CH₂CH₂Ph)₂}₉] ( 4 ) was produced by the ligand exchange reaction on a new derivative of 1 , that is [Cu₂₀H₁₁{S₂P(O ⁿPr)₂}₉] ( 3 ). Solid state structures of both clusters 2 and 4 were unequivocally established by single‐crystal X‐ray diffraction studies and cluster 4 epitomizes exceptional case to preserve both the shape and size of the nanocluster during the course of ligand exchange. Structurally precise cluster 2 is the second example where the copper hydride nanocluster is stabilized by Se‐donor ligands. The anatomy of 2 can be visualized as a twisted cuboctahedral Cu₁₃ core, two triangular faces of which are capped by a Cu₆ cupola and a single Cu atom along the C₃ rotational axis.     

Composition and stability of copper(II), nickel(II), and cobalt(II) complexes with mono- and bis(2-carboxy)-2-pycolylamine

Complexation of N-(2-pyridyl)methyl-3-aminopropionic (HL¹) and N-(2-pyridyl)methyliminodipropionic (H₂L²) acids with copper(II), nickel(II), and cobalt(II) ions is studied. The composition of complexes is determined using the Starik–Barbanel relative yield method. The acid dissociation constants of HL¹ and H₂L² are determined potentiometrically; the stability constants of HL¹ and H₂L² complexes with metal ions are calculated.     

水在HfO2(111)和(110)表面的吸附与解离

运用广义梯度近似密度泛函理论方法(GGA-PW91)结合周期平板模型, 研究水分子在二氧化铪(111)和(110)表面不同吸附位置在不同覆盖度下的吸附行为. 通过比较不同吸附位的吸附能和几何构型参数发现:(111)和(110)表面铪原子(top 位)是活性吸附位. 水分子与表面的吸附能值随覆盖度的变化影响较小. 在(111)和(110)表面, 水分子都倾向以氧端与表面铪原子相互作用. 同时也计算了羟基、氧和氢在表面的吸附, Mulliken 电荷布居, 态密度及部分频率. 结果表明, 在两种表面羟基以氧端与表面铪相互作用, 氧原子与表面铪和氧原子同时成键, 而氢原子直接与表面氧原子相互作用形成羟基. 通过过渡态搜索, 水分子在(111)和(110)表面发生解离, 反应能垒分别为9.7和17.3 kJ·mol^-1, 且放热为59.9和47.6 kJ·mol^-1.     

丙烯腈在Cu(100)表面化学吸附的密度泛函理论研究

利用密度泛函方法, 模拟金属铜原子簇Cu₁₄(9,4,1)的(100)表面, 对丙烯腈(CH₂＝CHCN)在Cu(100)面上不同吸附位的吸附状况进行了理论研究. 结果表明: 丙烯腈分子通过端位N原子垂直吸附在金属表面上为弱化学吸附, 部分电荷从丙烯腈分子转移至铜金属簇; 由N原子的孤对电子与金属铜形成弱σ共价键; 顶位是最佳吸附位, 吸附能为40.7391 kJ•mol^－1, N原子与金属表面间的平衡距离为0.2279 nm; 其次为桥位和穴位, 吸附能分别为36.2513和30.2158 kJ•mol^－1, 平衡距离为0.2194和0.2886 nm; 吸附后C≡N键的强度降低, 活化了丙烯腈分子. 化学吸附使体系的熵减小, 是由于丙烯腈分子的平动和转动因吸附而被限制.     

Synthesis,properties, and crystal structures of mononuclear nickel(II) and copper(II) complexes with 2-oximino-3-thiosemicarbazone-2,3-butanedione

The tridentate ligand 2-Oximino-3-thiosemicarbazone-2,3-butanedione (Hotsb) reacts with MCl₂ (M = Ni²⁺ or Cu²⁺) to give rise to the mononuclear complexes [Ni(Hotsb)₂]Cl₂ · H₂O (1) and [Cu(Hotsb)Cl₂] · H₂O (2). These complexes have been characterized by X-ray crystallography, spectroscopy, and cyclic voltammetry. The nickel(II) ion in (1) is in a six-coordinate octahedral environment being bonded to the two protonated tridentate ligands which occupy mer positions. The copper(II) ion in (2) is in a five-coordinate square-pyramidal geometry, in which the basal plane is made up the two nitrogens, sulfur, and chloride atom, while the other chloride atom is coordinated at the axial position. The cyclic voltammogram of the complexes displays two one-electron waves corresponding to M^II/M^III and M^II/M^I processes. The electronic as well as infrared spectral properties of the title complexes are reported and discussed.     

Oxidative addition of dihydrogen to Ni(II) complexes.ab initio MO/MP4 calculations of the electronic structure of NiH2Cl2(PH3)2 complex

Electronic state d⁶ Ni(IV) in the complex [NiH₂Cl₂(PH₃)₂] was studied by means ofab initio MO/MP4 calculations.     

Study of kinetics and mechanism of the acid dissociation of copper(II) complex of novel C-functionalized macrocyclic dioxotetraamines

The kinetics of the acid dissociation of copper(II) complexes of novel C-functionalized macrocyclic dioxotetraamines has been studied by means of a stopped-flow spectrophotometer. The acid dissociation rate follows the law V_d = C_comkK₁K₂H ²/(1+K₁H+K₁K₂H ²). From the experimental facts we have obtained, the dissociation kinetics are interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in a pre-equilibrium step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in the strongly acidic solution. By means of temperature coefficient method, ΔH ^φ, ΔS ^φ of the pre-equilibrium step and ΔH ^≠, ΔS^≠ of the rate-determining step were obtained. The results of 13-membered macrocyclic dioxotetraamines have been discussed. The influence of the substituents to the acid dissociation rates has also been discussed. The Bronsted type linear free energy relationships do also exist in these C-functionalized dioxotetraamine copper(II) complexes.     

Spectroscopic studies of bridged binuclear complexes of Co(II), Ni(II), Cu(II) and Zn(II)

Binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of general composition [M₂L^1-2(μ-Cl)Cl₂] · nH₂O with the Schiff-base ligands (where L¹H and L²H are the potential pentadentate ligands derived by condensing 2,6-diformyl-4-methylphenol with 4-amino-3-antipyrine and 2-hydroxy-3-hydrazinoquinoxiline, respectively) have been synthesized and characterized. Analytical and spectral studies support the above formulation. ¹H-NMR and IR spectra of the complexes suggest they have an endogenous phenoxide bridge, with chloride as the exogenous bridge atom. The electronic spectra of all the complexes are well characterized by broad d–d and a high intensity charge-transfer transitions. The complexes are chloro-bridged as evidenced by two intense far-IR bands centered around 270–280 cm⁻¹. Magnetic susceptibility measurements show that complexes are antiferromagnetic in nature. The compounds show significant growth inhibitory activity against fungi Aspergillus niger and Candida albicans and moderate activity against bacteria Bacillus cirroflagellosus and Pseudomonas auresenosa.     

trans-Bis(azido-κN)bis(pyridine-2-carboxamide-κ2N1,O2)nickel(II)

In the title compound, [Ni(N₃)₂(C₆H₆N₂O)₂], the Ni^II atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N—H...N hydrogen bonds.     

Copper(II) and nickel(II) complexes of mono-oxocyclam(5-oxo-1,4,8,11-tetraazacyclotetradecane). Synthetic and potentiometric studies

Summary The macrocyclic mono-oxotetraamine, 5-oxo-1,4,8,11-tetraazacyclotetradecane (mono-oxocyclam=LH) has been prepared by reaction of methyl acrylate with 2,3,2-tetra(1,9-diamino-3,7-diazanonane). The protonation constants of the ligand are log K₁=9.40, log K₂=6.65 and log K₃=2.87 at 25 °C (I=0.1 mol dm^–3 NaClO₄). Detailed potentiometric studies of the interaction of the base with copper(II) and nickel(II) have been carried out. In the pH range 2.5–7.0 two complexes, [CuLH]²⁺ and [CuL]⁺, form; the deprotonated complex being 100% abundant at pH 7. For nickel(II), only [NiL]⁺ forms (log _11–1 = 3.90), the yellow low spin nickel complex reaching its maximum concentration above pH 6. The [CuL][ClO₄] · H₂O and [NiL][ClO₄] 0.5 H₂O complexes have been characterised in the solid state. The nickel(II) complex is square planar with a d-d band at 22625 cm^–1.     

Hexaaquacobalt(II) bis(hypophosphite) and hexaaquacobalt(II)/nickel(II) bis(hypophosphite)

The title compounds, hexa­aqua­cobalt(II) bis­(hypophosphite), [Co(H₂O)₆](H₂­PO₂)₂, and hexa­aqua­cobalt(II)/nickel(II) bis(hypophosphite), [Co_0.5Ni_0.5(H₂O)₆](H₂PO₂)₂, are shown to adopt the same structure as hexa­aqua­magnesium(II) bis­(hypophosphite). The packing of the Co(Ni) and P atoms is the same as in the structure of CaF₂. The Co^II(Ni^II) atoms have a pseudo‐face‐centred cubic cell, with a = b～ 10.3 Å, and the P atoms occupy the tetrahedral cavities. The central metal cation has a slightly distorted octahedral coordination sphere. The geometry of the hypophosphite anion in the structure is very close to ideal, with point symmetry mm2. Each O atom of the hypophosphite anion is hydrogen bonded to three water mol­ecules from different cation complexes, and each H atom of the hypophosphite anion is surrounded by three water mol­ecules from further different cation complexes.     

Contracted CI calculations of models for catalytic reactions involving transition metals

Theoretical models for reductive elimination from transition metal containing molecules have been studied using large scale contracted CI calculations. Four different models were treated, namely, NiH₂, PdH₂, Ni(CH₃)₂, and Pd(H₂O)₂H₂, in order to study the effects of adding ligands, exchanging hydrogens with methyl groups, and comparing nickel and palladium. The most interesting result already appeared for the simplest system NiH₂. A closed-shell-type ¹A₁ state with a small bond angle of only 57° is bound compared to Ni and H₂ with only a very small barrier for formation. The bond distance is short, shorter than in NiH, and the d orbitals are strongly involved in the binding. The hydrogen atoms bind both to nickel and to each other. With methyl groups rather than hydrogens, this double sided bonding situation is destroyed and Ni(CH₃)₂ has a negative binding energy with the carbon bonds pointing towards nickel. For PdH₂ only a weakly bound complex between an essentially unchanged H₂ and Pd was found. The bond distance is very long. Adding H₂O ligands to Pd shortens the bond distance and significantly opens up the bond angle. The methods used in the investigation and the chemical implications of the results are discussed.     

Kinetic and equilibrium studies of the acid dissociation of the copper(II) and nickel(II) complexes of 5,7-dioxo-1,4,8,11-tetra-azacyclotetradecane

The acid catalysed dissociation of the copper(II) and nickel(II) complexes of 5,7-dioxo-1,4,8,11-tetra-azacyclo-tetradecane (dioxocyclam = LH₂) has been studied using nitric acid solutions over a range of temperatures at I = 1.0 mol dm si-³. The kinetic data for the copper complex can be fitted to the rate expression k _obs = k K ₂[H⁺]/(1 + K ₂ [H⁺] with K = 24.7s⁻¹ and K ₂ = 65dm³mol⁻¹ at 25° C. The analogous constants for the nickel(II) complex are K = ³.³s⁻¹ and K ₂ = 45dm³mol⁻¹. The acid dissociation can be rationalized in terms of the kinetic scheme

Characterization and reactivity of nanoscale La(Co,Cu)O3 perovskite catalyst precursors for CO hydrogenation

The characterization of La(Co,Cu)O₃ perovskites has been performed by several techniques including XRD, BET, H₂-TPR, O₂-TPO, TPRS, and the solids tested as catalysts for the hydrogenation of CO. The reducibility of the perovskites is strongly affected by the preparation route, calcination temperature, catalyst morphology, and the amount of remnant alkali. Compared with the citrate-derived perovskite, LaCoO₃ sample prepared by mechano-synthesis has various distinct Co³⁺ ions in perovskite lattice, which are reduced at different temperatures. Under typical conditions, the reduction of cobalt ions occurs in two consecutive steps: Co³⁺/Co²⁺ and Co²⁺/Co⁰, while the intra-lattice copper ions are directly reduced from Cu²⁺ to Cu⁰. The reducibility of cobalt ions is promoted by the presence of metallic copper, which is formed at a lower reduction temperature. The re-oxidation of the reduced lanthanum cobaltite perovskite could regenerate the original structure, whereas that of the reduced Co-Cu-based samples is less reversible under the same experimental conditions.The cobalt atom in the reduced perovskites plays an important role in the dissociation of CO, but the presence of a neighboring copper along with remnant sodium ions on the catalyst surface has remarkably affected the reactivity of cobalt for CO hydrogenation. The addition of copper into the perovskite framework leads to a change in the product distribution of CO hydrogenation and a decrease in reaction temperature. An increased copper content leads to a substantial decline in the rate of methanation and an increase in the formation of higher alcohols. A close proximity between cobalt and copper sites on the Na⁺-modified catalyst surface of the reduced nanocrystalline Co-Cu-based perovskites plays a crucial role in the synthesis of higher alcohols from syngas.     

Catalytic activity of nickel(II), copper(II) and oxovanadium(II)‐dihydroindolone complexes towards homogeneous oxidation reactions

Three novel paramagnetic metal complexes (MH₂ID) of Ni²⁺, Cu²⁺ and VO²⁺ ions with 3‐hydroxy‐3,3’‐biindoline‐2,2’‐dione (dihydroindolone, H₄ID) were synthesized and characterized by different spectroscopic methods. The ligand (H₄ID) was synthesized via homocoupling reaction of isatin in presence of phenylalanine in methanol. Complexation of low valent Ni²⁺, Cu²⁺ ions and high valent VO²⁺ ions with H₄ID carried out in 1: 2 molar ratios. A comparison in the catalytic potential of paramagnetic complexes of low and high valent metal ion was explored in the oxidation processes of cis‐cyclooctene, benzyl alcohol and thiophene by an aqueous H₂O₂, as a green terminal oxidant, in the presence and absence of acetonitrile, as an organic solvent, at 85 °C. NiH₂ID, CuH₂ID and VOH₂ID show good catalytic activity, i.e. good chemo‐ and regioselectivity. VOH₂ID has the highest catalytic potential compared to both Ni²⁺‐ and Cu²⁺‐species in the same homogenous aerobic atmosphere. Catalytic oxidation of other alkenes and alcohols was also studied using NiH₂ID, CuH₂ID or VOH₂ID as a pre‐catalyst by an aqueous H₂O₂. A mechanistic pathway for those oxidation processes was proposed.     

A DFT study of H2O dissociation on metal‐precovered Fe (100) surface

The H₂O adsorption and dissociation on the Fe (100) surface with different precovered metals are studied by density functional theory. On both kinds of metal‐precovered surface, H₂O molecules prefer adsorb on hollow sites than bridge and top sites. The impurity energy difference is proportional to the adsorption energy, but the adsorbates are not sensitive to the adsorption orientation and height relative to the surface. The Hirshfeld charge analysis shows that water molecules act as an electron donor while the surface Fe atoms act as an electron acceptor. The rotation and dissociation of H₂O molecule occur on the Co‐ and Mn‐precovered surfaces. Some H₂O molecules are dissociated into OH and H groups. The energy barriers are about 0.5 to 1.0 eV, whose are consistence with the experimental data. H₂O molecules can be dissociated more easily at the top site on Co‐precovered surface 1 than that at bridge site on Mn‐precovered surface 2 because of the lower reaction barrier. The dispersion correction effects on the energies and adsorption configurations on Co‐precovered surface 1 were calculated by OBS + PW91. The dispersion contributions can improve a bit of the bond energy of adsorbates and weaken the hydrogen bond effect between adsorption molecules a little.