The crystal chemistry of copper(II) dipicolinates

The molecular structure of a new copper dipicolinate, Cu(dipic)(H₂dipic)·H₂O, and a refinement of the previously reported Cu(dipic)(H₂dipic)·3H₂O are presented. The Jahn-Teller effect, as operative in six-coordinated Cu^II surrounded by two planar tridentate ligands, is responsible for the presence of a dianion and a neutral acid molecule in the structure. As opposed to previously reported copper dipicolinates, water molecules do not coordinate and in the trihydrate dehydration is facile because interstital water finds easy dehydration pathways; the mechanism involves nucleation and fast bidimensional growth. The monohydrate, however, presents tightly bound (through hydrogen bonds) water and no easy dehydration pathways are available; the dehydration mechanism involves fluid-flux nucleation, mediated by fusion. Five different copper(II) dipicolinates are known; because of the strong tendency of this ligand to form tridentate mononuclear complexes, all of them, except monoclinic Cu(dipic)·2H₂O, belong to the class of molecular solids. In the monoclinic dihydrate, carbonyl O atoms are involved in defining chains that run parallel to [001] planes.     

Kinetics and mechanism of the reduction of 1,10-phenanthroline—copper(II) complex

The cyclic voltammetric study of 1,10-phenanthroline—copper(II) complex was carried out in acidic buffer solution. It was found from the current—mole ratio (copper (II): 1,10-phenanthroline) relationship that the maximum coordination number of 1,10-phenanthroline—copper(II) complex was four under the present experimental condition. The reduction mechanism and kinetics of copper(II) was studied in the presence of various concentrations of 1,10-phenanthroline.     

The formation of mixed copper(II) sulfide—silver(I) sulfide membranes for copper(II)-selective electrodes

Several methods for the preparation of mixed copper(II) sulfide—silver(I) sulfide precipitates have been investigated. Pellets of these materials have been tested for their suitability as copper(II)-selective membranes. Homogeneous membranes with satisfactory electrochemical properties can be prepared only from precipitates obtained by addition of the metal salts to sodium sulfide Membrane leakages, limits of detection, calibration curves and titration curves with different types of precipitate are discussed.     

Two-dimensional carboxylate bridged network of europium(III)-transition metal(II) glutarate compounds

Four new heterometallic glutarate coordination polymers, [Eu2M(H2O)4][O2C(CH2)3CO2]4.2H2O (M = Mn (1), Fe (2), Co (3) and Ni (4)) have been obtained under hydrothermal synthesis. The single-crystal X-ray diffraction analyses showed that they have two-dimensional frameworks based on the linear polyhedral chains consisting of two nine-coordinated Eu(III)O9 and a six-coordinated M(II)O6. These 1-D MO6-Eu2O16 chains are cross-linked by glutarate ligands as an interchain pillared architecture, whose conformations vary depending upon the transition metals. The magnetic behavior of the compounds show a weak antiferromagnetic interaction, in which shielding of the 4f electrons by the outer shell electrons effectively precludes significant coupling interactions between the Eu-4f electrons and transition metal (M)-3d electrons.     

Preparation and study of bis(theophyllinato) copper(II) compounds

Bis(theophyllinato) copper(II) dihydrate and its anhydrous form, were prepared. Their thermal, spectral and magnetic behaviours were investigated. Magnetic susceptibility studies show that the dihydrate form can be fitted to the Curie law. The magnetic behaviour of the anhydrous form is interpreted in terms of antiferromangetically exchange-coupled pairs of copper atoms. The change in magnetic properties as the dihydrate is dehydrated implies that structural rearrangement in first coordination sphere of copper accompanies the dehydration process. For bis(theophyllinato)copper(II) dihydrate we propose a pseudo octahedral coordination of copper(II) in a polymeric chain, and for the anhydrous form four-coordination in binuclear units.     

Coordination compounds of copper(II) with substituted 3-{[(2-hydroxyphenyl)methylidene]amino}propane-1,2-diols

3-{[(2-Hydroxyphenyl)methylidene]amino}propane-1,2-diol, its 5-chloro-,5-bromo-, 5-nitro-, 3-methoxy derivatives, and 3-{[(2-hydroxynaphthyl-1)methylidene]amino}propane-1,2-diol react with hydrates of copper(II) chloride, bromide and nitrate in ethanol to form coordination compounds Cu(L)X·nH₂O. Template condensation reaction between 3-aminopropane-1,2-diol and 2,3-, 2,4- or 2,5-dihydroxybenzaldehyde in the presence of copper(II) nitrate trihydrate results in similar compounds Cu(L)NO₃·nH₂O. Structure of some of the condensation products was identified by X-ray analysis. Thermolysis of the substances obtained occurs through the dehydration step (70–90°C) and complete thermal decomposition (290–560°C).     

Thermal decompositions of formates. Part VI. Thermal dehydration reaction of copper(II) formate dihydrate

The thermal dehydration reactions of two kinds of copper(II) formate dihydrate, which differ in origin and preparation history, have been investigated by means of TG, DTA and DSC. The kinetics of isothermal dehydration were studied by weight loss, and the difference in kinetic behavior between these two samples was related to the difference in origin and preparation history. On the whole, the dehydration mechanisms of these two samples were found to be phase boundary controlled contracting interface reactions.     

Extraction of lead(II) and copper(II) from salicylate media by tributylphosphine oxide.

Tributylphosphine oxide (TBPO) is proposed as an extractant for the extraction of lead(II) and copper(II) from salicylate media. The optimum conditions were evaluated by varying the experimental parameters, such as the pH, sodium salicylate concentration, tributylphosphine oxide (TBPO) concentration, shaking period and various diluents. The probable extracted species, deduced from log-log plots were Pb(HSal)2.2TBPO and Cu(HSal)2.2TBPO. The extraction took place through a solvation mechanism. The method permits the binary separation of lead(II) and copper(II) from commonly associated elements as well as the mutual separation of lead(II) and copper(II). The method is applicable to the determination of lead(II) and copper(II) in various alloys as well as environmental and pharmaceutical samples.     

Deaquation and denitration studies on copper nitrate trihydrate

Previous studies on the thermal degradation of copper nitrate trihydrate have been reviewed. These indicate that the conditions used strongly influence the processes involved. The degradation has been studied here using slow heating rates and in vacuum, so reducing these effects. Possible mechanisms using these conditions have been discussed, using data for the degradation of the ammine complex to supplement the study.     

Thermal studies on nickel(II) and copper(II) complexes of monoethanol- and diethanol-dithiocarbamic acids

Thermoanalytical data (TG/DTA) have been obtained for bis-monoethanoldithiocarbamato nickel(II) and bis-diethanoldithiocarbamato nickel(II) and copper(II) complexes. A thermal decomposition mechanism is proposed for bis-monoethanoldithiocarbamato nickel(II).     

Thermal investigation of bis(methoxy-β-diketonates) of copper(II) — novel CVD precursors of copper films. Crystal structure of bis(2,2,6,8-tetramethyl-6-methoxynonan-3,5-dionato)copper(II)

Seven copper(II) bis-chelates derived from novel sterically hindered ligands — methoxy-β-diketones     

On the preparation of copper sulphate trihydrate by a derivatograph

Copper sulphate trihydrate was prepared by dehydration from the pentahydrate sulphate by quenching the latter compound from the Derivatograph from 90 ?C to room temperature.     

Kinetics of reduction of copper(II) by sodium tetrahydroborate

Summary The kinetics of reduction of copper(II) ion by sodium tetrahydroborate in buffered aqueous solution have been investigated. The rate of the reaction is first order in the concentrations of each of the reactants. The activation parameters were evaluated and a plausible mechanism for the reduction of copper(II) ion is proposed.     

Tetraalkoxyaluminates of nickel(II), copper(II), and copper(I)

The syntheses and structural details of tetraisopropoxyaluminates and tetra-tert-butoxyaluminates of nickel(II), copper(I), and copper(II) are reported. Within the nickel series, either Ni[Al(OiPr)4]2.2HOiPr, with nickel(II) in a distorted octahedral oxygen environment, or Ni[Al(OiPr)4]2.py, with nickel(II) in a square-pyramidal O4N coordination sphere, or Ni[(iPrO)(tBuO)3Al]2, with Ni(II) in a quasi-tetrahedral oxygen coordination, has been obtained. Another isolated complex is Ni[(iPrO)3AlOAl(OiPr)3].3py (with nickel(II) being sixfold-coordinated), which may also be described as a "NiO" species trapped by two Al(OiPr)3 Lewis acid-base systems stabilized at nickel by three pyridine donors. Copper(I) compounds have been isolated in three forms: [(iPrO)4Al]Cu.2py, [(tBuO)4Al]Cu.2py, and Cu2[(tBuO)4Al]2. In all of these compounds, the aluminate moiety behaves as a bidentate unit, creating a tetrahedrally distorted N2O2 copper environment in the pyridine adducts. In the base-free copper(I) tert-butoxyaluminate, a dicopper dumbbell [Cu-Cu 2.687(1) A] is present with two oxygen contacts on each of the copper atoms. Copper(II) alkoxyaluminates have been characterized either as Cu[(tBuO)4Al]2, {Cu(iPrO)[(iPrO)4Al]}2, and Cu[(tBuO)3(iPrO)Al]2 (copper being tetracoordinated by oxygen) or as [(iPrO)4Al]2Cu.py (pentacoordinated copper similar to the nickel derivative). Finally, a copper(II) hydroxyaluminate has been isolated, displaying pentacoordinate copper (O4N coordination sphere) by dimerization, with the formula {[(tBuO)4Al]Cu(OH).py}2. The formation of all of these isolated products is not always straightforward because some of these compounds in solution are subject to decomposition or are involved in equilibria. Besides NMR [copper(I) compounds], UV absorptions and magnetic moments are used to characterize the compounds.     

Reactivity of mononuclear alkylperoxo copper(II) complex. O-O bond cleavage and C-H bond activation

A detailed reactivity study has been carried out for the first time on a new mononuclear alkylperoxo copper(II) complex, which is generated by the reaction of copper(II) complex supported by the bis(pyridylmethyl)amine tridentate ligand containing a phenyl group at the 6-position of the pyridine donor groups and cumene hydroperoxide (CmOOH) in CH3CN. The cumylperoxo copper(II) complex thus obtained has been found to undergo homolytic cleavage of the O-O bond and induce C-H bond activation of exogenous substrates, providing important insights into the catalytic mechanism of copper monooxygenases.     

The dehydration of copper(II) acetate monohydrate

The thermal dehydration of copper(II) acetate hydrate has been studied between 353 and 406 K, over a range of humidities. The dehydration is controlled by nucleation-and-growth kinetics at low temperatures, with an activation energy of 154 kJ·mol⁻¹, which changes to contracting-disc kinetics at higher temperatures with a lower activation energy of 76 kJ·mol⁻¹. Frequency factors have also been derived; the value for the high temperature process is low (10⁷s⁻¹) and that for the low temperature step is high (10¹⁷s⁻¹). Optical microscopy has been used to clarify the bulk kinetics; there is evidence for a reactive layer at the surface of the decomposing solid. In celebration of the 60^th birthday of Dr Andrew K. Galwey     

The benzoyloxylation of norbornadiene and homologues by copper(III) and copper(II) benzoate complexes

Oxidation of norbornadiene and benzonorbornadiene by copper(III) and copper(II) benzoate complexes in pyridine gave the corresponding 7-benzoyloxy derivatives. The proposed mechanism suggests two single-electron oxidations by copper(III) and/or copper(II).     

Kinetics and mechanism of copper(II) induced decomposition of 9-diazofluorene

The kinetics and products of the decompositon of 9-diazofluorene by copper(II) tetrafluoroborate in acetonitrile solvent have been investigated. The reaction is first order with respect to both 9-diazofluorene and copper(II) tetrafluoroborate. A reaction mechanism has also been proposed.     

Thermal degradation, dielectric and magnetic studies on copper tartrate trihydrate crystals

Single crystals of copper tartrate trihydrate (CTT) with orthorhombic structure were grown in silica gel medium, by the controlled chemical reaction method. The Fourier transform infrared spectrum in the range 400–4,000 cm^?1 were recorded and the vibrational bands corresponding to different functional groups are assigned. Thermal stability of the grown crystals was investigated by differential thermal analysis, thermogravimetric and differential scanning calorimetry studies. The presence of water molecules and the dehydration stages are discussed. The dielectric studies on CTT crystals were performed in the frequency range of 100–5 MHz at three different temperatures which indicated that the dielectric constant decreases with frequency and increases with temperature. The ac conductivity is found to increase with frequency and temperature. The vibrating sample magnetometer studies on these crystals confirmed the diamagnetic nature of the CTT crystals.     

The electrochemical reactions of copper(II) and copper(I) chloride in n,n-dimethylformamide

Polarographic, voltammetric and controlled-potential coulometric studies of copper(II) and copper(I) chloride in dimethylformamide are reported. The two chloride complexes of copper(II) are reduced in a total of three electrochemical steps to two copper(I)-chloride complexes and to copper(0). The two copper(I)-chloride species are reduced to copper(0) and oxidized to copper(II)-chloride complexes. The dissociation constant of the tetrachlorocuprate(II) complex has been polarographically estimated to be 10^-25.