Uranyl chelates of phthalic acid and its substituted derivatives

The interactions of uranyl ion with phthalic acid and 3-chloro, 3-bromo, 3-iodo, 3-nitro, 4-nitro and 3 : 6-dichloro phthalic acids have been investigated by the Calvin-Bjerrum titration technique. The stability constants of these complexes have been determined at 30°C at 0.1 M (NaClO₄) ionic strength. Uranyl ion forms 1 : 1 complexes with all the ligands, while a 1 : 2 complex is formed only with phthalic acid. All the 1 : 1 uranyl complexes except those of 3 : 6-dichloro and 3-iodo phthalic acids follow the relationship log K = apk + b. The deviation of the two chelates from the linear relationship is explained on the basis of steric effects and L → M π-bonding.     

Mixed ligand complex formation of copper(II) and zinc(II) ions with 3-hydroxynaphthoate and picolinate ions as ligands in dioxane-water mixtures

Cu(II)-hydroxynaphthoate-picolinate and Zn(II)-hydroxynaphthoate-picolinate ternary systems were studied in dioxane-water (1 : 1, ν/ν) solutions at a 0.2 mol dm⁻³ ionic strength and 25°C. From EMF data the mixed ligand complexes M(hna)(pic) for M = Cu(II) and Zn(II) and M(hna)(pic)₂ for M = Zn(II) were detected and their formation constants evaluated (log K_f = 18.94± 0.03, 18.09±0.08 and 23.4±0.07, respectively). Factors contributing to the stabilization of these complexes are discussed and optimum experimental conditions for their predominance established.     

Adduct formation of copper(II) chelates of 1-hydroxypyrazole 2-oxides with substituted pyridines

Equilibrium constants have been determined for the adduct formation of 10 copper(II) chelates of the derivatives of 1-hydroxypyrazole 2-oxide with nine substituted pyridines at room temperature in chloroform solution. These adducts were shown to have 1:1 stoichiometry. All the stabilities of the adducts were governed by: (1) σ-donating ability of the nitrogen atom in the substituted pyridines to the copper(II) chelates, (2) electron-attracting forces of substituents at the 3- and 4-positions of the phenyl ring in the chelate ligands, and (3) the magnitude of the polar substituent constant of the substituents in the pyrazole ring of the chelate ligands.     

Bis(perfluoroalkyl and aryl substituted acetylacetonate)beryllium(II) chelates

The synthesis of eight beryllium chelates having substituted beta-diketone ligands, RCOCH₂COR′, is reported (R=methyl, 2′-thienyl, 2′- furyl, phenyl; R′=CF₃, C₂F₅, C₃F₇). ¹³C, ¹⁹F and ¹H NMR spectra data are compared to give a shielding order. These four-coordinate pseudo- tetrahedral complexes of idealized C₂ symmetry all give a more deshielded ring carbon than the corresponding ring carbon resonances of the same ligand in four-coordinate square planar complexes. Some dipole moment data are also presented.     

Studies on mononuclear chelates derived from substituted Schiff-base ligands (part 6): synthesis and characterization of a new 3-ethoxysalicyliden- p -aminoacetophenoneoxime and its complexes with cobalt(II), nickel(II), copper(II) and zinc(II)

Schiff-base complexes of cobalt(II), nickel(II), copper(II) and, zinc(II) with 3-ethoxysalicyliden-p-aminoacetophenoneoxime (HL) were prepared and characterized on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, electronic spectra, magnetic susceptibility measurements, molar conductivity and thermogravimetric analyses (TGA). A tetrahedral geometry has been assigned to the complexes.     

Iron(II), cobalt(II), nickel(II) and copper(II) chelates of 1,1′-Dibenzoylacetylferrocene

Summary 1,1-Dibenzoylacetylferrocene (DBAFc) complexes of iron(II), cobalt(II), nickel(II) and copper(II) have been prepared and characterized. The physical properties of the complexes are discussed on the basis of uv-visible, Mössbauer spectra and magnetic measurements.     

Potentiometric study of the protonation and binary complexation equilibria between the hydrogen ion,copper(II) ion and zinc(II) ion and the picolinate ion in dioxane-water mixtures

Protonation constants of picolinic acid and stability constants of Cu(II) and Zn(II) picolinate complexes were determined potentiometrically in 50% (v/v) dioxane-water solution at 25°C and 0.2 M KNO₃. The values obtained for the constants were: protonation constants for picolinate ion: logβ₁ = 5.36±0.01 and logβ₂ = 6.80±0.04; stability constants for copper(II) complexes: logβ_1.1 = 7.766±0.001 and logβ_1.2 = 16.826±0.007; stability constants for the Zn(II) complexes: logβ_1.1 = 6.10±0.05, logβ_1.2 = 11.47±0.03 and logβ_1.3 = 15.77±0.08. No protonated nor hydroxo-complex was detected in the metal ion-picolinate systems.     

Studies on bis (cyclopentadienyl) titanium (IV) chelates of biologically active O-hydroxynaphthoquinone and its derivatives

A convenient method for the preparation of Cp₂Ti(L) complexes, where Cp is cyclopentadienyl and L is the conjugate base of O-hydroxynaphthoquinone or its derivatives, has been described. The new complexes have been characterized on the basis of chemical analysis, infrared and NMR spectral studies. These studies indicate that the complex is formed in 1:1 ratio and the ligand L chelates through the oxygen of the O-hydroxy group.     

Complexing between copper(II) and bulky substituted 3-benzoyl thioureas in copper(II) hexacyanoferrate(II) gelatin-immobilized matrix systems

A novel route to complexes of CuII with various bulky substituted 3-benzoylthioureas: [(1-(2-hydroxy)phenyl-, 1-(4-hydroxy)phenyl-, 1,1-dibenzyl-, 1-methyl-1-phenyl-, 1-N-pentamethylene-] and 1-N-3-oxatetramethylene-3-benzoylthiourea, complexed to a CuII hexacyanoferrate- (II) gelatin-immobilized matrix in contact with aqueous alkali (pH 12.0) solutions of the ligands indicated, has been developed. Under the conditions specified, coordination of each ligand is preceded by decomposition of CuII-hexacyanoferrate(II) to give polymeric copper(II) hydroxide under the influence of OH– ions. With CuII-1-(4-hydroxy)phenyl-3-benzoylthiourea, three different water-insoluble coordination compounds are formed; in the other CuII-ligand systems, two types of complexes are formed, whereas complexing in solution or solid phase in these systems results, as a rule, in the formation of only one coordination compound. In systems such as CuII-1-naphthyl-3-benzoylthiourea, CuII-1-(4-hydroxy-3,5-di-t-butyl)benzyl-3-benzoylthiourea and CuII-1-(4-hydroxy-3,5-di-t-butyl) phenethyl-3-benzoylthiourea, complexing in CuII hexacyanoferrate(II) gelatin-immobilized matrices (GIM) is not observed.     

Iron(II), cobalt(III), nickel(II) and copper(II) chelates of furan and thiophene azo-oximes

Summary Complexes of furan and thiophene azo-oximes with iron(II), cobalt(III), nickel(II) and copper(II) have been prepared and characterised. Iron(II), cobalt(III) and copper(II) complexes are diamagnetic in the solid state. The diamagnetism of the copper(II) chelates is suggestive of antiferromagnetic interaction between two copper centres.¹H n.m.r. spectral data suggest atrans-octahedral geometry for the tris-chelates of cobalt(III). Nickel(II) complexes are paramagnetic, in contrast to the diamagnetism of the analogous complexes of arylazooximes. The electronic spectra are suggestive of octahedral geometry for the iron(II), cobalt(III) and nickel(II) complexes, andD _4h -symmetry for copper(II). Infrared data indicate N-bonding of the oximino-group to the metal ions.     

Synthesis and characterization of organometallic thio-Schiff bases and their copper(II) chelates

Summary Four organometallic thio-Schiff base ligands derived from ferrocene of general formula C₅H₅FeC₅H₄CR=NNHCSSR' (R = H or Me, R = Me or CH₂Ph) (HL), and their copper(II) chelates [CuL₂] and [Cu(HL)₂]Cl₂, were prepared and characterized by physicochemical and spectroscopic methods. The thio-Schiff bases act as bidentate ligands and coordinate to copper(II) in the enolic form in EtOH and in the keto form in THF.     

Metal benzoylpivaloylmethanates. Part II. 1,4-dioxane adducts of copper(II) chelates

Summary 1 : 1 Dioxane adducts of Copper(II) chelates withpara-subtituted benzoylpivaloylmethanes have been synthesized and their u.v., vis., i.r., mass, e.p.r. spectra as well as their magnetic moments and thermal stabilities investigated. Powdered samples of undiluted magnetically adducts were found to give well resolved e.p.r. spectra; the (S = 1) g_| signal being split into nine lines. Magnetic susceptibilities measured down to 4 K did not reveal exchange interactions. The uncommon structure of the e.p.r. spectra is believed to be due to the dimeric structure of the adduct in which an interion dipolar zero-field splitting of the triplet state occurs. The Cu-Cu distance estimated from the e.p.r. D_dd parameter is found to be 7.4 Å.     

Synthesis and spectral studies of novel copper(II) chelates of sulphur-containing oximes

Summary Copper complexes of benzil--monoxime-2-iminoethanethiol (BMETH₂), benzil--monoxime-2-iminobenzenethiol (BMBTH₂), benzil--monoximethiosemicarbazone (BMTH₂) and benzil--monoximesemicarbazone (BMSH₂) were synthesized and characterized by physicochemical and spectroscopic measurements. The molar conductivities show that all of the complexes are nonelectrolytes. The i.r. spectra suggest that the ligands are tetradentate in all cases, whilst the electronic spectra suggest planar geometries for all the complexes. The calculated e.s.r. parameters show an axial dx ² - y ² ground state and suggest coordination through sulphur, in agreement with the i.r. results. In all of these complexes, the =N—;O group acts as a bridging function to give dimeric structures.     

Synthesis and liquid crystal properties of copper(II) and palladium(II) chelates with new ferrocene-containing enaminoketones

Heterometallic liquid crystals are of special interest because of the possibility to combine optical, magnetic and electric properties of different metal ions in one mesogenic molecule. In order to investigate new heteropolynuclear mesogenic systems, a series of β-aminovinylketone ligands derived from acetyl ferrocene have been synthesized. Subsequently Cu(II) and Pd(II) ions were incorporated into the enaminoketone chelate core. The obtained ligands and complexes were characterized by element analysis, ¹H NMR, IR and UV–Vis spectroscopies. According to thermal polarizing microscopy and DSC studies, the ligands and Cu(II) complexes exhibit disordered soft crystal phases upon cooling from the isotropic liquid state. The Pd(II) complexes showed monotropic smectic C mesomorphism. The metal centres in the synthesized heteropolynuclear mesogens are in close vicinity to each other, which is of considerable interest from the viewpoint of the potential electron-transfer interactions between a ferrocene core and the central ions.     

Studies on mononuclear chelates derived from substituted Schiff-base ligands (part 2): synthesis and characterization of a new 5-bromosalicyliden- p -aminoacetophenoneoxime and its complexes with Co(II), Ni(II), Cu(II) and Zn(II)

In this study, 5-bromosalicyliden-p-aminoacetophenoneoxime (LH) was synthesized starting from p-aminoacetophenoneoxime and 5-bromosalicylaldehyde. Complexes of this ligand with Co^+?2, Ni^+?2, Cu^+?2 and Zn^+?2 were prepared with a metal?:?ligand ratio of 1?:?2. Their structures have been elucidated on the basis of elemental analyses, IR, ¹H and ¹³C NMR spectra, electronic spectra, magnetic susceptibility measurements, molar conductivity and thermogravimetric analyses (TGA).     

Differential pulse polarographic behaviour of copper(II)-ethyleneglycol-bis-(2-aminoethylether)-tetraacetate and copper(II)-ethylenediaminetetraacetate chelates in the presence of Lanthanum(III)

Summary The substitution reduction waves of copper(II)-EGTA and copper(II)-EDTA chelates were investigated with differential pulse and tast polarographic methods. The reduction wave of copper(II)-EGTA chelate shifts to more positive potential in the presence of lanthanum(III) and a new differential pulse peak appears. The peak height increases linearly with increasing concentration of lanthanum(III) between 5 and 25 M. When the copper(II)-EDTA chelate is reduced in a supporting electrolyte containing no buffer solution, lanthanum(III) gives a substitution reduction peak, but in acetate buffer solution the lanthanum(III) peak disappears.

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Differential-Puls-Polarographisches Verhalten des Kupfer(II)-Ethylenglykol-bis-(2-aminoethylether)-tetraacetat-Chelats und des Kupfer(II)-Ethylendiamintetraacetat-Chelats in Gegenwart von Lanthan(III)

Zusammenfassung Die Substitutionsreduktionswellen des Kupfer(II)-EGTE- und des Kupfer(II)-EDTE-Chelats wurden mit Hilfe der Differential-Puls- und der Tast-Polarographie untersucht. Die Reduktionswelle des Kupfer(II)-EGTE-Chelats verschiebt sich in Gegenwart von Lanthan(III) zu positiverem Potential und ein neuer Differential-Puls-Peak erscheint. Die Peakhöhe nimmt mit steigender Lanthanionkonzentration zwischen 5 und 25 M linear zu. Wenn Kupfer(II)-EDTE-Chelat im pufferfreien Leitelektrolyt reduziert wird, gibt Lanthan(III) einen Substitutionsreduktions-Peak, in Acetat-Pufferlösung jedoch verschwindet der Lanthan(III)-Peak.