2-thiouracil-based cobalt(II), nickel(II) and copper(II) complexes

Summary Cobalt(II), nickel(II) and copper(II) complexes of 2-thiouracil and its arylazo derivatives were prepared. The elemental analysis suggest a range of 11, 21 and 13 stoichiometries. Electronic spectra and magnetic susceptibility measurements were used to infer the structures and the i.r. spectra of the ligands and their complexes to identify the type of bonding.     

Metal complexes of 1-hydroxy-2,3-dimethyl-4-(3′-methyl-4′-amino-5′-mercapto-1′, 2′, 4′-triazole)-1,4-diaza-1, 3-butadiene with manganese(II), cobalt(II), nickel(II) and copper(II)

Summary Binuclear metal complexes of the type [M(HDDB)-(H₂O)₂]₂: where HDDB=1-hydroxy-2,3-dimethyl-4-(3-methyl-4-amino-5-mercapto-1, 2, 4-triazole)-1,4-diaza-1, 3-butadiene and M=manganese(II), cobalt(II), nickel(II) and copper(II), have been prepared and characterised by elemental and thermal analyses, magnetic measurements, electronic and i.r. spectra. Octahedral geometry around the metal(II) ions is proposed and the crystal field parameters of the cobalt(II) and nickel(II) complexes are also calculated. Fungicidal screening of the complexes has been made aginstHelminthosporium oryzae andFusarium oxysporium.     

Complexes with diimine ligands. Syntheses and magnetic behaviour of dinuclear complexes of copper(II), nickel(II) and cobalt(II) with 2,5-bis(2-pyridyl)pyrazine

Summary The synthesis, characterization and voltammetric and magnetic behaviour of a series of dinuclear complexes -(2,5-DPP)[M(hfacac)₂]₂, in which hfacac is hexafluoro-acetylacetonate, 2,5-DPP is 2,5-bis(2-pyridyl)pyrazine and M = copper(II), nickel(II) and cobalt(II), are described. As with the dinuclear complexes derived from 2,3-bis(2-pyridyl)-pyrazine (2,3-DPP) and analogous ligands, magnetic measurements show that these systems are not coupled. On the basis of magnetic data, we propose that, in contrast to related ligands such as 2,2-bipyridyl, the coordinated 2,5-DPP cannot be planar.     

New complexes of iron(II), cobalt(II), nickel(II) and copper(II) with 2,2′-dipyridylmethane

Summary 2,2-Dipyridylmethane reacts with iron(II), cobalt(II), nickel(II) and copper(II) salts to form complexes of a varied stereochemistry depending upon the metal and the anion involved,Pseudo-tetrahedral, octahedral and square-planar complexes containing this ligand have been prepared and characterized by elemental analysis, conductivity data, room temperature magnetic moments and electronic spectra.     

Synthesis and spectral studies of chromium(III), cobalt(II) and nickel(II) complexes with phenylhydrazonoamidoxime

Summary Mononuclear complexes of chromium(III), nickel(II) and cobalt(II) derived from 3-oxo-2-phenylhydrazonobutane1-carbamidoxime (OPCA) were prepared and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements and electronic and i.r. studies. The chromium(III) and nickel(II) ions form 1:2 complexes, whereas cobalt(II) forms a 1:1 complex in which the ligand chelates through the nitrogen of the amidoxime and the carbonyl oxygen. An octahedral structure is assigned to these complexes and the ligand field parameters such as Dq, B and were calculated. The nephelexautic parameter, , has values of 0.68, 0.84 and 0.78 for the chromium(III), cobalt(II) and nickel(II) complexes, respectively, suggesting the presence of covalent metal-ligand -bonds.     

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.     

Copper(II), nickel(II), cobalt(II) and oxovanadium(IV) complexes of 1-(3-hydroxy-2-naphthyl)-5-(p-X-phenyl)pent-4-ene-1,3-diones

Complexes of 1-(3-hydroxy-2-naphthyl)-5-(p-X-phenyl)pent-4-ene-1, 3-diones (HXNP) (X = H, Cl, Me or OMe) with divalent metal ions, having the formula M(HXNP)2 (M = Cu, Ni or Co) and M(HXNP)2 · nB (n = 0,2: B = H2O or Py), have been prepared and characterized by elemental analyses, i.r., electronic, 1H-n.m.r. and e.s.r. spectroscopies and by magnetic susceptibility measurements. Spectral assignments show the metal ions to be coordinated through both carbonyl oxygen atoms and the effect of conjugation of the ligand structure (d–* interaction) is strong enough to stabilize the metal ligand bond. The observed hyperfine splitting constants and magnetic moments suggest that the copper complexes are monomers with a slightly distorted planar structure, having more covalent in plane -bonding. The magnetic and spectral properties of the dihydrates and dipyridinates of the cobalt and nickel complexes are commensurate with monomeric high-spin octahedral geometries; polymerization takes place on dehydration–depyridination of nickel(II) complexes. Oxovanadyl complexes of these -diketones have also been prepared; the ligand-to-metal ratio is 2:1 with square pyramidal geometry. The e.s.r. spectra of the complexes show the presence of one unpaired electron in the dxy orbital and the hyperfine splitting constants are sensitive to a change in solvent. The effect of bases on the redox behaviour of copper(II) complexes owing to geometry change is discussed.     

Synthesis and characterization of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with acetylacetone bis-benzoylhydrazone and acetylacetone bis-isonicotinoylhydrazone

Summary Acetylacetone bis-benzoylhydrazone (PhCONHN=CMe)₂ CH₂(LH₂) and acetylacetone bis-isonicotinoylhydrazone (NC₅H₄CONHN=CMe)₂CH₂(LH₂) complexes of the types [ML] and [ML] (M = Co^II, Ni^II, Cu^II or Zn^II) have been prepared and characterized. All the complexes are non-electrolytes and the cobalt(II) complexes are lowspin, the nickel(II) complexes are diamagnetic and the copper(II) complexes are paramagnetic. The ligands chelate via two C=N groups and two deprotonated enolate groups. The e.s.r. spectra of the copper(II) complexes indicate a tetragonally distorted dimeric structure. The X-ray diffraction parameters for [CoL] and [NiL] correspond to a tetragonal crystal lattice.     

Cobalt(II), nickel(II) and copper(II) complexes of bidentate bibenzimidazoles

Summary Complexes of cobalt(II), nickel(II) and copper(II) with novel bidentate bibenzimidazoles, [M(L-L)Cl₂], where L-L are methylenebis(1, 1-benzimidazole), methylenebis(2, 2-benzimidazole) and dimethylenebis(2, 2-benzimidazole) are described and characterized by different physical measurements. The four coordinate complexes have distorted tetrahedral or square coplanar structures. The bridging entity between the two donor groups apparently influences the ligand field strength and the ligands occupy a higher position than that of benzimidazole in the spectrochemical series.     

Cobalt(II) and nickel(II) chloride complexes with some 2-(4′-Methyl-2′-pyridyl and 2′- or 8′-quinolyl)benz-X-azoles

Summary Complexes of general formula ML_mCl₂ · nH₂O, where M=cobalt(II) or nickel(II); L=2-(4-methyl, 2-pyridyl)-benzimidazole (mpbi), 2-(4-methyl, 2-pyridyl)benzothiazole (mpbt), 2-(4-methyl, 2-pyridyl)benzoxazole (mpbo), 2-(4-methyl, 2-quinolyl)benzoxazole (mqbo), or 2-(4-methyl, 8-quinolyl)benzoxazole (mqbo); m=1,2; n=0–3, were prepared and characterized by t.g.a., conductance and magnetic measurements, i.r. and diffuse-reflectance electronic spectra.All the ligands behave as bidentate and coordinate through the pyridine- and isoxazole-nitrogen atoms.The nickel complexes have distorted octahedral or fivecoordinate structures. The cobalt complexes arepseudo-tet- rahedral except Co(mpbo)₂Cl₂·2H₂O where the metal is six-coordinate.     

Morpholine complexes of copper(II) alkanoates and chloroacetates

Summary Morpholine complexes of copper(II) alkanoates and chloroacetates of formula Cu(O₂CR)₂(Morph)_n (where R = H, Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, CH₂Cl, CHCl₂ and CCl₃; Morph = Morpholine and n=1 and/or 2) have been isolated by the direct interaction of morpholine with the respective copper(II) carboxylates in a suitable organic medium and characterized by elemental analyses and various physicochemical techniques. Molecular weight determinations show that 11 complexes are dimeric whereas 21 complexes are monomeric in solution. Electronic spectra and magnetic moments suggest that 11 complexes are dinuclear carboxylate bridged species while 21 addition complexes have atrans-octahedral configuration. The i.r. spectra indicate that morpholine behaves as a monodentate ligand and coordinates through its nitrogen atom.     

Synthesis and characterization of barbituric and thiobarbituric acid complexes

Summary Synthesis of barbituric and thiobarbituric acid complexes derived from cobalt(II), nickel(II) and copper(II) salts were carried out. The elemental analyses suggest a range of stoichiometries, 11, 12 and 13. Electronic spectra and magnetic susceptibility measurements were used to infer the structures. The i.r. spectra of the ligands and their complexes are used to identify the type of bonding.     

Study of the complex formation between 4, 6-diamine-1, 2-dihydro-2-thiopyrimidine and cobalt(II), cobalt(III), nickel(II) and copper(II) ions

Summary Reactions of 4, 6-diamine-1, 2-dihydro-2-thiopyrimidine (HDATP) with cobalt(II), nickel(II) and copper(II) ions in 12 metal:ligand ratio in aqueous media at 25°C and 0.1 M ionic strength (KNO₃), lead to the formation of both [M(DATP)]⁺ and [M(DATP)₂] species, whose stability constants were obtained.On the other hand, in aqueous or ethanolic media, solid complexes with 11, 12, or 13 stoichiometries were isolated. These have been characterized by analytical, i.r. and electronic spectral and magnetic measurement studies, and tentative structures are proposed.     

Thermal decomposition kinetics of vanillidene anthranilic acid complexes of cobalt(II), nickel(II), copper(II) and zinc(II)

The thermal decomposition of cobalt(II), nickel(II), copper(II) and zinc(II) complexes of the Schiff base vanillidene anthranilic acid was studied by TG. The chelates show somewhat similar TG plots when heated in an atmosphere of air. Thermoanalytical data (TG and DTG) of these chelates are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the differential method employing the Freeman-Carroll equation, the integral method using Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. On the basis of experimental findings in the present course of studies, it is concluded that the relative thermal stability of vanillidene anthranilic acid chelates can be aligned as Co(II)Ni(II)>Zn(II)>Cu(II).

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Zusammenfassung Die thermische Zersetzung von Cobalt(II)-, Nickel(II)-, Kupfer(II)- und Zink(II)-Komplexen der Schiffschen Base Vanillidenanthranilsäure wurde thermogravimetrisch untersucht. Die Chelate zeigen in einer Luftatmosphäre ähnliche TG-Kurven. Thermoanalytische Daten (TG and DTG) dieser Chelate werden mitgeteilt, interpretiert und mathematisch analysiert. Ebenfalls werden die Reaktionsordnung und die Energie und Entropie der Aktivierung nach der von Freeman-Carroll angewandten differentiellen Methode, nach der auf der Coats-Redfern-Gleichung basierenden integralen Methode und nach der die Horowitz-Metzger Gleichung benutzenden Näherungsmethode bestimmt. Aus den Befunden wird geschlossen, dass die thermische Stabilität von Vanillidenanthranilsäure-Chelaten in der Reihenfolge Co(II)Ni(II)>Zn(II)> >Cu(II) abnimmt.

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, , . - . . , , - , , - . , Ni>Zn>u.

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We thank Dr. C. P. Savariar, Professor of Chemistry, University of Calicut for encouragement. We are also grateful to the University Grants Commission for the award of a Senior Research Fellowship to one of us (J. C).     

Synthesis and spectroscopic studies on (4,5-dimethyl-3-pyrazolyl) aldazine nickel(II) complexes

Summary (4,5-Dimethyl-3-pyrazolyl)aldazine, L, reacts with nickel(II) salts to form 11 and 12 complexes. The 11 binuclear systems involve two ligands bridging two nickels, in which L behaves as a tetradentate ligand, and the nickel(II) complexes have pseudo-octahedral stereo-chemistry. Some of the 11 and 12 complexes contain coordinated H₂O and bridging OH. Structures of these complexes are proposed on the basis of elemental analyses, conductivity, spectral data (u.v.-vis. and i.r.) and magnetic susceptibilities.     

Synthesis of new dinuclear dicopper(II) and dinickel(II) complexes. The kinetics of catechol oxidase and electrochemistry of a dicopper(II) complex

A new dinuclear ligand L, ethylene[OO-bis-salicylidene--diketone] bearing two symmetrical coordination sites was synthesized by the condensation of salicylaldehyde and acetylacetone, L, with 1,2-dibromoethane under reflux. The ligand L in a 1:1 ratio was treated with CuCl₂ and NiCl₂ to yield the complexes, tetrachloro bis[OO-bis- salicylidene--diketone copper(II)] and bis[OO-bis-salicylidene--diketone nickel(II)] chloride. The complexes were subsequently characterized by spectroscopic techniques, elemental analysis, i.r., ¹H-n.m.r., ¹³C-n.m.r., u.v.–vis., e.p.r. spectroscopy, and conductance measurements. The conductance measurements in DMF reveal that the Cu^II complex is covalent while the Ni^II complex is ionic and the spectral data support the Cu^II complex to be distorted octahedral whereas the Ni^II complex has square-planar geometry. The dioxygen binding was studied spectrophotometrically by the oxidation of tetrachloro bis[OO-bis-salicylidene--diketone copper(II)] with pyrocatechol in the presence of oxygen. The kinetic experiments were performed with the copper complex in DMF by monitoring the increase in absorbance over time at pH 8.0 in the presence of pyrocatechol at 25 °C. The kinetic parameters V_max and K_M were determined on the Michaelis–Menten Approach. Redox behavior of the dinuclear copper(II) complex was investigated by cyclic voltammetry in the presence of O₂ with the pyrocatechol (substrate) and also without the substrate. The large difference in potentials E⁰ is indicative of reversible oxygen binding of the complex and distinct catalytic activity.     

Metal complexes of 2-(2′-or 8′-quinolyl)benzimidazoles and benzothiazoles

Summary The copper(II), cobalt(II) and nickel(II) chloride and bromide complexes with the ligands 2-(2-quinolyl)-benzimidazole (qbi), 2-(4-methyl-2-quinolyl)benzimidazole (mqbi), 2-(4-methyl-8-quinolyl)benzothiazole (m'q'bt) have been prepared and characterized by analytical methods, magnetic measurements as well as by electronic absorption, e.s.r. and far i.r. spectra. Complexes of various stoichiometries have been isolated, namely MLX₂ (all cobalt complexes with exception of the bromide qbi complex; the chloride and bromide nickel m'q'bt and mq'bt complexes), ML₂X₂ (M=Co,L=qbi and X=Br; M=Ni, L=mqbi, X=Cl or Br, M=Ni, L=qbi, X=Cl) and ML₃X₂(M=Ni, L=qbi or mqbi, X=Br). The cobalt ion has a distorted tetrahedral N₂X₂ coordination in all the CoLX₂ complexes, whereas Co(qbi)₂Br₂ is six-coordinate. The following conclusions may be drawn for the nickel complexes: in those with the 11 metal-to-ligand molar ratio the metal ion is four-or five-coordinate; in those with the 12 and 13 ratios the metal ion is hexa-coordinate, being essentially bound to four nitrogen atoms with halogens, oxygens from water or methanol or nitrogen atoms (from the third ligand) occupying the axial positions.     

Synthesis and characterization of 2,3-bis(hydroxyimino)-1,2,3,4-tetrahydro-pyrido[2,3-b]pyrazine and its nickel(II), cobalt(II), copper(II), palladium(II), cadmium(II) and cobalt(III) complexes

Summary 2,3-Bis(hydroxyimino)-1,2,3,4-tetrahydro-pyrido[2,3-b]pyrazine (H₂L), prepared from 2,3-diaminopyridine and cyanogen-di-N-oxide has been converted into nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) complexes (H₂L) with a 12 metal:ligand ratio. The ligands coordinate through the two N atoms, as do most vicinal dioximes. [(LH)Cl(H₂O)Cd], contains a six-membered chelate ring. [Co(HL)₂(L)Cl] has also been prepared using triphenylphosphine, triphenylarsine, thiophene and chloride as axial ligands. The structure of thevic-dioxime and its complexes are proposed on the basis of elemental analysis, i.r.,¹H-n.m.r. and uv-visible measurements.     

Convenient synthesis of 2-(2-pyridyl)-1, 3-diaminopropane,and its copper(II), nickel(II), and cobalt(III) complexes

Summary 2-(2-Pyridyl)-1, 3-propanediol was converted into the diacetate, which was then condensed with phthalimide. The product was hydrolyzed with hydrochloric acid to give 2-(2-pyridyl)-1, 3-diaminopropane. The free amine gave 12 complexes with copper(II), nickel(II), and cobalt(III), which were characterized spectroscopically and magnetically. Features of the amine as a ligand are discussed. A few related complexes were also studied.     

Thermal decomposition of some N-oxide complexes of cobalt(II), nickel(II) and copper(II) carboxylates

Thermal decomposition of mono pyridine N-oxide complexe; of cobalt(II), nickel(II) and copper(II) propionates and mono quinoline N-oxide complex of copper(II) ben zoate has been studied by TG and DTA techniques. These dimeric complexes are stable upto 350–380 K and decompose in two stages: (i) successive elimination of the two ligand molecules (mostly endothermic); and (ii) decomposition of the resulting anhydrous metal(II) carboxylates by an exothermic multistep process in air.

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Zusammenfassung Die thermische Zersetzung der Monopyridin N-oxidkomplexe der Kobalt(II)-, Nickel(II) und Kupfer(II)-propionate sowie des Monochinolin N-oxidkomplexes von Kupfer(II)-benzoat wurden durch TG und DTA-Methoden untersucht. Diese dimeren Komplexe sind bis zu 350–380 K stabil und werden in zwei Stufen zersetzt: (i) sukzessive Eliminierung der zwei Ligandmoleküle (hauptsÄchlich endotherm); und (ii) Zersetzung der entstehenden wasserfreien Metall(II)carboxylate durch einen mehrstufigen exothermen Vorgang in Luft.

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Résumé On a étudié, par TG et ATD, la décomposition thermique des propionates des complexes mono-pyridine N-oxyde de cobalt(II), de nickel(II) et de cuivre(II) ainsi que du benzoate mono-quinoline N-oxyde de cuivre(II). Ces complexes dimères sont stables jusqu'à 350–380 K et se décomposent en deux étapes: (i) élimination successive des deux moléculesligands (la plupart du temps endothermique); et (ii) décomposition des carboxylates anhydres des métaux(II) formés par un processus en plusieurs étapes dans de l'air.

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-N- (II), (II) (II), -N- (II). 350–380 : (1) (2) .

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The authors are thankful to Dr. R. K. Dewan, Head of the Chemistry Department, University of Jammu, Jammu for providing necessary facilities in the department. The authors are also indebted to Dr. O. P. Vig, Head of the Chemistry Department, Panjab University, Chandigarh for assistance provided. One of the authors (R. K.) is grateful to University Grants Commission, New Delhi for the award of Junior Research Fellowship.