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.     

Iron(III), cobalt(II,III), copper(II) and zinc(II) complexes of 2-pyridineformamide 3-piperidylthiosemicarbazone

Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)₂]ClO₄, [Cu(HAmpip)Cl₂]·CH₃OH and [Zn(HAmpip)Br₂]·C₂H₆SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively.     

Direct electrochemical synthesis of N-oxopyridine-2-thionato complexes of nickel(II), cobalt(II) and cobalt(III)

Summary The electrochemical oxidation of anodic metal (nickel or cobalt) in MeCN solutions of 1-hydroxy-2-pyridinethione (HPT) gives [Ni(PT)₂], [Co(PT)₂] or [Co(PT)₃]. When 1,10-phenanthroline (phen) or 2,2-bipyridine (bipy) are added to the electrolytic phase the product is a complex, [Ni(PT)₂L] or [Co(PT)₂L] (L = bipy or phen). The i.r., u.v. and ¹H- and ¹³C-n.m.r. spectra of the complexes are discussed.This paper was presented at the 5th Inorganic Chemistry Meeting of the Royal Spanish Chemical Society, Tossa de Mar, Girona, Spain, September 1991.     

Bis -(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine complexes of copper(II), nickel(II), and cobalt(II)

A series of Cu(II), Co(II), and Ni(II) complexes of bis-(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine C₁₅H₂₆N₅P (1), prepared from 3-aminopropylphosphine and 1-hydroxymethyl-3,5-dimethylpyrazole were characterized. The nature of bonding and the geometry of the complexes have been deduced from elemental analysis, infrared, electronic, ¹H NMR, ³¹P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate octahedral geometry for nickel complex and square pyramidal geometry for copper and cobalt complexes. The EPR spectra of copper complex in acetonitrile at 300 K and 77 K were recorded. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus by well-diffusion method. The zone of inhibition values were measured at 37°C for a period of 24 h. The electrochemical behavior of copper complexes was studied by cyclic voltammetry. Catalytic study indicates the copper complex has efficient catalytic activity in oxidation of amitriptyline.     

Acetylsalicylhydroxamic acid and its cobalt(II), nickel(II), copper(II) and zinc(II) complexes

Acetylsalicylhydroxamic acid (AcSHA) was prepared and characterized. Its pK_a value was determined as 7.78. Solid metal complexes of AcSHA were also prepared and characterized by elemental analysis, electronic and i.r. spectroscopies, and by magnetic moment measurements. The shift of both hydroxamic and acetyl carbonyl vibrations to lower frequencies clearly indicates that AcSHA is bonded through oxygen atoms to the metal ions as a tridentate ligand. On the basis of the experimental data, structures for the complexes are purposed.     

Structural and spectral studies of di-2-pyridyl ketone 3-piperidyl- and 3-hexamethyleneiminylthiosemicarbazone and their cobalt(II), nickel(II) and copper(II) complexes

Cobalt(II), nickel(II) and copper(II) complexes of di-2-pyridyl ketone 3-piperidyl- and 3-hexamethyleneiminyl-thiosemicarbazones (HDPypip and HDPyhexim, respectively) have been prepared and characterized by physical and spectral methods. Use of 1:2 thiosemicarbazone-to-metal chloride molar ratios in the preparation of the complexes has produced both mononuclear and polynuclear species for the three metal ions. Crystal structures of the HDPypip, HDPyhexim and [Ni(DPyhexim)Cl] have been determined and aid the assignments of the i.r., n.m.r., u.v.–vis. n.i.r. and e.s.r. spectra for the various complexes.     

Cobalt(III), nickel(II), and copper(II) complexes of 1-thia (or oxa)4,7-diazacyclononane and related mixed-ligand cobalt(III) complexes

Summary To investigate the effect of substitution of an oxygen or a sulphur donor atom for a nitrogen donor atom in a cyclic triamine, 1,4,7-triazacyclononane (tacn), cobalt(III), nickel(II), and copper(II) complexes of 1-oxa-4,7-diazacyclononane (taon) and 1-thia-4,7-diazacyclononane (tasn), and related mixed ligand cobalt(III) complexes were prepared and characterized. The coordination ability of an ether-oxygen or a thioether-sulphur atom increases when these atoms are incorporated into cyclic terdentate ligands. Electronic spectra reveal that ligand field strengths of these atoms are enhanced significantly. The presence of these heteroatoms affects circular dichroism spectra because of the increased flexibility of the chelate rings.     

Dicyanamide complexes of copper(II), nickel(II) and cobalt(II) with benzimidazole and its 2-alkyl-derivatives

Summary Dicyanamide complexes of Cu^II, Ni^II and Co^II of the type M[N(CN)₂]₂L₂, where L = benzimidazole, 2-methyl- or 2-ethylbenzimidazole, have been prepared and studied by spectroscopy and magnetochemistry. The complexes, except for Co[N(CN)₂]₂ (benzimidazole)₂, are six-coordinate, involving bidentate bridging dicyanamide groups. While the Ni^II complexes have practically octahedral structures, the Cu^II complexes are pseudooctahedral with similar tetragonal distortion. The ligand field strength in these complexes depends mainly on the steric effect of the benzimidazole ligands. The Co^II complex of benzimidazole is monomeric tetrahedral, but that of 2-ethylbenzimidazole is tetragonal octahedral. The oridging function of dicyanamide in the six-coordinate complexes is realized either through both cyanide or through amide and cyanide nitrogens. The complex Cu[N(CN)₂]₂ (2-methylbenzimidazole)₂ is a weak antiferromagnet (J = -0.1 cm^–1), exhibiting under ca. 15 K a long-range antiferromagnetic ordering.     

Polymetallic complexes: Part V. ONNO tetradentateN,N′-bis(acetoacetanilide)-1, 3-diaminopropane complexes of cobalt(II), copper(II) and zinc(II)

Summary Ten complexes of composition [Co₂L₂X₄] (X=Cl, Br, NO₃ or ClO₄); [Cu₂L₂(NO₃)₄]; [Zn₂L₂X₄ (X=Cl, SCN or ClO₄); [CuCl₂L] and [ZnBr₂L] have been synthesized, where L is the ONNO tetradentate ligand,N,N-bis(acetoacetanilide)-1,3-diaminopropane. The complexes have been characterised by elemental analysis, conductance, magnetic susceptibility, molecular weight and i.r., and electronic spectral measurements.Author to whom all correspondence should be directed.     

Synthesis and characterization of biacetyldihydrazone complexes of cobalt(II), copper(II), nickel(II) and iron(III)

Summary Biacetyldihydrazone (BdH) complexes [M(BdH)₃](ClO₄)₂ (M=Co^IIor Cu^II) and [M(BdH)₃](NO₃)_2,3 (M = Ni^IIor Fe^III) have been prepared and characterized by chemical analysis, conductance measurements, electronic, i.r. and e.p.r. spectral studies and magnetic subsceptibilities measurements. A mononuclear octahedral configuration is proposed for all complexes studied.     

Synthesis,characterization and electrical conductivities of 1,2-bis-(2-pyridyl)methyleneiminobenzene cyano complexes of nickel(II), copper(II) and cobalt(II)

Transition Metal Chemistry -     

Cobalt(III), copper(II), and nickel(II) complexes of 1-thia-4,7-diazacyclononane-S-oxide

Summary The title complexes [ML₂]ⁿ⁺=Co^III, Cu^II, Ni^II; L=1-thia-4,7-diazacyclononane-S-oxide) have been prepared and characterized spectroscopically. The sulphoxide group is coordinated through the oxygen atom and the complexes have atrans-O,O geometry. The nickel(II) complex of bis(2-amino-ethyl)sulphoxide has also been studied.     

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.     

New complexes of iron(III), cobalt(II), nickel(II) and copper(II) with 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol

Summary Fe^III, Co^II, Ni^II and Cu^II complexes of a new Schiff base, 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol (PTCAP), have been synthesized and characterized by elemental analyses, molar conductance and magnetic susceptibility measurements, and by u.v.-vis., i.r. and e.p.r. spectral observations. The studies indicate an octahedral structure for the complexes with the general formula [ML₂] (M = Co^II, Ni^II or Cu^II.; L = PTCAP) or [M′(OH)L₂] (M′ = Fe^III). The i.r. spectra suggest that the ligand acts as a tridentate (NNO) donor towards Co^II, Ni^II and Cu^II, and, in the Fe^III complex, one of the two ligand molecules acts as a bidentate (NO) donor and the other as a tridentate donor. The M?ssbauer spectrum of the Fe^III complex suggests the presence of a spin equilibrium at room temperature. Cyclic voltammograms are also recorded for the Cu^II and Fe^III complexes.     

Coordination modes of 1-allyl benzotriazole: synthesis and characterization of cobalt(II), nickel(II), copper(II), copper(I) and silver(I) complexes

Summary The synthesis and coordination behaviour of 1-allylbenzotriazole (ABT), containing both -donating heterocyclic ring nitrogen(s) and a -bonding olefinic group, has been studied by complexation with Co^II, Ni^II, Cu^II, Cu^I and Ag^I salts. The solid complexes M(ABT)₂X₂ (M=Co, Ni or Cu and X=a counterion) and M(ABT)X (M=Cu or Ag and X=Br, I, or NO₃) have been characterised by¹H-n.m.r. (representative Cu^I species) and other physical data. Different modes coordination for the title ligand have been proposed based upon i.r. data which indicate the participation of a -donating ring nitrogen only in complexes with bivalent metal salts, and the involvement of both the ring nitrogen and the allylic olefinic component in bonding to a monovalent metal ion.¹H-n.m.r. data are qualitatively commensurate with participation of the allyl group in monovalent metal complexes.     

New complexes of iron(III), cobalt(II), nickel(II) and copper(II) with Schiff bases derived from 2-aminocyclopent-1-ene-1-dithiocarboxylic acid

Summary Fe^III, Co^II, Ni^II and Cu^II, complexes of a new Schiff base ligand, prepared by condensing 2-aminocyclopent-1-ene-1-dithiocarboxylic acid with benzaldehyde (ACB), and also Cu^II and Ni^II complexes of a second Schiff base ligand prepared by condensing 2-aminocyclopent-1-ene-1-dithiocarboxylic acid with salicylaldehyde (ACS), have been prepared and characterized by elemental analyses, conductivity measurements, magnetic and spectral (electronic, i.r. and e.p.r.) studies. The i.r. spectra suggest that both ACB and ACS are acting as bidentate ligands, coordinating through one of the sulphur atoms and through the azomethine nitrogen atom. The magnetic moment of the Fe^III complex indicates spin crossover behaviour. Square planar structures have been assigned to the Cu^II and Ni^II complexes and a tetrahedral structure to the Co^II complex. The e.p.r. spectra of the Cu^II complexes suggest a square planar environment with rhombic distortion around the Cu^II ion.     

Chromium(III), manganese(II), iron(III), cobalt(II), nickel(II) and copper(II) complexes with a pentadentate, 15-membered new macrocyclic ligand

Complexes of Cr^III, Mn^II, Fe^III, Co^II, Ni^II and Cu^II containing a macrocyclic pentadentate nitrogen–sulphur donor ligand have been prepared via reaction of a pentadentate ligand (N₃S₂) with transition metal ions. The N₃S₂ ligand was prepared by [1 + 1] condensation of 2,6-diacetylpyridine with 1,2-di(o-aminophenylthio(ethane. The structures of the complexes have been elucidated by elemental analyses, molar conductance, magnetic susceptibility measurements, i.r., electronic and e.p.r. spectral studies. The complexes are of the high spin type and are six-coordinate.     

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.     

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.