Catalase activity of cobalt(II) complexes with N,N,N′,N′-tetrasubstituted thiocarbamoylsulfenamides

On the base of the kinetic and activation parameters of the hydrogen peroxide decomposition in the presence of chelates of CoX₂ salts (X = Cl, Br, I, NCS) with N,N,N′,N′-tetrasubstituted thiocarbamoylsulfenamides containing exocyclic (out-of-chelate) fragments of dimethylamine (I), piperidine (II), and piperazine (III) the nature of acido-ligands influence on catalase activity of complexes I–III was revealed, depending on the structure and composition of the chelating ligand. Mononuclear complexes I(Br) and II(Br) can transform into 10-membered binuclear macrochelate intermediates.     

Electrochemical and electrocatalytic studies of the N,N′-(1R,2R)-(–)-1,2-cyclohexylenebis(salicylideneiminato)cobalt(II) complex

The electrochemical properties and catalytic activity of a Co(II) complex with the optically active Schiff base derived from (1R,2R)-(–)-cyclohexanediamine and salicylaldehyde have been studied in non-aqueous solutions. When dissolved in deoxygenated non-aqueous solutions, the complex exhibits reversible redox properties for the Co(II)/Co(III) couple. Electrochemical reduction of oxygen and oxidation of cobalt(II) was observed on cyclic voltammograms of solutions containing both dioxygen and the Schiff base-cobalt(II) complex. An anodically formed film on a platinum electrode, studied by means of X-ray photoelectron spectroscopy, revealed the presence of the oxidized Co(III) species. Cyclic voltammetry of oxygenated solutions examined after a period of time indicates an electrochemical activity of coordinated superoxo/peroxo species in the 0.7–1.1 V potential range. In the presence of 4-methyl-1-cyclohexene the cyclic voltammetry curves reveal changes similar to those caused by the removal of oxygen. The GC-MS technique was used to identify some of the products formed by the catalytic oxidation of cyclohexene and 4-methyl-1-cyclohexene. Electronic Publication     

Complexation in cobalt(II) valinate-α,α-dipyrrolylmethene system

The reaction of 3,3,5,5-tetramethyl-4,4-dibutyldipyrrolylmethene (HL) with cobalt(II) valinate (CoVal₂) in DMF was studied by spectrophotometric method of molar ratios. The formation of a mixed-ligand complex CoValL was established and its electronic absorption spectrum was measured. The thermodynamic constant of complexation was calculated.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 177–178.Original Russian Text Copyright © 2005 by Guseva, Antina.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Syntheses and structures of cobalt(II), nickel(II), and copper(II) complexes with N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides (O-daap) containing nitrate as the counter ion

Reactions of M(NO₃)₂?·?xH₂O [M?=?Co(II), Ni(II), and Cu(II)] with N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides(O-daap) in CH₃CN yield [Co(O-dmap)(NO₃)₂] (1), [Co(O-deap)(NO₃)₂] (2), [Co(O-dpap)(NO₃)₂] (3), [Ni(O-dmap)(H₂O)₃](NO₃)₂] (4), [Ni(O-deap)(H₂O)₂(NO₃)](NO₃)] (5), [Cu(O-deap)(NO₃)₂] (6), and [Cu(O-dpap)(NO₃)₂] (7). X-ray crystal structures of 1, 2, 4, 5, and 7 reveal that O-daap ligands coordinate tridentate to each metal, O–N–O, with nitrate playing a vital role in molecular and crystal structures of all the complexes. The coordination geometry in the two Co(II) complexes, 1 and 2, is approximately pentagonal bipyramidal with nitrate bonded in a slightly unsymmetrical bidentate chelating mode. [Ni(dmap)(H₂O)₃](NO₃)₂ (4) and [Ni(deap)(H₂O)₂(NO₃)](NO₃) (5) exhibit octahedral geometry, the former containing uncoordinated nitrate while the latter has one nitrate coordinated unidentate and the other nitrate outside the coordination sphere. The Cu(II) in [Cu(dpap)(NO₃)₂] (7) occupies a distorted square pyramidal geometry and is linked to two unidentate nitrates, although one nitrate is also involved in a weak interaction with the metal through its other oxygen. IR spectra and other physical studies are consistent with their crystal structural data. O-dmap?=?N,N,N′,N′-tetramethylpyridine-2,6-dicarboxamides; O-deap?=?N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamides; and O-dpap?=?N,N,N′,N′-tetraisopropylpyridine-2,6-dicarboxamides.     

Synthesis and X-ray crystal structures of N,N,N′,N′-tetraalkylpyridine-2,6-dithiocarboxamides (S-dapt) complexes of cobalt(II) and nickel(II)

Reactions of anhydrous CoX₂ (X?=?Br^?, SCN^?) and Ni(ClO₄)₂ with N,N,N′,N′-tetraisobutylpyridine-2,6-dithiocarboxamides (S-dbpt), N,N,N′,N′-tetraisopropyl pyridine-2,6-dithiocarboxamides (S-dppt), and N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamides (S-dept) lead to the formation of [Co(S-dbpt)Br₂] (1), [Co(S-dppt)(SCN)₂] (2), and [Ni(S-dept)₂]·(ClO₄)₂·H₂O (3), respectively. The X-ray crystal structures of the three S-dapt ligands and three complexes along with spectroscopic analyzes are presented. The molecular structure investigations of the S-dapt ligands show that the thiamide planes are twisted with respect to the pyridine ring, which is more in the case of phenyl groups. The structures of the Co(II) complexes reveal that an increase in steric crowding on the amide side arms of the ligands has no substantial effect on the geometry adopted by the corresponding complexes. The Co(II) gives only 1?:?1 five-coordinate, ion-paired complexes with a distorted square pyramidal geometry. Ni(II), on the other hand, prefers an octahedral geometry with 1?:?2 metal–ligand ratio. The coordination behavior of S-dapt has been compared to the analogous oxo(O-daap) ligands. Lesser propensity of S atom to get involved in H-bonding interactions ensures an S-N-S type of tridentate coordination by S-dapt.     

Synthesis,crystal and molecular structure of the novel complex [dinitrato{N,N-bis(1–methylbenzimidazol-2–ylmethyl)methylamine}]cobalt(II)

Co(NO3)2·6H2O reacts with N,N-bis(1–methylbenzimidazol-2–ylmethyl)methylamine (Me2L) in MeOH/ Et2O solution at ca. 5°C, yielding a novel, penta-coordinate complex, formulated as [Co(NO3)2(Me2L)], which was characterized by means of structural, spectroscopic and magnetic measurements. The Co atom is coordinated in distorted trigonal bipyramidal geometry by three N and two O atoms. The ligand Me2L is coordinated in a facial mode and two coordinated O atoms from the nitrato ligands are in cis-positions.     

Kinetics of aquation of trans-dichlorobis(N,N′-dimethylethylenediamine)cobalt(III) ion in water–methanol in water–propan-2-ol media

The complex trans-[Co(dmen)2Cl2]Cl (dmen=N,N-dimethylethylenediamine) has been prepared and characterized by elemental analysis, u.v.-vis. and i.r. spectra. The kinetics of the primary aquation of trans-[Co(dmen)2Cl2] in H2O, H2O–MeOH and H2O–i-PrOH have been examined over a wide range of solvent compositions and temperatures (40–55°C). Plots of rate constants (log k) versus the reciprocal of the dielectric constant of the medium (Ds–1) and Grunwald–Winstein values of the solvent (Y) were found to be non-linear. The variation of enthalpies (H) and entropies (S) of activation with solvent composition has been determined. Plots of H or S versus the mole fraction of each solvent exhibit extrema at x2=ca. 0.16 and 0.27 for MeOH and at x2=ca. 0.03 and 0.14 for i-PrOH. Furthermore, the cycle relating the free energy of activation in H2O to that in H2O–co-solvent shows that the stabilizing influence of the changes in the solvent structure is greater on the emergent five-coordinate cation in the transition state than that on the complex ion in the initial state, with the difference becoming greater as the mole fraction of the co-solvent increases.     

Soft template synthesis in copper(II)–dithiooxamide–methanal,copper(II)–dithiooxamide–ethanal and copper(II)–dithiooxamide–propanone triple systems in a copper(II)hexacyanoferrate(II) gelatin-immobilized matrix

Novel complexing processes in the Cu^II–dithiooxamide–methanal, Cu^II–dithiooxamide–ethanal and Cu^II–dithiooxamide–propanone triple systems proceeding under specific conditions, to copper(II)hexacyanoferrate(II) gelatin-immobilized matrix systems in contact with aqueous-alkaline (pH 12) solutions containing dithiooxamide and methanal, ethanal or propanone, have been studied. It has been shown that template synthesis leading to the formation of macrocyclic coordination compounds (2,8-dithio-3,7-diaza-5-oxanonandithioamide-1,9)copper(II), (2,8-dithio-3,7-diaza-4,6-dimethyl-5-oxanonandithio-amide-1,9)copper(II) and (4,4,6-trimethyl-2,8-dithio-3,7-diazanonen-6-dithioamide-1,9)copper(II), respectively, takes place under such conditions. Dithiooxamide, methanal, ethanal and propanone act as ligand synthons in these processes.     

Kinetics of the oxidation of [N-(2-hydroxyethyl)-ethylene-diamine-N,N′,N′-triacetato]cobalt(II) by N-bromosuccinimide

The kinetics of the oxidation of [N-(2-hydroxyethyl)-ethylene-diamine-N,N,N-triacetato] cobalt(II), [Co^II-(HEDTA)]^–, by N-bromosuccinimide, NBS, have been studied in aqueous solutions and water-methanol solvent mixtures under various conditions. The reaction stoichiometry indicates that one mole of NBS reacts with one mole of [Co^II(HEDTA)]^–. In aqueous solutions the reaction obeys the following rate law:

Kinetics of solvolysis of the trans-dichlorobis(R-ethylenediamine)cobalt(III) ion (R = N-methyl or N,N′-dimethyl) in urea–water mixtures

First order solvolysis rates of the trans-dichlorobis(R-ethylenediamine)cobalt(III) ion (R=N-Me or N,N-Me₂) complex have been investigated in mixtures formed by adding urea to H₂O, which enhances the dielectric constant and decreases solvent structure. Differential effects of the changes in solvent structure on the initial and transition states are found to be important factors controlling changes in the rate constant with solvent composition. The variation of the enthalpy and the entropy of activation with solvent composition are contrasted with their variations found for the solvolysis of the complexes in mixtures where solvent structure is enhanced by additions of a co-solvent to water. The application of a free energy cycle to the process of the initial state going to the transition state suggests that the cationic cobalt(III) complexes in the transition state are more stable than the cationic cobalt complexes the initial state in the water+urea mixtures.     

Synthesis,structure and methyl methacrylate polymerization of cobalt(II), zinc(II) and cadmium(II) complexes with N,N′,N-bidentate versus N,N′,N-tridentate N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines

Mononuclear Co(II), Zn(II) and Cd(II) complexes derived from bidentate or tridentate N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines (L_n = L_A, L_B), where L_A is N,N-bis((1H-pyrazol-1-yl)methyl)-3-methoxypropan-1-amine and L_B is 3-methoxy-N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)propan-1-amine, have been synthesized and characterized. The geometry at Co(II) and Cd(II) for [L_ACoCl₂], [L_BCoCl₂] and [L_BCdBr₂] with N,N′,N-tridentate ligands (L_n = L_A, L_B) can be described as a distorted trigonal bipyramid achieved by coordinative interaction of N_pyrazole, two halides and the nitrogen of amine moiety. However, the molecular structure of four-coordinate [L_AZnCl₂] can be best described as tetrahedral, resulting in an eight-membered chelate ring. [L_ACoCl₂] polymerized methyl methacrylate in the presence of modified methylaluminoxane at 60 °C and resulted in poly(methylmethacrylate) (PMMA) with higher molecular weight and narrower polydispersity index compared to the other synthesized complexes. However, all the synthesized complexes yielded syndiospecific PMMA, characterized using ¹H NMR spectroscopy, with ca. 0.70.     

Heterobinuclear copper(II)–lanthanoid(III) complexes bridged by N,N′-oxamidobis(benzoato)cuprate(II)

Eight new -oxamido-bridged copper(II)–lanthanoid(III) heterobinuclear complexes described by the overall formula Cu(obbz)Ln(Me-phen)₂NO₃ (Ln = Y, La, Nd, Eu, Gd, Tb, Ho, Er), where obbz denotes the oxamidobis(benzoato) and Me-phen represents 5-methyl-1,10-phenanthroline (Me-phen), have been synthesized and characterized by the elemental analyses, spectroscopic (i.r., u.v., e.s.r.) studies, magnetic moments (at room temperature) and by molar conductivity measurements. The temperature dependence of the magnetic susceptibility of Cu(obbz)Gd(Me-phen)₂NO₃ has also been measured over the 4.2 300 K range. The least-squares fit of the experimental susceptibilities based on the spin Hamiltonian operator, = –2 J ₁ · ₂, yielded J = + 2.18 cm^–1. The observed Gd^III–Cu^II coupling is ferromagnetic. A plausible mechanism for a ferromagnetic coupling between Gd^III–Cu^II is discussed in terms of spin-polarization.     

Cobalt(III)-dithiooxamide,cobalt(III)-N,N′-diphenylthiooxamide and cobalt(III)-N,N′-diphenyldithiooxamide complexing in the KCo[Fe(CN)6]-gelatin-immobilized matrices

Novel complexing processes by Co^III-dithiooxamide, Co^III-N,N-diphenylthiooxamide and Co^III-N,N-diphenyldithiooxamide systems, with a cobalt(III)hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the corresponding ligand, have been observed and analyzed. Under the specific conditions described, four different coordination compounds are formed in the Co^III-dithiooxamide system, three of which are insoluble in water, whereas in each of the Co^III-N,N-diphenylthiooxamide and Co^III-N,N-diphenylthiooxamide systems, three water-insoluble coordination compounds are formed. In solution or the solid phase, formation of only one complex is observed, in each of the systems studied.     

Structural characterization of dicyanidobis-(N,N′-dimethylthiourea-κS)cadmium(II)

A cadmium(II) complex dicyanidobis(N,N′-dimethylthiourea-S) cadmium(II) [Cd(Dmtu)₂(CN)₂] (1) is prepared and its structure in the solid state is determined by single crystal X-ray structural analysis. The cadmium(II) ion is four-coordinate having a distorted tetrahedral geometry composed of two cyanide C atoms and two thione S atoms of N,N′-dimethylthiourea (dmtu). The molecular structure is stabilized by intermolecular N-H…N(CN) hydrogen bonding interactions that lead to a 3D network structure. The complex was also characterized by IR and NMR spectroscopy.     

Dinuclear complexes of cobalt(II) with N,N′-substituted dithioxamides derived from α-aminoacids

Summary The coordination behaviour of N,N-bis(1-carboxymethyl)dithioxamide (GLYDTO), N,N-bis(1-carboxyethyl)dithioxamide (ALADTO), N,N-bis(1-carboxy-2-methylpropyl) dithioxamide (VALDTO) and N,N-bis(1-carboxy-3-methylbutyl)dithioxamide (LEUDTO) has been investigated by isolating and characterizing the dinuclear, neutral cobalt(II) complexes, [Co₂(L-4H)(H₂O)₂] (L = GLYDTO, ALADTO, VALDTO or LEUDTO) and [Co₂(L-4H)(H₂O)₆] (L = ALADTO or VALDTO). All ligands were characterized by mass, i.r., and ¹H- and ¹³C-n.m.r. spectroscopy. The complexes possess distorted octahedral structures as revealed by the magnetic and electronic (diffuse reflectance) spectral data. The i.r. data indicate that the ligands are bis-tridentate, bis-dianions coordinated to each metal ion through the carboxylate oxygen, deprotonated thioamide nitrogen and thiocarbonyl sulphur atoms.     

Synthesis,structures and magnetic properties of four 3D heterometallic cobalt(II)–barium(II) coordination polymers

Four heterometallic complexes, namely {[CoBa(2,5-pdc)₂(H₂O)₃]_n·2nH₂O} (1), [CoBa(2,5-pdc)₂(H₂O)₄]_n (2), [CoBa(2,5-pdc)₂(H₂O)₅]_n (3) and [CoBa₂(2,5-pdc)₃(μ₂-H₂O)₂(H₂O)₄]_n (4) (2,5-H₂pdc?=?pyridine-2,5-dicarboxylic acid), have been hydrothermally synthesized and characterized both structurally and magnetically. All four complexes exhibit 3D frameworks, in which the Co(II) centers are chelated by pyridine nitrogen and carboxyl oxygen atoms in a five-membered ring. The Ba(II) centers are chelated and bridged by carboxyl oxygen atoms to extend the structures into 3D frameworks. The networks of the complexes can be controlled via rationally choosing the appropriate ligand and tuning the ratio of the two types of metal centers. The magnetic properties of complexes 1, 2 and 4 have been investigated from 2 to 300 K.     

Copper(II)–8-mercaptoquinoline,copper(II)–5,8-dimercaptoquinoline and copper(II)–5-thiomethyl-8-mercaptoquinoline complexing in a copper(II)hexacyanoferrate(II) gelatin-immobilized matrix

Novel complexing processes in the Cu^II–8-mercaptoquinoline, Cu^II–5,8-dimercaptoquinoline and Cu^II–5-thiomethyl-8-mercaptoquinoline systems proceeding in the copper(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous solutions of the ligands indicated, have been studied. Under the conditions specified for complexing in the Cu^II–8-mercaptoquinoline system, only a monomeric water-insoluble coordination compound was formed. In the Cu^II–5,8-dimercaptoquinoline system, three coordination compounds were formed and, in the Cu^II–5-thiomethyl-8-mercaptoquinoline system, two such compounds were formed. Conversely, complexing in solution or solid phase results in the formation only coordination compounds in each of the system studied.     

Complex Species in Aqueous Solutions of 4-Chloro-1,2-Phenylenediamine-N,N,N′,N,'-Tetraacetic Acid with Magnesium(II), Calcium(II), Strontium(II), Barium(II), Zinc(II) and Cadmium(II)

Abstract

The coordination in aqueous solution of 4-chloro-1,2-phenylenediamine-N',N',N',N'-tetraacetic acid (4-Cl-o-PDTA) with Be(II) and with the transition metal cations cobalt(II), nickel(II) and copper(II) was reported in earlier publications.^1,2 In this note a study is presented of the coordination in aqueous solution (25°C, 1 = 0.1 M in KC1) of 4-CI-o-PDTA acid with magnesium(II), calcium(II), strontium(II), barium(II), zinc(II) and cadmium(II).     

Synthesis of N,N′-bis(isopropylaminoethyl)-1,10-phenanthroli ne- 2,9-dimethanamine and N,N′-bis(diethylaminoethyl)-1,10-phenanthroline -2,9-dimethanamine and potentiometric determination of the formation constants of their complexes with manganese(II), cobalt(II), copper(II) and zinc(II)

Two hexadentate compounds incorporating 1,10-phenanthroline and four alkylamino donors have been prepared. The protonation constants and the formation constants of dipositive ion (Mn2+, Co2+, Cu2+ and Zn2+) complexes have been determined in aqueous solution by pH titration at 25 ± 0.1 °C and I = 0.1 mol·dm–3 NaNO3.