Diazabutadiene cobalt(II) complexes

Summary Studies on the chelates of cobalt(II) with the bidentate ligands 1,4-diphenyl(2,3-dimethyl-1,4-diazabutadiene) (PMB) and 1,4-di(p-methoxyphenyl)-2,3-dimethyl-1,4-diazabutadiene (MPMB) have been carried out. On the basis of elemental analyses, the complexes are [Co(PMB)Cl₂], [Co(PMB)₂(C1O₄)₂], [Co(MPMB)Cl₂] and [Co(MPMB)₂(ClO₄)₂].Both ligands are bidentatevia nitrogen atoms in all the complexes. The magnetic susceptibility and i.r. and u.v.-visible spectra are reported and discussed. The chloro-compounds involving two chlorine ligands and, in the perchlorate compounds, the ClO ₄ ^– groups are bound to the cobalt(II) centre.     

Steric interaction of solvation and sterically enhanced halogeno complexation of manganese(II), cobalt(II) and nickel(II) ions inN,N-dimethylacetamide

The complexation of manganese(II), cobalt(II) and nikel(II) with bromide ions has been studied in N,N-dimethylacetamide(DMA) by calorimetry and spectrophotometry. The formation of [MBr]⁺, [MBr₂] and [MBr₃]^– (M=Mn, Co, Ni) was revealed in all the metal systems. Interestingly, the complexation is significantly enhanced in DMA over N,N-dimethylformamide (DMF). This is unusual because physicochemical properties of DMA and DMF as solvent are similar. Furthermore, extracted electronic spectra of individual complexes of Ni^II suggested the presence of a geometry equilibrium, [NiBr(DMA)₅]⁺=[NiBr(DMA)₄]⁺+ DMA, in DMA. A similar geometry equilibrium is also suggested, [NiBr₂(DMA)₃]=[NiBr₂(DMA)₂]+DMA. Such geometry equilibria were not observed in DMF. With regard to cobalt(II), electronic spectra show the presence of the four-coordinated [CoBr(DMA)₃]⁺ complex in DMA, unlike the six-coordinated [CoBr(DMF)₅]⁺ one in DMF. These facts suggest that a specific strong steric interaction operates between coordinating solvent molecules, which plays a key role in the complexation behavior of the divalent transition metal ions in DMA.     

Template synthesis and characterization of cobalt(II) complex nanoparticles entrapped in the zeolite-Y

Zeolite encapsulated complex nanoparticles “[Co([18]py₂N₄)]²⁺, [Co([20]py₂N₄)]²⁺, [Co(Bzo₂[18]py₂N₄)]²⁺ or [Co(Bzo₂[20]py₂N₄)]²⁺” were successfully prepared by the template synthesis of 2,6-diacetylpyridine with [Co(N–N)₂]²⁺ (N–N = 1,2-diaminoethane, 1,3-diaminepropane, 1,2-diaminobenzene, 1,3-diaminobenzene) within the zeolite-Y. These complex nanparticles were entrapped in the Y-zeolite by a two-step process in the liquid phase: (i) inclusion of a Co(II) precursor complex, [Co(N–N)₂]²⁺@NaY, and (ii) template synthesis of the cobalt(II) precursor complex with the 2,6-diacetylpyridine. The new complex nanoparticles entrapped in the zeolite Y “[Co([18]py₂N₄)]²⁺@NaY, [Co([20]py₂N₄)]²⁺@NaY, [Co(Bzo₂[18]py₂N₄)]²⁺@NaY, [Co(Bzo₂[20]py₂N₄)]²⁺@NaY” were characterized by several techniques: chemical analysis and spectroscopic methods (FT-IR, UV/VIS, XPS, XRD, BET, DRS). Analysis of the data indicates that the cobalt(II) complex nanoparticles are encapsulated in the zeolite-Y and exhibit different property from those of the free complexes, which can arise from distortions caused by steric effects due to the presence of sodium cations, or from interactions with the zeolite matrix.     

Equilibria in complexes ofN-Heterocyclic molecules,part XXIII. Reaction of hydroxide ion with bis-[2,4,6-tri-(2-pyridyl)-1,3,5-triazine] cobalt(II) and nickel(II)

Summary The reactions of [Ni(TPT)₂]²⁺ and [Co(TPT)₂]²⁺ with aqueous hydroxide ion involve the formation of pseudo-base species prior to the dissociation of a ligand molecule. The [M(TPT)(H₂O)₃]²⁺ or [M(TPT)(OH)₃]^– species thus formed react further with hydroxide ion to yield compounds previously described. The kinetics of pseudo-base formation have been followed in each case and the results are compared with a number of other reactions of analogous compounds with hydroxide ion and with water.Part XXII, ref. 3.     

Synthesis,Structure and Characterization of the Cyano-Bridged Heteropolymer Poly{[Bis(Trimethylenediamine)Copper(II)][Hexacyanocobalt(III)]} Perchlorate Dihydrate with a Two-Dimensional Framework

The complex [Cu(tn)₂]₂[Co(CN)₆](ClO₄)·2H₂O (tn = trimethylenediamine) has been prepared and characterized by elemental analysis, IR, electronic and electronic spin resonance spectra and magnetic properties. The x-ray structure analysis shows that each [Co(CN)₆]^3? ion coordinates to four [Cu(tn)₂]²⁺ cations through four cyano nitrogen atoms in the same plane, providing a two-dimensional square network structure, formed from Co-CN-Cu(tn)₂-NC-Co linkages.     

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.     

Crystal structure of tris(ethylenediamine)cobalt(III) (aqua)hexachloromercurate(II) chloride [Co(En)3]2[Hg2(H2O)Cl6]Cl4

The compound [Co(En)₃]₂[Hg₂(H₂O)Cl₆]Cl₄ (I, En is ethylenediamine) has been synthesized and studied by X-ray diffraction. The crystals of I (a = 21.8745(14) Å, b = 10.6008(6) Å, c=15.4465(12) Å, space group Pna2₁) consist of tris(ethylenediamine)cobalt(III) complexes (the unit cell contains two [Co(En)₃]³⁺ cations of opposite chirality). [Hg₂(H₂O)Cl₆]^2? anions, and isolated chloride ions. The complex anion consists of the tetrahedral [HgCl₄]^2? group (Hg-Cl, 2.44–2.56 Å) and the hydrated molecule [Hg(H₂O)Cl₂] (Hg-Cl, 2.301 and 2.308 Å; Hg-O, 2.788 Å) combined by weak Hg-Cl interactions (2.915 and 3.220 Å).     

Spectrophotometric study of thiocyanato complexation of cobalt(II) and nickel(II) ions in micellar solutions of a nonionic surfactant triton X-100

Complexation of cobalt(II) and nickel(II) with thiocyanate ions has been studied by precise spectrophotometry in aqueous and micellar solutions of a nonionic surfactant Triton X-100 of varying concentrations (20–100 mmol-dm^–3). With regard to cobalt(II), the formation of [Co(NCS)]⁺, [Co(NCS)₂], and [Co(NCS)₄]^2– was established. The formation constant of [Co(NCS)₄]^2–, is increased with increasing concentration of the surfactant, suggesting that the [Co(NCS)₄]^2– complex is formed in micelles. In contrast, the formation constants of [Co(NCS)]⁺ and [Co(NCS)₂] are remained practically unchanged. On the other hand, with nickel(II), the formation of sole [Ni(NCS)]⁺ and [Ni(NCS)₂] was established in both aqueous and micellar solutions examined, their formation constants being also remained unchanged. Interestingly, no higher complex was confirmed in the nickel(II) system, unlike cobalt(II). The unusual affinity of the [Co(NCS)₄]^2– complex with micelles will be discussed from thermodynamic and structural points of view.     

Two new cobalt(II) fumarates and a redetermination of tetraaquacobalt(II) fumarate monohydrate

Poly[triaqua‐μ₄‐fumarato‐cobalt(II)], [Co(C₄H₂O₄)(H₂O)₃]_n, (I), contains two symmetry‐independent octahedrally coordinated Co²⁺ ions, both on inversion centers. One Co²⁺ ion is coordinated by two water molecules and four fumarate dianions, whereas the other Co²⁺ ion is surrounded by four water molecules and two fumarate dianions. Each fumarate dianion is bonded to three Co²⁺ ions, leading to a two‐dimensional structure. The fumarate dianions are nonplanar; the angle between the planes of the two carboxylate groups is 54.9 (2)°. The cobalt(II) fumarate layers are connected by hydrogen bonding into a three‐dimensional network. Compound (I) is not isostructural with calcium(II) fumarate trihydrate [Gupta et al. (1972). Acta Cryst. B 28 , 135–139]. In poly[μ₄‐fumarato‐dimethanolcobalt(II)], [Co(C₄H₂O₄)(CH₄O)₂]_n, (II), the Co²⁺ ions are octahedrally coordinated by four fumarate dianions and two methanol molecules, leading to a three‐dimensional structure. The fumarate group is planar. The Co²⁺ ions and the fumarate dianions both lie on inversion centers. Additionally, the one‐dimensional structure of catena‐poly[[[tetraaquacobalt(II)]‐μ₂‐fumarato] monohydrate], {[Co(C₄H₂O₄)(H₂O)₄]·H₂O}_n, (III), was redetermined at a higher resolution, and the space group C2/c was confirmed.     

Stereoselective association between optically active tris(1,10-phenanthroline)ruthenium(II) and tris(acetylacetonato)cobalt(III) in water

Stereoselective interactions between tris(acetylacetonato)cobalt(III) [Co(acac)₃] and optically active Λ-(+)₅₄₆-tris(1,10-phenanthroline)ruthenium(II) chloride [Λ-[Ru(phen)₃]Cl₂] were investigated by measuring the distribution coefficients of racemic Co(acac)₃ between carbon tetrachloride and water containing Λ-[Ru(phen)₃]²⁺ or pure water, and the optical rotations of the aqueous phase was measured over the temperature range 10–40° C. The Λ-isomer of Co(acac)₃ is “salted-in” more strongly by Λ-[Ru(phen)₃]²⁺ than the Δ-isomer. The association constants between Λ-[Ru(phen)]²⁺ and Λ- or Δ-Co(acac)₃ were calculated by using the optical rotation to give K(Λ-Λ) = 3.86 and K(Λ-Δ) = 3.80 at 25°C, respectively. The temperature dependence of the association constants showed that the enthalpy and entropy changes for the Λ-Λ association is slightly more positive than those for the Λ-Δ association. This was discussed from the viewpoint of hydrophobic interactions.     

Komplexe des m-Methylbenzamidoxims mit Co(II) und Ni(II)

The complex formation of Co²⁺ and Ni²⁺ with m-methyl benzamide oxime was studied spectrophotometrically in 60% methanol. The complexes [Co(mMB)₂] and [Ni(mMB)₂] appear in alkaline solution. The formation constants are lgK=4.15±±0.04 for [Co(mMB)₂] and lgK=4.08±0.04 for [Ni(mMB)₂] at 25°. The decadic molar extinction coefficients are ε=5000 for [Co(mMB)₂] and ε=560 for [Ni(mMB)₂], resp.     

The infrared spectra (600-140 cm−1 of the imidazole,pyrazine and pyrimidine adducts of cobalt(II), nickel(II) and zinc(II) acetylacetonates

Summary The complexes M(acac)₂(imidazole)₂ (M = Co or NO and [M(acac)₂B]_n (M = Co, Ni or Zn; B = pyrazine or pyrimidine) have been prepared and their i.r. spectra determined over the 600–140 cm^–1. range. The metal-oxygen and metal-nitrogen stretching frequencies, (M-O) and v(M-N), are assigned on the basis of the band shifts induced by deuteriation of the adducted base and by substitution of the metal ion. Three or fourv(M-O) bands are observed within the 600-200 cm^–1 range. The twov(M-O) bands of higher frequency are considered to the coupled with internal ligand modes. TwovM-N) bands are observed within the 280–170 cm^–1. range. The metal-ligand stretching frequencies are in good agreement with the values previously established for these vibrations in the [M(imidazole)₆]²⁺ and Ni(acac)₂(pyridine)₂ complexes.     

Equilibria in complexes ofN-heterocyclic molecules,part XXII. The reaction of triaquo(2,4,6-tri-(2-pyridyl)-1,3,5-triazine) copper(II) and its nickel(II) and cobalt(II) analogues with water and hydroxide ion

Summary The kinetics of the reaction of [Cu(TPT)(H₂O)₃]²⁺ and [Ni(TPT)(H₂O)₃]²⁺ with H₂O have been followed and it has been shown that the formation of covalent hydrates is important in the understanding of these systems. The [Co(TPT)(OH)₃]^– compound and its Ni analogue are attacked by HO^– initially to form pseudo-base species and in, the case of Ni , the ligand then hydrolyses to yield a compound related to the carboximate formed when HO^– reacts with [Cu(TPT)(OH)₃]^–. In this reaction too, the formation of a pseudo-base, involving attack of HO^– at the triazine ring in the ligand is significant.Part XXI, ref. 2.     

EXAFS studies on the methanol and ethanol solutions of cobalt(II) bromides

The results of an EXAFS investigation of methanol and ethanol solutions of CoBr₂ are reported. The curve fitting analysis gives the coordination numbers and the Co–Br and Co-solvent distances. The results for both 0.2M and 3.8M CoBr₂ in ethanol show the existence of [CoBr₂(C₂H₅OH)₂] as the dominant species, although a considerable amount of octahedral species also exists in the solutions. In 0.2 and 3.3M CoBr₂ methanol solutions, the dominant species are [Co(CH₃OH)₆]²⁺ and [CoBr(CH₃OH)₅]⁺, respectively.     

Electrocarboxylation of chloroacetonitrile mediated by electrogenerated cobalt(I) phenanthroline

The electrocarboxylation of chloroacetonitrile mediated by [Co(II)(phen)₃]²⁺ has been investigated. Cyclic voltammetry studies of [Co(II)(phen)₃]²⁺ have shown that [Co(I)(phen)₃]⁺, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give [RCo(III)(phen)₂Cl]⁺. The unstable one-electron-reduced complex underwent Co–C bond cleavage. In carbon dioxide saturated solution, CO₂ insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen).     

The infrared spectra (3500—150 cm-1) of aniline complexes of cobalt(II), nickel(II), copper(II) and zinc(II) halides

The IR spectra (3500—150 cm^?1) of the complexes [M(aniline)₂,X₂ (M = Co, Ni, Cu, Zn; X = Cl, Br), [Zn(aniline)₂I₂] are discussed. Assignments of the internal ligand vibrations are based on the band shifts which result from ¹⁵N-labelling of the amino group. The metal—ligand stretching frequencies, ν(M—N) and ν(M—X), are assigned on the basis of the band shifts which occur on ¹⁵N-labelling and metal ion and halogen substitution. Two bands within the range 350–450 cm^?1 are assigned to ν(M—N) while the ν(M—X) bands occur within the range 170–320 cm^?1. The effects of structure and coordination number on ν(M—N) and ν(M—X) are discussed. The spectra of two ethanol adducts, [M(aniline)₂-(ethanol)₂Cl₂] (M = Co, Ni) compared with those of the unsolvated species [M(aniline)₂-Cl₂], exhibit a unique band near 480 cm^?1 which is insensitive to ¹⁵N-labelling and is assigned to ν(M—O).     

Synthesis of four new vic-dioximes and their nickel(II), cobalt(II), copper(II) and cadmium(II) complexes

Four unsymmetrical vic-dioximes: [L¹H₂] N-(4-butylphenyl)amino-amphi-glyoxime, [L²H₂] N-(4-butylphenyl)amino-anti-glyoxime, [L³H₂] N-(4-phenylazophenyl)amino-amphi-glyoxime and [L⁴H₂] N-(4-phenylazophenyl)amino-anti-glyoxime have been prepared from amphi-chloroglyoxime, anti-chloroglyoxime, 4-butylaniline and 4-(phenylazo)aniline respectively. The complexes of these vic-dioximes with Ni^II, Co^II, Cu^II and Cd^II ions have been investigated. All are insoluble in common solvents. Their i.r. spectra and elemental analyses are given, together with mass and ¹H-n.m.r. spectra of the ligands.     

Über Reaktionen oxygenierter Kobalt(II)-Chelate. II. Konfigurationsisomere Oxygenierungsprodukte von Tetraäthylenpentaminkobalt(II)

On oxygenation of alcoholic solutions of tetraethylenepentamine cobalt(II) two isomeric forms of [(tetren)CoO₂Co(tetren)]⁴⁺ are obtained in which the configuration of the pentadentate ligand is either α or β. The binuclear complex can be crystallized as thiocyanate or as perchlorate. Oxygenation at 35° produces the pure α isomer. At lower temperature a mixture of α and β is obtained. The isomers differ slightly in their absorption spectra and their reactivity. The ligand configuration has been elucidated by transforming the perchlorates into the [ZnCl₄]^2? salts of the corresponding mononuclear chelates [Co(tetren)Cl]²⁺. The latter have also been prepared starting from a compound of known configuration according to the literature. The IR. spectra of the α and β forms differ characteristically in the NH stretch bands.     

Outer-sphere interactions between octahedral chiral cobalt(iii) complexes and water-soluble calixarenes

The structures and stability of outer-sphere associates of sulfonate derivatives of thiacalix[4]arene and calix[4]resorcinarene with coordinatively saturated cobalt(iii) bis- and tris-chelates ([Co(L-His)₂]⁺, [Co(en)₂ox]⁺, [Co(en)₃]³⁺, and [Co(dipy)₃]³⁺) were compared based on the data from UV, CD, 1D ¹H NMR, and 2D (2D NOESY) ¹H NMR spectroscopy and conductometry. Outer-sphere association is accompanied by partial penetration of the chelate rings of the complexes into the hydrophobic cavity of calixarene, which induces changes in the spectroscopic and spectropolarimetric properties of the cobalt(iii) complexes.     

Copper(II), nickel(II), cobalt(II), manganese(II), iron(III) and oxovanadium(IV) complexes of biacetylmonoquinolylhydrazone (BAMQH)

Octahedral complexes of the general composition [M(II)(BAMQH)₂]X₂ (where M = Cu(II), Ni(II), Co(II); X = Cl⁻, I⁻, ClO⁻₄ and BAMQH is biacetalmonoquinolylhydrazone); [M(II)(BAMQH)Cl₂.H₂O] (where M = Mn(II), Fe(III)) and penta-coordinated [VO(BAMQH)₂]SO₄ have been synthesized and characterized by magnetic susceptibility, optical and ESR studies in the polycrystalline and frozen states. [Ni(II)(BAMQH)₂]Cl₂ has tetrahedral geometry. Bidentate nature of the ligand is assumed in [Ni(II)(BAMQH)₂]Cl₂ and [VO(BAMQH)₂]SO₄ complexes.