Cobalt Carboxylate Research Articles

A mononuclear cobalt(III) carboxylate complex with a fully O-based coordination sphere: CoIII-O bond homolysis and controlled radical polymerisation from [Co(acac)2(O2CPh)

The addition of benzoyl peroxide to [CoII(acac)2] in a 1 : 2 ratio selectively produces [CoIII(acac)2(O2CPh)], a diamagnetic (NMR) mononuclear CoIII complex with an octahedral (X-ray diffraction) coordination geometry. It is the first reported mononuclear CoIII derivative with a chelated monocarboxylate ligand and an entirely O-based coordination sphere. The compound degrades in solution quite slowly by homolytic CoIII-O2CPh bond cleavage upon warming above 40 °C to produce benzoate radicals and can serve as a unimolecular thermal initiator for the well-controlled radical polymerisation of vinyl acetate. Addition of ligands (L = py, NEt3) induces benzoate chelate ring opening and formation of both cis and trans isomers of [CoIII(acac)2(O2CPh)(L)] for L = py under kinetic control, then converting quantitatively to the cis isomer, whereas the reaction is less selective and equilibrated for L = NEt3. The py addition strengthens the CoIII-O2CPh bond and lowers the initiator efficiency in radical polymerisation, whereas the NEt3 addition results in benzoate radical quenching by a redox process. In addition to clarifying the mechanism of the radical polymerisation redox initiation by peroxides and rationalizing the quite low efficiency factor for the previously reported [CoII(acac)2]/peroxide-initiated organometallic-mediated radical polymerisation (OMRP) of vinyl acetate, this investigation provides relevant information on the CoIII-O homolytic bond cleavage process.

Carboxylate pentapyridines: Pathway to surface modification and tuneable catalytic proton reduction

The ability to synthetically tune catalytic performance is a key advantage in the use of molecular catalysts. A series of cobalt pentapyridine carboxylate esters [Co(Py5Me2COOMe)(CH3CN)]2+(Co-Me), [Co(Py5Me2COOn-Pr)(CH3CN)]2+(Co-Pr) and [Co(Py5Me2COOPh)(CH3CN)]2+(Co-Ph) were successfully synthesised and characterised through HD-MS, FT-IR and cyclic voltammetry. Electrochemical studies reveal the complexes are active for electrocatalytic proton reduction in acetonitrile with acetic acid as the proton source. At an acid concentration of 2 mM, the required overpotential for proton reduction was calculated to be 465 mV for Co-Me, 485 mV for Co-Pr and 360 mV for Co-Ph. The rate constant is calculated to be 9.41 s−1, 4.09 s−1 and 7.25 s−1 for complexes Co-Me, Co-Pr and Co-Ph respectively. The cobalt carboxylate complex [Co(Py5Me2COO−)(OH−)]1+ (Co-COOH) was used to prepare chemically modified electrodes from fluorine doped tin oxide (FTO) coated glass and glassy carbon with a calculated surface coverage of 6.38 × 10−11 mol/cm2 and of 6.18 × 10−11 mol/cm2 respectively. The successful reduction of catalytic overpotential through esterification offers an alternative pathway for the design of molecular catalysts.

SYNTHESIS OF METAL CARBOXYLATES FROM ALMOND SEED OIL (TERMINALIA CATAPPA

TThe less exploited seed oil of almond was investigated for its potential utilization as a raw material for the synthesis of metal carboxylates. The oil was extracted from the almond seeds and a yield of 42% was obtained. The oil was characterized and used to synthesize the carboxylates of barium, calcium, cobalt, copper, iron, magnesium, nickel and zinc. The functional groups of fatty acid carboxylates produced were confirmed by FTIR. The characteristic colours of the carboxylates were white (barium, calcium, magnesium and zinc carboxylates), ash (Cobalt carboxylate), mint green (copper carboxylate), brown (iron carboxylate), and lemon green (nickel carboxylate). The pH of the solutions of the metal carboxylates varies from 6.6 to 10 with no free alkaline. The foam stability test revealed a length of 1.3 cm for barium carboxylate and 0.3 cm for magnesium carboxylate while other carboxylates did not foam.

Copper(II) and Cobalt(II) Carboxylates Containing the 1,3,4-Oxadiazole Fragment: Structures and Properties

Copper(II) and Cobalt(II) Carboxylates Containing the 1,3,4-Oxadiazole Fragment: Structures and Properties

Trigonally Distorted Hexacoordinate Co(II) Single-Ion Magnets.

By simple reactions involving various cobalt(II) carboxylates (acetate and in situ prepared pivalate and 4-hydroxybenzoate salts) and neocuproine (neo), we were able to prepare three different carboxylate complexes with the general formula [Co(neo)(RCOO)2] (R = –CH3 for 1, (CH3)3C– for 2, and 4OH-C4H6– for 3). The [Co(neo)(RCOO)2] molecules in the crystal structures of 1–3 adopt a rather distorted coordination environment, with the largest trigonal distortion observed for 1, whereas 2 and 3 are similarly distorted from ideal octahedral geometry. The combined theoretical and experimental investigations of magnetic properties revealed that the spin Hamiltonian formalism was not a valid approach and the L-S Hamiltonian had to be used to reveal very large magnetic anisotropies for 1–3. The measurements of AC susceptibility showed that all three compounds exhibited slow-relaxation of magnetization in a weak external static magnetic field, and thus can be classified as field-induced single-ion magnets. It is noteworthy that 1 also exhibits a weak AC signal in a zero-external magnetic field.

Green Synthesis of Iron-Doped Cobalt Oxide Nanoparticles from Palm Kernel Oil via Co-Precipitation and Structural Characterization.

In this study, a bio-derived precipitating agent/ligand, palm kernel oil, has been used as an alternative route for the green synthesis of nanoparticles of Fe-doped Co3O4 via the co-precipitation reaction. The palm oil was extracted from dried palm kernel seeds by crushing, squeezing and filtration. The reaction of the palm kernel oil with potassium hydroxide, under reflux, yielded a solution containing a mixture of potassium carboxylate and excess hydroxide ions, irrespective of the length of saponification. The as-obtained solution reacts with an aqueous solution containing iron and cobalt ions to yield the desired metallo-organic precursor, iron cobalt carboxylate. Characterization of the precursors by IR and gas chromatography (GC) attests to the presence of carboxylate fatty acids in good agreement with the proportion contained in the oil, and ICP confirms that the metallic ratios are in the proportion used during the synthesis. Analysis of the products thermally decomposed between 400 °C and 600 °C by XRD, EDX, TEM and ToF-SIMS, established that cobalt iron oxide nanoparticles (Co(1−x)Fex)3O4 were obtained for x ≤ 0.2 and a nanocomposite material (Co(1−x)Fex)3O4/Fe3O4 for x ≥ 0.2, with sizes between 22 and 9 nm. ToF-SIMS and XRD provided direct evidence of the progressive substitution of cobalt by iron in the Co3O4 crystal structure for x ≤ 0.2.

Effect of Accelerators on the Curing of Unsaturated Polyester Resins: Kinetic Model for Room Temperature Curing

Several iron and vanadium compounds were evaluated as accelerators for curing of unsaturated polyester resins, serving as alternatives to toxic cobalt(II) carboxylates currently in widespread use in the composite industry. The catalytic power of the given metal-based compounds has been verified by gelation time measurements on a multipurpose unsaturated polyester/styrene/methyl ethyl ketone peroxide system. Due to different demands of the application sphere, our detailed investigation of the curing process has covered two extreme situations: the behaviors of the accelerators under adiabatic and isothermal conditions. Exothermic behavior in the thermally isolated system, followed by a K-type thermocouple, enabled recognition of the inhibition of the curing process at high concentration of the accelerator and verification of its thermal stability. At isothermal conditions, a radical copolymerization process has been followed by real-time near-infrared spectroscopy, which enabled the establishment of a kinetic model for precise quantification of the catalytic effect for given accelerators.

Coordination of Hexahydro-1,3,5-trimethyl-1,3,5-triazine in Cadmium(II) and Cobalt(II) Carboxylate Complexes

Coordination of Hexahydro-1,3,5-trimethyl-1,3,5-triazine in Cadmium(II) and Cobalt(II) Carboxylate Complexes

Oxidovanadium(V) dithiocarbamates as driers for alkyd binders

A series of oxidovanadium(V) dithiocarbamates were synthesized by the conventional synthetic procedure and characterized by analytical methods. Structures of two representatives were determined by X-ray diffraction analysis on single crystals. The initial screening of catalytic alkyd drying, performed on a commercial solventborne alkyd resin of medium oil length, revealed a promising activity of oxidovanadium(V) dithiocarbamates, which was further proved on several alkyd formulations including slow-drying high-solid binders. Kinetic behavior of the catalyzed autoxidation process, investigated by time-resolved infrared spectroscopy on a thin alkyd film, was found to be very different from commercial cobalt carboxylates. Appearance of oxidovanadium(IV) species upon the curing process was evidenced by EPR spectroscopy. Oxidovanadium(V) dithiocarbamates were established as primary driers for solventborne and high-solid alkyd formulations. The kinetic behavior of the catalyzed autoxidation process, investigated by time-resolved infrared spectroscopy on a thin alkyd film, was found to be different from commercial cobalt carboxylates. Appearance of oxidovanadium(IV) species upon the curing process was evidenced by EPR spectroscopy.

Thermal Decomposition of Acidic Cobalt(II) Carboxylates with Unsaturated Dicarboxylic Anions

The thermal decomposition of acidic cobalt carboxylates (ACCs) with unsaturated carboxylic anions has been studied by TG/DTA in combination with DSC and mass spectrometry of gaseous thermolysis products. The temperature ranges of the main ACC thermal decomposition stages have been determined as (1) 50–225°С for dehydration (2) 210–450°C for dehydrated carboxylate polymerization, and (3) 370–500°C for decarboxylation. It has been concluded that the listed stages may superimpose on one another and occur simultaneously.

Synthesis, Structure, and Magnetic Properties of a Three‐Dimensional Cobalt Carboxylate Metal‐Organic Framework

AbstractUnder hydrothermal condition, a new three‐dimensional (3D) cobalt carboxylate metal‐organic framework Co3(H2O)L1.5(H2O)3 (H4L=1,4,5,8‐naphthalenetetracarboxylic acid) (1) has been successfully synthesized. Single‐crystal X‐ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and magnetic measurement for 1 were presented. 1 shows a new 3D framework with a 4,8‐connected {416.612}{44.62}2 topology. Crystal data for 1 are as follows: hexagonal cell; space group P6/m, with a=12.612(5) Å, b=12.612(5) Å, c=9.978(5)(3) Å, a;=90°, β=90°, and γ=120°; volume V=1374.5(15) Å3; and Z=2. The static magnetic behavior of 1 was conducted. The corresponding structural and magnetic parameters have been discussed in detail.

One-Pot Seed-Mediated Growth of Co Nanoparticles by the Polyol Process: Unraveling the Heterogeneous Nucleation.

The one-step seed-mediated synthesis is widely used for the preparation of ferromagnetic metal nanoparticles (NPs) since it offers a good control of particle morphology. Nevertheless, this approach suffers from a lack of mechanistic studies because of the difficulties of following in real time the heterogeneous nucleation and predicting structure effects with seeds that are generated in situ. Here, we propose a complete scheme of the heteronucleation process involved in one-pot seed-mediated syntheses of cobalt nanoparticles in liquid polyols, relying on geometrical phase analysis (GPA) of high-resolution high-angle annular dark field (HAADF)-STEM images and in situ measurements of the molecular hydrogen evolution. Cobalt particles of different shapes (rods, platelets, or hourglass-like particles) were grown by reducing cobalt carboxylate in liquid polyols in the presence of iridium or ruthenium chloride as the nucleating agent. A reaction scheme was established by monitoring the H2 evolution resulting from the decomposition of metal hydrides, formed in situ by β-elimination of metal alkoxides, and from the polyol dehydrogenation, catalytically activated by the metal particles. This is a very good probe for both the noble metal nucleation and the heterogeneous nucleation of cobalt, showing a good separation of these two steps. Ir and Ru seeds with a size in the range 1-2 nm were found exactly in the center of the cobalt particles, whatever the cobalt particle shape, and high-resolution images revealed an epitaxial growth of the hcp Co on fcc Ir or hcp Ru seeds. The microstructure analysis around the seeds made evident two different ways of relaxing the lattice mismatch between the seeds and the cobalt, with the presence of dislocations around the Ir seeds and compression zones of the cobalt lattice near the Ru seeds. The relationship between the nature of the nucleating agent, the reaction steps, and the microstructure is discussed.

Assessment of destruction of polyethylene modified with pro-oxidants in the context of environmental safety

The paper presents the results of the evaluation of the destruction of polyethylene LDPE (hereinafter-PE), modified by prooxidants based on iron, copper and cobalt carboxylates (in the amount of 1.5 mass. % ) with accelerated thermal and ultraviolet aging for 192 hours. The assessment of degradation in the context of environmental safety included the determination of the degree of compliance of the materials with the requirements of state standard 33747-2016 "Oxo-biodegradable packaging", according to which the criterion of the efficiency of oxobiodestructionpolyolefins may be a decrease in strength and elongation at break of the sample at accelerated aging, as well as the quantitative determination of the release of formaldehyde during thermal degradation modified with prooxidants PE for comparison with the maximum permissible concentration. The rheological parameters of the materials were studied and a comparative assessment of the melt viscosity reduction and reduction with respect to elongation at break in the dynamics of accelerated thermal and UV aging of the PE modified with prooxidants in the selected time interval of 192 hours of exposure was carried out. A decrease in the relative elongation at rupture of PE containing cobalt - based prooxidant by 94% at thermal aging for 192 hours, and by 46% at ultraviolet was established. For PE modified with copper carboxylate, these values were 64 and 33 %, respectively, for PE modified with iron carboxylate – 35% and 40%, respectively. The reduction of strength by 95% of the initial value for 192 hours of temperature exposure was achieved in a sample modified with cobalt, which confirms its compliance with state standard 33747-2016. For other samples, the degree of strength reduction in the selected time interval does not allow to assess compliance with the specified standard. The release of formaldehyde during thermal aging for 192 hours per 1 g of the PE sample modified with cobalt carboxylate was 0.051 mg/m3, for PE modified with copper carboxylate – 0.032 mg/m3, for PE modified with iron carboxylate – 0.034 mg/m3. Installed excessive concentrations of formaldehyde in air hood PH with the carboxylate of cobalt 1.2 times under thermal aging 96 hours and 1.5 times the thermal ageing of a maximum of 192 hours. The reduction of the viscosity of PE containing cobalt – based prooxidant by 90% at thermal aging for 192 hours and by 10% at ultraviolet was recorded. For PE modified with copper carboxylate, these values were 9 and 2 %, respectively, for PE modified with iron carboxylate – 8 and 5%, respectively.

One Novel 3D Supramolecular Network Based on Dicobalt-Carboxylate Secondary Building Units with Polycarboxylate Ligands 1, 2, 3, 4-Butanetetracarboxylic Acid

A novel cobalt–carboxylate framework constructed from secondary building units (SBUs), {[Co16(btca)8(H2O)40]·16H2O}n (1) (H4btca = 1,2,3,4-butanetetracarboxylic acid) has been hydrothermally synthesized and characterized by techniques of single-crystal X-ray diffraction analyses, elemental analyses, infrared spectra, powder X-ray diffraction and thermogravimetric analyses. The complex exhibits 2D 4-connected sql net with (44 × 62) topology symbol built from [Co2(COO)4(H2O)5] SBUs and is further extended into a 3D supramolecular architecture via strong O–H···O hydrogen bonds. Moreover, the magnetic measurements indicate complex 1 exhibit antiferromagnetic behavior.

Change in the Hydrocarbon and Component Compositions of Heavy Crude Ashalchinsk Oil Upon Catalytic Aquathermolysis

A physical model has been developed for the aquathermolysis of heavy crude oil from the Ashalchinsk oil field at 250°, 300°, and 350°C. Nickel and cobalt carboxylates were used as oil-soluble catalyst precursors. In the presence of a hydrogen proton donor at 300°C, the oil content was found to rise considerably and the resin content was found to decrease by a factor of 1.8, which leads to a decrease in crude oil viscosity by 91% and a decrease in density from 960 to 933 kg/m3. The hydrocarbon composition of the liquid aquathermolysis products was studied by chromate-mass spectrometry. The average molecular weight of the asphaltenes was determined by matrix-assisted laser desorption/ionization (MALDI) spectrometry. The maximum disproportionation of the hydrocarbons into n-alkanes, alkylcyclohexanes, and alkylbenzenes occurs at 300° and 350°C. The composition of the hydrogen proton donor (tetralin) conversion products at these aquathermolysis temperatures was determined.

Embedding 1D or 2D cobalt-carboxylate substrates in 3D coordination polymers exhibiting slow magnetic relaxation behaviors: crystal structures, high-field EPR, and magnetic studies.

By utilizing well-designed bifunctional ligands derived from 1H-imidazole-4,5-dicarboxylic acid, magnetic coordination polymers (CPs) that exhibit slow magnetic relaxation at the low temperature regions were constructed and further structurally characterized. In 1, 1D cobalt-carboxyl chains were stabilized in the final structure. In contrast, by adjusting the length of the substituted arms on imidazole-4,5-dicarboxylic acid, a novel 3D CP, 2 containing 2D 63 cobalt-carboxyl layer was obtained. A combination of Quantum Monte Carlo (QMC) simulations and the first-principles Density functional theory (DFT) calculations showed that compound 2 features weak ferro- and antiferro-magnetic coupling mechanisms with two different super-exchange paths of -/+/- for syn-anti carboxylate bridges and -/-/- for syn-syn carboxylate bridges. Through HF-EPR measurements performed on polycrystalline samples over the frequency range of 60-260 GHz and field range of 0-12 T, the effective g-values of 1 and 2 were all larger than 2.00, and the signs of their D values were probably positive.

The structural organization of oligonuclear cobalt(II, III) and cobalt(III) carboxylates

The review deals with the topology of homonuclear carboxylate complexes of cobalt(II, III) and cobalt(III) whose structures are built from the monocarboxylate anions RCOO– (R is a radical containing no electron-donating substituents), water, and its deprotonated forms.

ChemInform Abstract: Non‐Precious‐Metal Catalytic Systems Involving Iron or Cobalt Carboxylates and Alkyl Isocyanides for Hydrosilylation of Alkenes with Hydrosiloxanes.

AbstractThe catalyst systems are expected to be applicable to industrial processes for modification of silicon fluids and generation of silicon gels.

Bench-Stable, Substrate-Activated Cobalt Carboxylate Pre-Catalysts for Alkene Hydrosilylation with Tertiary Silanes

High-spin pyridine diimine cobalt(II) bis(carboxylate) complexes have been synthesized and exhibit high activity for the hydrosilylation of a range of commercially relevant alkenes and tertiary silanes. Previously observed dehydrogenative silylation is suppressed with the use of sterically unencumbered ligands, affording exclusive hydrosilylation with up to 4000 TON. The cobalt precatalysts were readily prepared and handled on the benchtop and underwent substrate activation, obviating the need for external reductants. The cobalt catalysts are tolerant of epoxide, amino, carbonyl, and alkyl halide functional groups, broadening the scope of alkene hydrosilylation with earth-abundant metal catalysts.

Non-Precious-Metal Catalytic Systems Involving Iron or Cobalt Carboxylates and Alkyl Isocyanides for Hydrosilylation of Alkenes with Hydrosiloxanes.

A mixture of an iron or a cobalt carboxylate and an isocyanide ligand catalyzed the hydrosilylation of alkenes with hydrosiloxanes with high efficiency (TON >10(3)) and high selectivity. The Fe catalyst showed excellent activity for hydrosilylation of styrene derivatives, whereas the Co catalyst was widely effective in reaction of alkenes. Both of them catalyzed the reaction with allylic ethers. Chemical modification and cross-linking of silicones were achieved by choosing the right catalyst and reaction conditions.