Cobalt Halides Research Articles

Complexes of dibenzoyldisulphide with metal halides. Part III. Complexes of dibenzoyldisulphide with cobalt(II), nickel(II), manganese(II), copper(II), iron(III) and chromium(III) halides

Adducts (1:1) of halides of cobalt(II), nickel(II), manganese(II), copper(II), iron(III) and chromium(III) with dibenzoyldisulphide have been isolated and characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility, infrared spectra, molecular weight and thermogravimetric analysis data.

Thermal Decomposition of Cobalt(II) Halide Complexes of Tetramethylurea and Related Cyclic Ureas

Abstract TG-DTA studies revealed that the complexes CoX2L2 (L=tmu, dmeu or dmpu (see text); X=Cl, Br or I) decompose into CoX2 and 2L by slight heating. The ease of this decomposition decreases in the orders of tmu>dmeu>dmpu and Cl>Br>I, corresponding to the orders of coordination abilities of these ligands.

The formation of cobalt(II) halide complexes containing neutral bidentate ligands

Preparation of cobalt(II) halide complexes with neutral bidentate ligands, including 2-pyridyl alkyl ketones, is reported. 2-Pyridyl alkyl ketones act as monodentate or bidentate ligands depending on the reaction solvent used. Tetrahedral complexes are isolated for all potential σ-donating neutral ligands.trans-Octahedral complexes are formed only if the neutral ligands are strong σ-donors and π-acceptors. The stereochemistry of cobalt(II) halide complexes is discussed in relation to the nature of the neutral ligands.

Cobalt(II) complexes of creatinine

Cobalt(II) complexes of creatinine [Co(creat)2X2] (X = Cl, Br, I or NCS) and [Co(creat)2X2(H2O)2] (X = HCO2, HOCH2CO2 or CNCH2CO2) have been prepared. Their i.r. spectra show an increase in ν(NH) of the cyclic secondary amine group, compared to free ligand (3300 cm−1), indicating that cyclic nitrogen is involved in coordination. The thiocyanate group coordinates through nitrogen and carboxylates coordinate as univalent unidentate ligands. The electronic spectra and magnetic moments suggest a d7 configuration for cobalt: a tetrahedral geometry (4.4 B.M.) for halide and thiocyanate complexes, and an octahedral geometry (5.0 B.M.) for the carboxylate complexes. On heating, the ligand moiety is lost and the respective cobalt halide or cobalt carboxylate is formed, which is converted finally into Co3O4. There is a correlation between the high intensity electronic transitions and the polarographic half-wave potentials.

Pressure and Temperature Effects on Octahedral-Tetrahedral Equilibria in Pyridine Solutions of Some Cobalt(II) Halides. II

Abstract Temperature and pressure effects on the configuration equilibrium of cobalt(II) iodide in pyridine solution have been studied spectrophotometrically. High temperature favors the tetrahedral species but high pressure favors the octahedral species, the heat and volume changes being 65.3 kJ mol−1 and −6 cm3 mol−1, respectively. Comparisons among three kinds of halide are also made.

COBALT(II), NICKEL(II), AND COPPER(II) HALIDE COMPLEXES OF 7-OXA-2,12-DITHIA(13)(2,6)PYRIDINOPHANE

Abstract A new macrocyclic ligand, 7-oxa-2, 12-dithia (13) (2, 6)-pyridinophane (1, SNSO) was synthesized and characterized by its elemental analytical data, nmr, ir, and mass spectra. Its cobalt(II), nickel(II), and copper(II) halide complexes (MLX2, where X = Br and Cl) were investigated. Probable structures of these complexes are proposed on the basis of electrical conductivity measurements, magnetic susceptibility data, electronic and infrared spectra. The nickel(II) bromide complex is five coordinate and the other complexes are six-coordinate. The electronic spectral bands due to selected d-d transitions are tentatively assigned.

Complexes of 1,8-bis(2-pyridyl)-3,6-dithiaoctane with cobalt(II) halides

Several cobalt(II) halide complexes derived from 1,8-bis(2-pyridyl)-3,6-dithiaoctane (bpdto) are described. Chemical analysis suggests their formulae to be: Co(bpdto)X2 (X=Cl−, Br−, or I−). Electrolytic conductivities in acetonitrile, magnetic moments at different temperatures, solid state i.r. and u.v.-visible spectra support a tetrahedral stereochemistry around the cobalt(II). The ligand is bidentate andN-bonded in all cases.

Selective hydrogenation of the CC-triple bond in PhCCPh by tris(triphenylphosphine)cobalt activated NaBH 4; deuterium tracing experiments

Sodium borohydride does not on its own react with diphenylacetylene, but becomes an active hydrogenation agent in the presence of (Ph 3P) 3CoCl. Unlike systems involving other catalysts, e.g. cobalt halides in ethanol, this is a selective reagent for hydrogenation in which an alkyne is selectively hydrogenated to cis and trans alkenes. The role of NaBH 4 in this hydrogenation and isomerization has been studied by deuterium labelling. A brief comparison is made with other active catalysts in this system like (Ph 3P) 3CoBH 4.

Pressure and Temperature Effects on Octahedral-Tetrahedral Equilibria in Pyridine Solutions of Some Cobalt(II) Halides

Abstract The visible absorption spectra of CoX2 (X=Cl, Br) in pyridine solutions have been measured in the ranges 1 bar—3 kbar at room temperature, and ≈4—≈70 °C at 1 atm. The equilibrium, [CoX2(py)2](tetrahedral)+2py\ightleftharpoons[CoX2(py)4](octahedral), is found to be followed over these pressure and temperature ranges. High pressure favors the octahedral species, with the volume changes, −41 cm3/mol for the chloride and ≈−30 cm3/mol for the bromide at 1 atm. The pressure dependence of the volume change is less for the bromide than for the chloride. High temperature, however, favors the tetrahedral species, with the heats of reaction, 57.3 and 60.7 kJ/mol for the chloride and the bromide, respectively. Some discussions on both the effects are also presented.

Novel adducts of ethanedialdioxime with halides of nickel(II) and cobalt(II)

Ethanedialdioxime (glyoxime, gH2) readily combines with dry CoCl2, NiCl2, and NiBr2 in non-aqueous medium to yield the novel adducts CoCl2(gH2), NiCl2(gH2), and NiBr2(gH2). Synthesis, conventional characterization and magnetic moment data collected in the temperature range 95–293 K are reported for these diamagnetic adducts.

Phosphinomacrocycles. Part 12. (Tertiary phosphinomacrocycle)cobalt(II) halide coordination chemistry. Identification and interconversion of four types of complexes

Phosphinomacrocycles. Part 12. (Tertiary phosphinomacrocycle)cobalt(II) halide coordination chemistry. Identification and interconversion of four types of complexes

Selective hydrogenation of 1,3-diolefins catalyzed by cobalt(I)-bipyridyl complexes

Selective hydrogenation of nonbranched 1,3-diolefins mainly to cis-2-olefins was carried out in THF-ethanol by the catalysis of CoX(bpy) 2 (X = halogen, bpy = 2,2′-bipyridyl) prepared in situ from cobalt halides, 2,2′-bipyridyl, and zinc. The induction period, the rate, and stereoselectivity depend on the time when 1,3-butadiene and hydrogen are introduced to the catalyst. The rate is proportional to the hydrogen pressure and to the catalyst concentration, and changes with the concentration of 1,3-butadiene. An excess of butadiene inhibits hydrogenation and leads to dimerization. A mechanism is proposed which involves an anti-1-methyl-π-allylcobalt complex as an intermediate.

Bridged C5Me5CoII Complexes— Reactive Intermediates in the Cyclopentadienylation of Cobalt(II) Halides

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 230. DOI:10.1002/anie.198202300

Oxazolidine-2-thione as ligand towards cobalt(II) halides

Although oxazolidine-2-thione (oxt) is unstable enough to give a ring opening, it reacts with cobalt(II) halides forming Co(oxt 2)X 2 complexes (X = Cl, Br, I). The complexes are S-bonded; using i.r. spectroscopy it can be seen that the cobalt-halogen vibrations are in the expected range, while a common vibration at 234 cm −1 is tentatively attributed to v CoS. Colour and magnetic studies carried out on the chloro-derivative as well electronic spectra support a tetrahedral stereochemistry around cobalt(II). From the electronic spectra in the solid state, the crystal field parameters have been calculated and the oxt is inserted in the spectrochemical series of cobalt(II).

The Infrared Spectra of Cobalt(II) Halide Complexes with Trimethylphosphine Oxide (TMPO)

Abstract The infrared spectra (4000–150 cm−1) of molecular complexes of cobalt(II) halides with trimethylphosphine oxide (TMPO), CoCl2.2TMPO, Cobr2.2TMPO and Col2.2TMPO, are investigated for polycrystalline samples. The band assignments for TMPO ligand fundamentals are made for a C3v local symmetry. The skeletal stretching vibrations are assigned in the 450–400 cm−1 region for μ(Co-O) and in the 320–150 cm−1 region for μ(Co-X). The frequency ratios μa(Co-X)/μs(Co-X) are compared with the ratios calculated from G matrix elements √Ga(Co-X)/Gs (Co-X) and result a tetrahedral geometry (C2v symmetry) for the CoX2O2 skeleton. The any characteristic infrared bands in this frequency region. From the relative intensities, the formers are attributable as μaCo-O and the latters as μsCo-O. The observed band positions are quite comparable with those reported for other TMPO complexes.

Hydrodimerization of methyl vinyl ketone catalyzed by Co(I)-bipyridyl complexes

Methyl vinyl ketone was hydrodimerized to 2,7-octanedione in an alcoholic solution by CoX(bpy) 2 ( X = halogen, bpy = 2,2′-bipyridyl) prepared in situ from cobalt halides, 2,2′-bipyridyl, and zinc. The catalytic activity decreased in the order I > Br > Cl. The addition of alkali halides, of which sodium iodide was the most effective, gave higher yields of the hydrodimer in the presence of zinc. The cohydrodimerization between methyl vinyl ketone and excess methyl acrylate was carried out to yield methyl 6-ketoheptanoate and 2,7-octanedione in approximately equal ratio.

Hydrodimerization of Methyl Acrylate Catalyzed by Halogenotris(triphenylphosphine)cobalt

Abstract Methyl acrylate was hydrodimerized in a methanolic solution by CoX(PPh3)3 (X=halogen) into dimethyl adipate. The in situ prepared cobalt complexes from cobalt halides, triphenylphosphine, and zinc gave higher yields of the hydrodimer in the presence of alkali halides. A mechanism is proposed which involves the protonation of Co(I)–methyl acrylate π-complex to give (2-methoxycarbonylethyl)cobalt complex, followed by a further addition of methyl acrylate.

Cobalt(II) halide complexes with imidazolidine-2-selone derivatives

CoL2X2 (X = Cl, Br or I) complexes were obtained by reacting cobalt(II) halides withN-methyl-,N-ethyl-,N,N′-dimethyl- andN,N′-diethyl-imidazolidine-2-selone. The same ligands with cobalt(II) tetrafluoroborate gave CoL4(BF4)2 complexes only with the disubstituted ligands. On the basis of i.r. and electronic spectra all the complexes are considered to be Se-bonded to the metal with a tetrahedral stereochemistry, as supported by magnetic measurements and colours. The ligand field parameters (Dq, B′ and β) for the [CoL4]2+ ion are evaluated by using the averaged ligand field approximation. The influence of the substituents on these parameters are discussed and compared with those obtained for the analogous complexes with the sulphur parent ligands.

Stereochemical trends for complexes of cobalt(II) halides and thiocyanate with a series of mono-, di- and tri-methyl-pyridines

The electronic and vibrational spectra of the cobalt(II) complexes of methy-substituted pyridines have been systematically investigated in an effort to establish a general relationship between the electronicsteric requirments of the ligands and the stoichiometry, stereochemistry, and stability of the complexes. Some sixty complexes were examined, in which the anions were chloride, bromide, iodide and thiocyanate. The ligands included all possible isomers of the mono- and di-methyl-pyridines, as well as two of the isomeric tri-methyl-pyridines. In the course of this study some twenty new complexes were obtained and characterized, and of special interest among these was an unusual series of square pyramidal cationic species.

Complexes of metal ions with phosphorus or arsenic containing ligands. Part XVIII. Chelates ofo-phenylenebis(diarylarsines) with cobalt(II) and nickel(II) halides and pseudohalides

Ten complexes of nickel(II) and cobalt(II) witho-phenylenebis(diphenylarsine), (pdpa) ando-phenylenebis(di-p-tolylarsine), (pdta) have been synthesised. The stoichiometry of complexes is markedly dependent upon the reaction temperature, thus reaction atca. 0° gives the M(A-A)2X2 chelates, [M = Ni, X = Br, (A-A) = pdpa; M = Ni, X = I, (A-A) = pdpa, pdta; M = Co, X = CNS, (A-A) = pdpa] whereas at higher temperatures the M(A-A)X2 chelates [M = Ni, X = Br, I, (A-A) = pdpa, pdta; M = Co, X = CNS, (A-A) = pdpa or pdta] are obtained. The Ni(A-A)2I2 compounds can be converted into Ni(A-A)I2 by boiling under reflux in n-BuOH; the conversion can be reversed by cooling a CH2Cl2 solution of the latter at or below 0°. Stereochemical assignments of all the new complexes have been made on the basis of room temperature μeff values, molar conductance, i.r. and u.v. data.