Cobalt preparation

Ferric boride, produced by heating together boron and wrought-iron in an electric furnace, consists of brilliant yellowish-grey crystals, burning brilliantly when heated in oxygen, and attacked by nitric acid. The corresponding compounds of nickel and cobalt, prepared in the same... 

FIGURE 1 Change of the normalized electrical resistance (GMR effect) as a function of the magnetic field for a granular thin film of silver/cobalt prepared by molecular beam epitaxy. SOURCE Alof, 2000. 

Floriani, C., and F. Calderazzo (1969). Oxygen adducts of Schiffs base complexes of cobalt prepared in solution. J. Chem. Soc. A 6, 946-953. 

For a more precise measurement of light colors below 15 platinum-cobalt, prepare color standards from the stock solution in accordance with Table 3 by diluting the required volumes to 100 mL with water in the Nessler tubes. Use a semi-microburet for measuring the required amount of stock solution. 

Pathmamanoharan C and Philipse A P 1998 Preparation and properties of monodisperse magnetic cobalt colloids grafted with polyisobutene J. Colloid Interface Sol. 205 304-53... 

These are practically insoluble in water, are not hydrolysed and so may be prepared by addition of a sufficient concentration of sulphide ion to exceed the solubility product of the particular sulphide. Some sulphides, for example those of lead(II), copper(II) and silver(I), have low solubility products and are precipitated by the small concentration of sulphide ions produced by passing hydrogen sulphide through an acid solution of the metal salts others for example those of zincfll), iron(II), nickel(II) and cobalt(II) are only precipitated when sulphide ions are available in reasonable concentrations, as they are when hydrogen sulphide is passed into an alkaline solution. 

The reaction provides a valuable method of preparing anhydrous chlorides of metals. It has been used to prepare the anhydrous chlorides of copper(II), zinc, cadmium, chromium(III), iron(III). cobalt(Il) and nickel. 

The higher iodides, however, tend to be unstable and decomposition occurs to the lower iodide (PI5 -> PI3). Anhydrous chlorides and bromides of some metals may also be prepared by the action of acetyl (ethanoyl) halide on the hydrated ethanoate (acetate) in benzene, for example cobalt(II) and nickel(II) chlorides ... 

Cobaltilll) nitrate Co(N03)3 has been prepared by the reaction of dinitrogen pentoxide with cobalt(III) fluoride. 

A key intermediate, 163, which possesses all but one chiral center of (+ )-brefeldin, has been prepared by the enantiocontrolled cycloaddition of the chiral fi,/3-unsaturated ester 162 to 154[107], Synthesis of phyllocladane skeleton 165 has been carried out by the Pd-catalyzed cycloaddition of the unsaturated diester 164 and cobalt-catalyzed cycloaddition of alkynes as key reactions[108]. Intramolecular cycloaddition to the vinylsulfone in 166 proceeds smoothly to give a mixture of the trans and cis isomers in a ratio of 2.4 1[109], Diastereocontrolled cycloaddition of the hindered vinylsulfone 167 affords a single stereoisomeric adduct, 168, which is used for the synthesis of the spirocarbocyclic ring of ginkgolide[l 10],... 

The 3.8-nonadienoate 91, obtained by dimerization-carbonylation, has been converted into several natural products. The synthesis of brevicomin is described in Chapter 3, Section 2.3. Another royal jelly acid [2-decenedioic acid (149)] was prepared by cobalt carbonyl-catalyzed carbonylation of the terminal double bond, followed by isomerization of the double bond to the conjugated position to afford 149[122], Hexadecane-2,15-dione (150) can be prepared by Pd-catalyzed oxidation of the terminal double bond, hydrogenation of the internal double bond, and coupling by Kolbe electrolysis. Aldol condensation mediated by an organoaluminum reagent gave the unsaturated cyclic ketone 151 in 65% yield. Finally, the reduction of 151 afforded muscone (152)[123]. n-Octanol is produced commercially as described beforc[32]. 

The first identified complexes of unsubstituted thiazole were described by Erlenmeyer and Schmid (461) they were obtained by dissolution in absolute alcohol of both thiazole and an anhydrous cobalt(II) salt (Table 1-62). Heating the a-CoCri 2Th complex in chloroform gives the 0 isomer, which on standirtg at room temperature reverses back to the a form. According to Hant2sch (462), these isomers correspond to a cis-trans isomerism. Several complexes of 2,2 -(183) and 4,4 -dithiazolyl (184) were also prepared and found similar to pyridyl analogs (185) (Table 1-63). Zn(II), Fe(II), Co(II), Ni(II) and Cu(II) chelates of 2.4-/>is(2-pyridyl)thiazole (186) and (2-pyridylamino)-4-(2-pyridy])thiazole (187) have been investigated. The formation constants for species MLr, and ML -" (L = 186 or 187) have been calculated from data obtained by potentiometric, spectrophotometric, and partition techniques. 

Manufacture. Furan is produced commercially by decarbonylation of furfural in the presence of a noble metal catalyst (97—100). Nickel or cobalt catalysts have also been reported (101—103) as weU as noncatalytic pyrolysis at high temperature. Furan can also be prepared by decarboxylation of 2-furoic acid this method is usually considered a laboratory procedure. 

Solution polyacrylamides can also be prepared at high polymer soHds by radiation processes (80,81). Polyacrylamides with molecular weights up to 20 million can be prepared by inradiation of acrylamide and comonomers in a polyethylene bag with cobalt-60 gamma radiation at dose rates of 120-200 J/kg-h. The total dose of radiation is controlled to avoid cross-linking. 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

Cobalt trifluoride is readily prepared by reaction of fluorine (qv) and C0CI2 at 250°C or C0F2 at 150—180°C. Direct fluorination of C0F2 leads to quantitative yields of 99.9% pure CoF (4). 

Many perfluoroaUphatic ethers and tertiary amines have been prepared by electrochemical fluorination (1 6), direct fluorination using elemental fluorine (7—9), or, in a few cases, by fluorination using cobalt trifluoride (10). Examples of lower molecular weight materials are shown in Table 1. In addition to these, there are three commercial classes of perfluoropolyethers prepared by anionic polymerization of hexafluoropropene oxide [428-59-1] (11,12), photooxidation of hexafluoropropene [116-15-4] or tetrafluoroethene [116-14-3] (13,14), or by anionic ring-opening polymeriza tion of tetrafluorooxetane [765-63-9] followed by direct fluorination (15). 

Tetrafluorobenzene. This compouad has beea prepared by fluoriaatioa of hen2ene with cobalt trifluoride and subsequent combination of the dehydrofluoriaation and defluoriaation steps. Its ioni2ation potential is 9.01 V. Nitration gives 2,3,4,5-tetrafluoronitroben2ene [5580-79-0] ia 75% yield, an iatermediate to fluoroquinolone antibacterials (218). 

Pentafluorobenzene. Pentafluoroben2ene has been prepared by several routes multistage saturation—rearomati2ation process based on fluorination of ben2ene with cobalt trifluoride reductive dechlorination of chloropentafluoroben2ene with 10% pabadium-on-carbon in 82% yield (226,227) and oxidation of penta uorophenylbydra2ine in aqueous copper sulfate at 80°C in 77% yield (228). Its ioni2ation potential is 9.37 V. One measure of toxicity is LD q = 710 mg/kg (oral, mouse) (127). 

MMA and MAA can be produced from ethylene [74-85-1/ as a feedstock via propanol, propionic acid, or methyl propionate as intermediates. Propanal may be prepared by hydroformylation of ethylene over cobalt or rhodium catalysts. The propanal then reacts in the Hquid phase with formaldehyde in the... 

Naphthaleneacetic acid has also been prepared by the carbonyl-insertion reaction of 1-chloromethylnaphthalene cataly2ed by carbonyl cobalt cation (90,91). Carboxylation of 1-chloromethylnaphthalene in the presence of the catalyst Pd[P(CgH )2]2Cl2 under phase-transfer conditions gave 1-naphthaleneacetic acid in 78% yield (92). 

Ma.nufa.cture. Nickel carbonyl can be prepared by the direct combination of carbon monoxide and metallic nickel (77). The presence of sulfur, the surface area, and the surface activity of the nickel affect the formation of nickel carbonyl (78). The thermodynamics of formation and reaction are documented (79). Two commercial processes are used for large-scale production (80). An atmospheric method, whereby carbon monoxide is passed over nickel sulfide and freshly reduced nickel metal, is used in the United Kingdom to produce pure nickel carbonyl (81). The second method, used in Canada, involves high pressure CO in the formation of iron and nickel carbonyls the two are separated by distillation (81). Very high pressure CO is required for the formation of cobalt carbonyl and a method has been described where the mixed carbonyls are scmbbed with ammonia or an amine and the cobalt is extracted as the ammine carbonyl (82). A discontinued commercial process in the United States involved the reaction of carbon monoxide with nickel sulfate solution. 

Two blue pigments can be prepared in transparent form cyanide iron blue and cobalt aluminum blue. These pigments are used in achieving a blue shade of the metal effect pigments in metallic paints. Transparent cyanide iron blue is prepared by a precipitation reaction similar to the one used for the preparation of the opaque pigment, but considerably lower concentrations of solutions are used. It is produced by Degussa (Germany), Manox (U.K), and Dainichiseika (Japan). 

Transparent cobalt aluminum blue is prepared by the precipitation of diluted solutions of cobalt and aluminum with alkaHes. The formed precipitate of hydroxides is washed, filtered off, dried, and calcined at about 1000°C. 

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