Cobalt complexes fluoride

The cobalt complex is usually formed in a hot acetate-acetic acid medium. After the formation of the cobalt colour, hydrochloric acid or nitric acid is added to decompose the complexes of most of the other heavy metals present. Iron, copper, cerium(IV), chromium(III and VI), nickel, vanadyl vanadium, and copper interfere when present in appreciable quantities. Excess of the reagent minimises the interference of iron(II) iron(III) can be removed by diethyl ether extraction from a hydrochloric acid solution. Most of the interferences can be eliminated by treatment with potassium bromate, followed by the addition of an alkali fluoride. Cobalt may also be isolated by dithizone extraction from a basic medium after copper has been removed (if necessary) from acidic solution. An alumina column may also be used to adsorb the cobalt nitroso-R-chelate anion in the presence of perchloric acid, the other elements are eluted with warm 1M nitric acid, and finally the cobalt complex with 1M sulphuric acid, and the absorbance measured at 500 nm. 

By running a potentiometric precipitation titration, we can determine both the compositions of the precipitate and its solubility product. Various cation- and anion-selective electrodes as well as metal (or metal amalgam) electrodes work as indicator electrodes. For example, Coetzee and Martin [23] determined the solubility products of metal fluorides in AN, using a fluoride ion-selective LaF3 single-crystal membrane electrode. Nakamura et al. [2] also determined the solubility product of sodium fluoride in AN and PC, using a fluoride ion-sensitive polymer membrane electrode, which was prepared by chemically bonding the phthalocyanin cobalt complex to polyacrylamide (PAA). The polymer membrane electrode was durable and responded in Nernstian ways to F and CN in solvents like AN and PC. 

Propane31 gives a much more complex mixture of products. Over cobalt(III) fluoride at 150°C, 27 partially fluorinated propanes are identified (Table 1). 

The products from the partial fluorinations of butane32 and 2-methylpropane33 over cobalt(lll) fluoride are even more complex, 51 and 27 compounds, respectively, being identified. Most are C4F H10 n isomers which retained the original carbon skeletons, but up to 2% in each case has the carbon skeleton of the isomer (i.e., 2-methylpropane fluorination yields ca. 2% of products with the butane skeleton). From butane, at 140-230 C, only two compounds are present as more than 10% of the reaction product, 1 //,3//-octafluorobutane (11%) and 1 //,27f,4//-heptafluorobutane (14%). 2-Methylpropane is similar, at 140- 200°C only four compounds are present as over 10% of the product 2-(difluoromethyl)-l,1,1,2,3-pentafluoro-propane (14%), 2-(difluoromethyl)-l,l,2,3,3-pentafluoropropane (16%), 1,1,2,3,3-pentafluo-ro-2-(fluoromethyl)propane (24%), and l,l,2,3-tetrafluoro-2-(fluoromethyl)propane (15%). 

Malononitrile over potassium tetrafluorocobaltate(III) gives a mixture of at least 35 products and the benzonitrile product is almost as complex." However, over cesium tetra-fluorocobaltate(III) at 300°C, benzonitrile gives100 a much simpler mixture and perfluorocyclo-hexanecarbonitrile (ca. 30%) is the major product, with perfluorocyclohexane and per-fluorobenzonitrile as minor ones. Perfluorobenzonitrile is converted, in over 50% yield, by both cobalt(III) fluoride (165-170°C) and potassium tetrafluorocobaltate(III) (210°C), into mainly the nonconjugated monoene perfluoro(cyclohex-3-enecarbonitrile). 

An anionic complex 30 has been synthesized from fluoride attack on Fe-(l-4-f/4-octafluorocyclohexa-l,3-diene)(CO)3] (75), and the cobalt complex 31 is the product of the reaction of perfluorocyclopentadiene with [Co2-(CO)8] (76). No subsequent chemistry of these compounds has been reported. 

Due to the low solubility of cobalt(II) fluoride in most solvents, formation of cobalt fluoro N-donor complexes (which are the only low-valent cobalt fluorides which are reliably reported) features a variety of starting materials. A common theme that runs throughout this work has been the use of [Co(BF4)2] as the fluoride source, and the subsequent controlled decomposition to obtain a metal-bound fluoride. This has been done, for example, with tris- (3,5-dimethyl-pyrazol-l-yl)methyl amine (amtd) to give [M2(amtd)2F(BF4)3(EtOH)Y(H20)] (M = Co, Cu, Zn x = 0-1.5, y = 1-2). The cobalt complex has been structurally characterised by X-ray diffraction [Fig. 3] [57]. Similarly, the combination of [M(BF4)2] (M = Mn, Co, Ni), [M(N03)2], NH4(NCS) and 3,5-diethyl-1,2,4-triazole (detrH) produces... 

F4OW, Tungsten fluoride oxide, 24 37 F4SE, Selenium tetrafluoride, 24 28 FsCJH, Benzene, pentafluoro-cobalt complexes, 23 23-25 lithium and thallium complexes, 21 71,... 

Chromium dioxide, 928 Chromium fluoride, 932 Chromium tetrafluoride, 927 Chromium trioxide, 941 Chromyl bromide, 940 Chromyl chloride, 940 Chromyl halides, 933, 935, 938 Chromyl nitrate, 940 Chromyl perchlorate, 940 CitratoteUurates, 303 Cobalt complexes boron ligands, 99 Cobalt(ll) complexes reduction... 

Althou silver(n) fluoride and potassium tetrafluoroargentate(in) (KAgF4) are slightly less active fluorinating agents than cobalt(in) fluoride, the reaction of either silver compound with benzene at 300—380 °C gives mainly dodecafluoro-cyclohexane (see also p. 6). A similar result is obtained from the complex fluoride at 120°C, but at this temperature silver(n) fluoride itself affords significant... 

Cyclized products are obtained from the vapour-phase fluorination of cycloalkanes using cobalt(iii) fluoride, e.g., cyclo-octane gives a mixture of eight fluorocarbons including perfluorobicyclo[3,3,0]octane and cyclodecane gives a complex mixture including perfluoro-cis- and -tra s-bicyclo[4,4,0]decanes. ... 

In 2010, a cooperative dual-catalyst system was reported to promote the highly enantioselective fluoride ring opening of various meso epoxides having alkene, ester, and protected amine functionalities. The reactions were conducted with a chiral (Salen)cobalt complex, (-)-tetramisole, benzoyl fluoride as a latent source of fluoride in the presence of HFIP. The efficient catalytic enantioselective reaction is explained by the generation of a (Salen)Co(III) fluoride under the cocatalytic conditions that occurred in good yields with up to 95% ee (Scheme 44.32). Racemic terminal epoxides, such as styrene oxide, were also studied, but they almost exclusively lead to the fluorine in the primary position therefore, the fluorine atom was not introduced on a stereogenic center. 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

Assay of beryUium metal and beryUium compounds is usuaUy accompHshed by titration. The sample is dissolved in sulfuric acid. Solution pH is adjusted to 8.5 using sodium hydroxide. The beryUium hydroxide precipitate is redissolved by addition of excess sodium fluoride. Liberated hydroxide is titrated with sulfuric acid. The beryUium content of the sample is calculated from the titration volume. Standards containing known beryUium concentrations must be analyzed along with the samples, as complexation of beryUium by fluoride is not quantitative. Titration rate and hold times ate critical therefore use of an automatic titrator is recommended. Other fluotide-complexing elements such as aluminum, sUicon, zirconium, hafnium, uranium, thorium, and rate earth elements must be absent, or must be corrected for if present in smaU amounts. Copper-beryUium and nickel—beryUium aUoys can be analyzed by titration if the beryUium is first separated from copper, nickel, and cobalt by ammonium hydroxide precipitation (15,16). 

There is also clear evidence of a change from predominantly class-a to class-b metal charactristics (p. 909) in passing down this group. Whereas cobalt(III) forms few complexes with the heavier donor atoms of Groups 15 and 16, rhodium(III), and more especially iridium (III), coordinate readily with P-, As- and S-donor ligands. Compounds with Se- and even Te- are also known. Thus infrared. X-ray and nmr studies show that, in complexes such as [Co(NH3)4(NCS)2]" ", the NCS acts as an A -donor ligand, whereas in [M(SCN)6] (M = Rh, Ir) it is an 5-donor. Likewise in the hexahalogeno complex anions, [MX ] ", cobalt forms only that with fluoride, whereas rhodium forms them with all the halides except iodide, and iridium forms them with all except fluoride. 

Sulphuric acid is not recommended, because sulphate ions have a certain tendency to form complexes with iron(III) ions. Silver, copper, nickel, cobalt, titanium, uranium, molybdenum, mercury (>lgL-1), zinc, cadmium, and bismuth interfere. Mercury(I) and tin(II) salts, if present, should be converted into the mercury(II) and tin(IV) salts, otherwise the colour is destroyed. Phosphates, arsenates, fluorides, oxalates, and tartrates interfere, since they form fairly stable complexes with iron(III) ions the influence of phosphates and arsenates is reduced by the presence of a comparatively high concentration of acid. 

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