Cyanide complexes cobalt

Metal salts in alkaline solution Cuprammonium complex Nickel and cobalt ammonia complex Cyanides (q.v.) Copper pyrophosphates Plumbites Zincates... 

Many of these cobalt complexes will catalyze the reduction of organic compounds by borohydride, hydrazine, thiols, etc. Cobalt cyanide complexes will catalyze the reduction of a,j8-unsaturated acids by borohydride (105) DMG complexes the reduction of butadiene and isoprene by borohydride, but not by H2 (124) Co(II) salen, the reduction of CHCI3 and CH3CCI3 to the dichloro compounds by borohydride (116) and cyanocobalamin, the selective reduction of -CCI2- by borohydride to -CHCl- in compounds such as aldrin, isodrin, dieldrin, and endrin without... 

Alkali metal boratabenzenes have a wide synthetic applicability just like alkali metal cyclopentadienides. Two syntheses have been developed Ashe s synthesis via organotin intermediates (23) and our cyanide degradation of bis (boratabenzene) cobalt complexes (61). 

Alkali metal boratabenzenes may be liberated from bis (boratabenzene) cobalt complexes 7 and 13 by reductive degradation with elemental Li, sodium amalgam, or Na/K alloy (60), or alternatively by degradation with cyanides (61). The latter method has been developed in detail (Scheme 4). It produces spectroscopically pure ( H-NMR control) solutions of the products 26 the excess alkali metal cyanide and the undefined cyanocobalt compounds produced are essentially insoluble in acetonitrile. 

The bis(boratabenzene)cobalt complexes 7 and 13 may also undergo substitution of a C5H5BR ligand. With Ni(CO)4 in refluxing toluene, the substitution products Co(CO)2(C5H5BR) 15 and 11 are formed (47,49). The cyanide degradation is another important example (Section V,B,2). 

Cobalt in its trivalent state forms many stable complexes in solution. In these complexes, the coordination number of Co + is six. The Co2+ ion also forms complexes where the coordination number is four. Several complexes of both the trivalent and divalent ions with ammonia, amines, ethylene diamine, cyanide, halogens and sulfur ligands are known (see also Cobalt Complexes). 

Nickel may he measured quantitatively hy several microanalytical gravimetric methods that include (l)formation of a red precipitate with dimethyl-glyoxime, (2) precipitation as a hlack sulfide with ammonium sulfide, (3) precipitating as a complex cyanide hy treating with alkali cyanide and bromine, and (4) precipitation as a yellow complex hy treating an ammoniacal solution of nickel with dicyandiamide sulfate (Grossman s reagent), followed hy the addition of potassium hydroxide. All of these methods can separate nickel from cobalt in solution. 

In a classic study, Hume and KolthofF[13] obtained polarographic evidence that, in a 1 M aqueous solution of potassium cyanide, Co(H20)(CN)s is irreversibly reduced at a dropping mercury electrode to a cobalt(I) species, the composition of which was not elucidated. furthermore, the cobalt(I) complex was reported to undergo neither oxidation nor reduction. In addition, the cobalt(III) complex, Co(H20)(CN)5 , was seen to be reducible at the dropping mercury electrode, whereas Co(CN)6 is not electroactive. In earlier work [14], cobalt(II) cyanide complexes were reduced electrolytically to cobalt(I) cyanide species. 

Mechanisms of Substitution Reactions of Cobalt (III) Cyanide Complexes... 

The final product is ferrocyanide and cobaltic EDTA, but this goes through an intermediate which can be isolated, and which is an adduct of these twro. Dr. Wilkins tried this system out in his rapid flow rate system and found a rate of association which was about right for substitution rates on a cobaltous ion. So this seemed to be a case where perhaps the nitrogen end of a cyanide was able to coordinate into a cobaltous complex, with either concomitant cr subsequent charge transfer. Yet no transfer of ligand occurs in the overall reaction. 

Although iron, cobalt, and nickel occur in the same triad in Group VIII., the three elements differ considerably in their ability to form addition compounds with ammonia. Iron forms few ammino-salts, most of which are unstable, and its tendency to complex-salt formation of the ammine type appears in the complex cyanides and not in the ammines themselves. 

Alkali metal 1-methyl- and 1-phenyl-borinates are also available from bis(borinato)cobalt complexes (see below) on treatment with sodium or potassium cyanide in an aprotic solvent like acetonitrile. Cobalt cyanide precipitates and the alkali borinate remains in solution. After addition of thallium(I) chloride to some complexes, thallium 1-methyl- or 1-phenyl-borinate could be isolated as pale yellow solids, the only main group borinates isolated hitherto. They are insoluble in most organic solvents but readily soluble in pyridine and DMSO. The solids are stable on treatment with water and aqueous potassium hydride, but are decomposed by acids <78JOM(153)265). 

Based on the avidity of cobalt for cyanide ions, intravenous injection of the cobalt EDT A complex has been recommended as being the best antidote in cyanide poisoning73). Earlier therapy was based on sodium nitrite and sodium thiosulphate, with partial conversion of haemoglobin to methaemoglobin. 

Rollier, M. A. and E. Arreghini Structure of Copper Salts of Some Complex Cyanides I. Structure of Copper Salts of the Hexacyanides of Cobalt and Chromium. Gazz. chim. Ital. 69, 499 (1939). 

Very recently Geus and co-workers [44, 45] have applied another method based on chemical complexes. This is the complex cyanide method to prepare both monocomponent (Fe or Co) and multicomponent Fischer-Tropsch catalysts. A large range of insoluble complex cyanides are known in which many metals can be combined, e.g. iron(n) hexacyanide and iron(m) hexacyanide can be combined with iron ions, but also with nickel, cobalt, copper, and zinc ions. Soluble complex ions of molybdenum(iv) which can produce insoluble complexes with metal cations are also known. Deposition precipitation (Section A.2.2.1.5) can be performed by injection of a solution of a soluble cyanide complex of one of the desired metals into a suspension of a suitable support in a solution of a simple salt of the other desired metal. By adjusting the cation composition of the simple salt solution, with a same cyanide, it is possible to adjust the composition of the precursor from a monometallic oxide (the case when the metallic cation is identical to that contained in the complex) to oxides containing one or several foreign elements. 

Cobalt, like iron, yields complex cyanide derivatives known respectively as cobalto-eyanides,M4Co(CN)(),andcobalti-cyanides, M3Co(CN)s. Of these, the latter alone are important. Rhodium and iridium in a similar manner yield rhodi-cyanides, M3Rh(CN)6, and iridi-cyanides, M3Ir(CN]6. 

A comparison is interesting of the configurations of the complex cyanides of di- and tri-valent cobalt and iron (Fig. 17). 

Detection of traces of nickel in cobalt salts. The solution containing the cobalt and nickel is treated with excess concentrated potassium cyanide solution, followed by 30 per cent hydrogen peroxide whereby the complex cyanides [Co(CN)6]3- and [Ni(CN)4]4 respectively are formed. Upon adding 40 per cent formaldehyde solution the hexacyanocobaltate(III) is unaffected (and hence remains inactive to dimethylglyoxime) whereas the tetracyanato-nickelate(II) decomposes with the formation of nickel cyanide, which reacts immediately with the dimethylglyoxime. 

The first compound of this type that was obtained was the cobalt complex [CpCo[P(OR)20]3]2Co + (56) (Scheme 37) of Co . It is formed when cobaltocene is treated with P(OR)3 at about 120 °C in a reaction that comprises substitution of a Cp by P(0R)3 followed by a triple Arbuzov rearrangement (see Arbuzov Rearrangement) and complexation of the cobalt ion liberated during the reaction. When (56) is treated with cyanide, the central cobalt ion is extracted as Co(CN)e, thereby liberating the free ligand (55) (Scheme 37). Remarkably, the very inert cobalt atom incorporated in the... 

Russian workers have reported some terpyridyl complexes of co-balt(III) 35), and the bis(terpyridyl) cobalt(II) ion is now known. The magnetic properties of Co(terpy) depend critically on the anion present in the crystal thus, at 20°C the magnetic moments are 4.3 (perchlorate), 2.7 (bromide dihydrate), 2.1 (chloride monohydrate), and 2.2 B. M. (aqueous solution). A study of the temperature dependence of the moment for Co(terpy)2Br2 2H20 indicated that no simple explanation was possible 379). The subject has been considered more recently by Judge and Baker 412a). Some peculiar bipyridyl derivatives of cobalt(II) cyanide were reported some years ago 571) these could warrant further investigation. The UV spectra of Co(II) and Co(III) complexes have also been measured. 

The Chromic and Cobaltic Complexes. Tervalent chromium and cobalt combine with cyanide ion, nitrite ion, chloride ion, sulfate ion, oxalate ion, watei. ammonia, and many other ions and molecules to... 

The cobalt(II) cyanide complex Co(CN)5 " in aqueous solution acts as a homogeneous catalyst for the selective hydrogenation of conjugated dienes to monoenes (81). The initial step in this catalysis is the reaction... 

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