Hexaamminecobalt chloride

In the complex [Co(NH3)6]Cl3, the cation is [Co(NH3)6]3+, and it is named first. The coordinated ammonia molecules are named as ammine, with the number of them being indicated by the prefix hexa. Therefore, the name for the compound is hexaamminecobalt(III) chloride. There are no spaces in the name of the cation. [Co(NH3)5C1]C12 has five NH3 molecules and one CN coordinated to Co3+. Following the rules just listed leads to the name pentaamminechlorocobalt(III) chloride. Potassium hexacyanoferrate(III) is K3[Fe(CN)6j. Reinecke s salt, NH4[Cr(NCS)4(NH3)2], would be named as ammonium diamminetetrathiocyanatochro mate (III). In Magnus s green salt, [Pt(NH3)4][PtCl4], both cation and anion are complexes. The name of the complex is tetraammineplatinum(II) tetrachloroplatinate(II). The compound [Co(en)3](N03)3 is named as tris(ethylenediamine)cobalt(III) nitrate. 

Most authorities attribute the discovery of the first metal ammine to Tassaert, a Parisian chemist about whom virtually nothing is known — not even his first name. In his short article12 he is identified only as Citoyen Tassaert — Citizen Tassaert. Some chemists imply or even openly state that Tassaert was the first to prepare hexaamminecobalt(III) chloride, [Co(NH3)6]C13, the parent compound from which all cobalt ammines may be considered to be derived. Yet he merely observed the brownish mahogany color of the solution formed when excess aqueous ammonia is added to a solution of cobalt chloride or cobalt nitrate, and he failed to follow up his accidental discovery. 

Kekule s instability criterion failed completely in the case of many coordination compounds, which were classified as molecular compounds by sheer dint of necessity although they were extremely resistant to heat and chemical reagents. For example, although hexaamminecobalt(III) chloride contains ammonia, it neither evolves this ammonia on mild heating nor does it react with acids to form ammonium salts. Also, addition of a base to its aqueous solution fails to precipitate hydrated cobalt(III) hydroxide. 

Luteocobaltic chloride (modern, [Co(NH3)6]C13, hexaamminecobalt(III) chloride) is a stable yellow-orange compound.55 In solution, all the chlorine is immediately precipitated by silver nitrate. Treatment with hydrochloric acid at 100 °C does not remove any ammonia. Treatment with sulfuric acid does not remove any ammonia, but yields the compound Co2(S04)3T2NH3, i.e. the chlorine atoms are replaced by sulfate groups. Clearly, some sort of very stable metal—ammonia bonding but much less stable metal—chlorine bonding is indicated. 

Friend88 specifically criticized Werner s theory and emphasized the differences between his own latent valencies and Werner s Nebenvalenzen. He applied his new theory of valency to ammonium salts, metal ammines and halide double salts , and he proposed that for hexacoordinate central atoms a hexatomic shell forms around the metal but that all the elements or groups are joined together by latent valencies and not necessarily to the metal itself. In 1916, Friend applied his cyclic theory of complexes in detail to the structures of the chlorides of hexaamminecobalt(III), chloro-pentaamminecobalt(III) and dichlorotetraamminecobalt(III) and emphasized four basic differences between his theory and Werner s.89... 

The ammines of cobalt(II) are much less stable than those of cobalt(III) thermal decomposition of [Co(NH3)6]Cl2 is characterized by reversible loss of ammonia, whereas that of [Co(NH3)6]Cl3 is not. In his classic dichotomy of complexes, Biltz regarded [Co (NH 3)3] Cl 2 as the prototype of the normal complex and [Co(NH3)6]Cl3 as that of the Werner or penetration complex. Hexaamminecobalt-(II) chloride has been prepared by the action of gaseous ammonia on anhydrous cobalt (II) chloride or by displacing water from cobalt(II) chloride 6-hydrate with gaseous ammonia. It may also be synthesized in nonaqueous solvents by passing dry ammonia through solutions of cobalt(II) chloride in ethanol, acetone, or methyl acetate. Syntheses in the presence of water include heating cobalt(II) chloride 6-hydrate in a sealed tube with aqueous ammonia and alcohol and the treatment of aqueous cobalt(II) chloride with aqueous ammonia followed by precipitation of the product with ethanol. The latter method is used in this synthesis. Inasmuch as the compound is readily oxidized by air, especially when wet, the synthesis should be performed in an inert atmosphere. 

Twenty-five grams (0.47 mol) of ammonium chloride is dissolved in 150 ml. (about 2.2 mols) of concentrated (14.7 M) aqueous ammonia in a 1-1. Erlenmeyer flask. The solution is continuously agitated while 50 g. (0.21 mol) of finely powdered cobalt (II) chloride 6-hydrate is added in small portions, each portion being dissolved before the next is added. A yellow-pink precipitate of hexaamminecobalt(II) chloride forms with the evolution of heat. 

The black crystalline compound [Co(NH3)8(NO)]Cl2 can be prepared in pure form by saturating an ammoniacal solution of cobalt(II) chloride with nitrogen(II) oxide. Previously reported methods of preparation " result in a product contaminated with hexaamminecobalt(II) chloride, which is only slightly soluble in the solutions used and precipitates together with the black chloride. It should be noted that analysis for cobalt, chlorine, or nitrogen cannot reveal the presence of as much as 10% [Co(NH3)6]Cl2 in a sample of (Co(NH3)b(NO)]C12. The best tests for purity are microscopic examination or magnetic measurements. ... 

In order to avoid this contamination, the procedure described herein utilizes a somewhat higher temperature and a lower concentration of ammonia than has previously been suggested. " The formation of the pink precipitate of hexaamminecobalt(II) chloride is thereby completely eliminated. An additional advantage of the procedure is that no special apparatus is required. - - ... 

A solution of hexaamminecobalt(III) chloride (0.43 g., 0.0016 mole) in 70 ml. of 3.4 M HCl is heated to 70° on a hot plate. To this solution iron(III) chloride 6-hydrate (1.4 g., 0.005 mole) in 10 ml. of hot water is added. The resulting solution is heated for a few minutes until orange crystals begin to form. After the mixture has been cooled to room temperature, the crj stals are collected on a Buchner funnel, washed with alcohol and ether, and dried in an evacuated desiccator over potassium hydroxide or sulfuric acid. A typical jdeld is 0.42 g. (first crop, 60%) plus 0.10 g. (second crop, 14%). Anal. Calcd. for [Co(NH3)6]-[FeCb] N, 19.54 H, 4.18 Cl, 49.55. Found N, 19.52 H, 4.13 Cl, 48.42. (The volumetric chloride anabasis is difficult because of the interference of iron with the end point.)... 

Bis(2,4-pentanedionato)diaquocobalt(II) was first obtained b Gach by warming 2,4-pentanedione (acetylacetone) with precipitated cobalt(II) hydroxide. Jones prepared the compound by adding 2,4-pentanedione to an aqueous solution of hexaamminecobalt(II) ion. Recent workers have employed the method of Charles and Pawlikowski, which consists of adding sodium acetate solution to a water-methanol solution of cobalt(II) chloride and 2,4-pentanedione, followed by recrys-tallization from methanol. Bullen grew crystals from dimethyl-formamide for an x-ray diffraction study. 

Hexaamminecobalt(Ill) ion exhibits two absorption maxima at 475 and 340 nm with extinction coefficients of 58 and 49, respectively. The solubility of the chloride form in water at 20° is 0.26 moles/L. The solubility of the acetate salt is about 1.9 moles/L at 20°. In addition, it has fair solubility in aliphatic and aromatic alcohols. 

The method of Neville and Gorin —allowing glycine to react with hexaamminecobalt(III) chloride in a boiling aqueous potassium hydroxide solution under reflux—favors formation of the fac isomer. 

The coordination number of a metal atom or ion in a complex is the number of donor atoms to which it is coordinated, not necessarily the number of ligands. The coordination sphere includes the metal or metal ion (called the central atom) and its ligands, but no uncoordinated counterions. For example, the coordination sphere of hexaamminecobalt(III) chloride, [Co(NH3)g]Cl3, is the hexaamminecobalt(III) ion, [CofNLIj) ]. These terms are illustrated in Table 25-5. 

Many complexes originating from cobalt ions comply with the regular octahedron structure. If one prepares the yellow crystalline hexaamminecobalt(III) chloride from pink-colored cobalt(II) chloride, one obtains the octahedral structure of a hexaamminecobalt(III) ion it is a building unit of the crystal lattice. If it is dissolved in water, the complex ion remains intact ... 

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