Cobalt complexes colors

Formazan, l-(2-hydroxy-5-suIfophenyl)-3-phenyl-5-(2-carboxyphenyl)-zinc detection, 6, 83 Formazans cobalt complexes dyes, 6, 81 metal complexes bidentate, 6, 78 color photography, 6,111 dyes, 6, 77 tetradentate, 6, 81 tridentate, 6, 79... 

The most intriguing results were obtained for cobalt(III) chloride. By 1890, several ammonia compounds of C0CI3 had been isolated. These coordination compounds differed in several of their properties, the most striking of which were their beautiful colors. At the time, the formulas of these cobalt complexes were written as follows ... 

P.Y.179, an isoindolinone/cobalt complex pigment, was introduced to the market only few years ago but the production has recently been discontinued. It was recommended for use in paints, especially in automotive finishes. The pigment produces a reddish yellow shade. High lightfastness and excellent weatherfastness are an asset in pastel colors. Besides, good transparency made P.Y.179 a suitable product for metallic finishes. Yet, it is not quite as weatherfast as the equally reddish yellow P.Y.24, a flavanthrone pigment. 

Several recent examples of this technique are outlined in Scheme 70.l99 20li20S 206 The starting cobalt complexes are highly colored, air stable compounds that require no special precautions in handling. The process is relatively cost effective most cobalt precursors are less expensive per mole than tributyltin hydride. The reactions are conducted by visible light irradiation in a variety of solvents and can often be followed by color changes characteristic of the different oxidation states of cobalt. A disadvantage is that... 

The iron compound readily sublimes and yields well-formed, black lustrous crystals. The cobalt complex will also readily sublime, but dependent upon the temperature at which the crystals are formed, they can be either black or brown in color. The crystal structures of both the cobalt and iron complexes have been determined.3 The nickel complex sublimes only in small amounts with difficulty. All three complexes are unstable to air and water, and the nickel complex readily undergoes thermal decomposition above 100°C. All three compounds will also readily form complexes with a variety of donor ligands such as tertiary arsines or phosphines. The nickel compound usually forms 2 1 adducts such as [(C6HS )3P]2Ni(NO)I, while the iron and cobalt complexes often undergo disproportionation.5... 

Anodized aluminum is a good acceptor for water soluble 1 2 chromium and cobalt complex dyes. For example, the cobalt complex 38 [112144-04-4] imparts a black color to this substrate [63],... 

From the optical properties of the solutions it is clear that the blue color is associated with cobalt complexing (Table XI and Figure 11). At low concentrations of AlEt2Cl the blue color of the cobaltamine complex persists, but at the higher concentrations of AlEt2Cl when the color is yellow it is reasonable... 

An example of the effect of temperature on an endothermic reaction is illustrated in Figure 12. The following equation describes an equilibrium that involves the two colored cobalt complex ions. 

Q5.1 Why is [Co(ox)]33 sensitive to light and heat and the other complexes not Q5.2 Note the colors of all four cobalt complexes prepared in the lab. Provide an explanation for this. 

The equilibrium of the following two cobalt complexes shows a change of the structure and of the coordination number. This equilibrium can also be demonstrated as being dependent on temperature. If hydrochloric acid is added to a pink-colored cobalt(II) chloride solution, the solution changes to blue due to the chloro complex (see E9.10). If the solution is diluted again with water, the pink color returns ... 

Problem In order to intensify the idea of equilibrium and the dependence on temperature, cobalt complexes are useful with a mixture of water molecules and chloride ions as ligands for cobalt complexes the blue colored tetra chloro cobalt complex proves stable in heat, the pink colored hexa aqua cobalt complex in the cold solution, respectively. A cross-linkage to the idea of equilibrium (see Chap. 6) is possible. 

In the variant of the procedure adapted by the European Pharmacopoeia, no amine ligand is added. Instead, calcium is added, and this gives a variant of the above complexes of a structure, which has not been elucidated. The complex is insoluble in methanol. The presence of calcium also explains the violet-blue color, since most of the complexes with amines are violet. The cobalt complexes are more likely to precipitate when making the test solution... 

Synthesis of the phthalocyanine-2,9,16,23-tetracarboxylic acid tetrachloride cobalt complex 48 (R = -COCl M = Co(II)) 0.5 g of the tetracarboxylic acid was added to 1.5 mL thionyl chloride containing 2 drops of pyridine. The mixture was heated for 20 h under reflux at 80 °C. After centrifugation the blue-colored acid chloride was dried at 100 °C in vacuo over P4O10. Yield 0.48 g (88%). IR (KBr) 1657, 1522, 1323, 1091, 749, 719 cm". ... 

For example, there are at least three different cobalt(III) complexes that can be isolated when C0CI2 is dissolved in aqueous ammonia, and the product is then oxidized in air so it can form into the 3+ oxidation state. Table 13-1 lists the formulas of some cobalt complexes and the colors they display. 

As the oxidation mechanism the Shibata brothers proposed the activation of water molecules which were replaced by the aquation reaction of anionic ligands in a complex ion. They summarized the results of their early 16 papers, and in 1936 they published a book Katalytische Wirkungen der Metallkomplexverbindungen 34). This book was not frequently cited in the chemical literatures of English- speaking countries probably because it was written in German, and the publication was close to the outbreak of World War II. In 1974, however, 40 years after the publication of this book, Eastman Kodak Co. requested a US patent on the use of a cobalt complex such as [Co(NH3)6]Cl3 as an amplifier in the development of color films (55). Although no reference is made to the works of Shibata, it is supposed that the chemists at Eastman Kodak Co. studied the works of Shibata and co-workers. 

Terpositive chromium and cobalt combine with cyanide ion, nitrite ion, chloride ion, sulfate ion, oxalate ion, water, ammonia, and many other ions and molecules to form a very great number of complexes, with a wide range of colors that are nearly the same for corresponding chromic and cobaltic complexes. Most of these complexes are stable, and are formed and decomposed slowly. Representative are the members of the series... 

---