Cobalt ammonia complexes

For this reaction, charcoal is a catalyst if this is omitted and hydrogen peroxide is used as the oxidant, a red aquopentammino-cobalt(lll) chloride, [Co(NH3)jH20]Cl3, is formed and treatment of this with concentrated hydrochloric acid gives the red chloro-p0itatnmino-coba. t(lll) chloride, [Co(NH3)5Cl]Cl2. In these latter two compounds, one ammonia ligand is replaced by one water molecule or one chloride ion it is a peculiarity of cobalt that these replacements are so easy and the pure products so readily isolated. In the examples quoted, the complex cobalt(III) state is easily obtained by oxidation of cobalt(II) in presence of ammonia, since... 

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

Spectra of a variety of chromium compoimds in the +3 valence state are included in Fig. 16. The principal peak is centered at about 22-25 ev. in all cases. The CrjOa spectrum is almost identical to that of Mn02 of Fig. 5. Spectra of the oxalato complex and the ammonia complex are almost identical to spectra of the corresponding cobalt compounds of Figs. 13 and 11. 

Forms a number of coordination compounds (ammonia complex) with several metals adds to AgCl forming soluble complex [Ag(NH3)2]Cl forms tetraamine complex [Cu(NH3)4]S04 with CUSO4 and forms many hexaamine complexes with cobalt, chromium, palladium, platinum and other metals. 

Additive compounds of ammonia and cobalt salts were first observed by Tassaert in 1799, although at that time the reaction which takes place when an aqueous ammoniacal solution of cobalt salt is exposed to air was not recognised as one involving the addition of ammonia to the molecule. From that time onwards research has been carried out on these complexes.1... 

Formation and Structure of a Monomeric Oxygen Adduct of a Cobalt(II)-Ammonia Complex in a Co(II)Y Zeolite... 

In this work, 1 1 oxygenated low-spin cobalt(II)-ammonia complexes were synthesized within the zeolite framework by the adsorption of NH3 and 02 in Co(II)Y zeolites with differing cobalt(II) content. Spin densities and the nature of the superoxide anion (02 ) were estimated by introducing oxygen-17 in the ammoniated Co(II) zeolites. Questions concerning the equivalence of the two oxygen atoms have arisen in studies on oxygen adducts of Co (II) Schiff base compounds (7), and it was of interest to study this problem in cobalt(II) ammonia complexes. 

Upon adsorption of excess ammonia in a Co(II)Y zeolite a white, high-spin cobalt(Il)-ammonia complex with a spin configuration of (fe )5-(eg)2 is formed. According to studies of cobalt (II) complexes in solutions, salts, and in zeolites, a hexacoordinate Co(II)-ammonia complex is the most likely form when an excess of ammonia is present (3, 4> ) Indeed,... 

As shown in Table I, the magnetic parameters of the oxygenated Co (Il)-ammonia complex in the zeolite are comparable with other mononuclear Co(II)-02 complexes, regardless of the nature of the cobalt (II) ligands. The very similar spectrum observed by Fujiwara et ah (9) for... 

An examination of the reversibility of the oxygenation shows that upon evacuation of the 02 the high-spin cobalt(II)-ammonia complex was re-... 

We may conclude that the divalent cobalt ions move out into the large cavities upon adsorption of NH3 to form a hexacoordinate cobalt(II)-ammonia complex. Following adsorption of 02 in the ammoniated Co(II)Y zeolites, oxygen enters the coordination sphere of the Co2+ ions. This is accompanied by a charge-transfer process to form a [Co(III) (NH3)502 ]2+ complex. The general intermolecular redox process can be approximated by the reactions... 

According to T. Curtius, feme chloride is reduced by hydrazine to ferrous chloride a reaction investigated by E. Miiller and G. Wegdin, and F. Schrader. E. J. Cuy found that in the reaction between hydrazine and a ferric salt in acid soln., one mol of hydrazine requires between one and two eq. of ferric salt for oxidation. The limiting reaction may be expressed as follows N2H 5-)-Fe" =NH 4+JN2+H +Fe". A. W. Browne and F. F. Shetterly showed that ferric oxide and hydrazine in aq. soln, yield ammonia, but no hydrazoic acid, while nickel sesquioxide and cobalt sesquioxide yield ammonia and traces of hydrazoic acid. H. Franzen and 0. von Mayer made complex cobalt salts—e.g. CoC12(N2H4)2, etc.—with hydrazine in place of ammonia. T. Curtius found that platinum is precipitated when a soln. of hydrazine is added to a neutral soln. of platinum... 

Figure 7-12. The reaction of [Co(en)3]3+ with formaldehyde and ammonia gives cobalt(m) sepulchrate 7.13. A representation of the complex ion in the solid state is also presented.

The acidopentamminecobalt(III) salts have characteristic colors dependent upon the atom coordinated, i.e., salts in which there is a cobalt-oxygen bond vary in color from pink to red the fluoro complex is pink the chloro, red the bromo, purple the iodo, olive green and the nitro, orange. The nitrate salts of most of these complexes are only slightly soluble in water. None of these compounds is soluble in nonpolar solvents. Solutions of the compounds may decompose after long standing, liberating ammonia and cobalt hydroxide. Rates of aquation and of hydrolysis... 

Although a statistical factor contributes to the equilibrium constants for many types of reactions, it is in reactions of the type being considered here—the replacement of one neutral ligand by another neutral ligand— that this factor may be the principal factor in causing variation of Kn with n. Other series of reactions of this type are the formation of ammonia complexes in aqueous solution. The variation of Kn with n observed for the chromium (III)/water-methyl alcohol system is slightly smaller than observed for ammonia complexes of cobalt(II) (18) and nickel(II) (19) ... 

Table 1.4 Formulations of cobalt(+3) chloride-ammonia complexes...

In 1893, at the age of 26, Alfred Werner stepped outside the box and proposed his coordination theory that revolutionized the held of inorganic chemistry. Werner s work, in part, made use of colorful cobalt compounds prepared by the reaction of ammonia with cobalt salts. Fortunately, these cobalt salts are quite stable ( robust ) in aqueous solution. This stability, along with the rapid development of qualitative and quantitative analytical techniques, enabled Werner to carry out the rigorous and in-depth analyses that led to the determination of molecular formulas and prediction of structures and geometries. His work opened the door to understanding bonding and stability (Chapter 3) and reactivity (Chapters 4 and 5) in metal coordination complex systems. 

Verbing" a noun—do not turn nouns into verbs. incorrect ammonia complexes to cobalt ions... 

Electronic reflectance spectra of the Co(II)-exchanged dehydrated Type A zeolite, Co(II)A, show that the cobalt ions enter the S-II positions, where they form complexes with nitrous oxide, cyclopropane, water, and ammonia. These molecules represent ligands of increasing bond strength and, with the exception of ammonia, form reversible complexes with Co(II)A. In the case of nitrous oxide and cyclopropane, these complexes have a C3y symmetry water and ammonia complexes are tetrahedral. On a long exposure to water and ammonia, the Co(II) ions become highly coordinated to these ligands. 

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