Trivalent cobalt

La(Mn,Ga)03 (225), and (La,Ba)(Mn,Ti)03 (308). With less than 50% cobalt, trivalent cobalt is diamagnetic Co111 ( 2). Ga3+ and Ti4+ are also diamagnetic. The electronic configuration of Ni111 may also be correlated with the lattice vibrations (quasistatic model). In Figure 60 are shown the ratios c/ /2a for the lanthanum sys-... 

Despite the above similarities, many differences between the members of this triad are also to be noted. Reduction of a trivalent compound, which yields a divalent compound in the case of cobalt, rarely does so for the heavier elements where the metal, univalent compounds, or hydrido complexes are the more usual products. Rhodium forms the quite stable, yellow [Rh(H20)6] " ion when hydrous Rh203 is dissolved in mineral acid, and it occurs in the solid state in salts such as the perchlorate, sulfate and alums. [Ir(H20)6] + is less readily obtained but has been shown to occur in solutions of in cone HCIO4. 

When tt o d eigenfunctions are available, as in trivalent cobalt, quadrivalent palladium and platinum, etc., six equivalent bond eigenfunctions of strength 2.923 and directed toward the comers of a regular octahedron can be formed. These form the bonds in a great many octahedral complexes. 

It is interesting to note, as pointed out to me by Mr. J. L. Hoard, that these considerations lead to an explanation of the stability of trivalent cobalt in electron-pair bond complexes as compared to ionic compounds. The formation of complexes does not change the equilibrium between bivalent and trivalent iron very much, as is seen from the electrode potentials, while a great change is produced in the equilibrium between bivalent and trivalent cobalt. 

Partenheimer showed (ref. 15) that when toluene was subjected to dioxygen in acetic acid no reaction occurred, even at 205 °C and 27 bar. He also showed that when a solution of cobalt(II) acetate in acetic acid at 113 °C was treated with dioxygen ca. 1 % of the cobalt was converted to the trivalent state. In the presence of a substituted toluene two reactions are possible formation of a benzyl radical via one-electron oxidation of the substrate or decarboxylation of the acetate ligand (Fig. 9). Unfortunately, at the temperatures required for a reasonable rate of ArCH3 oxidation (> 130 °C) competing decarboxylation predominates. As noted earlier, two methods have been devised to circumvent this undesirable... 

Cobaltites with spinel stractnre have compositions MC02O4, where M is a metal forming divalent cations, snch as zinc, cadminm, magnesinm, nickel, manganese, and divalent cobalt. In contrast to the perovskites, the cobaltites have a rather high catalytic activity already at room temperatnre. Experiments show that the activity increases with increasing spinel structure content (i.e., increasing number of Co ions) of the catalyst snrface. The trivalent cobalt ions promote the withdrawal of... 

Chemical precipitation is used in porcelain enameling to precipitate dissolved metals and phosphates. Chemical precipitation can be utilized to permit removal of metal ions such as iron, lead, tin, copper, zinc, cadmium, aluminum, mercury, manganese, cobalt, antimony, arsenic, beryllium, molybdenum, and trivalent chromium. Removal efficiency can approach 100% for the reduction of heavy metal ions. Porcelain enameling plants commonly use lime, caustic, and carbonate for chemical precipitation and pH adjustment. Coagulants used in the industry include alum, ferric chloride, ferric sulfate, and polymers.10-12... 

This small class of blue copper-complex dyes has made a significant contribution to the acid and reactive ranges in recent years (sections 5.4.2, 5.4-3 and 7.5.8). The essential chromogen is the bicyclic 1 1 chelated grouping illustrated (1.20). Trivalent metals such as chromium, nickel or cobalt will give tetracyclic 1 2 complexes with a central metal atom, analogous to conventional 1 2 metal-complex azo dyes. 

In isolation the electron distribution in the trivalent chromium (III) ion consists of three unpaired electrons in the d shell, as indicated in line (a) of Table 5.1. In line (b) the six electron pairs donated to the central chromium atom by oxygen atoms of water molecules give rise to sp3d2 hybridisation. This is characteristic of an octahedral structure. A similar situation arises with the trivalent cobalt(III) complex in line (e), where each of the three t2g levels is doubly occupied by an electron pair from each cyano ligand. 

Symmetrical premetallised 1 2 metal-dye complexes of unsulphonated monoazo structures with aluminium (5.57) or trivalent iron (5.58) have been patented recently for use as solvent dyes [36]. They contain a polar methoxypropylaminosulphone grouping in each diazo component and are marketed as alkylamine salts. It remains to be seen, however, whether a full colour gamut of bright aluminium and iron complex dyes can be discovered with light fastness performance equivalent to that of currently available chromium and cobalt complex dyes. 

As we have seen earlier that the trivalent metal complexes are normally bound still more firmly due to the formation of four rings (unlike three rings with divalent metal complexes) and stable in strongly acidic solutions, for instance cobalt (Co2+) EDTA complex is fairly stable in concentrated hydrochloric acid ( 11.5 N). 

In studies of the concentrations of arsenic, bromine, chromium, copper, mercury, lead and zinc in south-eastern Lake Michigan, it was shown that these elements concentrated near the sediment water interface of the fine-grained sediments. The concentration of these elements was related to the amount of organic carbon present in the sediments (161). However, it was not possible to correlate the concentration of boron, berylium, copper, lanthanum, nickel, scandium and vanadium with organic carbon levels. The difficulty in predicting the behaviour of cations in freshwater is exemplified in this study for there is no apparent reason immediately obvious why chromium and copper on the one hand and cobalt and nickel on the other exhibit such variations. However, it must be presumed that lanthanium might typify the behaviour of the trivalent actinides and tetravalent plutonium. 

There have been a number of studies of the physical and bonding behavior of these mixed transition-metal oxides, which conclude that in the fully lithiated compounds the cobalt is trivalent, the nickel predominantly divalent, and the manganese tetra-valent. Thus, the electrochemically active species is predominantly nickel with the cobalt playing an... 

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