Metal Sulfonated Cobalt Complexes

In the synthesis of the 1 1 cobalt complex 17 by the nitrite method, a mixture of CoS04-7 H20 and NaN02 in water and the dye formed by acid coupling of diazotized 2-amino-4,6-dinitrophenol with 2-phenylaminonaphthalene-4 -sulfonic acid is subjected to dropwise addition of dimethylformamide. Metallization commences immediately and is complete within 2 h. The 1 1 cobalt complex 17 is precipitated by addition of NaCl and isolated. It is a suitable intermediate for producing unsymmetrical 1 2 cobalt complex dyes such as 18. 

The fact that only one proton is lost from an o.o -diaminodiarylazo compound on metal complex formation is not only of theoretical interest but has important practical implications in the synthesis of unsymmetrical 2 1 chromium(III) and cobalt(III) complex dyestuffs for wool. The most important complexes of these types are those which are doubly negatively charged (Section 58.1) and are obtained from one molecule of a sulfonated tridentate azo compound and one molecule of an unsulfonated tridentate azo compound. In general the latter are insoluble in water and it is necessary to use organic solvents in the manufacture of complexes such as (10). This is very undesirable from the point of view of the dyestuffs manufacturer and any means of avoiding the use of solvents is attractive to him. The use of sulfonated o,u -diaminodiarylazo compounds in combination with, for example, sulfonated o,o -dihydroxydiarylazo compounds opened up one such possibility, e.g. (77), although this has not yet been exploited commercially. 

First, 1 2 metal complexes of (mainly mono-) azo dyes, without sulfonic or carboxylic acid groups, and trivalent metals (see Section 3.11). The metals are preferably chromium and cobalt nickel, manganese, iron, or aluminum are of lesser importance. Diazo components are mainly chloro- and nitroaminophenols or amino-phenol sulfonamides coupling components are (3-naphthol, resorcinol, and 1-phe-nyl-3-methyl-5-pyrazolone. Formation of a complex from an azo dye and a metal salt generally takes place in the presence of organic solvents, such as alcohols, pyridine, or formamide. An example is C.I. Solvent Red 8, 12715 [33270-70-1] (1). 

Transition metal complexes, either as anions or as neutral molecules, are often very good nucleophiles for alkyl halides and sulfonates. Some of them, such as vitamin B12s, a cobalt (I) species, and the solvent-separated ion pair, Na+ S Fe(CO)42-, where S is N-methylpyrrolidinone, are among the most reactive known (1, 2). Reactions are of several types, for example... 

Phthalocyanlnes. Gebler (18) has reported the attachment of a variety of metal phthalocyanines to both 8% and 20% dlvlnylbenzene polystyrene copolymer beads. The attachment of the phthalocyanine unit was either ly a sulfonamide or a sulfone linkage. Nickel, vanadyl, cobalt, iron and manganese complexes were formed in this way. Since solution aggregation accounts for a diminution of the catalytic activity, it was anticipated that polymer immobilization would Increase reactivity. Such an effect was not observed and little advantage over the homogeneous catalysts could be observed in the oxidation of cyclohexene. Oxidations of thiols by immobilized phthalocyanines have been reported (19-20) by both Schutten and Brouwer. 

Transition metals may also be separated via ion-pair chromatography on mac-roporous PS/DVB resins or chemically bonded silica [45]. The mobile phase contains complexing agents and a corresponding ion-pair reagent. If these columns are equilibrated with a surface-active acid such as octanesulfonic acid, metal ions such as copper, nickel, zinc, and cobalt elute in the same order as they do on surface-sulfonated cation exchangers. This suggests that in this case. 

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