Zinc -, tetrachlorozincate

As the range of components available for use in the azoic dyeing process expanded, research was simultaneously targeted on improvements designed to make the process more attractive to the commercial dyer. The necessity for the dyer to diazotise the Fast Base was removed with the introduction of stabilised diazonium salts [111], known as Fast Salts. Stabilisation was achieved by a judicious selection of the counter-ion to the diazonium cation various anions have found use in commercial Fast Salts and some examples are listed in Table 4-4. Particularly effective is the diazonium tetrachlorozincate, which can be readily prepared by adding an excess of zinc chloride solution to a solution of the diazonium salt. The precipitated complex diazonium salt is usually admixed with an inert diluent, which enhances its stability, and in use the dyer only needs to dissolve the powder in water to prepare the necessary diazonium salt solution. 

Two further miscellaneous classes of macrocyclic metal complexes are included in this section because they have structural features such as aza linkages and a high degree of unsaturation associated with fused aromatic rings. Ogawa and coworkers have shown that when 2,4-di-chloro-l,10-phenanthroline is fused with ammonium tetrachlorozincate, a macrocyclic zinc complex is produced. The metal can be removed subsequently by acidic treatment (Scheme 57).244 The free macrocycle can also be prepared by non-template methods, which however do not appear to be as effective as they require reaction of the dichlorophenanthroline with 2,9-diaminophen-anthroline.245... 

All of the product of the reaction given in Sec. A above can be isolated as the tetrachlorozincate if zinc chloride (ca. 2 g.) is added to the cold solution after neutralization with acid. No ammonium chloride is added in this case. The ratio of yields of the two products [Ru(NH3)6]C12 and [Ru(NH3)6][ZnCl4] may vary from preparation to preparation, but the total yield of [Ru(NH3)6]2+ will remain constant. The variation appears related to the concentration of ammonia in Sec. A at the time of isolation of the product. The yield is increased by increasing the ammonia concentration. 

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