Pyrazolones metal complexes

In mordant dyes, phenols, naphthols, and enolizable carbonyl compounds, such as pyrazolones, are generally the couplers. As a rule, 2 1 metal complexes are formed ia the afterchroming process. A typical example of a mordant dye is Eriochrome Black T (18b) which is made from the important dyestuff iatermediate nitro-l,2,4-acid, 4-amiQO-3-hydroxy-7-nitro-l-naphthalenesulfonic acid [6259-63-8]. Eriochrome Red B [3618-63-1] (49) (Cl Mordant Red 7 Cl 18760) (1, 2,4-acid — l-phenyl-3-methyl-5-pyrazolone) is another example. The equiUbrium of the two tautomeric forms depends on the nature of the solvent. 

Pyrazolone, l(4-bromophenyl)-3-methyl-4-(2-methyl-6-carboxyphenylazo)-chromium complex geometrical isomerism, 6, 69 5-Pyrazolone, o-carboxyarylazo-metal complexes geometrical isomerism, 6,68... 

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). 

Pyrazolone, o-carboxyarylazo-metal complexes geometrical isomerism, 68... 

Solid-phase acidic dyes ai e also used in the study of the ternai y systems with pyrazolone derivatives. In addition, the colorless complex of the investigated metals with pyrazolone derivatives has been studied by means of the metal-indicator method. 

Another type of tautomerization was observed in the complexation reaction of 5-oxo tautomers of pyrazolone with metal chlorides 362 (89ZNK 2966). 

The pyrazolone derivatives (126) give intensely coloured complexes with zinc(II) ions and have been advocated as reagents for the colorimetric determination of the metal.869... 

Zinc can be separated from Cd and Pb in the iodide system [17,18]. It can also be separated from other metals as the chelate complex with oxine (CHCI3, 1,2-dichloroethane) [19-22], diphenylcarbazone [23] HTTA [24], and A-phenylcinnamoylhydroxamic acid (chloroform in the presence of stearylamine) [25]. Zn has been separated from the excess of Cd with the use of l-phenyl-3-methyl-4-stearoyl-5-pyrazolone in benzene solutions [26]. 

Less general reactions include the C-auration of pyrazolone derivatives with (phosphine)gold(I) halide in the presence of an aqueous base49, and the auration of a palladium(II) phosphinoenolate complex with [AuCl(PPh3)] in the presence of AgBF4, resulting in the metallation of the Ca carbon atom of the former enolate moiety (equation ll)50 (Table 2)... 

Nucleophilic addition to a ketone by a pyrazole-3-one can also take place via a pyrazolon-4-yl anion generated from a halogen-metal exchange reaction. Akgiin and Pindur (84M197) (Scheme 106) reported one such example, namely the addition of pyrazole-3-one lithium salt 342, obtained by treating 4-bromopyrazol-3-one 341 with n-BuLi in THF at —78 °C, to benzophenone. The addition product 343 was quenched with tetrafluoroboric acid-diethyl ether complex to afford, after loss of water, (3-oxopyrazol-4-yl) (diphenyl)methylium tetrafluoroborate 344. 

Trace amounts of cyanide are usually determined by flow injection spectrophotometric procedures. The target species is first halogenated with chlora-mine-T, after which it reacts with a mixture of pyrazolone or barbituric acid and isonicotinic acid or pyridine to form a bluish-violet polymethine dye. The implementation of gas-diffusion modules in the flow setup for hydrogen cyanide separation avoids matrix interferences and enables the adaptation of inherently nonselective detectors, such as metallic silver-wire electrodes for potentiometric measurements. Total inorganic cyanide, including free and complexed species, such as iron-cyanide complexes, may be determined by sample decomposition with UV irradiation and further photometric or amperometric analysis. 

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