Copper complexes reactivity

Forma n dyes bear a formal resemblance to a2o dyes, since they contain an a2o group but have sufficient stmctural dissimilarities to be considered as a separate class of dyes. The most important forma2an dyes are the metal complexes, particularly copper complexes, of tetradentate forma2ans. They are used as reactive dyes for cotton (81) is a representative example. 

The carbene-copper complex was not isolated but generated in situ by deprotonation of the imidazolinium salt 77 by n-BuLi in ether, in the presence of copper(II) triflate (Scheme 51). The use of two equivalents of ligand caused a dramatic decrease in reactivity. 

The 1 1 copper complex azo dyes are used both as reactive dyes for cotton and as direct dyes for paper. (For definitions of reactive dyes, which form covalent linkages with the substrate, and direct dyes, which bind more weakly, see refs. 23 and 24, respectively.) Typical monoazo dyes are Cl Reactive Violet 1 (23) and Cl Reactive Blue 13 (25), and the bis-copper-ed dye, Cl Direct Blue 80 (26). The navy blue dye, Cl Reactive Blue 82 (27), is a typical disazo dye. 

There are bi-, tri-, and tetradentate formazan dyes7 but only the tetradentate copper complex formazan dyes have found use as commercial products. The dye Cl Reactive Blue 160, of generic structure (41), is a representative example. Because of the intensity of their colors, the metal complex formazan dyes have also found application in analysis. Thus, the dye (42) detects zinc at a concentration of 1 part in 50 million.31... 

The yellow ink jet dyes (and pigments) are metal-free azo dyes, such as Cl Direct Yellow 132 and Cl Acid Yellow 23 (Tartrazine).48,49 Most of the magentas are azo dyes derived from H-acid (l-amino-8-naphthol-3,6-disulfonic acid), such as (62), and xanthenes, such as Cl Acid Red 52 and Cl Acid Red 289.48,49 Where high lightfastness is a requirement, a copper complex azo dye, Cl Reactive Red 23 (63), is used. However, such dyes are dull (see Section 9.12.3.2). Nickel complex PAQ dyes, such as (22), are claimed to be brighter and to have similar high lightfastness... 

Activation of a C-H bond requires a metallocarbenoid of suitable reactivity and electrophilicity.105-115 Most of the early literature on metal-catalyzed carbenoid reactions used copper complexes as the catalysts.46,116 Several chiral complexes with Ce-symmetric ligands have been explored for selective C-H insertion in the last decade.117-127 However, only a few isolated cases have been reported of impressive asymmetric induction in copper-catalyzed C-H insertion reactions.118,124 The scope of carbenoid-induced C-H insertion expanded greatly with the introduction of dirhodium complexes as catalysts. Building on initial findings from achiral catalysts, four types of chiral rhodium(n) complexes have been developed for enantioselective catalysis in C-H activation reactions. They are rhodium(n) carboxylates, rhodium(n) carboxamidates, rhodium(n) phosphates, and < // < -metallated arylphosphine rhodium(n) complexes. 

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. 

The only copper complexes of tridentate azo compounds are 1 1 structures, since copper(II) has a CN of 4. They can be prepared by the reaction of the azo compound with a copper(II) salt in an aqueous medium at 60 °C. The major application for copper-complex azo dyes is as direct or reactive dyes for the dyeing of cellulosic fibres. They are seldom developed for use on wool or nylon, although various orange and red 1 1 copper-complex azopyrazolones (5.42) were synthesised recently and evaluated on these fibres by application from a weakly acidic dyebath [24]. 

An appropriate ion-specific electrode was found to provide a convenient, precise and relatively inexpensive method for potentiometry of copper(II) ion in copper-complex azo or formazan dyes. Copper(II) ion in copper phthalocyanine dyes can be quantified after anion exchange. Twelve commercial premetallised dyes evaluated using this technique contained copper(II) ion concentrations in the range 0.007 to 0.2%. Thus many copper-complex direct or reactive dyes are likely to contribute low but possibly significant amounts of ionic copper to textile dyeing effluents [52]. 

The presence of residual unbound transition-metal ions on a dyed substrate is a potential health hazard. Various eco standards quote maximum permissible residual metal levels. These values are a measure of the amount of free metal ions extracted by a perspiration solution [53]. Histidine (5.67) is an essential amino acid that is naturally present as a component of perspiration. It is recognised to play a part in the desorption of metal-complex dyes in perspiration fastness problems and in the fading of such chromogens by the combined effects of perspiration and sunlight. The absorption of histidine by cellophane film from aqueous solution was measured as a function of time of immersion at various pH values. On addition of histidine to an aqueous solution of a copper-complex azo reactive dye, copper-histidine coordination bonds were formed and the stability constants of the species present were determined [54]. Variations of absorption spectra with pH that accompanied coordination of histidine with copper-complex azo dyes in solution were attributable to replacement of the dihydroxyazo dye molecule by the histidine ligand [55]. 

On immersion of cellophane films dyed with four copper-complex azo reactive dyes in aqueous histidine, the absorption spectra of the dyeings changed as a result of abstraction of... 

These are reddish blue 1 1 copper-complex monoazo dyes derived from a 2-naphthylamine-or 2-aminonaphtholsulphonate as diazo component and another aminonaphtholsulphonate as coupler. Often such dyes are more easily prepared using a 2-naphthylaminesulphonate and oxidatively coppering the resulting monoazo dye (section 5.5.3). In orthodox structures the imino link of H acid carries the reactive system (7.99), but in other instances the naphthylamine diazo component provides the site of attachment of a haloheterocyclic (7.100) or sulphatoethylsulphone (7.101) grouping. 

Three major approaches have been followed to provide reactive dyes in this important sector. One category is closely related to the reddish blue monoazo 1 1 copper complexes already described (section 7.5.8). To provide the higher substantivity and deeper intensity for build-up to navy blue shades, a second unmetallised azo grouping is introduced. As with the brown dyes, the A—>M—>E pattern is adopted for their synthesis. Component A is normally a sulphonated aniline, M an aminophenol or aminocresol and E a sulphonated naphthol or aminonaphthol. The reactive system (Z) is usually, but not invariably, located on the E component and the copper atom always coordinates with an o,o -dihydroxyazo grouping provided by the M and E components (7.109). 

At present, synthetic routes to more than 40 metal complexes other than the copper complex are known. Apart from a cobalt phthalocyanine pigment (P.B.75) which was introduced to the market just recently, none of the resulting products, however, has stimulated commercial interest as a pigment. Nickel complexes, however, are found in reactive dyes, while cobalt complexes of this basic structure are employed as developing dyes. 

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