Hydroquinone-amine complexes

Remarkably, the same Shvo complex can be used for the catalytic transfer dehydrogenation of aromatic amines to give imines (Scheme 7.14) [80]. This reaction produces high yields when carried out for 2-6 h in refluxing toluene with 2 mol.% catalyst. A quinone is used as the hydrogen acceptor, giving the corresponding hydroquinone. 

Metal complexes catalyze oxidation of compounds having mobile hydrogens, such as ascorbic acid, hydroquinone, phenols, and amines, in the presence of molecular oxygen [Eq. (16)]. In this reaction, a substrate coordinates to the metal catalyst,... 

The H-bonded sheets create distorted super-cyclohexane boats (and not chairs ) that are neither zincblende-nor wurtzite-like super-structures. A careful revision of the literature reveals other interesting examples of super-structures formed by alcohols and amines. For example, during their studies dealing with the preparation of a stable form of hydrazine, Toda and co-workers [41] reported the formation of the supramolecular 1 1 amine-alcohol complex 1 3 between hydrazine (1) and hydroquinone (3) (Scheme 3). 

Complexes of Cu halides with various oxazole or thiazole ligands can be used to produce copper images from physical developer baths in two ways. The first is conventional reduction by a reducing agent such as hydroquinone or ascorbic acid, generally in the presence of an amine base such as dimethylaminoethanol. Ag or Pd nuclei catalyze the process. In the second method, Ag or Pd catalyzes the disproportionation of the Cu complexes into Cu and Cu . A complexing agent for Cu such as triethylenetetramine is added to make the disproportionation thermodynamically favorable. ... 

An increase in the rate of oxidation of hydroquinone and pyrocatechol by the action of Cu(II), Co(II), Fe(Il), and Mn(II) metal complexes with PEI has been observed [94]. The rate of quinone accumulation depends on the type of metal ion entering the coordination sphere and increases in the following order Cu(II)>Co(II)>Fe(II)>Mn(II). Furthermore, the oxidation of hydroquinone catalyzed by Cu(II) complexes with PVI, PEI and vinyl-amine-vinyl acetate copolymer has been studied in an aqueous solution at 25 °C [95]. In addition, the oxidation of hydroquinone by PVI-Cu(II) and vinylimidazole-vinyl sulfide Vl-VS/Cu(II) complexes has exibited somewhat a typical behavior of copper complexes with copolymers [96]. For example, in respect of VI-VS/Cu(lI) complexes, hydroquinone is oxidized quite rapidly only during the initial phase of the reaction. However, thereafter it changes only slightly. Deviation from linearity has been observed on increasing the content of vinyl sulfide units in the VI-VS copolymer. 

Alternatively, under strong reductive conditions, e.g. electrochemical reduction, arylpalladium(II) halide (XIII) is reduced to arylpalladium(0) which, upon the second oxidative addition, gives diarylpalladium(II) complex, also capable of undergoing reductive elimination of biaryl similarly to XIV [10]. Isopropanol [50-52], amines [4,17,52-54], hydrazine [55], tetrakis(dimethylamino)ethylene [18], hydroquinone [56], tetrabutylammonium ftuoride [57], formates [58-60], zinc [61-64], and molecular hydrogen [65] have been used as stoichiometric reductants. Electro-reductive homocoupling of aryl halides was also reported [10]. The most important methods for... 

Organic compounds form many interesting charge-transfer complexes. An example is quinhydrone (a 1 1 complex of quinone and hydroquinone), which exhibits strong absorption in the visible region. Other examples include iodine complexes with amines, aromatics, and sulfides. 

The scope of the catalytic potential of the cerium(III) ion was intimated by Pratt (1962) in an investigation of the addition of aromatic amines to quinones. Use of hydrated cerous chloride in place of cupric acetate as an oxygen carrier in the oxidation of byproduct hydroquinone resulted in improved yields and easier product separation from metal complexes. 

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