Gold, divalent

In contrast to the main-group elements, metals of the d-block usually show one-electron separated oxidation states. Thus, the discrimination between metal-centred and ligand-centred electron transfer is not easy and must often be based on several spectroscopic and electrochemical methods. As examples Section 4.4 reports on recent investigations on the nickel-containing cofactor F430 and Section 4.5 on the famous oxidation catalyst system [(Por)Ru(CO)(L)]. Sometimes the peculiar electrochemistry of porphyrins allows unusual oxidation states as shown with the divalent gold species [(Por)Au(II)] in Section 4.6. 

Aurous bromide reacts with 1,3-diiminoisoindoline to form a gold-containing phthalocyanine of uncertain formula, having an electron-spin resonance spectrum characteristic of a gold(II) species (189). If properly substantiated, this will be the first divalent gold derivative to be synthesized. 

Figure 7 illustrates the formation of NP chains from divalent gold NPs carrying MUA at two opposite poles. The NPs were linked due to the reaction of activated MUA with DAH, thereby forming a chain. To analyze the kinetics of chain growth, the authors considered two reactions the attachment of carboxylic acid-terminated molecules to the NP poles (reaction 1) and the formation of NP chains (reaction 2), as shown in Figure 10. ... 

Kuroda and Tarui [498] developed a spectrophotometric method for molybdenum based on the fact that MoVI catalyses the reduction of ferric iron by divalent tin ions. The plot of initial reaction rate constant versus molybdenum concentration is rectilinear in the range 0.01-0.3 mg/1 molybdenum. Several elements interfere, namely, titanium, rhenium, palladium, platinum, gold, arsenic, selenium, and tellurium. 

Gold has a more marked tendency to form complex salts than either copper or silver, but the ammines of gold arc somewhat unstable. Gold forms two series of salts where the metal is monovalent or divalent respectively from both series of salts ammines have been obtained. 

Carbenes are speties with a divalent carbon atom with various substituents and a lone pair of electrons. Classic carbene gold complexes were synthesized in the coordination sphere of the gold atom, addition of amines or alcohols to the coordinated isocyanide ligands. N-Heterocyclic carbenes (Arduengo s carbenes)... 

Vanadium predpitates the metal from solutions of salts of gold, silver, platinum, and iridium, and reduces solutions of mercuric chloride, cupric chloride and ferric chloride to mercurous chloride, cuprous chloride, and ferrous chloride, respectively. In these reactions the vanadium passes into solution as the tetravalent ion. No precipitation or reduction ensues, however, when vanadium is added to solutions of divalent salts of zinc, cadmium, nickel, and lead. From these reactions it has been estimated that the electrolytic potential of the change, vanadium (metal)—>-tetravalent ions, is about —0 3 to —0 4 volt, which is approximately equal to the electrolytic solution pressure of copper. This figure is a little uncertain through the difficulty of securing pure vanadium.5... 

Phthalocyanine is a divalent ligand with a geometry appropriate for forming a four-coordinated square-planar complex and was thought ideal for generating an Au(II) species. The action of AuBr on molten 1,3-diiminoisoindoline in the absence of solvent indeed yields a neutral gold phthalocyanine (63). The EPR spectra of the complex in 1-chloronaphthalene at 77 K clearly showed the presence of Au(II), a d9 ion. The g value is 2.065, comparable to 2.042 for copper and 2.093 for silver phthalocyanine (64, 80). 

Many organo-derivatives of the Group Vb elements have been prepared. The substituted phosphines, arsines, and stibines (for example, CH3PH2, (CH3)2AsH, and (CH3)sSb) are, like their parent hydrides (p. 253), easily flammable, toxic, and only weakly basic toward H4. However, the fully substituted arsines and phosphines form surprisingly stable adducts with salts of univalent gold, divalent platinum and palladium,... 

The mixed-valent gold indium cluster [Au3ln3Cl6(dppe)2] is composed of In(I) and In(II) atoms. Synthetic details were presented in an earlier section. Insertion and redox reactions of In(I) halides have been described. For example, oxidative addition reactions of InX (X = Cl, Br, I) with PhSSPh yields indium(III) thiolates of the type (PhS)2lnX." Unexpected In(II) or In(III) products are common in reactions involving indium(I) halides, which result from facile disproportionation processes. Several such cases were described with divalent indium compounds. 

A number of inorganic species can be separated by extraction with suitable solvents. For example, a single ether extraction of a 6 M hydrochloric acid solution will cause better than 50% of several ions to be transferred to the organic phase included among these are iron(III), antimony(V), titanium(III), gold(IIl), molybde-num(VI), and tin(IV). Other ions, such as aluminum(IIl) and the divalent cations of cobalt, lead, manganese, and nickel, are not extracted. 

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