Tetrachloroaurate salts

Schreiter ER, Stevens JE, Ortwerth MF (1999) Gold compounds as ionic liquids synthesis, structures, and thermal properties of n, n-diaUsylimidazolium tetrachloroaurate salts. Inorg Chem 38 3935-3940... 

Coreduction of Mixed Ions. Coreduction of mixed ions is the simplest method to synthesize bimetallic nanoparticles. However, this method cannot be always successful. Au/Pt bimetallic nanoparticles were prepared by citrate reduction by Miner et al. from the corresponding two metal salts, such as tetrachloroauric(III) acid and hexachloroplatinic(IV) acid (24). Reduction of the metal ions is completed within 4 h after the addition of citrate. Miner et al. studied the formation of colloidal dispersion by ultraviolet-visible (UV-Vis) spectrum, which is not a simple sum of those of the two monometallic nanoparticles, indicating that the bimetallic nanoparticles have an alloy structure. The average diameter of the bimetallic nanoparticles depends on the metal composition. By a similar method, citrate-stabilized Pd/Pt bimetallic nanoparticles can also be prepared. 

Arylgold(III) complexes have also been obtained from the reactions of tetrachloroaurate(III) salts with substituted phenylhydrazines (303, 304). Thus were prepared the compounds R4N[AuCl3Ar] (R = Et or -Bu Ar = C6H5, p-ClC6H4, / -BrC6H4, or p-NC CsH, which were characterized by their H-NMR and vibrational spectra. Arylgold(III) species have been postulated as intermediates (3OS) in the thermal decomposition of [AuCl3(azobenzene)]. 

Also in the activation of alkynes for nucleophilic attack, gold salts prove to be soft, exceptionally carbophilic Lewis acids, as confirmed by the examples shown in Scheme 3 [10]. According to Utimoto and Fukuda both the addition of water as well as of amines to alkynes are catalyzed by gold(III) salts, in particular by sodium tetrachloroaurate ketones such as 8 and imines such as the ant toxin 10 are obtained as products in excellent yields [10a-e]. In the cyclization reaction giving the 1,4-dioxane 12 developed by Teles et al.,... 

Again, the authors tested some variations of the metal catalyst the entries with the copper triad metals are listed in Table 12.8. Copper(I) iodide was inactive (entry 1), silver tetrafluoroborate and AUCI3 both delivered the allene without cycloisomerization within 24 h (entries 2 and 4), and potassium tetrachloroaurate was inactive (entry 3). Without activation, phosphanegold(I) chlorides were inactive (entry 5), but after removal of the chloro ligand by silver salts, excellent yields were obtained in short reaction times of 40 min (entries 6-8). 

In order to prevent S-alkylation in the repetitive acid-cleavage steps required in a multistep peptide synthesis, the protection of methionine residues as sulfoxides was proposed by Iselin.f This approach has since been widely used for peptide synthesis in solution and on solid supports.Generally, oxidation of L-methionine yields a mixture of S- and R-sulf-oxides and, depending on the conditions used, even a mixture of the related sulfone. Thereby, at least by oxidation with hydrogen peroxide the R-sulfoxide is formed in a preferred manner (80%), whereas oxidation of L-methionine by tetrachloroauric(III) acid has been reported to produce stereospecifically the 5-sulfoxide diastereoisomer. Isomeric pure Met(O) derivatives are obtained by isolation of the isomers from the 5,/ -sulfoxide mixture, taking advantage of the differences in solubility of the picrate salts.0 ... 

Tetrachloroauric(III) acid in aqueous ethanol reacted with an excess of the phosphine-arsine undergoing reduction and chelation to give the cation, LXVII, precipitated as the colorless, highly stable iodide. The 4-coordinate aurous atom in this compound has the tetrahedral configuration, and attempts were made to resolve the cation into optically active forms. Fractional recrystallization of eight salts having different optically-active anions failed to give any indication of resolution. 

The formation of salts with melamine (1.3,5-triazine-2,4,6-triamine) is the most extensively studied reaction of this type. In most cases, melamine acts as a monoacidic base and forms salts with mineral acids, e.g. hydrochloric acid, nitric acid or sulfuric acid, inorganic complexes, e.g. hydrogen tetrachloroaurate(III) or dihydrogen hexachloroplatinate(IV) and a large variety of organic acids, e.g. acetic acid, oxalic acid, picric acid or some sulfonic acids.30... 

The ligand iso-maleonitriledithiolate was synthesized as the potassium salt, according to the procedure of Gomper and Topel [9]. Its gold complex was obtained by the reaction of potassium tetrachloroaurate with K2(i-mnt)2 in die presence of tetra-n-butylammonium bromide [10]. 

Various transition metals catalyze the aza-Michael addition of carbamates to enones. Among the most efficient are gold(I) and gold(III) salts (Scheme 4-66). The catalyst of the stoichiometry AuCl3-2H20 used by the authors is probably tetrachloroauric acid hydrate (HAuCU X H2O). In the corresponding reaction of... 

In a totally different type of study, through a novel use of the [AuCU] salt, (2i ,3i )-L-(—)-[2-D]carnitine tetrachloroaurate, Bau et al. have used single erystal nentron diffraction to determine the absolute stereochemistry of the erotonobetaine to earnitine transformation as it is catalyzed by L-carnitine dehydratase from Escherichia coli. 

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