Au-Ag interactions

As mentioned above, when a Pt-atom Is surrounded by Ag, Au, Sn, etc., that is, by atoms considerably less active than Cu, very well Isolated Ft atoms or small Ft ensembles can be created, which, even without any assistance of the neighbouring Ag, Au, Sn, etc., will tend to Isomerlze hexane rather than to split It. However, when the alloys are not well homogenized, as Is frequently the case with alloys on some supports, sufficient larger ensembles of Ft, but now more difficult to be selfpoisoned (like the smallest Ft particles), may coexist next to Au, Ag, Sn or their alloys and be responsible for higher hydrogenolytlc selectivity (J ). Such effects may be then easily misinterpreted as a consequence of an alloy - support (non specified. ) electronic Interaction. 

Based on the fact that pi-acids interact with the trinuclear gold] I) pi-bases, TR(carb) and TR(bzim), the trinuclear 3,5-diphenylpyrazolate silver(I) complex was reacted with each. Mixing [Au3(carb)3] or [Au3(bzim)3] with [Ag3(p,-3,5-Ph2pz)3] in CH2CI2 in stoichiometric ratios of 1 2 and 2 1 produced the mixed metal/mixed ligand complexes in the same gold-silver ratios. The crystalline products were not the expected acid-base adducts. It is suspected that the lability of the M-N bond (M=Au, Ag) in these complexes results in the subsequent cleavage of the cyclic complexes to produce the products statistically expected from the stoichiometry of materials used [74]. As a result of the lability of Au-N and Ag-N bonds, and the stability of... 

D and 8 0 data on fluid inclusions and minerals at main stage of epithermal Au-Ag mineralization clearly indicate that the dominant source of ore fluids is meteoric water. Meteoric water penetrates downwards and is heated by the country rocks and/or intrusive rocks. The heated water interacts with country rocks and/or intrusive rocks and extracts sulfur, Au, Ag and other soft cations (e.g., Hg, Tl) from these rocks. If hydrothermal solution boils, it becomes neutral or slightly alkaline, leading to the selective leaching of soft cations such as Au, Ag, Hg and Tl from country rocks. However, a contribution of sulfur gas and other components from magma cannot be ruled out. 

The CO2 concentrations of present-day geothermal waters in terrestrial environment have been also interpreted in terms of the interaction of hydrothermal solutions with country rocks (Giggenbach, 1981 Shikazono, 1978,1985). For example, as noted in section 2.4.3, Shikazono (1985) estimated /CO2 for epithermal Au-Ag and base-metal vein-type deposits in Japan which formed in terrestrial environments at Miocene-Pliocene age and showed that fco2 controlled by the alteration minerals (Fig. 3.6). Estimated /coi" temperature range for epithermal Cu-Pb-Zn vein-type deposits are clearly similar to those for the Kuroko and back-arc deposits in which base metals (Cu, Pb, Zn) are concentrated. 

The canonical spin glass consists of a noble metal (Au, Ag, Cu, or Pt) diluted with a transition metal ion, such as Fe or Mn. The magnetic interaction in such systems is mediated by the conduction electrons, leading to an indirect exchange interaction—the RKKY (Ruderman and Kittel [70], Kasuya [71], and Yosida [72]) interaction, whose coupling constant J R) oscillates strongly with distance r between the spins as... 

A further few ionic compounds based on unsupported heterometallic interactions between metal centers from the anion and the cation were reported only recently [604—606]. Thus, treatment of [Ag(Tab)2](PF6) with K[Au(CN)2] generated the complex [ (Tab)2Ag Au(CN)2 ]2 446 [605]. In the solid state [Ag(Tab)2]+ cations and [Au(CN)2] anions are held together via ionic interactions [Au-Ag 2.9598(7)/2.9185... 

A] to form [(Tab)2M][Au(CN)2] units. Two such fragments are further connected by one gold-gold aurophilic bonding interaction [Au-Au 3.0140(5) A] to form an uncommon Ag-Au-Au-Ag linear string structure with three ligand-unsupported metal-metal bonds [605]. 

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