Gold-silver interactions

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... 

Fernandez, E.J., Laguna, A., Lopez-De-Luzuriaga, J.M., Monge, M., Pyykko, P. and Runeberg, N. (2002) A study of the interactions in an extended unsupported gold-silver chain. European Journal of Inorganic Chemistry, (3), 750-753. 

Although the Ag- -Ag interactions are not very strong, there are many examples of complexes, which contain Ag-,M contacts. Silver forms very stable heteropolynuclear complexes with different structural motifs, among them it is worth mentioning the species where silver interacts with platinum, gold, iron, mercury, etc. 

Based on the previously described silver complex [Au2Ag2(Q)f,s)4(MeCN)2 , the same reaction with CuCl in acetonitrile but with addition of an equivalent of pyrimidine leads to the polymeric [CuAu(C6F5)2(MeCN)((J.2-C4H4N2)]n [66]. The polymerization of this complex is produced by covalent copper-pyrimidine bonds. The environment of the copper centers also comprises unsupported gold-copper interactions of 2.8216(6) A and one molecule of acetonitrile, leading to a distorted tetrahedral arrangement (see Figure 6.26). 

The first descriptions of heteronuclear luminescent supramolecular complexes were given by Fackler et al. in 1988 and 1989. In these studies, one gold-thallium and one gold-lead complex were reported. As in the case of the gold-silver dinuclear systems, the extended systems appeared as a result of the unidirectional polymerization of dinuclear or trinuclear units through metal-metal interactions. These were prepared by reaction of the gold precursor [PPN][Au(MTP)2] (PPN = N(PPh3)2 ... 

As in the case of the gold-silver analogous systems, perhaps the most productive method for preparing extended systems through metallophilic interactions is the acid-base process, in which basic gold(I) precursors react with metallic Lewis acids forming supramolecular networks via acid-base stacking. The cation-anion interactions assist the formation of extended chains. 

Some elements found in hody tissues have no apparent physiological role, hut have not been shown in he toxic. Examples arc rubidium, strontium, titanium, niobium, germanium, and lanthanum. Other elements are toxic when found in greater than trace amounts, and sometimes in trace amounts. These taller elements include arsenic, mercury, lead, cadmium, silver, zirconium, beryllium, and thallium. Numerous irlhcr elements are used in medicine in non-nulrieni roles. These include lithium, bismuth, antimony, bromine, platinum, and gold. The interactions of mineral nutrients with carbohydrates, fats, and proteins, minerals with vitamins (qv). and mineral nutrients with toxic elements are areas of active investigation. 

The most common strategy in the synthesis of heteronuclear complexes is the use of bidentate donor ligands bearing different donor centers. In that way both donor atoms can be coordinated selectively to two different metal centers in a consecutive way. If the space between the donor atoms of the ligands is short, interactions between both metals usually appear, normally intramolecular. Sometimes, albeit not very often, the bidentate units bind to one another, leading to extended structures through metallophilic interactions. As we have commented, in the case of gold-silver derivatives the number of luminescent studies of these derivatives is very scarce. 

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