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Au, 79]
Published in Alina Kabata-Pendias, Barbara Szteke, Trace Elements in Abiotic and Biotic Environments, 2015
Alina Kabata-Pendias, Barbara Szteke
Gold (Au), a chemical element of the group 11 in the periodic table of elements, is one of the metals of the so-called group noble metals. Its abundance in the Earth’s crust averages 3–4 µg/kg. Its content in ultramafic igneous rocks is up to 5 µg/kg, and in sedimentary rocks, its content varies from 2–6 and in calcareous rocks and sandstones, its content is in the range of 3–7 µg/kg. In coal, Au may be concentrated within the range of 10–50 µg/kg.
Cooperativity effects between regium-bonding and pnicogen-bonding interactions in ternary MF···PH3O···MF (M = Cu, Ag, Au): an ab initio study
Published in Molecular Physics, 2020
Zan Zhang, Tian Lu, Luyang Ding, Guanyu Wang, Zhaoxu Wang, Baishu Zheng, Yuan Liu, Xun Lei Ding
Recently, the regium-bonding interaction [36–39] of the group 11 elements of the periodic table (noble metal Cu, Ag, Au) has received a great amount of attention due to their extensive application in homogeneous and heterogeneous catalysis reactions [40,41]. Like halogen-bonding interactions, the formation of these interactions is attributed to the existence of an electron-deficient σ-hole region in the extension of the chemical bond to the Cu, Ag, and Au atoms, in which the noble metal atom can also interact with electron-rich moieties to establish a directional non-covalent interaction. For example, MX can act as a Lewis acid forming a regium bonds in H2O/H2S/CO···MX (M = Cu, Ag, Au; X = F, Cl, Br, CH3, CF3) complexes,[42] analogous to hydrogen bonds or halogen bonds.
Structural and optical studies of silver sulfide nanoparticles from silver(I) dithiocarbamate complex: molecular structure of ethylphenyl dithiocarbamato silver(I)
Published in Journal of Sulfur Chemistry, 2020
Peter A. Ajibade, Nandipha L. Botha
Metal nanoparticles are of interest and can be prepared and functionalized to enhance their applications especially in biotechnology and targeted drug delivery [1–4]. Metal sulfide nanoparticles are versatile, broad and exciting class of inorganic compounds [5–7]. Interest in Group 11 metal complexes are due to their properties and diverse structural chemistry [8]. Silver sulfide is a semiconductor with unique properties such as enhanced optical nonlinearity and high photoluminescence that are useful in the design of new optoelectronic devices [9]. Potential applications of nanostructure materials depend on their crystallinity, porosity and hierarchical architecture [10] as well their morphologies [11–13] that can be controlled by capping agents or subtle changes in reaction conditions [14]. Among techniques used for the synthesis of silver sulfide nanoparticles, the thermolysis of silver(I) dithiocarbamate complexes as single source precursors have proven to be suitable for the synthesis of acanthite silver sulfide nanoparticles [15–18].
Gold(I)-assisted catalysis – a comprehensive view on the [3,3]-sigmatropic rearrangement of allyl acetate
Published in Molecular Physics, 2018
Marek Freindorf, Dieter Cremer, Elfi Kraka
Gold catalysis has attracted a lot of attention in the past two decades because it offers a large variety of organic transformations under mild reaction conditions and with high yields [1–12]. There exists an impressive diversity of reactions including the gold-catalysed assembly of complex molecules via C–H activation [13,14], cross-coupling reactions [14,15], or allylation reactions to densely functionalised compounds [16]. Gold has physical and chemical properties which differ from other transition metals even from those of group 11 (Cu, Ag) caused by relativistic effects reaching a maximum at gold and platinum [17–19]. Because of these effects, the s- and p-orbitals shrink, lowering their orbital energy, while the d- and f-orbitals expand due to the increased shielding of the nuclear charge by the contracted s- and p-orbitals. This leads to an increased Au–ligand bond strength influencing its catalytic activity, which is often orthogonal to that of other transition metal catalysts [1,7]. The s-orbital contraction and d-orbital expansion make cationic Au[I] species soft Lewis acids with high carbophilic character and a high affinity to coordinate with π-systems [17,18]. Therefore, cationic gold has proven in homogenous catalysis as an extraordinarily mild, yet effective, soft π-acid, capable of intra- or intermolecularly activating CC, CN or CO multiple bonds toward a nucleophilic attack [2,20–23].