Relativistic effects in gold chemistry. I. Diatomic gold compounds

Universität Siegen, Siegen, North Rhine-Westphalia, Germany
The Journal of Chemical Physics (Impact Factor: 3.12). 08/1989; 91(3). DOI: 10.1063/1.457082
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ABSTRACT An open access copy of this article is available and complies with the copyright holder/publisher conditions. Nonrelativistic and relativistic Hartree-Fock (HF) and configuration interaction (CI) calculations have been performed in order to analyze the relativistic and correlation effects in various diatomic gold compounds. It is found that relativistic effects reverse the trend in most molecular properties down the group (11). The consequences for gold chemistry are described. Relativistic bond stabilizations or destabilizations are dependent on the electronegativity of the ligand, showing the largest bond destabilization for AuF (86 kJ/mol at the CI level) and the largest stabilization for AuLi (-174 kJ/mol). Relativistic bond contractions lie between 1.09 (AuH+) and 0.16 A (AuF). Relativistic effects of various other properties are discussed. A number of as yet unmeasured spectroscopic properties, such as bondlengths (re), dissociation energies (De), force constants (k e), and dipole moments (?e), are predicted.

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Available from: W H Eugen Schwarz, Aug 01, 2015
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    • "Comparison of the two sets of profiles reveals that the solvated AuS species is more volatile and that the dependence of hydration on density is less pronounced than for the hydrated AuCl species. This can be explained by the observation that the relativistic bond stabilization is dependent on the ligand electronegativity, and that AuCl has a smaller dipole moment and will experience greater destabilization than AuS (Schwerdtfeger et al., 1989). "
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    ABSTRACT: Gold solubility and speciation in low density H2O–HCl vapour were investigated experimentally at temperatures between 300 and 450 °C, and pressures up to 366 bar using batch-type titanium autoclaves. Concentrations of total dissolved gold in the experimental condensates ranged from 0.9 ppb at 300 °C and 48 bar to 4.6 ppm at 400 °C and 297 bar. The hydrated gold monochloride species (AuCl(H2O)y) is the dominant gold species under the experimental conditions. Gold solubility increases with increasing water vapour pressure and can be expressed by the reaction, Aus+xHClg+yH2Og=AuClxH2Oy+x/2H2,gKs,y The hydration number (y) increases with increasing pressure, thereby indicating that solvation by H2O molecules in the gas-phase is analogous to that in liquid-like fluids. Results of extrapolation of the data using a linear relationship of log Ks,y with reciprocal temperature compare well with published experimental data for the solubility of gold at 1000 °C in dilute HCl-bearing water vapour. At high water vapour pressure, the solubility of gold in an aqueous vapour with an HCl fugacity of 0.1 bar is similar to that in a vapour with approximately 50 bar H2S, in which AuS is the dominant gaseous gold species. This indicates that hydrated gold monochloride species may play an important role in magmatic–hydrothermal systems dominated by low density aqueous fluids with high HCl concentrations. Modelling of the cooling and decompression of HCl-bearing intermediate-density (0.35 g cm−3) aqueous fluids shows that gold solubility reaches a maximum of 253 ppm at 500 °C. In fluids with densities of 0.20 and 0.10 g cm−3 the corresponding solubility maxima are reached at ∼400 °C, and are of 14.8 and 0.49 ppm, respectively.
    Geochimica et Cosmochimica Acta 02/2014; 127:305–325. DOI:10.1016/j.gca.2013.11.029 · 4.25 Impact Factor
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    • "Hydrogen has an atomic configuration of 1s 1 similar to gold that makes it interesting to study the interaction of small gold clusters with hydrogen atoms, both H and Au having single valence s electron . Gold hydrides have attracted considerable attention as they serve as important intermediates in gold catalyzed reactions [39] [40] such as hydrogenation [41], hydrosilylation [42], C–H bond activation [43], and aerobic oxidation of alcohols [44]. The study of gold hydride clusters is important to understand the adsorption of hydrogen onto metal surfaces. "
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    ABSTRACT: Density functional calculations at the PBE/DNP level have been carried out to investigate the structures, electronic and reactivity properties of Au6Hn (n = 1–12) clusters. Adsorption of hydrogen atoms stabilizes the Au6 cluster indicated by the high binding energies. The adsorption of H atoms till Au6H6 retains the planar triangular structure of Au6. However, the triangular structure is distorted on further addition of H atoms till Au6H9. In clusters Au6H10, Au6H11 and Au6H12, though the triangular structure is restored but the structures are non-planar. The averaged Hirshfeld atomic charges indicate the H atoms to be negatively charged in all the clusters. Odd–even alternation in HOMO–LUMO gap, chemical hardness, vertical ionization potential, adiabatic ionization potential and binding energy is observed with the clusters having even number of H atoms possessing higher values and are observed to be more stable than their congeners with odd number of H atoms. DFT based reactivity descriptors indicate that in Au6, the Au atoms forming the vertices of the outer triangle have higher relative electrophilicity value while those forming the vertices of the inner triangle have higher relative nucleophilicity value. However, in Au6H6, two nearby Au sites forming the vertices of the inner and outer triangle have the highest relative electrophilicity and relative nucleophilicity values. In Au6H12, these are located in the inner triangle.
    Computational and Theoretical Chemistry 12/2012; 1002:1-8. DOI:10.1016/j.comptc.2012.09.006 · 1.37 Impact Factor
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    • "The 6-311 + G(d) basis set was used for Cl, O, and H. The Stuttgart–Dresden (SDD) relativistic effective core potential (RECP) adopted in Schwerdtfeger et al. (1989) was used in most calculations for Au. This potential, combined with [7s-3p-4d] contraction for valence electrons, was used to approximate the Au inner electronic structure consisting of 60 electrons ([Kr] + 4d + 4f). "
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    ABSTRACT: Despite the growing body of experimental data on gold solubility in hydrothermal fluids, the identity, structure and stoichiometry of Au-bearing aqueous complexes remain poorly known. Here we present the first in situ measurements, using X-ray absorption fine structure (XAFS) spectroscopy, of the stability and structures of AuIII and AuI chloride complexes at elevated temperatures and pressures (T–P) typical of natural hydrothermal conditions. The HAuCl4–NaCl–HCl–Au(s) and NaCl–H2SO4–Au(s) systems were investigated to 500 °C and 600 bar using a recently designed X-ray cell which allows simultaneous determination of the absolute concentration of the absorbing atom (Au) and its local atomic environment in the fluid phase. XAFS data combined with Density Functional Theory quantum-chemical calculations of species structures and ab-initio modeling of XANES spectra show that the AuIIICl4− species is rapidly reduced to AuICl2− at temperatures above 100–150 °C in acidic NaCl–HCl solutions. In the latter complex, two chlorine atoms are aligned in a linear geometry around Au at an average distance of 2.267 ± 0.004 Å. Our data provide the first direct structural evidence for AuCl2−, which is the major Au-bearing species in acidic Cl-rich hydrothermal fluids over a wide T–P range, in agreement with previous solubility and Raman spectroscopy data. Total aqueous Au concentrations measured by XAFS in HAuCl4–HCl–NaCl and NaCl–H2SO4 solutions in the presence of Au(s) are, however, one to two orders of magnitude lower than those predicted by equilibrium thermodynamic calculations. This discrepancy is believed to be due to the combined effects of the cell properties, X-ray beam induced phenomena, and kinetic factors which may complicate the interpretation of high T–P spectroscopic data in redox-sensitive systems.
    Chemical Geology 02/2009; 259:17-29. DOI:10.1016/j.chemgeo.2008.09.007 · 3.48 Impact Factor
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