Kinetics and mechanism of ligand exchange of Au (III), Zn(II), and Cd(II) chlorides in aqueous solution: An NMR study from 28–98°C

Speciation and thermodynamic properties of zinc in sulfur-rich hydrothermal fluids: Insights from ab initio molecular dynamics simulations and X-ray absorption spectroscopy

“…These complexes maintain the same structure as the starting configuration with no ligand exchange over simulation periods of 21 ps. The apparent stability of the Zn(II)-HS À complexes at 25°C reflects the slow kinetics of the ligand exchange reactions between the Zn(II) and HS À ions, similar to what we observed for Zn(II)-Cl complexes (Mei et al, 2015a), which is consistent with the ligand exchange rate of $30 ns for Zn (II)-Cl as shown by Sharps et al (1993 (Fig. 2a).…”

“…However, as the residence time of inorganic ligands such as Cl À and H 2 O within Zn(II) complexes is in the range of nanoseconds to micro-seconds (Table 11.4 in Burgess, 1978;Sharps et al, 1993), it is difficult to observe the ion association/dissociation reactions within the relatively short ab initio MD simulation times (i.e., in the order of dozens of pico-seconds). To obtain quantitative information about association constants, the free energies of ligand exchange reactions of Zn(II)-HS complexes were calculated by thermodynamic integration (Resat and Mihaly, 1993;Sprik and Ciccotti, 1998;Bü hl et al, 2006Bü hl et al, , 2008 using a method similar to that described in our previous studies (Mei et al, 2013a(Mei et al, , 2015a.…”

Zinc complexation in chloride-rich hydrothermal fluids (25–600 °C): A thermodynamic model derived from ab initio molecular dynamics

“…In an early attempt to apply ab initio MD, Harris et al (2003) predicted the stability of octahedral [ZnCl n (H 2 O) 6Àn ] 2Àn (n = 1,2) complexes in dilute solutions at 25°C, and tetrahedral [ZnCl n (H 2 O) 4Àn ] 2Àn (n = 3,4) complexes in concentrated Cl À brines (up to 7.4 m Cl À ) over the temperature range of 25-300°C. However, due to limited computing capacity, ab initio MD simulations were only conducted for around one picosecond, too short to reach the steady state, as the ligand exchange rates for Zn(II)-Cl are around $300 ls at 25°C (Sharps et al, 1993). The exchange rate for Zn(II)-H 2 O is faster than Zn(II)-Cl ($30 ns, Sharps et al, 1993), but the magnitude is still beyond the computational capabilities of ab initio MD.…”

A spectrophotometric study of aqueous Au(III) halide–hydroxide complexes at 25–80°C

“…In contrast to Au(I), Au(III) has a 5d 8 electron configuration and, like many d 8 metals, shows a preference for four coordinate, square planar complexes (Farges et al, 1993;Sharps et al, 1993), although five-and six-coordinate species are also known (Smith, 1982). Au(III) forms chloride, hydroxide and mixed complexes from [AuCl 4 ] À to [Au(OH) 4 ] À depending on pH, chloride and gold activity (Peck et al, 1991;Farges et al, 1993;Murphy and Lagrange, 1998).…”