Metal organic complexes, thermodynamic properties

Impressive improvements in our knowledge of thermodynamic properties of the various organic hgands and of our capability of calculating metal-organic complexation constants at the various P and T conditions of interest come from the systematizations of Shock and Helgeson (1990) and Shock and Koretsky (1995), which evaluated equation of state parameters to be used in the revised... 

Shock E. L. and Koretsky C. M. (1995). Metal-organic complexes in geochemical processes Estimation of standard partial molal thermodynamic properties of aqueous complexes between metal cations and monovalent organic acid ligands at high pressures and temperatures. Geochim. Cosmochim. Acta, 59 1497-1532. 

Discrete values of the HKF model parameters for various organic aqueous species are listed in table 8.22. Table 8.23 lists standard partial molal thermodynamic properties and HKF model parameters for aqueous metal complexes of monovalent organic acid ligands, after Shock and Koretsky (1995). 

Used widely in synthetic macromolecular and natural biopolymer fields to evaluate structural and thermodynamic properties of macromolecular materials, thermal analytical methods have been applied to assist in the characterization of natural organic matter (NOM). Originally applied to whole soils, early thermal studies focused on qualitative and quantitative examination of soil constituents. Information derived from such analyses included water, organic matter, and mineral contents (Matejka, 1922 Tan and Hajek, 1977), composition of organic matter (Tan and Clark, 1969), and type of minerals (Matejka, 1922 Hendricks and Alexander, 1940). Additional early studies applied thermal analyses in a focused effort for NOM characterization, including structure (Turner and Schnitzer, 1962 Ishiwata, 1969) and NOM-metal complexes (e.g., Schnitzer and Kodama, 1972 Jambu et al., 1975a,b Tan, 1978). Summaries of early thermal analytical methods for soils and humic substances may be found in Tan and Hajek (1977) and Schnitzer (1972), respectively, while more current reviews of thermal techniques are provided by Senesi and Lof-fredo (1999) and Barros et al. (2006). 

Various chemical surface complexation models have been developed to describe potentiometric titration and metal adsorption data at the oxide—mineral solution interface. Surface complexation models provide molecular descriptions of metal adsorption using an equilibrium approach that defines surface species, chemical reactions, mass balances, and charge balances. Thermodynamic properties such as solid-phase activity coefficients and equilibrium constants are calculated mathematically. The major advancement of the chemical surface complexation models is consideration of charge on both the adsorbate metal ion and the adsorbent surface. In addition, these models can provide insight into the stoichiometry and reactivity of adsorbed species. Application of these models to reference oxide minerals has been extensive, but their use in describing ion adsorption by clay minerals, organic materials, and soils has been more limited. 

When it finally comes to continuous processing of transition metal catalysis in ionic liquid-organic biphasic reaction mode, some additional aspects have to be taken into account. First is the ease of phase separation that will determine the size of the separator unit and thus indirectly the ionic hquid hold-up required. Another very important aspect is the build-up of side-products or feedstock impurities in the ionic catalyst phase. Side-products and impurities that are likely to build up in the ionic liquid are relatively polar in nature and this brings along a significant risk of unfavorable interactions with the transition metal catalyst complex. Apart from this, all build-up of undesired components in the ionic hquid vnU also affect the ionic liquid s physicochemical properties. Therefore, a continuous build-up of components in the ionic catalyst phase that is not restricted by thermodynamic limits (e.g. solubility limits) will always require an extensive purge of the ionic catalyst solution. 

Two volumes edited by Lax include thermodynamic data on the ideal gas state properties of a wide range of elements and compounds, including organic compounds. Other publications in 1967 giving thermodynamic data include the work by Rudman et on phases in metals and alloys, by Klotz on biochemical reactions, by Mueller on metallurgical phenomena, and by Wendlandt and Smith on the thermal properties of metal ammine complexes. 

---