The continuum solvation model COSMO and its extension beyond the dielectric approximation (COSMO-RS) have been carefully parametrized in order to optimally reproduce 642 data points for a variety of properties, i.e., ∆G of hydration, vapor pressure, and the partition coefficients for octanol/water, benzene/water, hexane/ water, and diethyl ether/water. Two hundred seventeen small to medium sized neutral molecules, covering most of the chemical functionality of the elements H, C, N, O, and Cl, have been considered. An overall accuracy of 0.4 (rms) kcal/mol for chemical potential differences, corresponding to a factor of 2 in the equilibrium constants under consideration, has been achieved. This was using only a single radius and one dispersion constant per element and a total number of eight COSMO-RS inherent parameters. Most of these parameters were close to their theoretical estimate. The optimized cavity radii agreed well with the widely accepted rule of 120% of van der Waals radii. The whole parametrization was based upon density functional calculations using DMol/COSMO. As a result of this sound parametrization, we are now able to calculate almost any chemical equilibrium in liquid/liquid and vapor/liquid systems up to an accuracy of a factor 2 without the need of any additional experimental data for solutes or solvents. This opens a wide range of applications in physical chemistry and chemical engineering.

The most recent algorithmic enhancements of the COSMO solvation model are presented and the implementation in the TURBOMOLE program package is described. Three demonstrative applications covering homogeneous catalysis, tautomeric equilibria, and binary phase diagrams show the efficiency and general applicability of the approach. Especially when combined with the COSMO-RS extension, the method very reliably predicts thermodynamic properties of liquid mixtures.

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The resting state structure of the metallocene−alkyl cation, the coordination of the olefin to the preferred resting state structure, and the insertion process of the Ti-constrained geometry catalyst (CpSiH2NH)TiR+ have been studied with density functional theory. A combined static and dynamic approach has been utilized whereby “static” calculations of the stationary points on the potential surface are meshed with first principles Car−Parrinello molecular dynamics simulations. The first molecular dynamics simulation specifically addressing the structure of a metallocene−alkyl cation is presented showing rapid interconversion between γ- and β-agostic conformations. Complementary static calculations show a small energetic preference for a γ-agostic resting state. Coordination of the olefin to the Ti−alkyl resting state is likely to result in the formation of a β-agostic π-complex which is highly favored energetically over other π-complexes that may initially form. The whole propagation cycle was studied from π-complex to subsequent π-complex. The propagation barrier corresponds to the insertion process which was calculated to have a free energy barrier of ΔG ⧧ = 24.3 kJ/mol at 300 K. The initial β-agostic interactions which stabilize the π-complex are replaced by α-agostic bonds which stabilize the insertion transition state. A study of the back-side insertion process reveals that it may be competitive with the front-side insertion process.