Understanding (and possibly solving) chemical problems, especially of industrial relevance, is our main activity. To this end we use the armory of tools known as computational chemistry. The areas of interest span from understanding structure and function relationship in organometallic compounds, to unraveling the mechanistic of catalysts at work, to soft condensed matter simulations. Finally, we are not shy to tackle systems of biological interest. In all cases we try to interact as much as possible with experimentalists. Often we are unsatisfied with the available tools and/or models and we develop new ones. Particular interest is devoted to development of methods for modelling systems across time and length scales.

Following molecules rolling on the potential energy surface from reactants to products is another game we play. Here, there are three classes of reactions that we work on.

a) stereospecific olefin polymerizations. We have investigated in great details almost all aspects of propene polymerization by both heterogeneous and homogeneous catalytic systems. The main contribution in the field certainly is the rationalization of the mechanism of stereocontrol operative with these systems. Based on the original Corradini’s mechanism, that rationalizes the formation of iso- and syndiotactic polypropylene when C₂ and C_S-symmetric stereorigid group 4 metallocenes are used (chiral-site stereocontol), we extended it to rationalize the intriguing formation of syndiotactic polypropylene when a C₂-symmetric stereoflexible group 4 octahedral catalyst is used (chain-end stereocontrol), see Figure. Moreover, we also worked to rationalize the regiospecificity exhibited by different systems, and we studied the catalyst structure/molecular mass relationship exhibited by different systems.

Most favored transition state for propene (dark green) secondary insertion into the Ti-secondary chain (light green) for a bis(phenoxy-imine)Ti-based catalyst.

References
1) Corradini, G.; Guerra, G.; Cavallo, L., "Do New Century Catalysts Unravel the Mechanism of Stereospecificity of Old Ziegler-Natta Catlysts ?", Acc. Chem. Res., 2004, 37, 231.

2) Resconi, L.; Cavallo, L.; Fait, A.; Piemontesi, F., "Selectivity in Propene Polymerization with Metallocene Catalysts", Chem. Rev., 2000, 100, 1253.

b) Mn-catalyzed olefin epoxidations. The actual mechanism operative with this class of catalysts is a very debated topic. In this challenging field we benefited from a strong collaboration with Heiko Jacobsen. We and other have shown that two electronic states are in competition, and that some details of the actual reaction pathway depend on which electronic state the system is. Nevertheless, we have been able to close the catalytic cycle, including regeneration of the active species. Another contribution in the field certainly is the mechanism of enantioselectivity we proposed.

c) The Nobel 2005 reaction, i.e. Ru and Mo-catalyzed olefin metathesis. In this field we have contributed the first complete comparison of the phosphine and NHC-based Ru catalysts, i.e. of the first and second generation Grubbs’ catalysts, trying to stress differences in the steric and electronic properties of the two catalyst generations. Then, we have proposed a mechanism to rationalize the origin of enantioselectivity in the Ru-based asymmetric olefin metathesis, see Figure. We are currently extending this mechanism to the Mo-based Schrock’s catalysts.

Schematic representation of the different reactivity of Grubbs’ first and second generation catalysts.