Palladium-catalyzed reactions general features

Using quantum chemical molecular modelling tools we have examined the reaction mechanism of palladium catalyzed hydrosilylation of styrene by the precatalyst system, 1, developed by Togni and co-workers. One fundamental question that we have focused on is whether the reaction proceeds by the classical Chalk-Harrod mechanism or by an alternative mechanism such as the modified-Chalk-Harrod mechanism. In this section, the general features of the catalytic cycle are examined. 

Mechanistic aspects of the stoichiometric palladium-catalyzed portion of the reaction have been studied by Rivetti and Romano 109-112) using phosphine model complexes of the form PdX2(P)2 (where X = Cl or OAc and P = tertiary phosphine, generally PPh3). Reaction conditions in these systems are much milder, typically less than 80°C. These systems effectively mimic the features observed in the catalytic cycle and appear to be good models for them. The overall reaction is... 

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