Studio Teorico dei Dettagli Meccanicistici di Reazioni Organiche Catalizzate da Oro

Abstract

The catalytic chemistry of gold has had a relatively belated development with respect to other late transition metals, and this has been attributed to the preconception that gold is expensive and unreactive. The interest in gold has grown over the last thirty years, because both of these conceptions have been proven false, and successful applications of gold catalysis have emerged in chemical processing, pollution control, fuel cells design, and many others fields. These evidences have sparked a veritable “gold rush” in the field of catalysis, both homogeneous and heterogeneous. We investigated the role of gold in both homogeneous and heterogeneous catalytic processes. In fact, the theoretical study of mechanistic details for reactions, that involves and underline the characteristics of gold, have been the subjects of this thesis. Density functional theory (DFT) is the method of choice in this kind of studies. Regarding heterogeneous catalysis the synthesis of vinylacetate is the reaction on which we have focused our attention. In particular, a bimetallic catalyst containing low Pd coverage on Au surface (100 and 111) has been selected to outline the reaction mechanism of VAM formation. We have studied in detail both mechanisms proposed in literature, in order to selected the more active surface and the more likely mechanism. The homogeneous catalytic process that has been selected to point out the catalytic activity of gold is the hydration of 1,2-diphenylacetylene to yield benzyl phenyl ketone, catalyzed by a complex of Au(I) with triphenylposphine. This cationic complex coordinates to the alkyne in the first step of the catalytic cycle, thus rendering it more susceptible for a nucleophilic attack. That reaction is a relatively new synthetic strategy that have recently studied experimentally. Our aim is to elucidate the mechanism of the whole reaction.