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Altres ajuts: acords transformatius de la UAB The Nazarov cyclization is investigated in solution and within K[GaL] supramolecular organometallic cage by means of computational methods. The reaction needs acidic condition in solution but works at neutral pH in the presence of the metallocage. The reaction steps for the process are analogous in both media: (a) protonation of the alcohol group, (b) water loss and (c) cyclization. The relative Gibbs energies of all the steps are affected by changing the environment from solvent to the metallocage. The first step in the mechanism, the alcohol protonation, turns out to be the most critical one for the acceleration of the reaction inside the metallocage. In order to calculate the relative stability of protonated alcohol inside the cavity, we propose a computational scheme for the calculation of basicity for species inside cavities and can be of general use. These results are in excellent agreement with the experiments, identifying key steps of catalysis and providing an in-depth understanding of the impact of the metallocage on all the reaction steps.

In the present study the dependence of the reaction rate of carbon-carbon reductive elimination from R3 PAu(MeOH)(CH3 )2 (R=Me, Et) complexes inside [Ga4 L6 ]12- metallocage on the nature of the phosphine ligand is investigated by computational means. The reductive elimination mechanism is analyzed in methanol solution and inside the metallocage. Classical molecular dynamics simulations reveal that the smaller the gold complex (which depends on the phosphine ligand size) the larger the number of solvent molecules encapsulated. The size of the phosphine ligands defines the space that is left available inside the cavity that can be occupied by solvent molecules. The Gibbs energy barriers calculated at DFT level, in excellent agreement with experiment both in solution and in the metallocage, show that the presence/absence of explicit solvent molecules inside the cavity significantly modifies the reaction rate.