"Giorgio Modena Memorial Lecture"
HIGHLY SYMMETRIC, MULTIDENTATE LIGANDS FOR EFFECTIVE AND SELECTIVE OXYGEN TRANSFER CATALYTIC REACTIONS
The use of multidentate ligands is one of the current trends in catalyst design. Advantages include the high stability of the corresponding metal complexes, which often allows low catalyst concentrations without loss of catalyst integrity. Secondly, a nearly complete filling of all coordination sites of the metal by a single ligand reduces the chances of formation of multimeric and often undefined metal-species under catalytic conditions. The presence of only a single catalytically active species greatly facilitates mechanistic studies and catalyst optimization.
In the last years our group has been involved in the study of early transition metal complexes with amino triphenolates 1 and silsesquiloxane trisilanolate2 ligands.
Results on synthetic protocols for the ligand synthesis will be reported together with studies on their coordination chemistry with metal transition metals (Ti(IV), V(V), Mo(VI)) and their effective use as catalysts in the oxidation of olefins, sulfides , halides and nitrogen containing compounds with hydrogen peroxide and alkyl hydroperoxides, also in the presence of additives. Studies on the computational and spectroscopic elucidation of nature of the metal peroxo species active in the oxygen transfer process will be presented as well.
1. Mba, M.; Prins, L. J.; Licini, G. Org. Lett, 2007, 9, 21; Mba, M., Pontini, M., Lovat, S., Zonta, C. Bernardinelli, G., Kündig, E. P., Licini, G. Inorg. Chem., 2008, 47, 8616-8618; Romano, F.; Linden, A.; Mba, M.; Zonta, C. Licini, G. Adv. Synth. Catal. 2010, 352, 2937.
2. Lovat, S., Mba, M, Abbenhuis, H.C.L., Vogt, D., Zonta, C., Licini, G. Inorg. Chem., 2009, 48,4724.
The authors thank Progetti Eccellenza 2009/10 (NANO-MODule) Fondazione CARIPARO, PRIN 2008 (MIUR) and PRAT 2009 (Università di Padova) for financial support.
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