Invitación Seminario Dr. Jorge Martinez

Seminarios del Departamento de Ciencias Químicas 
Invita a la comunidad universitaria a la charla titulada
Catalytic activity in ethylene polymerization processes understood through the local hyper-softness  

Dr. Jorge Martínez
Departamento de Ciencias Químicas (DCQ), UNAB
Metallocene cations of group IV B have allowed an increase of plastic market since 1977 when Walter Kaminsky discovered the use of these organometallic compounds in this field.  Besides, the mechanism proposed by Cossee and Arlman has helped to understand the entire process of ethylene polymerization catalyzed by these organometallic compounds and the same mechanism is used as a guide to understand the catalytic effect exerted by new catalysts that have been used in similar polymerization reactions like cationic complexes based on iron coordinated to ligands of type bis(imino)pyridine. A pure experimental parameter that characterizes these organometallic compounds within the polymerization context is the so called catalytic activity that measures the mass of polyethylene produced per unit of gram or mol of catalyst, per unit of temperature and per unit of pressure of monomer. Values of catalytic activity are usually explained in terms of steric hindrance induced by the respective catalyst, however electronic effects exerted by substituent groups attached on the catalyst are often explained in terms of net electric charges localized on the catalytic sites of the catalyst. This talk will expose that local hyper-softness is a theoretical parameter that has demonstrated to be more suitable to rationalize the aforementioned electronic effects rather than the net electric charges. In consequence there is a link between catalytic activity and local hyper-softnesss that would lead to a more rational computational design of new catalysts.