Estudo da atividade catalítica do complexo [RuCl(p-cimeno)(O-O')] { O-O = íon acetilfenolato} na polimerização via metátese do 2-norborneno

Abstract

Herein, the complex [RuCl(p-cymene)(O-O')] was synthesized using 2-acetylphenolate as a ligand, carried out by deprotonation of 2-hydroxyacetophenone, and the binuclear precursor [RuCl2(p-cymene)]2. The complex was characterized through Elementary Analysis techniques; Spectroscopy in the Infrared Region; Spectroscopy in the UV/Visible region; Cyclic Voltammetry and Nuclear Magnetic Resonance of Carbon and Hydrogen. The catalytic potential of the [RuCl(p-cymene)(O-O')] complex is projected by its performance in the ROMP-metathesis reaction of 2-norbornene(NBE). The reaction was carried out in 1 ml of dichloromethane; 5µL of Ethyldiazoacetate (EDA) as carbene source and [NBE]/[Ru] ratio =178.5 at 28°C for 15 minutes, demonstrating conversion of NBE to polynorbornene of 9.3% and polymeric productivity of 6.33 kg mol-1 h-1 polymerization carried out under the same conditions as above, trying to keep the [NBE/[Ru] ratio close, but changing the reaction time to 1h, showing conversion of monomer to a polymer of only 0.08% and equal productivity at 0.14 kg mol-1 h-1. The characterization of the polynorbornene was done through Thermogravimetry and Differential Exploratory calorimetry Calorimetry analyses, wich showed a thermally stable structure up to approximately 400°C, but decomposed by complex at 450ºC, presenting only one mass loss event which may indicate its purity. The polymer exhibited a malleable structure with a glass transition (Tg) at 51.58°C. The Density Functional Theory calculations were performed to understand the low catalytic activity. The results obtained denounced the low reactivity of the carbene carbon in relation to the 2-norbornene substrate, when the carbene complex is formed by the addition of EDA, however, it was possible to observe, through a computer simulation, that the carbene complex formed with the initiator 3-methyl-2-butene-1-yl, presents a carbene carbon that is more reactive to NBE.