Electronic effects in oxidation reactions utilizing dinuclear copper complexes with the Bis[3-[2-hydroxybenzylldeneamino)phenyll sulfone ligand

• Main Authors: Guidoto, Armando M., Jr., Reyes, Ronald L., Kashihara, Riyo, Kurusu, Yasuhiko, Masuyama, Yoshiro
• Format: text
• Published: Animo Repository 2014
• Subjects: Complex compounds; Oxidation; Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/8728
• Institution: De La Salle University

Copper acetate and the ligands bis[3-(3-tert-butyl-2-hydroxy-5-methoxybenzylidene-amino)phenyl] sulfone and bis[3-(3,5-di-tert-butyl-2-hydroxybenzylideneamino)phenyl] sulfone were reacted to form the complexes with 2:1 copper:ligand ratio, Cu2[B(t-Bu) (OMe)BAPS](u-OCH3)2 (4) and with 2:2 copper:ligand ratio, Cu2[B(t-Bu)2BAPS]2 (5), respectively. Structures of 4 and 5 were determined based on IR, UV-Vis, and FAB-MS data in comparison with previously characterized related copper complexes. The two complexes 4 and 5 were utilized in the oxidation of the substrates 2,4- and 2,6-di-tert-butylphenol (dtbp) at -50C with H2O2 in CH2CI2. The coupling products are preferred in biphenol were achieved with the use 4 and 5, respectively. For 2,6-dtbp, yields of 1,900% and 400% of 3,3,5,5-tetra-tert-butyl-4,4-biphenol were realized utilizing 4 and respectively. These show that the methoxy groups activated the complex. Based on low temperature UV-vis results, a u-n2;n2-peroxo or a u-hydroperoxo intermediate was possibly formed by the reaction of 4 with the H2O2. This effected the oxidation of the 2,4-and 2,6- dtbp substrates but also resulted in the attack of other complexes which acted as substrates. A proposed oxidation mechanism using complex 4 and related complexes is presented.