Manganese(II) complexes of 2,3,5,6-tetra-(2-pyridyl)pyrazine – Syntheses, crystal structures, spectroscopic, magnetic and catalytic properties

• Published in: Polyhedron 2013-04, Vol.53, p.132-143
• Main Authors: Machura, B., Palion, J., Mroziński, J., Kalińska, B., Amini, M., Najafpour, M.M., Kruszynski, R.
• Format: Article
• Language: English
• Subjects: 2,3,5,6-Tetra(2-pyridyl)pyrazine; Catalytic activity; Magnetic properties; Manganese(II); X-ray structure
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2013.01.015

Several novel manganese(II) complexes of 2,3,5,6-tetra(2-pyridyl)pyrazine have been synthesised and characterised by means of elemental analysis, IR, EPR, magnetic measurements and single crystal X-ray analysis. Two of them, [Mn(NO3)2(tppz)(H2O)] and [Mn(N3)(NO3)(tppz)(H2O)], have been tested as catalysts in oxidation of alcohol to aldehydes/ketones using oxone (2KHSO5·KHSO4·K2SO4) as an oxidant under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature and as catalysts in oxidation of sulfides to sulfoxides with UHP (urea hydrogen peroxide) as oxidant. A systematic studies on complex formation between Mn(II) ions, 2,3,5,6-tetra(2-pyridyl)pyrazine and halide or pseudohalide (N3−, NCS− and N(CN)2−) ligands have been carried out and the following complexes [Mn2(μ-Cl)2Cl2(tppz)2] (1), [Mn2Cl2(μ-N3-κN1)2(tppz)2] (2), [MnCl(SCN)(tppz)(H2O)]·H2O (3), [MnCl(dca)(tppz)(H2O)0.57(MeOH)0.47] (4), [Mn(NO3)2(tppz)(H2O)] (5), [Mn(N3)(NO3)(tppz)(H2O)] (6), [Mn(SCN)2(tppz)] (7) and [Mn(NO3)(dca)(tppz)]n (8) have been obtained. The compounds were characterized by elemental analysis, IR, EPR, magnetic measurements and X-ray analysis. Two of them (5 and 6) have been tested as catalysts in oxidation of alcohol to aldehydes/ketones using oxone (2KHSO5·KHSO4·K2SO4) as an oxidant under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature and as catalysts in oxidation of sulfides to sulfoxides with UHP (urea hydrogen peroxide) as oxidant.