Comparative study of the catalytic activity of a series of β-brominated Mn–porphyrins in the oxidation of olefins and organic sulfides: Better catalytic performance of the partially brominated ones

• Published in: Polyhedron 2012-02, Vol.34 (1), p.102-107
• Main Authors: Rayati, Saeed, Zakavi, Saeed, Bohloulbandi, Elaheh, Jafarian, Majid, avei, Mehdi Rashvand
• Format: Article
• Language: English
• Subjects: Brominated porphyrins; Homogeneous catalyst; Olefin; Oxidation; Sulfide
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2011.12.021

Oxidation of alkenes and organic sulfides with tetra(n-butyl)ammonium periodate in the presence of the Mn(III) complexes of meso-tetraphenylporphyrin and the corresponding β-brominated analogues shows a complex order of catalytic activity for the used Mn–porphyrins which cannot be simply explained by the relative electron-deficient character of the Mn–porphyrins. [Display omitted] ► Catalytic activity of a series of partially and fully brominated porphyrins. ► Partially brominated porphyrins are more efficient catalysts compared to MnTPPBr8(OAc). ► Anodic shifts for the half-wave potential on going from MnTPP(OAc) to MnTPPBr8(OAc). The oxidation of olefins and organic sulfides with tetra-n-butylammonium periodate (TBAP) in the presence of a Mn(III) complex from a series of partially and fully brominated meso-tetraphenylporphyrins, MnTPPBrx(OAc) (x=0, 2, 4, 6 and 8) has been studied in a comparative manner. With the exception of MnTPPBr2(OAc), the half-wave potential for the Mn(III)/Mn(II) metal-centered process was gradually shifted to higher values on going from MnTPP(OAc) to MnTPPBr8(OAc). However, a complex order has been observed for the catalytic activity of the complexes; while the stability of the Mn–porphyrins towards oxidative degradation under the reaction conditions decreases in the order MnTPPBr8(OAc)>MnTPP(OAc)>MnTPPBr6(OAc)>MnTPPBr2(OAc)>MnTPPBr4(OAc), their catalytic activity has been found to follow the order MnTPPBr8(OAc)≪MnTPP(OAc)⩽MnTPPBr6(OAc)MnTPP(OAc)>MnTPPBr2(OAc)⩾MnTPPBr6(OAc)≫MnTPPBr8(OAc). The highest methyl phenyl sulfide conversion is 69% at room temperature.