Hydrocarbon oxidation catalyzed by iron and manganese porphyrins anchored on aminofunctionalized supports

Abstract

As metaloporfirinas de segunda geração (MePs), cloreto de [5,10,15,20-tetraquis(pentafluorofenil)porfirinaferro(III)], FeP, e cloreto de [5,10,15,20-tetraquis(pentafluorofenil)porfirinamanganês(III)], MnP, foram covalentemente ancoradas em suportes aminofuncionalizados, com o objetivo de preparar catalisadores sólidos seletivos para a oxidação de compostos orgânicos. Montmorillonita K10 funcionalizada com 3-aminopropiltrietoxissilano (Mont1) ou com 3-cloropropiltrietoxissilano seguida por reação com 1,6-diaminoexano (Mont2), e sílica gel funcionalizada com 3-aminopropiltrietoxissilano (Sil1) ou modificada com 3-cloropropiltrietoxissilano seguida por reação com 1,6-diaminoexano (Sil2) foram preparadas e caracterizadas por UV-Vis, IR, EPR, TGA e difratometria de raios X. As atividades catalíticas das MePs imobilizadas nestes suportes foram investigadas na oxidação de (Z)-cicloocteno, cicloexano e estireno por iodosilbenzeno (PhIO) ou H 2 O 2 . Os sistemas estudados foram catalisadores eficientes da oxidação de todos os substratos, especialmente utilizando PhIO como oxidante. Não se observou lixiviamento das MePs dos suportes, indicando que a ligação covalente é um método muito eficiente para a imobilização de catalisadores. As FePs imobilizadas foram catalisadores mais eficientes que as correspondentes MnPs, mesmo quando imidazol foi empregado como um co-catalisador para as MnPs ancoradas. Embora os rendimentos de produtos oxidados utilizando H 2 O 2 tenham sido mais baixos que aqueles obtidos com PhIO, alguns sistemas heterogêneos envolvendo MePs foram mais eficientes que as correspondentes MePs em solução, tanto em termos de rendimento de produto quanto de seletividade.The second-generation metalloporphyrins (MePs) [5,10,15,20-tetrakis(pentafluorophen yl)porphyrin iron(III)] chloride, FeP, and [5,10,15,20-tetrakis(pentafluorophenyl)porphyrin manganese(III)] chloride, MnP, were covalently attached to aminofunctionalized supports, with a view to preparing selective solid catalysts for the oxidation of organic compounds. Montmorillonite K10 functionalized with 3-aminopropyltriethoxysilane (Mont1) or modified with 3-chloropropyltriethoxysilane followed by reaction with 1,6-diaminohexane (Mont2), and silica gel functionalized with 3-aminopropyltriethoxysilane (Sil1) or modified with 3-chloropropyltriethoxysilane followed by reaction with 1,6-diaminohexane (Sil2) were synthesized and characterized by UV-Vis and IR spectroscopies, EPR, TGA, and X-ray diffractometry. The catalytic activities of the MePs immobilized on these supports were investigated for the oxidation of (Z)-cyclooctene, cyclohexane and styrene by PhIO or H 2 O 2 . The studied systems were efficient catalysts for the oxidation of all substrates, especially when PhIO was the oxidant. There was no MeP leaching from the supports, indicating that covalent binding is a very efficient method for catalyst immobilization. The immobilized FePs were more efficient catalysts than the corresponding MnPs, even when imidazole was employed as a cocatalyst for the supp...

Synthesis of new metalloporphyrin derivatives from [5,10,15,20-tetrakis (pentafluorophenyl)porphyrin] and 4-mercaptobenzoic acid for homogeneous and heterogeneous catalysis

“…Substitution of the p-fluorine atoms with a bulkier group may account for this result.As reported by Cook[89] in the case of heptane oxidation catalyzed by (5, 10, TTPPP)]OAc, in homogeneous medium, the introduction of bulky substituents can promote oxidation at the terminal positions. Nappa et al[78] observed this sameThe introduction of bulky groups favors the approach of terminal carbons to the active catalytic center. However, the carbons at position 2 of hexane are more exposed, which explains the larger oxidation at this position.…”

“…However, Assis et al [78] observed that FeP1 was more efficient than the corresponding MnP and attributed this fact to the presence of Mn(II) in the catalyst. with the tetra-substituted series ( Table 2, runs 6-10 for FeP6, 14-17 for MnP6, and 19-23 for CuP6).…”

“…Cyclohexane oxidation by PhIO catalyzed by MPx in homogeneous and heterogeneous media.Under heterogeneous conditions, the rise in product yields in the presence of a co-catalyst is not significant[78]. This probably accounted for the better performance of solid MnP6 as compared with MnP2 and MnP1 in solution and in the absence of a co-catalyst.…”

“…On the other hand, the presence of a cocatalyst drastically reduces the alcohol yield in the case of FeP1, from 90 to 65%. In FePs, the Fe(III) ion tends to form hexacoordinated complexes; i.e., imidazole coordinates to the two axial positions in FeP, making the formation of the active catalytic species more difficult[78].…”

Preparation of catalysts based on iron(III) porphyrins heterogenized on silica obtained by the Sol-Gel process for hydroxylation and epoxidation reactions

“…More recently, porous metalloporphyrin networks have proven to be potentially applicable as efficient heterogeneous catalysts 5 after immobilization in organic amorphous polymers, amorphous inorganic matrices, or crystalline inorganic materials such as silica, 6,7 zeolites, 8,9 clay from the smectite group (montmorillonite), [10][11][12] layered double hydroxides, 13,14 tubular and fibrous matrices, 15 silica matrix obtained by the sol-gel process, among others. [16][17][18][19][20][21][22][23] This versatile class of molecules is efficient and selective for the heterogeneous catalytic hydroxylation and epoxidation of a wide variety of organic substrates.…”