Synthesis of polymer‐supported metal‐ion complexes and evaluation of their catalytic activities

Abstract

Polymer-supported transition-metal-ion complexes of the N,N 0 -bis(o-hydroxy acetophenone) propylenediamine (HPPn) Schiff base were prepared by the complexation of iron(III), cobalt(II), and nickel(II) ions on a polymer-anchored N,N 0 -bis(5-amino-o-hydroxy acetophenone) propylenediamine Schiff base. The complexation of iron(III), cobalt(II), and nickel(II) ions on the polymeranchored HPPn Schiff base was 83.44, 82.92, and 89.58 wt %, respectively, whereas the unsupported HPPn Schiff base showed 82.29, 81.18, and 87.29 wt % complexation of these metal ions. The iron(III) ion complexes of the HPPn Schiff base showed octahedral geometry, whereas the cobalt(II) and nickel(II) ion complexes were square planar in shape, as suggested by spectral and magnetic measurements. The thermal stability of the HPPn Schiff base increased with the complexation of metal ions, as evidenced by thermogravimetric analysis. The HPPn Schiff base showed a weight loss of 51.0 wt % at 5008C, but its iron(III), cobalt(II), and nickel(II) ion complexes showed weight losses of 27.0, 35.0, and 44.7 wt % at the same temperature. The catalytic activity of the unsupported and supported metal-ion complexes was analyzed by the study of the oxidation of phenol and epoxidation of cyclohexene in the presence of hydrogen peroxide. The supported HPPn Schiff base complexes of iron(III) ions showed a 73.0 wt % maximum conversion of phenol and 90.6 wt % epoxidation of cyclohexene, but unsupported complexes of iron(III) ions showed 63.8 wt % conversion of phenol and 83.2 wt % epoxidation of cyclohexene. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 93.1 wt % and 98.1 wt % with the supported HPPn Schiff base complexes of iron(III) ions, but it was low with the supported Schiff base complexes of cobalt(II) and nickel(II) ions. The selectivity for CTL and ECH varied with the molar ratio of the metal ions but remained unaffected by the molar ratio of hydrogen peroxide to the substrate. The energy of activation for the epoxidation of cyclohexene and oxidation of phenol with the polymer-supported Schiff base complexes of iron(III) ions was 10.0 and 12.7 kJ/mol, respectively, but it was found to be higher with the supported HPPn Schiff base complexes of cobalt(II) and nickel(II) ions and with the unsupported HPPn Schiff base complexes of iron(III), cobalt(II), and nickel(II) ions.

Metal-containing polyurethanes from tetradentate Schiff bases: synthesis, characterization, and biocidal activities

“…Characteristic peak at 3350 cm À1 is due to -NH stretching and at 1540-1535 cm À1 to NH bending of the urethane group. Coordination of metal ion is further supported by the appearance of M-O stretches at 510-517 cm À1 [19] and M-N stretches at 442-458 cm À1 [20]. Medium to weak intensity bands due to coordinated water (M-H 2 O) are at 985-992 cm À1 (rocking) and 740-758 cm À1 (wagging) in spectra of …”

Fe-Catalyzed Oxidation Reactions of Olefins, Alkanes, and Alcohols: Involvement of Oxo- and Peroxo Complexes

“…In this respect, the iron complex of the Schiff base HPPn 15 (HPPn ¼ N,N 0 -bis(o-hydroxyacetophenone) propylene diamine) was supported onto cross-linked chloromethylated polystyrene beads. Interestingly, the supported catalyst showed higher catalytic activity than the free metal complex (Scheme 8) [50,51]. In terms of chemical stability, particularly with [55,56].…”

Selective oxidation of olefins and aromatic alcohols with tert‐butylhydroperoxide catalyzed by polymer‐anchored transition‐metal complexes

“…14 Transition‐metal complexes of Mn(III), Fe(III), Cu(II), and Co(II) with polymer‐supported ligands (N 2 O 2 donor set) have been shown to be active catalysts for the oxidation of alkane/alkene in the presences of hydrogen peroxide (H 2 O 2 ), PhIO, tert ‐butylhydroperoxide (TBHP), NaIO 4 , and so on as oxidants. 15–18 Apart from N 2 O 2 donor ligands, polymeric supports with coordinating ligands, such as β‐diketones (O,O), 19 dipyridylamine (N,N), 20 and diphosphine (P,P), 21 have frequently been used to form metal complexes for catalytic applications. The chemical modification of a polymer incorporating a bifunctional ligand such as an N,O donor, has, however, received less attention.…”