Polymer-bound Schiff-base ligand (PS-SalPhe) was prepared from polystyrene-bound salicylaldehyde and phenylalanine, and its complex (PS-SalPhe-M) (M ϭ Co, Mn) was also synthesized. The polymer ligand and its complex were characterized by infrared spectra, small area X-ray photoelectron spectroscopy, and ICP-AES. In the presence of the complex, cyclohexene can be effectively oxidized by molecular oxygen without a reductant. The major products of the reaction are 2-cyclohexen-1-ol (-OH), 2-cyclohexen-1-one (CAO), and 2-cyclohexen-1-hydroperoxide (-OOH ), which is different from the typical oxidation of cyclohexene. The mechanism of cyclohexene oxidation is also discussed. Long-chain linear aliphatic olefins, such as 1-octene, 1-decene, 1-dodecene, and 1-tetradecene, can be directly oxidized by molecular oxygen catalyzed by PS-SalPhe-M (M ϭ Mn, Co), which yields the 1,2-epoxy alkane.
Source of materialAm ixture of CaCl 2 (0.5 mmol, 0.05 g) and 2-ethyl-1H-imidazole-4,5-dicarboxylic acid (0.5 mmol, 0.95 g) in 15 ml of H 2 Osolution was sealed in an autoclave equipped with aTeflonlined stainless steel vessel (25 ml) and then heated at 373 Kfor 3d ays. Crystals of the title compound were obtained by slow evaporation of the solvent at room temperature.
Experimental detailsCarbon and nitrogen bound hydrogen atoms were placed at calculated positions and treated as riding on the parent atoms with In the title complex, the Ca II cation is eight-coordinated (N2O6), with two chelating rings from N,O-bidentate 2-ethyl-1H-imidazole-4,5-dicarboxylate anions, two carboxylate Oa toms from another two 2-ethyl-1H-imidazole-4,5-dicarboxylate anions, and two coordinated water molecules, generating a slightly distorted square-antiprismatic coordination. The Ca-N bond distances are both 2.584(2) Å,and the Ca-Obond lengths vary from 2.412(2) Å to 2.539(1) Å.The Ca II centres are interconnected by the ligands, whereby the ligand is functioning as tridentate and bridges Ca atoms into an infinite two-dimensional layer constructed of Ca 4 squares, the edge distances of the quasisquare are of 9.0568(9) Å and the angles are 85.090(1)°and 94.910(5)°,r espectively. The layers are further linked into a three-dimensional network by an extensive number of hydrogen bonds involving the coordinated water molecules and the 2-ethyl-1H-imidazole-4,5-dicarboxylate ligands.
The polymer bound Schiff-base ligand (PS-SalGlu) has been prepared from polystyrene bound salicylaldehyde and glutamic acid, and its complex (PS-SalGlu-Co) has also been synthesized. The polymer ligand and its complex were characterized by infrared spectroscopy, small area X-ray photoelectron spectroscopy, and inductively coupled plasma-atomic emission spectro (ICP-AFS). In the presence of the complex, cyclohexene can be effectively oxidized by molecular oxygen without reductant. The long-chain linear aliphatic olefins, such as 1-octene, 1-decene, 1-dodecene and 1-tetradecene, can be directly oxidized by molecular oxygen catalyzed by PS-SalGlu-Co, which affords the 1,2-epoxy alkane. Copyright
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