Heterogenization of [Cu(2,2′-bpy)Cl2] and [Cu(1,10-phen)Cl2] on Polyoxometalates: New Catalysts for the Selective Oxidation of Tetralin

Mononuclear Cu(II) bipyridine ( 1 ) and phenantroline complexes ( 2 ) were synthesized and immobilized by different procedures on H 3 PW 12 O 40 polyoxometalate (POM). Characterization by XRD and SEM-EDX were performed to assess the preservation of the Keggin structure and stoichiometry of the complex. The immobilized complexes were tested as heterogeneous catalysts for the partial oxidation of tetralin (1,2,3,4-tetrahydronaphthalene) using hydrogen peroxide as oxidant in acetonitrile/water as solvent. [Cu(2,2′-bpy)Cl][H 2 PW 12 O 40 ] and [Cu(1,10-phen)Cl][H 2 PW 12 O 40 ] oxidized tetralin at room temperature, with 16% conversion with ( 2 ), to 1-tetralone and 2-tetralone with 83% selectivity. However, the selectivity for 1-tetralone was only 56%. Different preparation methods for the heterogenization of these complexes on the POM Keggin unit were compared and used to enhance the selectivity to 1-tetralone to 75%. Cu(II) bipyridine and phenantroline complexes were immobilized on H 3 PW 12 O 40 polyoxometalate and used as heterogeneous catalysts for the selective oxidation of tetralin. A conversion of 16% with 83% selectivity for 1-tetralone and 2-tetralone were obtained with the [Cu(1,10-phen)Cl][H 2 PW 12 O 40 ] complex.