Zeolite confined nanostructured dinuclear ruthenium clusters: preparation, characterization and catalytic properties in the aerobic oxidation of alcohols under mild conditions

Zeolite confined nanostructured dinuclear ruthenium clusters as a novel material were prepared by a simple three step procedure: (i) the ion-exchange of Ru3+ ions with the extra-framework Na+ ions in zeolite-Y, (ii) reduction of the Ru3+ ions within the cavities of zeolite with borohydride ions in aqueous solution all at room temperature, (iii) drying the isolated samples under aerobic conditions at 100 +/- 1.0 degrees C. The composition, morphology and structure of zeolite confined nanostructured dinuclear ruthenium clusters, as well as the integrity and crystallinity of the host material, were investigated by using ICP-OES, XRD, XPS, SEM, TEM, HRTEM, TEM/EDX, Raman, FTIR, Ru K-edge XANES, EXAFS spectroscopies, and N-2-adsorption/desorption technique. The results of these multi-pronged analyses reveal the formation of nanostructured dinuclear ruthenium clusters within the cavities of zeolite-Y, in which each ruthenium center exists in the oxidation state of 3+ and is surrounded by one oxygen of the zeolite framework and three hydroxyl ligands, without causing alteration of the framework lattice, mesopore formation, or loss of crystallinity of the host material. The catalytic use of zeolite confined nanostructured dinuclear ruthenium(III) clusters was tested in the aerobic oxidation of activated, unactivated and heteroatom containing alcohols to carbonyl compounds and found to provide exceptional catalytic activity and selectivity under mild conditions (80 degrees C and 1 atm O-2 or air)