Cu(II) complexes as catalyst precursors in the process of selective hydrogenation of diene hydrocarbons

Abstract

The reaction of copper(II) acetate with 3-furancarboxylic acid (Hfur) and 5-nitro-2-furancarboxylic acid (Hnfur) with participation of 4-phenylpyridine (phpy) in acetonitrile resulted in mononuclear complexes [Cu(L)2(phpy)2(H2O)]·solv (L = fur (1), nfur (2); solv = phpy (1)) whose structures were determined by direct single crystal X-ray analysis. According to X-ray data, the complexing component in 1 and 2 is in a distorted square-pyramidal environment (CuN2O3); the pyramid base is formed by monodentate-bound oxygen atoms of fur-/nfur- anions and a pair of nitrogen atoms of the phpy moieties, while the water molecule occupies an axial position. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al2O3 obtained by chemical reduction of 1 and 2 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of monohydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD) to give tricyclo[5.2.1.02,6]dec-4-ene (5,6-dihydrocyclopentadiene, DHDCPD). The catalytic activity tests show high selectivity (up to 100 %) of the catalysts studied in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with hydrogen present in excess. Thermal behavior of 1 and 2 was studied by simultaneous thermal analysis (STA).