Synthesis, characterization and crystal structure of a cobalt(II) coordination polymer with 2,4,6-tris(2-pyridyl)-1,3,5-triazine and its use as an epoxidation catalyst

Abstract

The binuclear Co(II) coordination polymer [{CoIICl3}(tptz){CoIICl(H2O)}]·0.25H2O, where tptz is 2,4,6-tris(2-pyridyl)-1,3,5-triazine, was prepared and characterized by single crystal X-ray diffraction, FTIR, UV–Vis, TGA and elemental analysis techniques. The tptz ligand bridges the two Co(II) cations, with one CoII cation coordinated in a tridentate fashion and the second bound in a unidentate manner. The compound is in fact a linear coordination polymer, with the polymer propagated by Co1–Cl4–Co2 bridges to form infinite zig–zag chains along the crystallographic b axis. Formation of these bridges expands the coordination sphere of Co1 to six coordinate octahedral, while that of Co2 becomes four coordinate pyramidal. The complex [{CoIICl3}(tptz){CoIICl(H2O)}]·0.25H2O successfully catalyzes the epoxidation of cyclooctene, styrene, cyclohexene, trans-stilbene and norbornene with TBHP (tert-butyl hydroperoxide) with 50–95% conversions and 95–100% selectivities.