abstract
Reactions between CuCl2 and the functionalized scorpionate 2,2,2-tris(1-pyrazolyl)ethanol HOCH2C(pz)(3) 1 (pz = pyrazolyl) or 2,2,2-tris(1-pyrazolyl)ethyl methanesulfonate CH3SO2OCH2C(pz)(3) 2 yield the corresponding water soluble Cu-II complexes [CuCl2{HOCH2C(pz)(3)}](3) or [CuCl2{CH3SO2OCH2C(pz)(3)}](2) 4. In 3 the scorpionate ligand shows the typical N,N,N-coordination mode, whereas in the dinuclear complex 4 it binds the metal as a bidentate species. Compounds 1-4 have been characterized by IR, far-IR, elemental analysis and (for 2-4) single crystal X-ray diffraction. The new scorpionate complexes 3 and 4 are shown to act as catalyst precursors for the peroxidative oxidation of cyclohexane to cyclohexanol (main product) and cyclohexanone, under mild conditions (at room temperature and using an aqueous solution of H2O2) reaching TON values up to 186 in NCMe/H2O. Their hydrosolubility allows them to operate also in pure aqueous media (without any organic solvent, although less effectively), a rare feature of significance towards a green alkane oxidation process.
keywords
COPPER TRIETHANOLAMINE COMPLEXES; HYDROGEN-PEROXIDE; ALKANE OXIDATION; VANADIUM COMPLEXES; RHENIUM COMPLEXES; METAL-COMPLEXES; ACETIC-ACID; BIS(MALTOLATO)OXOVANADIUM COMPLEXES; EFFICIENT CATALYSTS; MOLECULAR-OXYGEN
subject category
Chemistry
authors
Silva, TFS; Mishra, GS; da Silva, MFG; Wanke, R; Martins, LMDRS; Pombeiro, AJL
our authors
Gopal Shankar Mishra
Post-Doc FellowshipGroups
acknowledgements
This work has been partially supported by the Fundacao para a Ciencia e a Tecnologia (FCT), Portugal, and its PPCDT (FEDER funded) programme. TFSS is grateful to FCT for a PhD grant (no. SFRH/BD/48087/2008). The authors gratefully acknowledge Dr Maria Candida Vaz (IST) for the direction of the elemental analysis service, Mr Indalecio Marques (IST) for MS and GC-MS analyses, and the Portuguese NMR Network (IST-UTL Center) for providing access to the NMR facility.