| Abstract |
New copper(l) and copper(II) pyrazolate compounds have been prepared by similar synthesis procedures. For the 3,5-NO2-pyrazole ligands, the dinuclear cyclic Cu(I) compound [Cu-2(mu-N,N-3,5(NO2)(2)pz)(2)(PPh3)(2)], 1, was the only compound isolated in high yield, while in the case of the 3,5-bis(trifluoromethyl)-pyrazole ligand a spontaneous rearrangement to the hexanuclear cyclic Itrans-Cu-6(mu-OH)(6)(mu-3,5-(CF3)(2)pz)(6)], 2, was observed. The formation of this latter compound ruled out an anion tern plating mechanism for the synthesis. X-ray diffraction analysis of 1 revealed that the copper cation is in a trigonal environment and involved in a six-membered Cu2N4 core; while the structural analysis of 2 showed that the metal adopts a square-planar geometry, forms five-membered Cu2N2O rings and ultimately gives rise to a large Cu-6(N2O)(6) crown-type assembly. Compounds 1 and 2 act as very effective homogeneous catalysts towards the neat microwave (MW) assisted peroxidative (with aq. tert-butyl hydroperoxide, TBHP) oxidation of cyclohexane to cyclohexanol and cyclohexanone (total yield up to 58\% in 30 min reaction time) via formation of cyclohexyl hydroperoxide (CyOOH) as the primary product. (C) 2017 Elsevier Ltd. All rights reserved. |
