852804-92-3Relevant academic research and scientific papers
Cyclohexane oxidation with dioxygen catalyzed by supported pyrazole rhenium complexes
Mishra, Gopal S.,Alegria, Elisabete C.B.,Martins, Luísa M.D.R.S.,Fraústo da Silva, Jo?o J.R.,Pombeiro, Armando J.L.
, p. 92 - 100 (2008)
The pyrazole complexes [ReCl2{N2C(O)Ph}(Hpz)(PPh3)2 ] 2 (Hpz = pyrazole), [ReCl2{N2C(O)Ph}(Hpz)2(PPh3) ] 3 and [ReClF{N2C(O)Ph}(Hpz)2(PPh3)] 4, and their precursor [ReOCl3(PPh3)2] 1, immobilized on 3-aminopropyl functionalized silica, catalyze the cyclohexane oxidation with dioxygen, to cyclohexanol and cyclohexanone (the main product), in the absence of solvent and additives and under relatively mild conditions. Complex 4, whose synthesis and characterization are reported herein for the first time, provides the best activity (ca. 16% overall conversion towards the ketone and alcohol, at the O2 pressure of 19 atm, at 150 °C, 8 h reaction time). The reaction is further promoted by pyrazinecarboxylic acid. TGA analysis shows that the supported complexes are stable up to ca. 200 °C. The use of radical traps supports the involvement of a free-radical mechanism via carbon- and oxygen-centred radicals. The effects of various factors were studied towards the optimization of the processes. Complex 4 also catalyzes the oxidation of other cycloalkanes to the corresponding cycloalkanols and cycloalkanones.
Syntheses and properties of Re(III) complexes derived from hydrotris(1-pyrazolyl)methanes: Molecular structure of [ReCl 2(HCpz3)(PPh3)][BF4]
Alegria, Elisabete C.B.,Martins, Luiísa M.D.R.S.,Guedes Da Silva, M. Fátima C.,Pombeiro, Armando J.L.
, p. 1947 - 1958 (2007/10/03)
The complexes [ReCl2{N2C(O)Ph}(Hpz)(PPh 3)2] (1) (Hpz = pyrazole), [ReCl2{N 2C(O)Ph}(Hpz)2(PPh3)] (2), [ReCl 2(HCpz3)(PPh3)][BF4] (3) and [ReCl2(3,5-Me2Hpz)3(PPh3)]Cl (4) were obtained by treatment of the chelate [ReCl2{η2-N, O-N2C(O)Ph}(PPh3)2] (0) with hydrotris(1-pyrazolyl)methane HCpz3 (1,3), pyrazole Hpz (1,2), hydrotris(3,5-dimethyl-1-pyrazolyl)methane HC(3,5-Me2pz)3 (4) or dimethylpyrazole 3,5-Me2Hpz (4). Rupture of a C(sp 3)-N bond in HCpz3 or HC(3,5-Me2pz) 3, promoted by the Re centre, has occurred in the formation of 1 or 4, respectively. All compounds have been characterized by elemental analyses, IR and NMR spectroscopy, FAB-MS spectrometry, cyclic voltammetry and, for 1 ? CH2Cl2 and 3, also by single crystal X-ray analysis. The electrochemical EL Lever parameter has been estimated, for the first time, for the HCpz3 and the benzoyldiazenide NNC(O)Ph ligands.
