150207-04-8Relevant academic research and scientific papers
Nickel(II) Complexes with Redox Noninnocent Octaazamacrocycles as Catalysts in Oxidation Reactions
Dobrov, Anatolie,Darvasiová, Denisa,Zalibera, Michal,Bu?insky, Luká?,Pu?kárová, Ingrid,Rapta, Peter,Shova, Sergiu,Dumitrescu, Dan,Martins, Luísa M.D.R.S.,Pombeiro, Armando J.L.,Arion, Vladimir B.
, p. 11133 - 11145 (2019/08/20)
Nickel(II) complexes with 15-membered (1-5) and 14-membered (6) octaazamacrocyclic ligands derived from 1,2- and 1,3-diketones and S-methylisothiocarbohydrazide were prepared by template synthesis. The compounds were characterized by elemental analysis, electrospray ionization mass spectrometry, IR, UV-vis, 1H NMR spectroscopies, and X-ray diffraction. The complexes contain a low-spin nickel(II) ion in a square-planar coordination environment. The electrochemical behavior of 1-6 was investigated in detail, and the electronic structure of 1e-oxidized and 1e-reduced species was studied by electron paramagnetic resonance, UV-vis-near-IR spectroelectrochemistry, and density functional theory calculations indicating redox noninnocent behavior of the ligands. Compounds 1-6 were tested in the microwave-assisted solvent-free oxidation of cyclohexane by tert-butyl hydroperoxide to produce the industrially significant mixture of cyclohexanol and cyclohexanone (i.e., A/K oil). The results showed that the catalytic activity was affected by several factors, namely, reaction time and temperature or amount and type of catalyst. The best values for A/K oil yield (23%, turnover number of 1.1 × 102) were obtained with compound 6 after 2 h of microwave irradiation at 100 °C.
