Tuning Cyclohexane Oxidation: Combination of Microwave Irradiation and Ionic Liquid with the C‑Scorpionate [FeCl2(Tpm)] Catalyst

• Published in: Organometallics Vol. 36; no. 1; pp. 192 - 198
• Main Authors: Ribeiro, Ana P. C, Martins, Luísa M. D. R. S, Kuznetsov, Maxim L, Pombeiro, Armando J. L
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09.01.2017
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.6b00620

For the first time, microwave (MW) irradiation was successfully applied to peroxidative cyclohexane oxidation catalyzed by a C-scorpionate complex, [FeCl2(Tpm)] (1; Tpm = hydrotris­(pyrazol-1-yl)­methane), providing a highly selective and fast eco-friendly procedure to produce a KA (cyclohexanol + cyclohexanone) oil mixture (up to ca. 100% selectivity) with 28% yield in 1 h at 50 °C in MeCN. Water, organics, and ionic liquids (ILs, [bmim]­[N­(CN)2] and [bmim]­[BF4]) were used as solvents, and their interactions with 1 were determined by DFT calculations. The possibility to recycle and reuse 1 (up to nine consecutive cycles) without loss of activity is also observed for the IL [bmim]­[BF4]. Moreover, higher catalytic activities under additive-free conditions are obtained with the ILs in comparison to those with the other solvents. Tuning the alcohol/ketone selectivity is also possible by choosing the appropriate IL solvent.