Oxido-Molybdenum(V) Corroles as Robust Catalysts for Oxidative Bromination and Selective Epoxidation Reactions in Aqueous Media under Mild Conditions
Inderpal Yadav, Ved Prakash, Mannar R. Maurya, Muniappan Sankar
Abstract
Two new meso -substituted oxido-molybdenum corroles were synthesized and characterized by various spectroscopic techniques. In the thermogram, MoO[TTC] ( 1 ) exhibited excellent thermal stability up to 491 °C while MoO[TNPC] ( 2 ) exhibited good stability up to 318 °C. The oxidation states of the molybdenum(V) were verified by electron paramagnetic resonance (EPR) spectroscopy and exhibited an axial compression with d xy 1 configuration. Oxido-molybdenum(V) complexes were utilized for the selective epoxidation of various olefins with high TOF values (2066–3287 h –1 ) in good yields in a CH 3 CN/H 2 O (3:2, v/v) mixture in the presence of hydrogen peroxide as a green oxidant and NaHCO 3 as a promoter. The oxidative bromination catalytic activity of oxido-molybdenum(V) complexes in an aqueous medium has been reported for the first time. Surprisingly, MoO[TNPC] ( 2 ) biomimics of the vanadium bromoperoxidase (VBPO) enzyme activity exhibited remarkably high TOF values (36 988–61 646 h –1 ) for the selective oxidative bromination of p -cresol and other phenol derivatives. Catalyst MoO[TNPC] ( 2 ) exhibited higher TOF values and better catalytic activity than catalyst MoO[TTC] ( 1 ) due to the presence of electron-withdrawing nitro groups evident from cyclic voltammetric studies.