Oxido-Molybdenum(V) Corroles as Robust Catalysts for Oxidative Bromination and Selective Epoxidation Reactions in Aqueous Media under Mild Conditions

Abstract

Two new <i>meso</i>-substituted oxido-molybdenum corroles were synthesized and characterized by various spectroscopic techniques. In the thermogram, MoO[TTC] (<b>1</b>) exhibited excellent thermal stability up to 491 °C while MoO[TNPC] (<b>2</b>) 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 <i>d_xy</i>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 CH₃CN/H₂O (3:2, v/v) mixture in the presence of hydrogen peroxide as a green oxidant and NaHCO₃ 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] (<b>2</b>) 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 <i>p</i>-cresol and other phenol derivatives. Catalyst MoO[TNPC] (<b>2</b>) exhibited higher TOF values and better catalytic activity than catalyst MoO[TTC] (<b>1</b>) due to the presence of electron-withdrawing nitro groups evident from cyclic voltammetric studies.