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

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 pcresol 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.

Highly Efficient β‐Functionalized Oxidomolybdenum(V) Corroles for Catalytic Oxidative Bromination of Phenols at Room Temperature

“…Mo-1 exhibits bathochromic shift of 8-9 nm in B and Q bands relative to meso-functionalized oxido-Mo corroles. [60,63] Mo-2 exhibits bathochromic shift in the most intense B (Δλ max = 26 nm) as well as Q band (Δλ max = 33 nm) relative to Mo-1 as seen in Figure 1. Also, Mo-2 exhibits bands at 324 and 398 nm, most likely due to the attachment of the strong chromophore-like DCV on the macrocycle.…”

“…[51][52][53][54] It has been observed that KBr with H 2 O 2 facilitates oxidative bromination reactions many folds. [55][56][57][58][59] Reports on molybdenum corroles have shown their utility in catalysis is scarce for brominating phenols, [60] hydrogen evolution, [61,62] and epoxidation of alkenes. [63] Brominated phenols are widely investigated using 3d transition metal complexes due to their utility in pharmaceutical industries for biological applications.…”

“…Earlier, we reported the catalytic potential of meso-functionalized oxido-molybdenum(V) corroles towards phenol bromination and proved that the electron-deficient ligated Mo corrole complex is better catalyst than electron-rich ligated Mo corrole complex. [60] For similar reasons, we have synthesized two new electron-deficient β-functionalized oxido-molybdenum(V) corroles, oxido[3-formyl-5,10,15-triphenylcorrolato]molybdenum(V) (Mo-1) and oxido[3-dicyanovinyl-5,10,15triphenylcorrolato]molybdenum(V) (Mo-2) (Scheme 1) to investigate how the β-functionalization affect the catalytic activities for oxidative bromination of phenols. We obtained extremely high TOF (59801-71174 h À 1 ) values for bromination reaction using H 2 O 2 -KBr-HClO 4 in 0.5 h in water at room temperature, suggesting the extremely good potency of these catalysts.…”

Synthesis, Spectral, Redox, and Sensing Studies of β-Dicyanovinyl-Appended Corroles and Their Metal Complexes

“…Apart from their sensitive electronic configuration, corroles exhibit very high structural diversity, unique coordination chemistry, and strong light absorption/emission properties in comparison to porphyrins. − A judiciously selected functionalization of the corrole ring’s periphery can change not only the molecule’s electronic properties, redox potentials, and coordination chemistry , but also lead to new possibilities in the areas of nonlinear optics, , near-infrared phosphorescence, − catalysis, − and fluorescence. , In addition to these areas of research, corrole macrocycles are good prospects for a range of sensing material applications due to their distinctive optical characteristics and synthetic adaptability. , In fact, the unusual behavior, reactivity, and high acidity of corrole imino protons have been utilized for the sensing of basic anions like CN – , F – , OAc – , and H 2 PO 4 – ions through an anion-induced deprotonation mechanism . Lodeiro and co-workers have investigated several gallium­(III) corroles for sensing toxic cyanide and fluoride anions, , while Gros and co-workers developed cobalt corrole-based porous organic polymers (POPs) for selective CO adsorption .…”

Catalytic activity of a new dioxidomolybdenum(vi) complex with a bipodal N2O-donor ligand in sulfur compound oxidation

“…In the last few decades, molybdenum has been employed in the synthesis of new bioinspired complexes coordinated by different ligands with biological importance like amino acids and carbohydrates. 1 These new molybdenum( vi ) complexes have been evaluated for their catalytic activity for reactions with industrial and biological significance like oxidation of alcohols, oxidative halogenations of organic substrates, 2 as well as extensively applied in oxygen atom transfer (OAT) processes, such as epoxidation reactions 3–9 and sulfide oxidations. 10–15 Industrially, molybdenum-based materials and complexes are widely applied in plenty of oxidation reactions, hydrocarbon dehydrogenations, polymerization reactions and alkene metatheses.…”