A Convenient and Stable Heterogeneous Nickel Catalyst for Hydrodehalogenation of Aryl Halides Using Molecular Hydrogen

Abstract

Hydrodehalogenation is an effective strategy for transforming persistent and potentially toxic organohalides into their more benign congeners. Common methods utilize Pd/C or Raney‐nickel as catalysts, which are either expensive or have safety concerns. In this study, a nickel‐based catalyst supported on titania (Ni‐phen@TiO2‐800) is used as a safe alternative to pyrophoric Raney‐nickel. The catalyst is prepared in a straightforward fashion by deposition of nickel(II)/1,10‐phenanthroline on titania, followed by pyrolysis. The catalytic material, which was characterized by SEM, TEM, XRD, and XPS, consists of nickel nanoparticles covered with N‐doped carbon layers. By using design of experiments (DoE), this nanostructured catalyst is found to be proficient for the facile and selective hydrodehalogenation of a diverse range of substrates bearing C−I, C−Br, or C−Cl bonds (>30 examples). The practicality of this catalyst system is demonstrated by the dehalogenation of environmentally hazardous and polyhalogenated substrates atrazine, tetrabromobisphenol A, tetrachlorobenzene, and a polybrominated diphenyl ether (PBDE).

Application of Raney Al-Ni Alloy for Simple Hydrodehalogenation of Diclofenac and Other Halogenated Biocidal Contaminants in Alkaline Aqueous Solution under Ambient Conditions

“…Gawel et al published that nanoparticles of iron are not effective for hydrodehalogenation of atrazine, and Fenton oxidation must be used for its removal [ 39 ]. Leonard et al described nickel catalyst effective for HDC of atrazine caused by pressurized gaseous hydrogen at 5 MPa and 140 °C [ 40 ]. Both atrazine and simazine are detoxified by nucleophilic substitution of bound chlorine by the action of alkaline hydrogen peroxide solution [ 41 ].…”

Recent Advances in Anode Electrocatalysts for Direct Formic Acid Fuel Cells – Part I – Fundamentals and Pd Based Catalysts

“…Nickel is one of the most widely used metal catalysts in catalysis for petrochemicals and energy because it is cheap, abundant and possess chemical properties suitable for catalyzing many important chemical reactions [144,145] . Nickel has been extensively used as an adatom for Pd for FAO oxidation.…”

Selective Nickel-Catalyzed Hydrodefluorination of Amides Using Sodium Borohydride

“…■ EXPERIMENTAL SECTION General Information. 1 H, 2 D, 13 C, and 19 F NMR spectra were acquired using a JEOL ECS-400 spectrometer. Infrared spectra were acquired using a JASCO FT/IR-4200 spectrometer.…”

“…Selective hydrodehalogenation is a family of reactions that have become more significant and essential in recent years, largely for applications in the destruction or recycling of polyhalogenated compounds that have been widely used over the past century but are now considered to be toxic and persistent environmental pollutants. These include polychlorinated biphenyls, pesticides, solvents, flame retardants, chlorofluorocarbons, and hydrofluorocarbons. − More recently, perfluoroalkyl compounds are now also considered to be major risks to human and environmental health despite being previously thought of as inert, and their destruction through hydrodefluorination or other methods is of immediate importance. , This is a particular challenge for hydrodefluorination due to the kinetic and thermodynamic inertness of the C–F bond, but, unfortunately, the vast majority of hydrodehalogenation reactions that have been reported are for activating C–Cl and C–Br bonds due to their relative ease. ,, In addition to the importance of hydrodehalogenation for environmental purposes, the reaction also has potential for use in synthetic organic chemistry and is complementary to a variety of known halogenation reactions. Unlike the heavier halogens, relatively specialized conditions and reagents are needed for breaking C–F bonds, which is both problematic but can also be beneficial in providing selectivity in multiple-step syntheses, and in forming new carbon–carbon or carbon-heteroatom bonds directly from fluorocarbons, which is a growing field. − The combination of fluorination and defluorination is also a valuable strategy for preparing specific polyfluorinated compounds for use as refrigerants and as drug targets, although this field is relatively undeveloped, and selectivity is essential for this type of precise molecular design. − Dehalogenation can be used to access unusual or otherwise impossible arene substitution patterns or to unblock reactive C–H positions.…”

“…4,5 This is a particular challenge for hydrodefluorination due to the kinetic and thermodynamic inertness of the C−F bond, but, unfortunately, the vast majority of hydrodehalogenation reactions that have been reported are for activating C−Cl and C−Br bonds due to their relative ease. 1,6,7 In addition to the importance of hydrodehalogenation for environmental purposes, the reaction also has potential for use in synthetic organic chemistry and is complementary to a variety of known halogenation reactions. Unlike the heavier halogens, relatively specialized conditions and reagents are needed for breaking C−F bonds, which is both problematic but can also be beneficial in providing selectivity in multiple-step syntheses, and in forming new carbon−carbon or carbon-heteroatom bonds directly from fluorocarbons, which is a growing field.…”