Catalytic hydrogenation of aromatic nitro compounds by functionalized ionic liquids-stabilized nickel nanoparticles in aqueous phase: The influence of anions

Abstract

Two kinds of nickel nanoparticles (NPs) well-dispersed in aqueous phase have been conveniently prepared by reducing nickel(II) salt with hydrazine in the presence of amino group (NH 2 ) functionalized ionic liquids:The Ni(0) particles are composed of smaller ones which assemble in a blackberry-like shape. The Ni nanoparticles stabilized with [AMMIM][AcO] are much larger than those stabilized with [AMMIM] [Br], and the former unexpectedly give much higher activity in the selective hydrogenation of citral and nitrobenzene (NB) in aqueous phase. The Ni(0) nanocatalysts dispersed in aqueous phase are stable enough to be reused at least five times without significant loss of catalytic activity and selectivity during the catalytic recycles. functionalized ionic liquid, nickel nanoparticles, aqueous phase, selective hydrogenation

Nickel Nanoparticles Stabilized by Trisimidazolium Salts: Synthesis, Characterization and Application as Recyclable Catalysts for the Reduction of Nitroarenes

“…The synthesis of nickel nanoparticles has been described in the literature through a thermal or chemical reduction of Ni(II) salts with NaBH 4, LiEt 3 BH or NaEt 3 BH,,,,–, dimethylaminoborane, hydrazine,,,, ethylene glycol, or oleylamine as reducing agents, among others. Moreover, dispersions of Ni NPs in different types of ionic‐liquids have been obtained by auto‐decomposition, or microwave‐induced decomposition of Ni(COD) 2 (COD=1,5‐cyclooctadiene).…”

“…The reduction of nitroarenes under catalysis by supported Ni NPs has been achieved with NaBH 4 as reducing agent,, by hydrogenation at high hydrogen pressure,,,,, and with hydrazine, or glycerol as hydrogen sources …”

“…The incorporation of N ‐heterocyclic carbenes (NHC) into the matrix or the use of these ligands for the stabilization of Ni NPs in solution have been described. Also imidazolium‐based ionic liquids,,, and poly(ionic liquids) have been employed to prepare dispersions of Ni NPs. Recently, we have developed palladium nanoparticles stabilized by mesitylene‐containing tris‐imidazolium species ( L1 and L2) for C−C coupling reactions and hydrosilylation of internal alkynes .…”

Nanocatalysts Based on Ni Nanoparticles in Functionalized Ionic Liquids for Chemoselective Hydrogenation and Transfer Hydrogenation of α,β‐unsaturated Carbonyl Compounds

“…[8] Well-defined Ni NPs can be generated in solution by the reduction of a nickel(II) salt, e. g. nickel(II) chloride (NiCl 2 ) with lithium and 4,4'-di-tert-butylbiphenyl (DTBB) as stabilizer, [11,12] or the reduction of nickel(II) acetate (Ni(OAc) 2 ) with aqueous hydrazine. [13] Also, nickel(II) bis(acetylacetonate) (Ni(acac) 2 ) can be used to synthesize size-tunable Ni NPs through thermal decomposition in the presence of n-trioctylphosphine as a capping ligand and alkylamines as a size-limiting agent. [14] An alternative and efficient method to obtain size-controlled Ni NPs in solution relies on the decomposition of an organometallic complex like bis(η 4 -1,5-cyclooctadiene)nickel(0) ([Ni-(COD) 2 ]) [15][16][17] under hydrogen in the presence of different stabilizing agents.…”

“…Well‐defined Ni NPs can be generated in solution by the reduction of a nickel(II) salt, e. g . nickel(II) chloride (NiCl 2 ) with lithium and 4,4′‐di‐ tert ‐butylbiphenyl (DTBB) as stabilizer, [11,12] or the reduction of nickel(II) acetate (Ni(OAc) 2 ) with aqueous hydrazine [13] . Also, nickel(II) bis(acetylacetonate) (Ni(acac) 2 ) can be used to synthesize size‐tunable Ni NPs through thermal decomposition in the presence of n ‐trioctylphosphine as a capping ligand and alkylamines as a size‐limiting agent [14] .…”