Synthesis of Metal Nanoparticles and Metal Fluoride Nanoparticles from Metal Amidinate Precursors in 1-Butyl-3-Methylimidazolium Ionic Liquids and Propylene Carbonate

Abstract

Decomposition of transition‐metal amidinates [M{MeC(NiPr)2}n] [M(AMD)n; M=MnII, FeII, CoII, NiII, n=2; CuI, n=1) induced by microwave heating in the ionic liquids (ILs) 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF4]), 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIm][PF6]), 1‐butyl‐3‐methylimidazolium trifluoromethanesulfonate (triflate) ([BMIm][TfO]), and 1‐butyl‐3‐methylimidazolium tosylate ([BMIm][Tos]) or in propylene carbonate (PC) gives transition‐metal nanoparticles (M‐NPs) in non‐fluorous media (e.g. [BMIm][Tos] and PC) or metal fluoride nanoparticles (MF2‐NPs) for M=Mn, Fe, and Co in [BMIm][BF4]. FeF2‐NPs can be prepared upon Fe(AMD)2 decomposition in [BMIm][BF4], [BMIm][PF6], and [BMIm][TfO]. The nanoparticles are stable in the absence of capping ligands (surfactants) for more than 6 weeks. The crystalline phases of the metal or metal fluoride synthesized in [BMIm][BF4] were identified by powder X‐ray diffraction (PXRD) to exclusively Ni‐ and Cu‐NPs or to solely MF2‐NPs for M=Mn, Fe, and Co. The size and size dispersion of the nanoparticles were determined by transmission electron microscopy (TEM) to an average diameter of 2(±2) to 14(±4) nm for the M‐NPs, except for the Cu‐NPs in PC, which were 51(±8) nm. The MF2‐NPs from [BMIm][BF4] were 15(±4) to 65(±18) nm. The average diameter from TEM is in fair agreement with the size evaluated from PXRD with the Scherrer equation. The characterization was complemented by energy‐dispersive X‐ray spectroscopy (EDX). Electrochemical investigations of the CoF2‐NPs as cathode materials for lithium‐ion batteries were simply evaluated by galvanostatic charge/discharge profiles, and the results indicated that the reversible capacity of the CoF2‐NPs was much lower than the theoretical value, which may have originated from the complex conversion reaction mechanism and residue on the surface of the nanoparticles.

Synthesis of plasmonic Fe/Al nanoparticles in ionic liquids

“…55,57 Imidazolium-ILs, in particular with the cation [BMIm] + are well established for the synthesis of small NPs. 18,19,54,[56][57][58][59][60] However, [BMIm] + contains a slightly acidic proton in the C-2 position which can lead to metal-carbene formation. 61 The cation [BPy] + was included here because of the absence of such acidic protons.…”

Synthesis of metal-fluoride nanoparticles supported on thermally reduced graphite oxide

“…The formation of metal fluorides instead of metal nanoparticles in the IL [BMIm][BF 4 ] must be rationalized from the fluoride content of the IL tetrafluoroborate anion. It is known that the [BF 4 ] − anion hydrolyzes or decomposes to fluoride, F − , in the presence of small amounts of residual water in the IL, which is very difficult to remove from hydrophilic [BMIm][BF 4 ] [ 63 ]. Water is used in IL synthesis during the washing process following the anion exchange from typically chloride to tetrafluoroborate.…”

“…In the synthesis of nanoparticles of the fluoridosilicates A 2 SiF 6 (A = Li, Na, K, Rb, Cs) the IL [BMIm][PF 6 ] was used both as solvent and fluoride source in an ionothermally assisted microwave synthesis [ 66 ]. Decomposition of transition-metal amidinates in [BMIm][BF 4 ] yielded metal fluoride nanoparticles for Mn, Fe and Co [ 63 ]. The reaction of metal acetate (hydrate) precursors in ethylene glycol and an excess of [BMIm][BF 4 ] gave fluoride nanoparticles [ 67 ].…”

Chemoselective reduction of heteroarenes with a reduced graphene oxide supported rhodium nanoparticle catalyst

“…Rh NPs derived from RhIJNO 3 ) 3 and supported on rGO have been used to catalyze the hydroformylation of 1-hexene. 24 Microwave induced thermal decomposition of metal precursors in ionic liquid (IL) media represents a promising variation of this approach, 25,26 as ILs efficiently absorb microwaves due to their high dielectric constants. 27,28 The microwave-assisted IL method combines the advantages of traditional microwave synthesis (fast and energy efficient) and IL solvents (microwave absorbers and structure-directing agents).…”