Abstract
Decomposition of transition-metal amidinates [M{MeC(NiPr)(2)} (n) ] [M(AMD) (n) ; M=Mn(II), Fe(II), Co(II), Ni(II), n=2; Cu(I), n=1) induced by microwave heating in the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF(4)]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF(6)]), 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 (MF(2)-NPs) for M=Mn, Fe, and Co in [BMIm][BF(4)]. FeF(2)-NPs can be prepared upon Fe(AMD)(2) decomposition in [BMIm][BF(4)], [BMIm][PF(6)], 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][BF(4)] were identified by powder X-ray diffraction (PXRD) to exclusively Ni- and Cu-NPs or to solely MF(2)-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 MF(2)-NPs from [BMIm][BF(4)] 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 CoF(2)-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 CoF(2)-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.