Crystal structures of low-melting ionic transition-metal complexes with N-alkylimidazole ligands

Hoogerstraete, Tom Vander; Brooks, Neil R.; Norberg, Bernadette; Hecke, Kristof Van; Meervelt, Luc Van; Binnemans, Koen

doi:10.1039/c2ce25470k

Cited by 40 publications

(29 citation statements)

References 30 publications

(47 reference statements)

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“…Furthermore, since the cathodic breakdown reaction of the ionic liquid is the desired electrodeposition of the metal, uncontrolled decomposition products are not formed (provided that a sacrificial anode is being used), making the electrolyte bath more sustainable. Several ionic liquids that can be considered as liquid metal salts have been reported in the literature, 11,12 including those containing silver(I), 13,14 copper(I) 15 and copper(II), 16,17 and cobalt(II). 18 Electrodeposition from this type of compounds has been described.…”

Section: Introductionmentioning

confidence: 99%

Cobalt(ii) liquid metal salts for high current density electrodeposition of cobalt

et al. 2018

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Cobalt(ii)-containing ionic liquids were synthesized using N,N-dimethylformamide, N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMAc), pyridine-N-oxide (py-O), 1,10-phenanthroline (phen), ethylenediamine (en) and dimethylimidazolidinone (DMI) as ligands. The weakly coordinating bis(trifluoromethylsulfonyl)imide (Tf2N-) was used as a counter anion. Several compounds had a melting temperature below 100 °C, and the compound [Co(DMAc)6][Tf2N]2 was liquid at room temperature, with a viscosity of only 18 mPa s at 80 °C. Several compounds were recrystallized to give high quality single crystals and their crystal structures were determined. EXAFS measurements were performed on [Co(DMAc)6][Tf2N]2 at different temperatures and it was observed that the [Co(DMAc)6]2+ ion partially dissociated at higher temperatures, which explains the temperature-dependent color change (thermochromism). The electrochemical properties of the compounds with the lowest melting points were also investigated. Adherent, crack-free metallic cobalt layers could be electrodeposited from [Co(DMAc)6][Tf2N]2, [Co(DMI)6][Tf2N]2 and [Co(NMP)6][Tf2N]2. From the first two, black deposits consisting of micrometer-sized needles were obtained, whereas the latter resulted in a dull grey cobalt layer consisting of micrometer-sized cobalt spheres. The Co(iii)/Co(ii) redox couple was not found to occur in any compound with an O-donor ligand, but the Co(iii)/Co(ii) redox couple was found to be quasi-reversible for [Co(phen)3][Tf2N]2 dissolved in [BMP][Tf2N].

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Section: Introductionmentioning

confidence: 99%

Cobalt(ii) liquid metal salts for high current density electrodeposition of cobalt

et al. 2018

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“…21 Ionic liquids comprising a metal cation that is coordinated by several neutral ligands such as acetonitrile or N-alkylimidazoles and charge balanced by non-or weakly coordinating anions such as Tf2N are liquid metal salts with low melting points. [22][23][24][25] The incorporation of the metal in the cation of the liquid metal salt makes it easier to electrodeposit the metal on the negatively charged cathode. [22][23][24][25] Metal bis(trifluoromethylsulfonyl)imides have also been used as Lewis acid catalyst in organic synthesis.…”

Section: Introductionmentioning

confidence: 99%

“…[22][23][24][25] The incorporation of the metal in the cation of the liquid metal salt makes it easier to electrodeposit the metal on the negatively charged cathode. [22][23][24][25] Metal bis(trifluoromethylsulfonyl)imides have also been used as Lewis acid catalyst in organic synthesis. [26][27][28][29][30][31] For example, Suzuki et al found that Yb(Tf2N)3 catalyzed Michael reactions of beta-ketoesters 27 and Duris et al showed that La(Tf2N)3 acted as catalysts for Friedel-Crafts acylations.…”

Section: Introductionmentioning

confidence: 99%

Crystal structures of hydrated rare-earth bis(trifluoromethylsulfonyl)imide salts

et al. 2015

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“…Only a few examples of these "liquid metal salts" can be found in the literature, 4,5,6,7 and their use for electrochemical purposes has only been rather scarcely investigated. 8,9,10,11,12,13,14 Our research group recently pointed to the potential of these liquid metal salts as electrolytes for the high-rate electrodeposition of copper, 15,16,17 and silver.…”

Section: Introductionmentioning

confidence: 99%

High current density electrodeposition of silver from silver-containing liquid metal salts with pyridine-N-oxide ligands

et al. 2014

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New cationic silver-containing ionic liquids were synthesized and used as non-aqueous electrolytes for the electrodeposition of silver layers. In the liquid state of these ionic liquids, a silver (i) cation is coordinated by pyridine-N-oxide (py-O) ligands in a 1 : 3 metal-to-ligand ratio, although in some cases a different stoichiometry of the silver center crystallized out. As anions, bis(trifluoromethanesulfonyl)imide (Tf2N), trifluoromethanesulfonate (OTf), methanesulfonate (OMs) and nitrate were used, yielding compounds with the formulae [Ag(py-O)3][Tf2N], [Ag(py-O)3][OTf], [Ag(py-O)3][OMs] and [Ag(py-O)3][NO3], respectively. The compounds were characterized by CHN analysis, FTIR, NMR, DSC, TGA and the electrodeposition of silver was investigated by cyclic voltammetry, linear potential scans, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX). With the exception of [Ag(py-O)3][Tf2N], which melts at 108 °C, all the silver(i) compounds have a melting point below 80 °C and were tested as electrolytes for silver electrodeposition. Interestingly, very high current densities were observed at a potential of -0.5 V vs. Ag/Ag(+) for the compounds with fluorine-free anions, i.e. [Ag(py-O)3][NO3] (current density of -10 A dm(-2)) and [Ag(py-O)3][OMs] (-6.5 A dm(-2)). The maximum current density of the compound with the fluorinated anion trifluoromethanesulfonate, [Ag(py-O)3][OTf], was much lower: -2.5 A dm(-2) at -0.5 V vs. Ag/Ag(+). Addition of an excess of ligand to [Ag(py-O)3][OTf] resulted in the formation of the room-temperature ionic liquid [Ag(py-O)6][OTf]. A current density of -5 A dm(-2) was observed at -0.5 V vs. Ag/Ag(+) for this low viscous silver salt. The crystal structures of several silver complexes could be determined by X-ray diffraction, and it was found that several of them had a stoichiometry different from the 1 : 3 metal-to-ligand ratio used in their synthesis. This indicates that the compounds form crystals with a composition different from that of the molten state. The electrochemical properties were measured in the liquid state, where the metal-to-ligand ratio was 1 : 3. Single crystal X-ray diffraction measurements showed that silver(i) is six coordinate in [Ag(py-O)3][Tf2N] and [Ag(py-O)3][OTf], while it is five coordinate in the other complexes. In [Ag3(py-O)8][OTf]3, there are two different coordination environments for silver ions: six coordinate central silver ions and five coordinate for the outer silver ions. In some of the silver(i) complexes, silver-silver interactions were observed in the solid state.

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Crystal structures of low-melting ionic transition-metal complexes with N-alkylimidazole ligands

Abstract: Visit the CrystEngComm website for more cutting-edge crystal engineering research

Cited by 40 publications

References 30 publications

Cobalt(ii) liquid metal salts for high current density electrodeposition of cobalt

Cobalt(ii) liquid metal salts for high current density electrodeposition of cobalt

Crystal structures of hydrated rare-earth bis(trifluoromethylsulfonyl)imide salts

High current density electrodeposition of silver from silver-containing liquid metal salts with pyridine-N-oxide ligands

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