The “Noncoordinating” Anion Tf₂N⁻ Coordinates to Yb²⁺: A Structurally Characterized Tf₂N⁻ Complex from the Ionic Liquid [mppyr][Tf₂N]

Abstract

Not as innocent as it looks: The first anionic Tf2N− complex, [Yb(Tf2N)4]2−, has been prepared in the ionic liquid [mppyr][Tf2N] (see crystal structure; blue: N, yellow: S, gray: C, green: F, orange: Yb, red: O; mppyr=1‐methyl‐1‐propyl‐pyrrolidinium, Tf=trifloromethanesulfonyl). The coordination of the presumed noncoordinating (“innocent”) Tf2N2− ion could have a decisive influence on reactions in ionic liquids.

Lanthanides and Actinides in Ionic Liquids

“…To force the bis-(trifluoromethylsulfonyl)imide anion to coordinate to the lanthanide ion, the authors reacted Pr(Tf 2 N) 3 4 ], where mppyr is 1-methyl-1-propylpyrrolidinium ( Figure 7). 96 Here, the coordinating unit is an anionic tetrakis complex, which shows similarities with the well-known tetrakis -diketonate complexes. 97 -anions result in coordination number eight.…”

“…125 Mudring et al reported that the divalent ytterbium ion is a stable species in a pyrrolidinium ionic liquid. 96 The redox behavior of the lanthanide complexes [Ln(Tf 2 N) 3 Tetravalent cerium is not stable in LiCl-KCl eutectic melts, because cerium(IV) is reduced by chloride ions. 127 Cerium-(IV) has a higher kinetic stability in AlCl 3 -[C 2 mim]Cl ionic liquids, but it is eventually reduced to cerium(III).…”

Solvation Structures of Some Transition Metal(II) Ions in a Room-Temperature Ionic Liquid, 1-Ethyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)amide

“…Both conformers coexist in neat RTIL, 22,32 whereas the C1 conformer is preferred in the coordination sphere around the metal ion. This is indeed seen in crystals of M(TFSA)n (M = Li, K, Ca, Sr, Ba and Yb), [25][26][27][28] and is ascribed to the dipole moment of the C1 conformer (4.3 D) being larger than that of the C2 conformer (0.0 D). The lithium ion binds not only the C1 conformer, but also the C2 conformer in the ionic liquid, unlike crystals, according to our Raman and DFT studies.…”

“…Indeed, only the C1 conformer is found in crystals of M(TFSA)n (M = Li, K, Ca, Sr, Ba and Yb). [25][26][27][28] Recently, we reported the solvation structure of the lithium ion in EMI + TFSA -studied by Raman spectra and DFT calculations. 29 These studies established that the lithium ion is four-coordinated -prefers the C1 conformer upon coordination to the metal ion.…”

Formation of Complexes in RTIL and Ion Separations

“…Cs + forms therefore only ML complexes with 18-crown-6 in water (E N T 10), DMSO (E N T 0. 5 ], where PMIM indicates 1-propyl-3-methylimidazolium and mppyr -1-methyl-1-propylpyrrolidinium (Murding, et al 2005), have demonstrated that it can coordinate as a bidentate ligand via oxygen atoms forming either 6-membered or 4-membered rings: (Babai & Murding, 2006). Even the alkali ions are found to form weak bonds with N(Tf 2 ) - (Yan et al, 2010).…”