Z. Anorg. Allg. Chem. 2006, 2163 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.zaac.wiley-vch.de 2163 DOI: 10.1002/zaac.200670174 SolventSolute Interactions in Ionic Liquids Arash Babai, Anja-Verena Mudring* Institut für Anorganische Chemie, Universität zu Köln, Greinstr. 6, D-50939 Köln Keywords: ionic liquids; lanthanides Ionic liquids (Ils) are salts that are liquid below 100 °C, most times even below room temperature [1]. Ils have gained great attention over the last decade in organic synthesis and electrochemistry. Lewis-acid catalysed reactions with trivalent rare-earth cations can give higher yields in ionic liquids than in conventional organic solvents [2]. But still, the solvation and coordination effects especially in bis(trifluoromethanesufonyl)-imide (Tf 2 N)-based ionic liquids are poorly understood but a thorough perception of these is a prerequisite to understand exactly the reaction cycles and mechanisms. We have now characterized the first Tf 2 N complexes of di- and trivalent f-elements from the ionic liquid [bmpyr][Tf 2 N] (bmpyr 1-butyl-1-methylpyrrolidinium) by single-crystal structure analysis. The structures show that the Tf 2 N anion is not as weakly coordinating as previously assumed (Figure) [3]. Together with optical spectroscopy a congruent picture of the solvation of lanthanide cations in Tf 2 N based ionic liquids can be drawn. Fig. 1 Coordination of Ln 3 by Tf 2 N in [bmpyr] 2 [Ln(Tf 2 N) 5 ], Ln LaTb (left) and in [bmpyr][Ln(Tf 2 N) 4 ], Ln DyLu (right). The compounds [bmpyr] 2 [Ln(Tf 2 N) 5 ], Ln LaTb and [bmpyr][Ln(Tf 2 N) 4 ] Ln DyLu are ionic liquids themselves as they melt between 83105 °C and may be interesting solvents for Lewis acid catalysis as they contain with the trivalent lanthanide cation surrounded by the weakly coordinating Tf 2 N ligands a highly acidic metal center. Currently we are investigating the ligand exchange processes at the Ln 3 centers in pyrrolidinium based Tf 2 N and OTf ionic liquids. [1] P. Wasserscheid, W. Keim, Angew. Chem. Int. Ed. Engl. 2000, 39, 3772; Ionic Liquids in Synthesis (Ed. P. Wasserscheid, T. Welton (Eds.), VCH-Wiley, Weinheim 2003; T. Welton, Chem. Rev. 1999, 99, 2071, and references therein. [2] C. E. Song, D. D. Jun, S. Y. Choung, E. J. Roh, S. Lee, Angew. Chem. Int. Ed. 2004, 43, 6183. [3] A.-V. Mudring, A. Babai, S. Arenz, R. Giernoth, Angew. Chem. Int. Ed. 2005, 44, 5485; A.-V. Mudring, Inorg.Chem. 2005, 44, 8168; A. Babai, A.-V. Mudring, Inorg.Chem. 2006, 45, 3249, A.-V. Mudring, A. Babai, Dalton Trans. 2006, 1828, A. Babai, A.-V. Mudring, Inorg.Chem. 2006, 45, 4874.

Solvent-Solute Interactions in Ionic Liquids

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Page 1: Solvent-Solute Interactions in Ionic Liquids

Z. Anorg. Allg. Chem. 2006, 2163 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.zaac.wiley-vch.de 2163

DOI: 10.1002/zaac.200670174

Solvent�Solute Interactions in IonicLiquidsArash Babai, Anja-Verena Mudring*Institut für Anorganische Chemie, Universität zu Köln,Greinstr. 6, D-50939 Köln

Keywords: ionic liquids; lanthanides

Ionic liquids (Ils) are salts that are liquid below 100°C, most timeseven below room temperature [1]. Ils have gained great attentionover the last decade in organic synthesis and electrochemistry.Lewis-acid catalysed reactions with trivalent rare-earth cations cangive higher yields in ionic liquids than in conventional organicsolvents [2]. But still, the solvation and coordination effectsespecially in bis(trifluoromethanesufonyl)-imide (Tf2N)-based ionicliquids are poorly understood � but a thorough perception of theseis a prerequisite to understand exactly the reaction cycles andmechanisms.We have now characterized the first Tf2N complexes of di- andtrivalent f-elements from the ionic liquid [bmpyr][Tf2N] (bmpyr �

1-butyl-1-methylpyrrolidinium) by single-crystal structure analysis.The structures show that the Tf2N anion is not as weakly coordina-ting as previously assumed (Figure) [3]. Together with opticalspectroscopy a congruent picture of the solvation of lanthanidecations in Tf2N based ionic liquids can be drawn.

Fig. 1 Coordination of Ln3� by Tf2N in [bmpyr]2[Ln(Tf2N)5], Ln �

La�Tb (left) and in [bmpyr][Ln(Tf2N)4], Ln � Dy�Lu (right).

The compounds [bmpyr]2[Ln(Tf2N)5], Ln � La�Tb and[bmpyr][Ln(Tf2N)4] Ln � Dy�Lu are ionic liquids themselves asthey melt between 83�105°C and may be interesting solvents forLewis acid catalysis as they contain with the trivalent lanthanidecation surrounded by the weakly coordinating Tf2N ligands ahighly acidic metal center. Currently we are investigating the ligandexchange processes at the Ln3� centers in pyrrolidinium basedTf2N and OTf ionic liquids.

[1] P. Wasserscheid, W. Keim, Angew. Chem. Int. Ed. Engl. 2000,39, 3772; Ionic Liquids in Synthesis (Ed. P. Wasserscheid, T.Welton (Eds.), VCH-Wiley, Weinheim 2003; T. Welton, Chem.Rev. 1999, 99, 2071, and references therein.

[2] C. E. Song, D. D. Jun, S. Y. Choung, E. J. Roh, S. Lee, Angew.Chem. Int. Ed. 2004, 43, 6183.

[3] A.-V. Mudring, A. Babai, S. Arenz, R. Giernoth, Angew. Chem.Int. Ed. 2005, 44, 5485; A.-V. Mudring, Inorg.Chem. 2005, 44,8168; A. Babai, A.-V. Mudring, Inorg.Chem. 2006, 45, 3249,A.-V. Mudring, A. Babai, Dalton Trans. 2006, 1828, A. Babai,A.-V. Mudring, Inorg.Chem. 2006, 45, 4874.