Colorless organometallic ionic liquids from cationic ruthenium sandwich complexes: thermal properties, liquid properties, and crystal structures of [Ru(η⁵-C₅H₅)(η⁶-C₆H₅R)][X] (X = N(SO₂CF₃)₂, N(SO₂F)₂, PF₆)

Abstract

A series of ionic liquids containing cationic ruthenium complexes ([Ru(C5H5)(C6H5R)](+)) were prepared, and their thermal properties were investigated (R = C4H9 (1a), C8H17 (1b), OCH2OCH3 (2a), O(CH2CH2O)2CH3 (2b), O(CH2)3CN (3a), O(CH2)6CN (3b), CO(CH2)2CH3 (4a), CO(CH2)6CH3 (4b)). Bis(trifluoromethanesulfonyl)amide (TFSA) and bis(fluorosulfonyl)amide (FSA) were used as counter anions. These ionic liquids were colorless and stable toward air and light. These salts exhibited glass transitions upon cooling from the melt (Tg = −82 °C to −55 °C), and the glass transition temperatures of the salts increased as the polarity of the substituents increased (alkyl < ether < cyano < carbonyl). The decomposition temperatures decreased in the order of alkyl > cyano > carbonyl > ether. The viscosities, solvent polarities, and refractive indices of the salts of 1a and 2a were also evaluated. Hexafluorophosphate (PF6) salts were also prepared, which were solids with high melting points (Tm = 65–127 °C). X-ray crystal structure analyses of these salts revealed the importance of intermolecular contacts involving the ring hydrogens. The PF6 salt of 2a exhibited an order–disorder phase transition.

Photogeneration of Microporous Amorphous Coordination Polymers from Organometallic Ionic Liquids

“…B(CN) 4 − acts as the anion and a bridging ligand to form the coordination polymer. The use of this anion is crucial because the corresponding ionic liquids with fluorinated anions such as [Ru(C 5 H 5 )(C 6 H 5 Bu)][(SO 2 F) 2 N] exhibit no photoreactivity . There are several ionic liquids that exhibit solidification upon photoirradiation based on photoisomerization or photodimerization .…”

Multifunctional Ionic Liquids from Rhodium(I) Isocyanide Complexes: Thermochromic, Fluorescence, and Chemochromic Properties Based on Rh−Rh Interaction and Oxidative Addition

“…The viscosity at room temperature was 121.0 mPa s, and it was a Newtonian fluid. This viscosity was more than two times higher than that of [Bmim][Tf 2 N] (49.0 mPa s; Bmim=1‐butyl‐3‐methylimidazolium cation) and comparable to that of another organometallic ionic liquid, [Ru(C 5 H 5 )(C 6 H 5 n Bu)][Tf 2 N] (136.6 mPa s) . [ 1 ][Tf 2 N] had a lower viscosity than an ammonium salt [N( n C 6 H 13 ) 4 ][Tf 2 N] (430 mPa s at 25 °C) with similar substituent length .…”

Effects of substituent branching and chirality on the physical properties of ionic liquids based on cationic ruthenium sandwich complexes

“…2 The data were fit using the VFT equation (Z = Z 0 e [DT0/(TÀT0)] ), where T 0 is the ideal glass-transition temperature and D is a parameter that reflects the deviation from Arrhenius behavior. 20 An increase in D for longer substituents is also observed in alkylimidazolium ionic liquids 2 and in ferrocene-based ionic liquids. 20 An increase in D for longer substituents is also observed in alkylimidazolium ionic liquids 2 and in ferrocene-based ionic liquids.…”

“…20 Fig. This structure contrasts with that of the sandwich complexes [Ru(C 5 H 5 )(C 6 H 5 R)]X that have heteroatoms in their substituents, 20 wherein lamellar structures do not form because of hydrogen-bond-like interactions between the heteroatoms and the hydrogens in the cation. The alkyl chains in [3][PF 6 ] and [3][FSA] are aligned parallel to each other.…”

“…Therefore, the effects of molecular structure, such as the length of alkyl substituents, on the physical properties of ionic liquids have been extensively investigated. [17][18][19][20][21] We examine herein how substituent branching and chirality affect the thermal properties of organometallic ionic liquids. [4][5][6][7][8][9][10][11] Although most ionic liquids contain organic cations such as imidazolium cations, various metal-containing ionic liquids that exhibit intriguing functionalities have recently been developed.…”