Organometallic ionic liquids from half-sandwich Ru(II) complexes with various chelating ligands

•Organometallic ionic liquids from half-sandwich Ru(II) complexes were prepared.•The salts exhibited high Tm and Tg values owing to the bulkiness of the ligands.•The salts exhibited catalytic activity for the oxidation of cyclohexanol.

Salts comprising of cationic half-sandwich Ru(II) complexes with various chelating ligands and the bis(trifluoromethanesulfonyl)amide anion (Tf2N−) were prepared. These salts can be represented as [(arene)RuCl(L–L)][Tf2N] (arene = C6Me5Bu, C6Me6, p-cymene, C6H6; L–L = 2-Py-CH2NHCMe2Et, 2-Py-CHNC6H13, H13C6NHCH2CH2NHC6H13, Me2NCH2CH2SC4H9, Me2CNCHCHNCMe2). Two of the eight salts are liquids at room temperature (∼20 °C), while the other salts are solids with melting points of 60–130 °C. Upon cooling from the melt, most salts exhibited glass transitions between −30 °C and −5 °C. The salts were found to catalyze the oxidation of cyclohexanol although decomposition occurred during the reaction. Crystal structures of related salts were also determined.

Graphical abstractSalts represented as [(arene)RuCl(L–L)]Tf2N were prepared, which contain bulky cationic half-sandwich Ru(II) complexes with various chelating ligands (L–L). Two of the eight salts are liquids at room temperature (∼20 °C), while the other salts are solids with melting points of 60–130 °C. These salts exhibited catalytic activity for the oxidation of cyclohexanol although decomposition occurred during the reaction.Figure optionsDownload full-size imageDownload as PowerPoint slide