Ionic liquids from cationic palladium(II) chelate complexes: preparation, thermal properties, and crystal structures

摘要

Metal-containing ionic liquids comprising cationic Pd~(II) chelate complexes and the bis(trifluoromethanesulfonyl) amide (Tf_2N) anion were prepared: [Pd(acac)(Me_4en)]Tf_2N (1), [Pd(acac)(BuMe_3en)]Tf_2N (2), and[Pd(C_8-acac)(Me_4en)]Tf_2N (3) (acac = 2,4-pentanedionate, C_8-acac = 3-octyl-2,4-pentanedionate, Me_4en= N,N,N',N'-tetramethylethylenediamine, BuMe_3en = N-butyl-N,N',N'-trimethylethylenediamine). These salts were yellow solids with melting points of 85.2 °C, 71.1 °C, and 62.3 °C, respectively. During cooling from the liquid state, complex 1 exhibited crystallization, whereas 2 and 3 exhibited only glass transitions at approximately -40 °C. X-ray structure determination revealed that the cations in 1 and 3 form dimerlike arrangements and that there were no direct contacts between the charged moieties of the cations and anions in the solid state.