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

Abstract

Metal-containing ionic liquids comprising cationic Pd^II chelate complexes and the bis(trifluoromethanesulfonyl)amide (Tf₂N) anion were prepared: [Pd(acac)(Me₄en)]Tf₂N (1), [Pd(acac)(BuMe₃en)]Tf₂N (2), and [Pd(C₈-acac)(Me₄en)]Tf₂N (3) (acac = 2,4-pentanedionate, C₈-acac = 3-octyl-2,4-pentanedionate, Me₄en = N,N,N′,N′-tetramethylethylenediamine, BuMe₃en = 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 dimer-like arrangements and that there were no direct contacts between the charged moieties of the cations and anions in the solid state.