Allyl-functionalised ionic liquids: Synthesis, characterisation, and reactivity

The two known Me- and allyl-substituted 1H-imidazol-3-ium bromides 1 and 2, respectively, were converted to the corresponding BF4- and BPh4- salts 3-6 (Scheme 1). Compounds 3 and 4 were liquids at ambient temperature. Reaction of 1 or 2 with [PdCl2] afforded the corresponding 2:1 imidazolium/metal complexes 7 and 8. The latter complex, melting at 58 degrees, can be regarded as a 'true' ionic liquid. Attempts to polymerise 7 by radical promotion (AIBN) were unsuccessful, but resulted in the centrosymmetric 2:1 complex 9. The allyl group of 1 could be arylated (giving rise to 10) or hydrogenated (at 100 bar H-2 pressure). The solid-state structures of compounds 5-7 and 9 were solved by means of single-crystal X-ray analyses (Figs. 1-4).