Sonochemical Reaction of [Fe(CO) 5 ] with 1‐Methylimidazole in An Ionic Liquid: Formation of [(1‐Methylimidazole) 6 Fe II ](PF 6 ) 2

The ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate, (BMI + )(PF 6 − ), has been used as a solvent in the sonochemical reaction of 1‐methylimidazole and [Fe(CO) 5 ] at 40−50 °C under air. The reaction afforded [(1‐methylimidazole) 6 Fe II ](PF 6 ) 2 , the structure of which was determined at 293 K by single‐crystal X‐ray diffraction methods. The salt crystallizes in the trigonal space group P $\bar 3$ with unit‐cell parameters of a = 11.4603(16) Å, c = 8.0172(11) Å, and Z = 1. The crystals showed twinning by merohedry, which was accounted for in the structure determination and refinement calculations. All the 1‐methylimidazole ligands are equivalent, with a Fe−N bond length of 2.204(3) Å. Mössbauer spectroscopy confirmed the presence of Fe 2+ . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)