Synthesis and Alkyne Insertion Reactions of NHC-Based Cyclometalated Ruthenium(II) Complexes

The series of NHC-based cyclometalated ruthenium(II) complexes 2a-k were synthesized by the reactions of aryl-substituted imidazolium salts with [(p-cymene)RuCl2](2) under mild conditions. These complexes could react with alkynes in MeOH at 80 degrees C, through alkyne insertion and subsequent reductive elimination, to give the new kinds of imidazolium salts 3a-q in high yields. All new compounds were fully characterized, and the molecular structures of 2a-d,f,g,i-k were determined by single-crystal X-ray diffraction analysis.