Promoting effect of ionic liquids on ligand substitution reactions

Ionic liquid solvents N-hexylpyridinium bistrifylimide ([C6pyr][Tf2N]] and 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) promoted the displacement of anionic ligands by pyridine derivatives in trans-(Ph3P)2Rh(CO)NO3 to a much greater extent than did dichloromethane. Thus, addition of a slight excess of 2-fluoropyridine to trans-(Ph3P)2Rh(CO)NO3 in [C4mim][PF6] gave a 29:71 product mixture of trans-(Ph3P)2Rh(CO)NO3:[trans-(Ph3P)2Rh(CO)(2-fluoropyridine)][NO3], while the ratio was 91:9 in dichloromethane.

Ionic liquid solvents promoted the displacement of anionic ligands by pyridine derivatives in trans-(Ph3P)2Rh(CO)X (X=NO3-,C6F5CO2-). Thus, addition of a slight excess of 2-fluoropyridine to trans-(Ph3P)2Rh(CO)NO3 in [C4mim][PF6] gave a 30:70 product mixture of trans-(Ph3P)2Rh(CO)NO3:[trans-(Ph3P)2Rh(CO)(2-fluoropyridine)][NO3], while the ratio was 91:9 in dichloromethane.Figure optionsDownload as PowerPoint slide