Mononuclear Indoline Complexes. 2. Synthesis, Structure, and Reactivity of [(Cymene)Ru(η¹-<i>N</i>-indoline)(CH₃CN)₂](OTf)₂

Abstract

The complex [(cymene)Ru(η1-indoline)(CH3CN)2](OTf)2, 1, has been synthesized by the reaction of [(cymene)Ru(OTf)2]x with indoline in acid solution and characterized by an X-ray diffraction study. Bond distances for the indoline ligand are compared to those reported recently for other η1- and η6-indoline complexes. Complex 1 rearranged to [(cymene)Ru(η6-indoline)](OTf)2 when heated in dichloromethane solution. The titration of an aqueous solution of 1 has been carried out, and the pKa of the coordinated ligand was determined to be 5.2. The value is similar to that reported for the indolinium ion. Ligand-exchange reactions of 1 have been studied. Deprotonation of the η1-indoline ligand in 1 results in dehydrogenation of the ligand to form free indole and ruthenium hydride products. The deprotonation of 1 in the presence of an alkene has been found to result in a hydrogen-transfer reaction to form alkane. Characteristics of the hydrogen-transfer reactions are discussed.