Immobilization of Cyclometalated Iridium Complex onto Multiwalled Carbon Nanotubes for Dehydrogenation of Indolines in Aqueous Solution

Increasing concerns about the potentially negative impacts of chemical production on sustainable development of the overall environment have spurred numerous attempts to seek greener reaction mediums, recyclable catalysts, and high-efficiency procedures. Herein, a cyclometalated Ir complex with a pyrene tag was successfully immobilized onto multiwalled carbon nanotubes via π–π stacking interactions, through which an easily reusable Ir catalyst was constructed. The immobilization process was effectively monitored by using a fluorescence spectroscopy technique, and the immobilized Ir catalyst was well characterized and evaluated. It is found that the immobilized Ir catalyst exerts activity comparable to that of the corresponding homogeneous Ir catalyst for the dehydrogenation of indolines in an aqueous solution. More importantly, the catalyst could be recycled seven times without obvious loss of the Ir-active center and noticeable decrease in the yield of the targeted product. Additionally, the observed slight deactivation of the catalyst during the recycle is also discussed.