Micellar Transfer Hydrogenation Catalysis in Water with Monocarbonyl Ruthenium(II)-poly(vinylphosphonate)-Containing Polymers: Achieving Reduction of Biomass-Derived Aldehydes

Abstract

With the aim to build a supramolecular organometallic catalyst for transfer hydrogenation (TH) reactions of hydrophobic substrates, micellar architectures of different sizes were obtained using amphiphilic diblock copolymers (BCPs) tethered to a Ru(II) monocarbonyl complex. An end-group functionalization strategy was employed to incorporate a bipyridyl end-group, used to further coordinate the cationic ruthenium fragment, to amphiphilic poly(2-vinylpyridine)-b-poly(diethyl vinylphosphonate). Owing to their amphiphilic character, the polymers form spherical micelles in water, which were characterized by different spectroscopic and analytical methods at different pH values and temperatures. The most suitable core–shell micellar system could level the catalytic activity of the ruthenium complex toward hydrophobic and biomass-derived aldehydes, which could be successfully reduced to the corresponding alcohols in water using potassium formate as a hydride source. Depending on the substrate’s hydrophobicity and concentration, the catalytic activity varied significantly. In addition, the polymer’s properties hardly changed during catalysis, facilitating effective recycling until the third catalytic cycle.