Olefin metathesis is a powerful tool in C-C double bond formation having numerous applications in polymer chemistry and material science. Ring-opening metathesis polymerization (ROMP) and ring-closing metathesis (RCM), in particular are versatile methods for the synthesis of functional materials. Ruthenium-based Grubbs and Hoveyda-Grubbs catalysts are certainly the most popular complexes in the field of olefin metathesis. Unfortunately, only a limited number of studies have been conducted where both recycling and ruthenium waste content are examined. Moreover, numerous papers do not report on the levels of contamination in the product, which clearly is a drawback when developing olefin metathesis for industrial procedures. The separation of the polymeric product and the catalyst is one of the major challenges facing metathesis polymerization. This process currently requires extra steps or additional chemical processes. Alternative processes that avoid a second process step, thus remain of interest. Our approach uses a scheme in which the solubility of the Ru catalyst byproducts is differentiated from the solubility of the product polymer. This strategy employs soluble polyisobutylene (PIB)-supported NHC-ligated Ru catalysts and a liquid/liquid biphasic separation of catalyst residues from the polymer products after a reaction. We will discuss the activity of PIB-supported 2ndgeneration Hoveyda-Grubbs complex in a series of ring opening metathesis polymerizations yielding high-molecular weight polymers with narrow polydispersities. The PIB-supported Ru complex is phase selectively soluble in the heptane phase of thermomorphic mixtures of heptane and polar solvents. The separability of these catalysts leads to lower Ru contamination (167 ppm levels) in the polymer products (white figure 1) in comparison to the non-supported Hoveyda-Grubbs catalyst (4764 ppm, black figure1). 

Lower ruthenium leaching using PIB-supported metathesis catalyst

245th National Meeting (2013)

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