Ruthenium (Ru)-catalyzed carbon-carbon double bond metathesis is an important reaction both for small molecule synthesis and for synthesis of polymers by reactions like Ring Closing Metathesis (RCM) or Ring Opening Metathesis Polymerization (ROMP). However, in some cases where Ru catalyst loadings are 0.1 mol % or greater, Ru leaching may contaminate the products. Such contamination can be undesirable either esthetically or in terms of potential toxicity. Here is an introduction to different strategies based for removal of Ru residues using polyolefins are described. The first process uses polyolefins as phase tags and/or as solvents for removing N-heterocyclic carbene complexes in a thermomorphic manner. This efficiently separates Ru from polymer products leading to Ru residues that are &lt;1% of the starting Ru catalyst loading. The second process uses a polyolefin quenching agent to remove the Ru. In this case, a polyisobutylene (PIB)-bound isocyanide was prepared. This reagent colorimetrically phase separated all of a dark green Hoveyda-Grubbs complex from a polar phase into a nonpolar phase. The resulting gravity based liquid/liquid separation of a heptane and polar phase then separated the Ru residues from products.

Strategies for recovery of Ru catalyst residues in olefin metathesis reactions

249th National Meeting (2015)

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