Separation of the transition metals routinely used in homogeneous catalysts from the reaction mixtures is a long-standing problem. Recently our group have proposed functionalized polyisobutylene (PIB) oligomers as a highly hydrocarbon selectively soluble support for the homogeneous catalysts. They can be quite effective at separating catalysts from reaction mixtures by simple liquid-liquid separation with negligible metal leaching. In the best example to date, the Pd content in the product solution is reduced by nearly five orders of magnitude to 2 ppb. At the same time, in case of the catalyst decomposition, selectively soluble ligands can facilitate phase separation of catalyst residues from products. Based on this concept, these PIB-bound ligands can be used also as an advantageous agents for metals sequestration. This approach would be especially attractive if the sequestrants can be prepared with minimal synthetic effort. Here we report a relatively simple ethanedithiol-functionalized PIB as an excellent sequestrant for Cu and Pd metal catalysts. It can be prepared via single step photoinitiated thiol-ene “click” reaction starting from inexpensive vinyl-terminated PIB and 1,2-ethanedithiol. Heptane solution of this sequestrant was used for efficient (&gt;99%) extraction of Cu, Pd and some other transition metal cations (Co2+, Ni2+, Zn2+, Ru3+ and Pd2+) from model solutions as well as from crude products obtained in Pd and Cu catalyzed reactions.

Ethanedithiol-functionalized polyisobutylene for biphasic extraction of transition metal catalysts

256th National Meeting (2018)

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