Using Soluble Polymers to Enforce Catalyst‐Phase‐Selective Solubility and as Antileaching Agents to Facilitate Homogeneous Catalysis

Abstract

The enforced phase-selective solubility of polyisobutylene (PIB)-bound Rh(II) catalysts in biphasic heptane/acetonitrile mixtures can be used not only to recycle these catalysts but also to minimize bimolecular reactions with ethyl diazoacetate. When cyclopropanation and O-H insertion reactions are carried out with PIB-bound Rh(II) catalysts either with or without addition of an unfunctionalized hydrocarbon polymer cosolvent, dimer by-product formation is suppressed even without slow syringe pump addition of the ethyl diazoacetate. This suppression of by-product formation is shown to be due to increased phase segregation of the soluble polymer-bound catalyst and the ethyl diazoacetate reactant. These studies also reveal that added hydrocarbon polymer cosolvents can function as antileaching agents, decreasing the already small amount of a soluble polymer-bound species that leaches into a polar phase in a biphasic mixture during a liquid/liquid separation step.

Functionalized Polyisobutylene and Liquid/Liquid Separations as a Method for Scavenging Transition Metals from Homogeneously Catalyzed Reactions

“…Hence, its leaching in water is also negligibly low. Such quantitative phase separation was further demonstrated in our previous studies [25].…”

Sustainable Hydrocarbon Oligomer Solvent Systems for Sequestration of Trace Organics from Water

“…To address the issue of insufficient sequestration levels for polar organics, we explored modifying PAO with a PAO‐phase‐anchored cosolvent to generate a sequestering phase that contained molecular‐recognition elements. Our experience with PIB‐bound dyes, ligands, catalysts, and polar nanoparticles is that hydrocarbon oligomeric solvents are very effective at phase‐anchoring PIB‐bound polar species . Thus, we reasoned that a PIB with a hydrogen‐bonding terminal catechol group (Figure ) could be phase‐anchored in PAO and could be used to facilitate sequestration of polar groups in PAO because the ability of catechol to form H‐bonds.…”

“…Our experience with PIB-bound dyes, ligands, catalysts, and polar nanoparticles is that hydrocarbon oligomeric solvents are very effective at phase-anchoring PIB-bound polar species. [9,[16][17][18] Thus, we reasoned that aP IB with ah ydrogen-bonding terminal catecholg roup ( Figure 2) could be phase-anchored in PAOa nd couldb eu sed to facilitate sequestration of polar groups in PAOb ecause the ability of catechol to form H-bonds. This benzene( 900) [a] 7.0 99 hexane (800) [a,d] < 0.1 > 99 benzene( 24) [b] < 0.1 > 99 dichloromethane (1450) [b] 72 95 benzene( 550) [c] 3.4 99 benzene( 450) [d] 8.1 98 1,2-dichloroethane (650) [c] 40 94 1,4-dichlorobenzene (17) [c] < 0.1 > 99 dichloromethane (7000) [c] 350 > 99 THF (11100) [c] 7700 (2820) [e] 30 (76) [e] THF (2820) [c] 330 [e] 88 [e] triethylamine (15 000) [c] 4500 (600) [ [a] Sequestration was performedb ym ixing the D 2 Os olution (3.5 g) containingt he organic impurity with the PAO 432 (1.5 g) with av ortexm ixer for 1min.…”

Recyclable Polyisobutylene‐Bound HMPA as an Organocatalyst in Recyclable Poly(α‐olefin) Solvents

“…Our prior work has shown that vinyl-terminated PIB is broadly useful as a precursor for formation of recyclable ligands, catalysts, and reagents that can be easily separated from products. [8][9][10][11][12][13][14] Such separations are effective because terminally functionalized PIB oligomers have excellent phase selective solubility in nonpolar alkanes versus polar solvents like acetonitrile (MeCN), MeOH and water. They are also highly soluble in poly(α-olefin)s (PAOs) like PAO 432 , the fully saturated trimer formed from trimerization of 1-decene.…”