title: 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.
authors.affiliation: Department of Chemistry, Texas A & M University, P.O. Box 30012, College Station, TX (USA).
authors.forename: Yannan
authors.initials: Y
authors.lastname: Liang
authors.forename: Mary L
authors.initials: ML
authors.lastname: Harrell
authors.forename: David E
authors.initials: DE
authors.lastname: Bergbreiter
keywords: biphasic catalysis; green chemistry; homogeneous catalysis; solvents; supported catalysts