We described an example of redox controlled olefin polymerization mediated by metal catalysts. Based on electro-chemical and NMR studies of a series of palladium complexes bearing ferrocene bridged phosphine-sulfonate ligands, the interconversion between the neutral and oxidized palladium complexes was shown to be facile and reversible. The activity of these palladium complexes could be controlled using redox reagents during ethylene homopolymerization, ethylene/methyl acrylate copolymerization, and norbornene oligomerization. Specifically in norbornene oligomerization, the neutral complexes were not active at all while the oxidized counterparts showed appreciable activity. In-situ switching between the neutral and oxidized forms resulted in an interesting "off" and "on" behavior in norbornene oligomerization. [1] Recently, we demonstrated that phosphine-sulfonate nickel complexes possessed extremely low activity in norbornene homopolymerization. The binding of B(C6F5)3 to sulfonate oxygen can efficiently reduce the electron density on the nickel center, and increase the NB polymerization activity by up to 4000 times.[2] A similar mechanism is probably operative in this system. The oxidized form of the ferrocene moiety reduces the electron density on the palladium center, which facilitated the NB binding and the subsequent NB insertion in this system.This work provides a new strategy to control the olefin polymerization process.[3]

Redox-controlled olefin (Co)polymerization catalyzed by ferrocene-bridged phosphine-sulfonate palladium complexes

253rd National Meeting (2017)

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