Ring-Expansion Metathesis Polymerization under Confinement
Patrick Probst, Moritz Lindemann, Johanna R. Bruckner, Boshra Atwi, Dongren Wang, Felix R. Fischer, Marc Högler, Matthias Bauer, Niels Hansen, Michael Dyballa, Michael R. Buchmeiser
Abstract
The cationic molybdenum alkylidyne N -heterocyclic carbene (NHC) complex [Mo(C- p -OMeC 6 H 4 )(OCMe(CF 3 ) 2 ) 2 (IMes)][B(Ar F 4 ] (IMes = 1,3-dimesitylimidazol-2-ylidene) was selectively immobilized inside the pores of ordered mesoporous silica (OMS) with pore diameters of 66, 56, and 28 Å and used in the ring-expansion metathesis polymerization (REMP) of cyclic olefins to yield cyclic polymers. A strong confinement effect was observed for cis -cyclooctene ( c COE), 1,5-cyclooctadiene (COD), (+)-2,3- endo,exo -dicarbomethoxynorborn-5-ene ((+)-DCMNBE), and 2-methyl-2-phenylcycloprop-1-ene (MPCP), allowing for the synthesis of low-molecular-weight cyclic polymers even at a high monomer concentration. The exclusive formation of cyclic polymers was demonstrated by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Confinement also influences stereoselectivity, resulting in a pronounced increase in Z-selectivity and in an increased cis -syndiospecificity.