RING-OPENING OLEFIN METATHESIS POLYMERIZATION OF SPIRO(BICYCLO[2.2.1]HEPT-2-ENE-7,1'-CYCLOPROPANE)

Spiro(bicyclo[2.2.1]hept-2-ene-7,1'-cyclopropane) was polymerized by ring-opening olefin metathesis polymerization (ROMP) to produce poly[2,1'-spirocyclopropane-1,3-cyclopentylenevinylene]. The polymerization reactions were carried out with conventional metathesis catalysts based on W and Ru. The steric bulk of the three-membered ring was not sufficient to prevent the approach of the catalytically active transition metal carbene species to the exo face of the monomer. However, steric hindrance had an important influence on the microstructure of the polymers formed. The resulting polymers contained a high proportion of trans carbon-carbon double bonds and a slight excess of racemic dyads. Models based on steric repulsion are proposed to describe trans cis and racemic, meso selectivity. Hydrogenation of the double bonds resulted in the formation of partially crystalline poly[2,1'-spirocyclopropane-1,3-cyclopentyleneethylene].