Stereospecific Ring-Opening Metathesis Polymerization of Cycloolefins Using Novel Molybdenum and Tungsten Complexes Having Biphenolate Ligands. Development of Crystalline Hydrogenated Poly(<i>e</i><i>ndo</i>-dicyclopentadiene) and Poly(norbornene)

Abstract

Novel molybdenum- and tungsten-based catalysts induced stereospecific ring-opening metathesis polymerization (ROMP) of cycloolefins to produce a new class of crystalline polymers. Various monomeric molybdenum(VI) and tungsten(VI) complexes of the general formula M(=O)(O−Ar)4 (M = Mo or W; (O−Ar)4 is two biphenolate or four phenolate ligands) were prepared. These catalysts exhibited moderate ROMP activity in the presence of cocatalyst such as n-BuLi and Et3Al. The molybdenum and tungsten complexes bearing substituted biphenolate ligands such as oxomolybdenum(VI) bis(racemic-5,5‘,6,6‘-tertamethyl-3,3‘-di-tert-butyl-1,1‘-biphenyl-2,2‘-diolate) promoted cis and isospecific ROMP of endo-dicyclopentadiene (cis > 90% and meso > 95%). The novel ternary and quarternary catalysts such as MoOCl4−biphenolate−n-BuLi (1:2:2) were developed as a new useful methodology to control the stereoselectivity of the ROMP. Hydrogenation of the cis-isotactic poly(endo-dicyclopentadiene)s and poly(norbornene)s provided novel crystalline polymers with high melting points (295 °C, ΔH = 50 J/g; 175 °C, ΔH = 60 J/g, respectively), which can be regarded as a new class of crystalline polymers.