Stereospecific Ring-Opening Metathesis Polymerization of Cycloolefins Using Novel Molybdenum and Tungsten Complexes Having Biphenolate Ligands. Development of Crystalline Hydrogenated Poly(endo-dicyclopentadiene) and Poly(norbornene)

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 Et 3 Al. 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 MoOCl 4 −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, Δ H = 50 J/g; 175 °C, Δ H = 60 J/g, respectively), which can be regarded as a new class of crystalline polymers.