Katayama and coworkers used TpRuCl(＝C＝CHPh)(PPh~3)[Tp=hydridotris (pyrazolyl)borate] as a catalyst precursor for ring-opening metathesis polymerization (ROMP) of norbornene (NBE). As Cp'RuCl·(PPh~3)[Cp'= (un)substituted cyclopentadienyl] compounds also can reacted with HC≡ CPh to form vinylideneruthenium complexes which might be active for the ROMP of NEB, we examined the activity of CpRuCl(PPh~3)~2 and HC≡ CPh system for the polymerization of NBE. But the activity of this system was poor. Lately, O~2 was used as cocatalyst instead of HC≡ CPh and found to form in situ an efficient catalyst system for the ROMP of NBE. The catalytic activity of another Ru complex [ (CH~3OCH~2CH~2Cp)RuCl(PPh~3)~2] was also examined in this article. The influence of different monomer/catalyst, O~2/catalyst and polymerization temperature is stuided. The polymerization conversion is a function of O~2/catalyst ratio, when the ratio is between 1 to 3, the polymerization conversion is high, when the ratio is higher or lower, the polymerization conversion is decreased. The ratio of monomer/catalyst has a little effect on the conversion, and the conversion can slightly be improved by elongating the polymerization time to 72 hour. the higher polymerization temperature is beneficial to the polymerization conversion. This implies that the catalytic centers are stable at higher temperature. The trans-content of the PNBE is dependent on O~2/catalyst molar ratio, polymerization temperature and the nature of the catalyst. Three typical polymer samples were characterized by ^1H NMR (CDCl~3). There were two signals at δ=9～10 in the ^1H NMR spectrum, these peaks may be the absorption of protons on aldehyde group formed in the polymerization process. According to our experiment and the work of Ivin and coworkers, we suggest a possible mechanism of polymerization of NBE catalyzed by Cp'RuCl(PPh~3)~2. First the ruthenium complex and oxygen react to form a ruthenium oxygen complex, then the complex reacts with NBE to钌催化降冰片烯开环移位聚合的研究

Key words: RUTHENIUM COMPOUNDS, NORBORNENE, RING CLEAVAGE REACTION