《Table 2 Effect of PPh3addition on butadiene polymerizationa)》

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《"A thermally robust cobalt complex bearing quinoline-oxazoline ligand for synthesis of cis-1,4-and 1,2-polybutadienes"》

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Polymerization in toluene at 20℃，other notes are the same as in Table 1.

Although the single crystal could not been obtained，the analysis data by MALDI-TOF，[L3c2Co]+[L3c2Co]+[CoCl4]2-（relative ratio）:（m/z）（[L3c2Co]+638.1） ，suggested that the complex was an ion-paired complex，similar to our previously reported bis（oxazoline）pyridine ligated cobalt complexes[3].Activated by methylaluminoxane（MAO），the complex catalized polymerization of butadiene at0℃and afforded polymers with high cis-1，4-unit mole fraction of97.2%in a high yield of 81.0%（Table 1）.It should be noted that the present catalyst exhibited high thermal stability；i.e.the polymer yield remained as high as 83.6%even at a high temperature of80℃.This result was in stark contrast to that of the previously reported late transition metal catalysts whose activities significantly decreased with increasing the temperature to 50℃and above[1]，probably due to that the ionic structure and the bulky ligand effectively stabilized the generated active species.On the other hand，the increase of temperature resulted in the decreases of cis-1，4-unit content and molecular weight，and broadening of molecular weight distribution，due to the accelerated favored anti-to syn-isomerization and chain transfer reaction at elevated temperatures，respectively. （1）