Polymerization of 1,3‐pentadiene by cobalt catalysts. Influence of the alkyl aluminum compound on the structure of the polymer

The Polymerization of 2,4-Hexadiene. Stereoregular Polymer and the Mechanistic Study for Its Preparation

“…Ni(acac)2-AlEt2Cl, both with regard to the polymer yield and the preparation of crystalline polymer, was similar to Co(acac);!-AlEt2-Cl in the polymerization of butadiene.2 In the case of 2,4-hexadiene, however, even the polymer obtained from the trans.trans isomer by the former catalyst was amorphous, although both catalysts showed the similar polymerization rate and both polymers obtained were composed of 1,4trans structure (Table II). The polymerization with both catalysts is likely to proceed through the bidentate coordination of monomer since rate of polymerization is similar in both catalysts and the properties of Ni are similar to those of Co. [3][4][5][6][7][8][9][10][11] The difference observed may be due to the irregular structure of monomer unit caused by isomerization of the active end through hydride shift in Ni(acac)2-AlEt2Cl (.3 == 4 5 == 6, Figure 10), because the irregularity is produced by the random distribution of two kinds of trans-1,4 structures and -allyl Ni complex might be more effective than -allyl Co complex in isomerization. [41][42][43][44] Conclusion.…”