| Popis: |
To extend the investigation of the applicability of 2,4-dimethylpentadienyl rare earth metal complexes as precatalysts for stereoselective butadiene polymerization, a selection of new neodymium, lanthanum, and yttrium complexes were previously supplied with detailed structural characterization. We report herein our observations on the catalytically nature of 2,4-dimethylpentadienyl rare earth metal complexes. Under standard conditions the complexes are catalytically inactive. In order to successfully activate the coordinatively saturated complexes, aluminium trialkyls AlMe3, AlEt3, and Al(iBu)3, aluminoxanes methylaluminoxane (MAO), hexaisobuthylaluminoxane (HiBAO), and modified methylaluminoxane with an Al(iBu)3 additive (MMAO) and diethylaluminium bromide were employed as cocatalysts. The actual catalyst is believed to be a soluble mono(2,4-dimethylpentadienyl)neodymium(III) dianion complex, through which an insertion of 1,3-butadiene in the pentadienyl-neodymium(III) bond causes the catalysis of the chain growth to be initiated. From these investigations a substantial further insight into the chemistry of (2,4-dimethylpentadienyl)lanthanide(III) complexes was gained and the special applicability of the neodymium complexes for the preparation of highly active catalyst for the 1,4-cis-polymerization of 1,3-butadienes was demonstrated. |
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