1,3-Pentadiene zirconocene complex

Zirconocene complexes (with s-cis geometry) of isoprene, 2,3-dimethylbutadiene, and 3-methyI-I,3-pentadiene are reported to give exclusively 1 1 addition with carbonyl substrates even if these are used in excess and the reaction temperature is fairly high (ca. 100 C). On the contrary, zirconocene complexes of 5-ci5-butadiene, 1,3-pentadiene, and 2,4-hexadiene ca, 1 1 mixture of the s-cis and s-trans isomers) easily accept (equation 53) 2 equiv. of either butanal or 3-pentanone, at low temperature ca. 30 C) in high yields (95%). This can be exploited for the stepwise insertion of two different electrophiles... 

Zirconocene complexes show much lower activity as the catalyst of 1,3-butadiene polymerization than the titanocene catalysts [15]. The catalyst composed of rac-[CH2(3-terf-butyl-l-indenyl)2]ZrCl2 and MAO promotes the 1,4-polymerization of 1,3-butadiene or (Z)-1,3-pentadiene and 1,2-polymerization of (E)-1,3-pentadiene and 4-methyl-1,3-pentadiene (Eq. 4) [16]. The bulky tert-butyl group of the ligand is essential for smooth polymeriza-... 

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