Neutral Group 3 Metallocene Complexes as Catalysts of Polymerization

2 Neutral Group 3 Metallocene Complexes as Catalysts of Polymerization 

On the other hand, the reaction of CpfLnR with propylene did not afford any polymers but rather an allyl complex, Cp Ln(f/3-allyl), via a cr-bond metathesis reaction [56,117]. One molecule of propylene can insert itself into the Lu-Me bond of CpfLuMe to give the corresponding isobutylene complex. The successive insertion of propylene is 1000-fold slower than the first insertion [57]. The gas-phase reaction of Sc(CH3)2 with propylene also produces a 

Recent Trends in the Polymerization of a-Olefins Catalyzed by Organometallic Complexes 17 

A scandium complex, Cp ScH, also polymerizes ethylene, but does not polymerize propylene and isobutene [125]. On the other hand, a linked amidocyclo-pentadienyl complex [ Me2Si( / 5-C5 Me4)( /1 -NCMe3) Sc(H)(PMe3)] 2 slowly polymerizes propylene, 1-butene, and 1-pentene to yield atactic polymers with low molecular weight (Mn = 3000-7000) [126, 115]. A chiral, C2-symmetric ansa-metallocene complex of yttrium, [rac-Me2Si(C5H2SiMe3-2-Buf-4)2YH]2, polymerizes propylene, 1-butene, 1-pentene, and 1-hexene slowly over a period of several days at 25°C to afford isotactic polymers with modest molecular weight [114]. 

Marks et al. reported the co-polymerization of ethylene and 1-hexene by using ansa-type complexes of lanthanide metals [127]. Recently, bulky alkyl substituted ansa-type metallocene complexes of yttrium have been reported to exhibit high activity for the polymerization of 1-hexane. [114, 119, 128] 

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