New C2-symmetric silylene-bridged metallocene compounds, [Me2Si(η5-RnC5H4−n)(η5-R′nC5H4−n)]MCl2 (M = Zr, Hf; Rn, R′n = Me, t-Bu, 2,4-Me, 2,3,5-Me3), were synthesized together with C1-symmetric ones (M = Zr, Hf; Rn = 2,3,5-Me3, 2,4-Me2, 3,4-Me2, t-Bu, Me; R′n = Me, H) for comparison and employed as the catalysts for isotactic polymerization of propylene in combination with methylaluminoxane. The C2-symmetric metallocenes bearing methyl groups at 2- or 5-positions gave polymers of the highest melting point (160–163 °C) and stereospecificity ([mmmm]: 97–99%).

In the oligomerization of propylene by (C5Me5)2MCl2 (M = Zr,Hf)/methylalumoxane, formation of abnormal oligomers such as 1-pentene(C5), 2,4-dimethyl-1-pentene(C7), 4-methyl-1-heptene(C8), and 2,4,6-trimethyl-1-heptene(C10) besides normal oligomers such as 4-methyl-1-pentene(C6) and 4,6-dimethyl-1-heptene(C9) is indicative of the mixing of unusual β-CH3 and usual β-H transfer terminations from each growing carbon chain which was initiated by insertion of propylene into either M–H or M–Me bond.

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