Polymerizations of higher alpha-olefins, 1-pentene, 1-hexene, 1-octene, and 1-decene were carried out at 30 degrees C in toluene by using highly isospecific rac-Me2Si(1-C5H2-2-CH3-4-Bu-t)(2)Zr(NMe2)(2) (rac-1) compound in the presence of Al(iBu)(3)/[CPh3] [B(C6F5)(4)] as a cocatalyst formulation. Both the bulkiness of monomer and the lateral size of polymer influenced the activity of polymerization. The larger lateral of polymer chain opens the pi-ligand of active site wide and favors the insertion of monomer, while the large size of monomer inserts itself into polymer chain more difficultly due to the steric hindrance. Highly isotactic poly(alpha-olefin)s of high molecular weight (MW) were produced. The MW decreased from polypropylene to poly(1-hexene), and then increased from poly(1-hexene) to poly(1-decene). The isotacticity (as [mm] triad) of the polymer decreased with the increased lateral size in the order: poly(1-pentene) > poly(1-hexene) > poly(1-octene) > poly(1-decene). The similar dependence of the lateral size on the melting point of polymer was recorded by differential scanning calorimetry (DSC). H-1 NMR analysis showed that vinylidene group resulting from beta-H elimination and saturated methyl groups resulting from chain transfer to cocatalyst are the main end groups of polymer chain. The vinylidene and internal double bonds are also identified by Raman spectroscopy.