Abstract: A novel Group IV elements-bridged metallocene complex is disclosed which is represented by the following formula (I): wherein R and R1 are different and are independently selected from the group consisting of &eegr;5-cyclopentadienyl group, substituted &eegr;5-cyclopentadienyl group, indenyl group, and fluorenyl group; R2 is selected from the group consisting of —N(CH3)2, —N(C2H5)2, halogen, alkoxy, —(C═O)NH2, and C6-12 hydrocarbyl group; M is a Group IVA element; and M1 is a Group IVB metal. When employing the metallocene complex to prepare olefin polymers, since it is bridged by a Group IV element, there are two catalytic sites in the single metallocene complex catalyst. Therefore, the olefin monomers can be polymerized to a bimodal olefin polymer by a single catalyst in a single reactor, resulting in lowered capital costs.

Abstract: A novel trivalent Group IVB metal complex for preparing syndiotactic vinyl aromatic polymers is disclosed which is coordinated by a bidentate ligand and is represented by the formula (I):(C.sub.5 R.sub.n H.sub.5-n)M(BD).sub.m Y.sub.p (I)wherein C.sub.5 R.sub.n H.sub.5-n is a substituted or unsubstituted cyclopentadienyl group, n is an integer between 0 and 5, and R is C.sub.1 to C.sub.12 alkyl, aryl, substituted alkyl, or substituted aryl; M is a trivalent Group IVB metal; (BID) is a bidentate ligand with -1 valence, having a coordinating group which is capable of forming a coordinating bond or a chelating bond with the metal M; Y is selected from the group consisting of alkyl, aryl, aralkyl, halogen and hydrogen; m is an integer of 1 or 2; and m+p=2.

Abstract: A novel trivalent Group IVB metal complex for preparing syndiotactic vinyl aromatic polymers is disclosed which is coordinated by a bidentate ligand and is represented by the formula (I):(C.sub.5 R.sub.n H.sub.5-n)M(BD).sub.m Y.sub.p (I)wherein C.sub.5 R.sub.n H.sub.5-n is a substituted or unsubstituted cyclopentadienyl group, n is an integer between 0 and 5, and R is C.sub.1 to C.sub.12 alkyl, aryl, substituted alkyl, or substituted aryl; M is a trivalent Group IVB metal; (BD) is a bidentate ligand with -1 valence, having a coordinating group which is capable of forming a coordinating bond or a chelating bond with the metal M; Y is selected from the group consisting of alkyl, aryl, aralkyl, halogen and hydrogen; m is an integer of 1 or 2; and m+p=2.