IN-SITU ACTIVATION OF RAC-(SBI)ZR(NME2)(2) FOR THE POLYMERIZATION OF PROPYLENE

Sequential NMR-scale reactions have been carried out in order to gener ate cationic methylzirconium complexes by the reaction of rac-(SBI)Zr( NMe2)(2) (1, SBI = Me2Si(indenyl)(2)) with methylaluminoxane (MAO) or various noncoordinating anions such as [HNMePh2] [B(C6F5)(4)], [HNEt2P h][B(C6F5)(4)], and [Ph3C][B(C6F5)(4)]. Reaction of 40 equiv. of MAO w ith 1 at room temperature was leaded to the formation of stable cation ic methylzirconium complexes which polymerize propylene to isotactic p olypropylene (IPP). For the activation of 1 with noncoordinating anion s 1 was firstly methylated with 4 equiv. of AlMe3 to give rac-(SBI)ZrM e2 (2), and then 1 equiv. of noncoordinating anions was added to the r esulting solution mixture containing 2 and various aluminum complexes dissolved in CD2Cl2 solvent. Complex 2 was immediately converted to ca tionic methylzirconium complex [rac-(SBI)Zr(mu-Me)(2)AlMe2](+) (3), th e adduct of the base-free rac-[(SBI)ZrMe](+) cation and AlMe3. Additio n of small amount of liquid propylene to the NMR tube containing 3 and other byproducts was leaded to the formation of iPP showing meso pent ad value of over 85%.