Abstract
Sequential NMR-scale reactions have been carried out in order to generate 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], [HNEt2Ph][B(C6F5)4], and [Ph3C][B(C6F5)4]. Reaction of 40 equiv. of MAO with 1 at room temperature was leaded to the formation of stable cationic methylzirconium complexes which polymerize propylene to isotactic polypropylene (iPP). For the activation of 1 with noncoordinating anions 1 was firstly methylated with 4 equiv. of AlMe3 to give rac-(SBI)ZrMe2 (2), and then 1 equiv. of noncoordinating anions was added to the resulting solution mixture containing 2 and various aluminum complexes dissolved in CD2Cl2 solvent. Complex 2 was immediately converted to cationic methylzirconium complex [rac-(SBI)Zr(μ-Me)2AlMe2]+(3), the adduct of the base-free rac-[(SBI)ZrMe]+ cation and AlMe3. Addition of small amount of liquid propylene to the NMR tube containing 3 and other byproducts was leaded to the formation of iPP showing meso pentad value of over 85 %.
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