Synthesis, Structure, and Polymerization Behavior of Bridged Zirconocenes Bearing Seven-Membered Rings

Abstract

Bridged zirconocenes bearing seven-membered rings dichlorodimethylsilylenebis(2-methyl-4-phenyl-4-H-azulenyl)zirconium (3a) and dichlorodimethylsilylenebis(2-methyl-4-phenyl-4-H-5,6,7,8-tetrahydroazulenyl)zirconium (4) were synthesized. A silylene-bridged ligand was obtained by the reaction of 2-methylazulene, phenyllithium, and dichlorodimethylsilane. After lithiation of the ligand by n-butyllithium, reaction with zirconium tetrachloride gave a rac and meso mixture of 3. The structure was confirmed by X-ray crystallographic analysis. It was found that both of the phenyl groups at the 4-position are oriented outside toward the metal center and the seven-membered ring is not planar. Furthermore, reaction with hydrogen in the presence of platinum oxide gave 4. When activated with methylaluminoxane, these complexes showed high catalytic activity for polymerization of propene to give isotactic polypropylene.

A new series of zirconium metallocenes derived from partially alkylated s-indacene with potential applications in the polymerization of ethylene

“…Also, this property results as a promising feature in homogenous catalysis, particularly in the polymerization of ethylene, as these catalytic systems have mostly been carried out successfully by bridged ansa-metallocenes [44,45].…”

Synthesis, Structure, and Polymerization Behavior of Novel Azulenyl Metallocenes Producing Propylene-Ethylene Pseudo-Copolymer

“…As previously reported, we have synthesized the bis-azulenyl zirconocenes bearing methyl groups at the 2-position and phenyl groups at the 4-position of the azulenyl rings: Me 2 Si(2-Me-4-Ph-4H-Azu) 2 ZrCl 2 . 6 We made a comparison between the bisazulenyl zirconocene and the bis-indenyl zirconocene, especially the difference of ring size in each system, i.e., six-membered and seven-membered, and the polymerization behavior was compared with that of the bisindenyl analogue, Me 2 Si(2-Me-4-Ph-Ind) 2 ZrCl 2 (5). The biggest difference between the two metallocenes is the carbon atom at the 4-position.…”

Synthesis, crystal structure and ethylene polymerization activity of zirconium complexes bearing mono-Cp and tridentate Schiff base [ONO] ligands

“…The quest for alteratives to the metallocene catalysts that can produce polymers with novel properties is one of the major goals of transition metal coordination chemistry over the last decade [1,2]. There are many reports concerning this topic especially using metallocene and non-Cp (cyclopentadienyl) catalysts [3][4][5]. Among them, mixed ligands titanium complexes of the type Cp 0 Ti(L)X 2 containing cyclopentadienyl ligand and non-Cp ligand have attracted considerable attention, because this type of catalyst has been expected to exhibit unique characteristics as olefin polymerization catalyst that would combine the merits of metallocene and non-Cp catalyst type [6][7][8][9][10][11][12].…”