Single-site organometallic catalysts for olefin polymerization

Abstract

Abstract

A novel ${\it C_s}$-symmetric yttrocene complex, {\it ansa}-Me$_2$Si($\eta^3$-Flu)( $\eta^5$-Cp’)YCl$_2$Li(OEt$_2$)$_2$ ({\bf 3}) (Flu = C$_13$H$_8$, fluorenyl; Cp’ = C$_5$Me$_4$) has been prepared via salt metathesis reaction from anhydrous YCl$_3$ and dilithium salt of the ligand {\it ansa}-Me$_2$Si(FluH)(Cp`H). Treatment of {\bf 3} with NaN(SiMe$_3$)$_2$ gave the corresponding bis(trimethylsilyl)amide derivative, {\it ansa}-Me$_2$Si(Flu)($\eta^5$-Cp’)YN(SiMe$_3$)$_2$ ({\bf 4}). The X-ray structure of {\bf 3} reveals unusual $\eta^3$-fluorenyl coordination to the Y$^{3+}$ ion. In {\bf 4}, the Y-Flu bonding being partially slipped toward $\eta^3$ from $\eta^5$, $\pi$-dative bonding nature in Y-N bond and a direct interaction of the Y atom with one methyl group of N(SiMe$_3$)$_2$ fragment are present. Both compounds constitute the first examples of structurally characterized fluorenyl {\it ansa}-yttrocenes. The neutral compound {\bf 4} is active for the polymerization of methyl methacrylate (MMA) in toluene, affording iso-rich poly(MMA)s. A series of novel ${\it C_1}$-symmetric group 4 {\it ansa}-metallocene complexes, Me$_2$Si(C$_5$Me$_4$)(R-Ind)MCl$_2$ (R = H, M = Ti ({\bf 5a}), Zr ({\bf 5b}); R = 2-Me, M = Ti ({\bf 6a}), Zr ({\bf 6b}); R = 3-Me, M = Ti ({\bf 7a}), Zr ({\bf 7b}); R = 3-{\it t}-Bu, M = Ti ({\bf 8a}), Zr ({\bf 8b})) were prepared from the reaction of dilithium salt of the corresponding ligands Me$_2$Si(C$_5$Me$_4$H)(R-IndH) (R = H ({\bf 5}), 2-Me ({\bf 6}), 3-Me ({\bf 7}), and 3-{\it t}-Bu ({\bf 8})) with appropriate group 4 metal halides. Crystal structures of {\bf 5a, 6a, 6b}, and {\bf 8b} have been determined by X-ray diffraction study, which showed chiral, ${\it C_1}$-symmetric nature of them irrespective of kinds of the metal and the ligand. The complexes {\bf 5a, 5b, 6a}, and {\bf 6b} were also tested for the polymerization of propylene in the presence of methylaluminoxane(MAO) under various reaction temperatures. All ...