The first fluorenyl ansa-yttrocene complexes: Synthesis, structures, and polymerization of methyl methacrylate

Abstract

A novel C-s-symmetric yttrocene complex, ansa-Me2Si(eta(3)-Flu)(eta(5)-Cp')YCl2Li(OEt2)(2) (3; Flu = C13H8, fluorenyl; Cp' = C5Me4), has been prepared via a salt metathesis reaction from anhydrous YCl3 and the dilithium salt of the ligand ansa-Me2Si(FluH)(Cp'H). Treatment of 3 with NaN(SiMe3)(2) gave the corresponding bis(trimethylsilyl)amide derivative ansa-Me2Si(Flu)(eta(5)-Cp')YN(SiMe3)(2) (4). The X-ray structure of 3 reveals unusual eta(3)-fluorenyl coordination to the Y3+ ion. In 4, the Y-Flu bonding being partially slipped toward eta(3) from eta(5), pi-dative bonding nature in the Y-N bond and a direct interaction of the Y atom with one methyl group of the N(SiMe3)(2) fragment are present. Both compounds constitute the first examples of structurally characterized fluorenyl ansa-yttrocenes. The neutral compound 4 is active for the polymerization of methyl methacrylate (MMA) in toluene, affording iso-rich poly(MMA)s.