The First Fluorenyl ansa-Yttrocene Complexes:  Synthesis, Structures, and Polymerization of Methyl Methacrylate

Abstract

A novel C s -symmetric yttrocene complex, ansa-Me 2 Si(η 3 -Flu)(η 5 -Cp′)YCl 2 Li(OEt 2 ) 2 (3; Flu ) C 13 H 8 , fluorenyl; Cp′ ) C 5 Me 4 ), has been prepared via a salt metathesis reaction from anhydrous YCl 3 and the dilithium salt of the ligand ansa-Me 2 Si(FluH)(Cp′H). Treatment of 3 with NaN(SiMe 3 ) 2 gave the corresponding bis(trimethylsilyl)amide derivative ansa-Me 2 -Si(Flu)(η 5 -Cp′)YN(SiMe 3 ) 2 (4). The X-ray structure of 3 reveals unusual η 3 -fluorenyl coordination to the Y 3+ ion. In 4, the Y-Flu bonding being partially slipped toward η 3 from η 5 , π-dative bonding nature in the Y-N bond and a direct interaction of the Y atom with one methyl group of the N(SiMe 3 ) 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 isorich poly(MMA)s.

Synthesis, structural characterization, and reactivity of organolanthanides derived from a new chiral ligand (S)-2-(pyrrol-2-ylmethyleneamino)-2′-hydroxy-1,1′-binaphthyl

“…Molecular weights and polydispersities of the polymers produced ranged from 27.0 to 47.8 kg mol À1 and 1.82 to 2.32, respectively. Our results show that the catalytic activities of 5 AE 2 C 6 H 6 and 6 AE 2C 6 H 6 resemble that of [Me 2 Si-(C 13 H 8 )(C 5 Me 4 )]YN(SiMe 3 ) 2 [18], while the microstructure of the resulting poly(MMA)s are similar to those initiated by [ i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]NdN(SiHMe 2 ) 2 (THF) [19] and [Me 2 Si(C 5 Me 4 )(C 5 H 3 R * )]LnE(SiMe 3 ) 2 (E = CH, N; R * = (À)-menthyl) [17]. Under similar reaction conditions, no detectable polymerization activity is observed for complexes 3 and 4, even at room temperature for one week.…”

Stereospecific polymerization of propylene with group 4 ansa-fluorenylamidodimethyl complexes

“…The thermal ellipsoids are drawn at the 30% probability level. ligand (a), g 3 bonded (b), e.g., in (g 5 :g 3 -CpSiMe 2 Flu)-YCl 2 Li(OEt 2 ) 2 [25] and (g 5 :g 3 -Flu) 2 Sm(THF) 2 [26], and symmetrically g 1 bonded (c) as in Me 2 Si(g 1 -Flu 0 )(g 1 -N-tBu)ZrCl 2 OEt 2 (Flu 0 = C 29 H 36 ) [27].…”

Rapid Determination of the Chemical Composition of Ethylene/Butadiene Copolymers Using FTIR Spectroscopy and Chemometrics

“…The preparation of complexes 1 and 2 was reported previously . Complex 3 was obtained as a green powder by reaction of Me 2 Si(C 13 H 8 )(C 5 Me 4 )Li 2 Et 2 O with Nd(BH 4 ) 3 (THF) 3 in tetrahydrofuran (THF).…”