6533b871fe1ef96bd12d17ed

RESEARCH PRODUCT

Group 3 and 4 metal alkyl and hydrido complexes containing a linked amido-cyclopentadienyl ligand: “constrained geometry” polymerization catalysts for nonpolar and polar monomers

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Abstract In order to understand the nature of the putative cationic 12-electron species [M(η 5 :η 1 -C 5 R 4 SiMe 2 NR′)R″] + of titanium catalysts supported by a linked amido-cyclopentadienyl ligand, several derivatives with different cyclopentadienyl C 5 R 4 and amido substituents R′ were studied systematically. The use of tridentate variants (C 5 R 4 SiMe 2 NCH 2 CH 2 X) 2− (C 5 R 4 =C 5 Me 4 , C 5 H 4 , C 5 H 3 t Bu ; X=OMe, SMe, NMe 2 ) allowed the NMR spectroscopic observation of the titanium benzyl cations [Ti(η 5 :η 1 -C 5 Me 4 SiMe 2 NCH 2 CH 2 X)(CH 2 Ph)] + . Isoelectronic neutral rare earth metal complexes [Ln(η 5 :η 1 -C 5 R 4 SiMe 2 NR′)R″] can be expected to be active for polymerization. To arrive at neutral 12-electron hydride and alkyl species of the rare earth metals, we employed a lanthanide tris(alkyl) complex [Ln(CH 2 SiMe 3 ) 3 (THF) 2 ] (Ln=Y, Lu, Yb, Er, Tb), which allows the facile synthesis of the linked amido-cyclopentadienyl complex [Ln(η 5 :η 1 -C 5 Me 4 SiMe 2 NCMe 3 )(CH 2 SiMe 3 )(THF)]. Hydrogenolysis of the linked amido-cyclopentadienyl alkyl complex leads to the dimeric hydrido complex [Ln(η 5 :η 1 -C 5 Me 4 SiMe 2 NCMe 3 )(THF)(μ-H)] 2 . These complexes are single-site, single-component catalysts for the polymerization of ethylene and a variety of polar monomers such as acrylates and acrylonitrile. Nonpolar monomers such as α-olefins and styrene, in contrast, give isolable mono-insertion products which allow detailed studies of the initiation process.