0000000000383313
AUTHOR
Piet-jan Sinnema
The Kinetic Stability of Cationic Benzyl Titanium Complexes that Contain a Linked Amido-Cyclopentadienyl Ligand: The Influence of the Amido-Substituent on the Ethylene Polymerization Activity of “Constrained Geometry Catalysts”
Cationic benzyl titanium complexes [Ti(η 5 : η 1 -C 5 Me 4 SiMe 2 NR')-(CH 2 Ph)] + were cleanly formed by the reaction of the dibenzyl titanium complexes [Ti(η 5 : η 1 -C 5 Me 4 SiMe 2 NR')(CH 2 Ph) 2 with B(C 6 F 5 ) 3 and [Ph 3 C][B(C 6 F 5 ) 4 ] in bromobenzene. NMR spectroscopic studies suggest that the benzyl titanium cations contain a fluxional η 2 -coordinated benzyl ligand. Kinetic analysis showed that the benzyl titanium cations decompose according to first-order kinetics and that the amido substituents R' (R' = Me, i Pr, t Bu) in the linked amido-cyclopentadienyl ligand influence the lability of these benzyl titanium cations. The order of the kinetic stability of the benzyl titan…
Non-bridged amido cyclopentadienyl complexes of titanium: synthesis, characterization, and olefin polymerization catalysis
Alkylation of Ti(η 5 -C 5 Me 5 )(NMe 2 )Cl 2 gives thermally stable, crystalline dialkyl complexes Ti(η 5 -C 5 Me 5 )(NMe 2 )R 2 (R=Me, CH 2 Ph, Ph). The molecular structure of the dibenzyl complex reveals an unprecedented conformation of the doubly bonded NMe 2 group which is turned parallel to the η 5 -C 5 Me 5 ligand, according to single-crystal X-ray diffraction studies. Treatment of the dibenzyl complex with B(C 6 F 5 ) 3 in d 5 -bromobenzene solution results in the quantitative formation of a thermally (>10°C) unstable monobenzyl cation as solvent-separated ion pair [Ti(η 5 -C 5 Me 5 )(NMe 2 )CH 2 Ph] + [PhCH 2 B(C 6 F 5 ) 3 ] − which efficiently polymerizes styrene syndiospecifically…
Group 3 and 4 metal alkyl and hydrido complexes containing a linked amido-cyclopentadienyl ligand: “constrained geometry” polymerization catalysts for nonpolar and polar monomers
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 pol…