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RESEARCH PRODUCT

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”

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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 titanium cations was found for both anions to follow the order R' = Me > i Pr > t Bu. The benzyl titanium cations generated with [Ph 3 C][B(C 6 F 5 ) 4 ] were found to undergo faster decomposition than those generated with B(C 6 F 5 ) 3 . The ethylene polymerization activity order for both systems was found to be the reverse: R' = t Bu > i Pr > Me. The decomposition of the benzyl titanium cations was suggested to occur via C-H activation with concomitant toluene elimination.