Binuclear ligand (�-CMe2-3,3')[1-(Me2SiNHtBu)cyclopentadienyl]2 (1  ) is synthesized and reacted with Ti(NMe2)4 to afford rac- and meso-(�-CMe2-3,3'){(?5-indenyl)[1-Me2Si(tBuN)][Ti(NMe2)2]}2 (2  ) in a 1:1 ratio. The two isomers, rac-2  and meso-2  are completely separated by recrystallization from pentane. Rac-2  and meso-2  react with AlMe3 in pentane and cleanly produce dimethyl analogues (�-CMe2-3,3'){(?5-indenyl)[1-Me2Si(tBuN)](TiMe2)2}2 (3  ), rac-3  and meso-3  , respectively. Rac-3  is completely decomposed in toluene at 100 �C over 1 hour, forming the new double methylene bridged (�-CMe2-3,3'){(?5-indenyl)[1-Me2Si(tBuN)][(�-CH2)Ti]}2 (rac-4  ), while meso-3  is thermal stable under identical conditions. Intriguingly, single methylene bridged rac-(�-CMe2-3,3'){(?5-indenyl)[1-Me2Si(tBuN)]}2{(�-CH2)[Ti���MeB(C6F5)3]}2 (rac-5  ) is obtained from rac-3  activated by B(C6F5)3 in toluene at room temperature. 1-5  are fully characterized by means of NMR spectroscopy and x-ray diffractions. In ethylene/1-octene copolymerization, rac-3  shows higher activity (3.4x) and 1-octene conversion (3.0x) using [Ph3C][B(C6F5)4] as cocatalyst with respect to meso-3  . Synthetic, analytical, spectroscopic, thermal stability, and olefin polymerization results will be discussed.

Significant proximity effects in constrained bimetallic titanium catalysts for ethylene (Co)polymerization

248th National Meeting (2014)

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