Alkene Polymerization Catalysts Bearing Tridentate Phenoxyamine Ligands with sp 3  C Donors

• Published in: ChemCatChem 2009-08, Vol.1 (1), p.122-130
• Main Authors: Edson, Joseph B., Keresztes, Ivan, Lobkovsky, Emil B., Coates, Geoffrey W.
• Format: Article
• Language: English
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.200900122

The reaction of vinyl‐appended phenoxyamine 2 with tetrabenzyltitanium provided the phenoxyaminetitanium(II) alkene complex [ rac ‐ Lig 2 TiBn], arising from intramolecular vinyl‐group insertion followed by toluene elimination. Whereas [ rac ‐ Lig 2 TiBn] was inactive for olefin polymerization upon benzyl abstraction, treatment with ethylene led to the formation of stable titanacyclopentane complex [ rac ‐ Lig 2 (CH 2 ) 2 TiBn]. Alternatively, six‐membered metallacyclic complexes [ rac ‐ Lig 1 ZrBn 2 ‐a/b] and [ rac ‐ Lig 1 HfBn 2 ‐a/b] were obtained from reaction of vinyl‐appended phenoxyamine 1 with tetrabenzylzirconium or tetrabenzylhafnium in a further rare example of intramolecular vinyl‐group insertion into neutral tribenzyl group IV precursors. Living and isoselective polymerization of 1‐hexene was promoted by [ rac ‐ Lig 1 HfBn 2 ‐a/b]/B(C 6 F 5 ) 3 at 0 °C, whereas [ rac ‐ Lig 1 ZrBn 2 ‐a/b]/B(C 6 F 5 ) 3 catalyzed the living and isoselective polymerization of propylene ([ m 4 ]=0.76) at 0 °C. This catalyst system was employed for the synthesis of a diblock copolymer featuring an isotactic polypropylene semicrystalline block and poly(ethylene‐ co ‐propylene) amorphous block.