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8403459 
Journal Article 
Termination Events in Sterically Hindered Metallocene-Catalyzed Olefin Oligomerizations: Vinyl Chain Ends in Oligooctenes 
Brant, P; Jiang, P; Lovell, J; Crowther, D 
2016 
1 
Organometallics
ISSN: 0276-7333
EISSN: 1520-6041 
American Chemical Society 
35 
17 
2836-2839 
English 
Sterically hindered rac-dimethylsilylbis(2-methyl-3-propylindenyl)hafnium dimethyl (1) activated with dimethylanilinium tetrakis(perfluoronaphthylborate) (2) gave high levels of allylic chain ends in the oligomerization of higher α-olefins such as 1-octene. Solution oligomerization of 1-octene in hexanes yielded atactic macromers with roughly 60 mol % vinyl termination and lesser amounts of trisubstituted (25%) and vinylidene (20%) termination. To further probe the mechanism of elimination, oligomerization with 1-octene (1-13C) was performed and the label distribution determined by 13C NMR spectroscopy. Enhancement of the methylene (H2C=C-) vinyl resonance was observed, supporting β-hexyl elimination as a possible mechanistic step and ruling out allylic formation by a chain-walking mechanism prevalent in late-transition-metal systems. © 2016 American Chemical Society.