Ferrocene-Based Olefin Polymerization Catalysts:  Activation, Structure, and Intermediates

This paper describes abstraction of a benzyl group from the Zr dibenzyl complex 1,1‘-Fc(NSiMe 3 ) 2 ]ZrBn 2 ( 1 ) using B(C 6 F 5 ) 3 and [Ph 3 C][B(C 6 F 5 ) 4 ] ( TB ). In both cases, clean formation of the corresponding cationic monobenzyl species LZrBn + (L = 1,1‘-Fc(NSiMe 3 ) 2 2 - ) was observed by NMR spectroscopy. In the case of [LZrBn][BnB(C 6 F 5 ) 3 ] ( 2 ), an X-ray crystal structure determination confirmed an η 6 coordination of the borate benzyl group to the cationic Zr center. Reaction of this complex with 1 equiv of C 2 H 2 or RCCR (R = Me, Ph) proceeded with rapid single insertion of the olefin or acetylene into the Zr−carbon σ-bond. With ethylene or 2-butyne further insertions occur more slowly and longer chains were obtained upon addition of more monomer. Activation of 1 with TB leads to an active ethylene polymerization catalyst, producing 102 g of PE mmol - 1 atm - 1 h - 1 . Compound 2 reacted with CH 2 Cl 2 to form the dimeric [LZrCl 2 ] 2, which was characterized crystallographically.