333334-61-5Relevant academic research and scientific papers
Protonation of the heterocyclic cp-anion equivalent [pyrrolyl-B(C6F5)3]Li - Formation of a useful neutral bronsted acid for the generation of homogeneous metallocene ziegler catalysts
Kehr, Gerald,Roesmann, Rolf,Froehlich, Roland,Holst, Christiane,Erker, Gerhard
, p. 535 - 538 (2007/10/03)
N-pyrrolyllithium (1) adds to B(C6F5)3 to yield [(C4H4N)B(C6F5)3 ] Li (3). The corresponding monoetherate (3·OEt2) was characterized by X-ray diffraction and shows an η5 coordination of the pyrrolyl moiety to the lithium cation. Treatment of 3 with HC1 in ether leads to H+ addition at a pyrrolyl α-position to yield the neutral dipolar Bronsted acid system [(C4H5N)B(C6F5)3 ] (4). The reagent 4 can be used to protonate Cp2Zr(CH3)3 to yield [Cp2Zr(CH3)+(C4H4N)B- (C6F5)3-] (6) and methane. H+ transfer from 4 to (butadiene)-zirconocene results in the formation of the (π-allyl)metallocene salt [(C4H7)ZrCp2+(C4 H4 (C6F5)3-] (8). In analogous reactions, the neutral Bronsted acid was employed as a protonating activator component for the generation of homogeneous Ziegler catalysts derived from a variety of (butadiene)-or (dimethyl)ansa-metallocenes. The systems generated by treatment with 4 show comparable activities in ethene or propene polymerization reactions as conventionally generated Group 4 metallocene Ziegler catalysts.
