499212-47-4Relevant academic research and scientific papers
The reaction of (butadiene)zirconocene with imines
Hoeltke, Carsten,Erker, Gerhard,Kehr, Gerald,Froehlich, Roland,Kataeva, Olga
, p. 2789 - 2799 (2007/10/03)
(Butadiene)zirconocene (s-trans-/s-cis-1 equilibrium mixture) reacts with the imine MeN=CHPh (7a) to form the 1:1 carbon-coupling product [κN-MeN-CHPh-CH2-η3- (CHCHCH2)]ZrCp2 (8a). The X-ray crystal structure analysis of 8a revealed a metallacyclic structure featuring a distorted π-allyl moiety and a planar-tricoordinate nitrogen atom. Only one of the two possible diastereoisomers is found in the crystal (cis-8a) as well as in solution. Treatment of 1 with the more bulky aldimine PhCH2N=CHPh (7b) selectively gave the corresponding 1:1 addition product trans-8b. Ketimines PhCH2N=C(CH2)4 (7c), HN=CPh2 (7d), or Δ1-2-methylpyrroline (7e) also reacted selectively with (butadiene)zirconocene to yield the analogous metallacyclic C-C coupling products 8c-e. Treatment of 8e with B(C6F5)3 proceeded cleanly by abstraction of a hydride anion from the carbon atom α to the nitrogen atom to form the intramolecularly coordinated imine product 10a {with the [HB(C6F5)3-] anion}. Similarly, Ph3C+ abstracts a hydride ion from 8e to yield 10b {isolated with the [B(C6H5)4-] anion}. Proton addition from HNR3+ reagents takes place selectively at the Zr-amido nitrogen atom of the complexes 8a or 8d to yield the substituted (π-allyl)zirconocene cation complexes 11 or 12, respectively. The cationic complexes 10, 11, and 12 polymerize ethene at room temperature/2 bar of ethene with moderate catalytic activities. ( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
