Gehinderte (RCp)M Rotation beit t-Alkyl Cp-substituierten (η4-s-cis-Butadien)zirconocen-Komplexen

A New Zirconocene Complex, [{η5-C5H4-C(CH2)5(CH2)2CH(CH3)2}2ZrCl2]

“…These values are normal and comparable with published data for many [(RCp)2ZrC12] complexes bearing, for example, bulky tert-alkyl substituents on the cyclopentadienyl rings (Howie, Mcquillan, Thompson & Lock, 1986;Erker et al, 1989). The substituted cyclopentadienyl ring systems are in a staggered orientation.…”

“…The C(CH2)5(CH2)2CH(CH3)2 side chains, which point away from each other, are positioned in a trans arrangement and directed towards the lateral sectors of the bent-metallocene unit. This conformational arrangement is similar to that found in many [(tert-alkylCp)2ZrC12] complexes (Erker et al, 1989;Howie, Mcquillan, Thompson & Lock, 1986). The substituent torsion angle, defined as 0s [C(1)---CEN---CENi--C(li), where CEN and CEN i are the centroids of the cyclopentadieyl ring and its symmetry-generated partner, respectively], is -178.8 (1) °, close to that found for the above mentioned [(tert-alkyl-Cp) metallocene, while the C(1)--C(7) vector points to the 'close' side of the bent-metallocene wedge.…”

“…The substituent torsion angle, defined as 0s [C(1)---CEN---CENi--C(li), where CEN and CEN i are the centroids of the cyclopentadieyl ring and its symmetry-generated partner, respectively], is -178.8 (1) °, close to that found for the above mentioned [(tert-alkyl-Cp) metallocene, while the C(1)--C(7) vector points to the 'close' side of the bent-metallocene wedge. This is in contrast to what was found in bis(l-methylcyciohexyl)-zirconocene dichloride (Erker et al, 1989). Attributed primarily to the interaction of the large substituent with the Ci atom, the cyclopentadienyl ring is asymmetrically bonded to Zr and tilted in such a way that the Zr--C(12) bond is the longest, resulting in a 'Zr-slippage" structure (Ogasa et al, 1991;Gelmini, Puddephatt & Vittal, 1993).…”

“…Studies on variations of the Group 4 metallocene structures (Erker et al, 1989) are a topic of great interest, primarily because of their unprecedented behaviour as catalyst precursors of homogeneous Ziegler-Natta polymerization systems (Sinn, Kaminsky, Vollmer & Woldt, 1980;. The addition of stereochemistry-controlling substituents to the cyclopentadienyl (Cp) tings of zirconocene catalyst precursors influences considerably their o~-olefin-polymerization activity (Kaminsky, 1986;Kaminsky, Engehausen, Zoumis, Spaleck & Rohrmann, 1992;Chien & Razavi, 1988;Tian & Huang, 1994), their molecular weight and their specific stereoseiectivity (Erker et al, 1991).…”

Reagent‐Controlled Stereoselectivity in Titanocene‐Catalyzed Epoxide Openings: Reductions and Intermolecular Additions to α,β‐Unsaturated Carbonyl Compounds

“…Collidine hydrochloride was dried prior to use by gentle heating under vacuum. The following compounds were purchased, prepared according to literature procedures, or have already been described in the literature: 1 ,28 2 ,28 3 ,29 7 ,14 8 ,16 9 ,16 10 ,17 13, 15 ,30 16 ,31 18 ,32 19, 21, 23, 25 ,33 26 ,34 28 ,35 31 ,35 33 ,36 36 36…”