Torsional isomerism of bent metallocene complexes. The structures of meso-and rac-bis(1-cyclohexyltetrahydroindenyl)zirconium dichloride in the solid state

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Abstract

Two molar equivalents of 1-cyclohexylindenyllithium were treated with ZrCl4(thf)2 to give a ca. 1:1 mixture of meso- and rac-bis(1-cyclohexylindenyl)ZrCl2 (meso-/rac-4). Catalytic hydrogenation yielded a corresponding mixture of the bis(1-cyclohexyl-4,5,6,7-tetrahydroindenyl)ZrCl2 diastereoisomers meso-5 and rac-5. In both cases the diastereomers were separated by fractional crystallization. Complexes meso- and rac-5 were characterized by an X-ray crystal structure study. In the crystal the molecular structure of complex rac-5 is C2-symmetric, with the annulated six-membered ring systems arranged towards the open front side of the bent metallocene wedge and the cyclohexyl substituents oriented anti-periplanarly in the lateral sectors. In contrast complex meso-5has only one of the cyclohexyltetrahydroindenyl ligands arranged in this way, the cyclohexyl substituent of the other one pointing towards a central front position and the annulated six-membered ring being situated in the lateral position (C1-symmetry).

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Cited by (44)

  • Zirconium bis-indenyl compounds. The influence of substituents on the ethene polymerization behavior of 1- and 2-substituted (R-Ind)<inf>2</inf>ZrCl<inf>2</inf>/MAO catalysts

    2002, Journal of Organometallic Chemistry
    Citation Excerpt :

    These steric effects can be understood by considering the ring conformations that the two indenyl ligands can adopt with respect to each other in the solid state. An analysis of X-ray crystal structures of indenyl zirconium complexes has revealed that the ring substituents influence the conformation adopted by the rings in the solid state [3,17–19,34,39], as shown in Fig. 6. The crystal structures of metallocene 10 [4,8,40] show that it exists in two conformations while metallocene 11 [34] exists in one conformation suggesting that there are fewer restrictions to the conformational change in 10.

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