Zirconium bis-indenyl compounds. Synthesis and X-ray crystallography study of 1- and 2-substituted bis(R-indenyl)zirconium dichloride metallocenes

A series of 1- and 2-substituted indenyl ligands were prepared and used in the synthesis of [1-R-Ind]2ZrCl2 [R=Me (2b), Et (4b), iPr (5b), tBu (6b), SiMe3 (8b), Ph (10b), Bz (12b), 1-Naph (14b)] and [2-R-Ind]2ZrCl2 [R=Me (1b), Et (3b), SiMe3 (7b), Ph (9b), Bz (11b), 1-Naph (13b)] metallocenes. An X-ray crystallographic study of 4b and 10b showed the complexes to be the racemic diastereomers (4b, both the R,R and S,S-enantiomers and 10b, the S,S-enantiomer). The X-ray data together with NMR spectral data revealed that the size of the substituent influenced the orientation the two indenyl ligands of the metallocenes. The 4b diastereomers are both found to crystallize with their ethyl groups syn (bis-central) with respect to each other whereas the larger phenyl groups in 10b results in an anti (bis-lateral) orientation of the indenyl ligands.