C-2-SYMMETRICAL ANSA METALLOCENES OF TITANIUM AND ZIRCONIUM WITH A LIGAND SYSTEM THAT YIELDS PURE RAC ISOMER - PREPARATION AND CRYSTAL-STRUCTURES OF ((ETA(5)-C5H2-2-SIME(3)-4-CME(3))(2)SIME(2))MCL(2) (M=TI OR ZR)

The preparation and structures of )-cyclopentadienyl)dimethylsilanedi chlorotitanium and cylcopentadienyl)dimethylsilanedichlorozirconium, ={(eta(5)-C5H2-2-SiMe(3)-4-CMe(3))(2)SiMe(2)};M=Ti or Zr) are describe d. The structures are analogous, although as expected, longer Zr atom distances result in less steric crowding. Repulsions of ring substitue nts on opposing rings can be seen by the differing angles about the al pha trimethylsilyl substituents. The MCl(2) and SiC2 planes of the  SiMe(2) bridge are twisted by 11 degree owing to intramolecular steri c repulsions.