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Synthesis, Molecular Structure, and Racemate−Meso Interconversion for rac-(Me2Si)25-C5H-3-(CHMe2)-5-Me}2MCl2 (M = Ti and Zr)

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journal contribution
posted on 11.11.1998, 00:00 by Shigenobu Miyake, Lawrence M. Henling, John E. Bercaw
Doubly [SiMe2]-bridged group IV metallocenes, rac-(Me2Si)25-C5H-3-(CHMe2)-5-Me}2MCl2 (M = Ti, Zr), have been synthesized, and a crystal structure of rac-(Me2Si)25-C5H-3-(CHMe2)-5-Me}2TiCl2 has been determined by X-ray diffraction methods. Racemate−meso interchange occurs in benzene solution just above room temperature, affording an approximately 1:1 mixture of rac-(Me2Si)25-C5H-3-(CHMe2)-5-Me}2TiCl2 and meso-(Me2Si)25-C5H-3-(CHMe2)-5-Me}2TiCl2. Measurements of the kinetics of the approach to equilibrium reveal ΔH = 18(1) kcal·mol-1 and ΔS = −7(2) eu. The corresponding zirconium compound is configurationally stable.