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Rearrangements and Stereomutations of Metallacycles Derived from Allenes and Imidozirconium Complexes

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posted on 16.02.2005, 00:00 by Forrest E. Michael, Andrew P. Duncan, Zachary K. Sweeney, Robert G. Bergman
The mechanisms of the rearrangements and stereoinversion of azametallacyclobutenes generated via [2+2] cycloaddition of allenes and imidozirconium complexes have been studied. Metallacycles derived from allenes bearing β-hydrogen atoms racemize at room temperature by reversible β-hydride elimination, a process which is also responsible for their eventual conversion to monoazadiene complexes. Metallacycles derived from diarylallenes racemize by reversible thermal bond homolysis at 95 °C; racemization of these metallacycles is also catalyzed by mild oxidants.