Reductive Coupling of an Indenylidene with Calcium to Form Bis(indenyl) Ansa-Metallocenes: Molecular Structures of Trans-Ph2c2h2-rac-(η5-4,7-me2c9h4)2ca(thf)2 and Trans-Ph2c2h2-rac-(η5-4,7-me2c9h4)2fe

1-E-benzylidene-4,7-dimethylindene (1) is reductively coupled by activated calcium to form two isomers, trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Ca(THF)2 (trans-rac-2) and cis-Ph2C2H2-meso-(η5-4,7-Me2−C9H4)2Ca(THF)2 (cis-meso-2) in an approximately 1:1 ratio. Reaction of the calcium species with FeCl2 produces a mixture of the corresponding trans-rac and cis-meso ferrocenophane species (3) along with another ferrocenophane isomer that is presumed to be either the trans-meso or cis-rac isomer. Thus, the relative geometry of the indenyl rings is not retained entirely during the transfer of the ligand framework from calcium to iron. A complete scrambling of the indenyl ring geometry appears to occur upon transfer of the ligand framework from calcium to zirconium. The results of X-ray crystal structure determinations of 1-E-benzylidene-4,7-dimethylindene, trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Ca(THF)2, and trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Fe are described.