Reductive coupling of an indenylidene with calcium to form bis(indenyl) ansa-metallocenes: Molecular structures of trans-Ph2C2H2-rac-(eta(5)-4,7-Me2C9H4)(2)Ca(THF)(2) and trans-Ph2C2H2-rac-(eta(5)-4,7-Me2C9H4)(2)Fe

1-E-benzylidene-4,7-dimethylindene (1) is reductively coupled by activated calcium to form two isomers, trans-Ph2C2H2-rac-(eta(5)-4,7-Me-2-C9H4)(2)Ca( THF)(2) (trans-rac-2) and cis-Ph2C2H2-meso-(eta(5)-4,7-Me-2-C9H4)(2)Ca(THF) (2) (cis-mesad) in an approximately 1:1 ratio. Reaction of the calcium spec ies with FeCl2 produces a mixture of the corresponding trans-rac and cis-me so ferrocenophane species (3) along with another ferrocenophane isomer that is presumed to be either the trans meso or cis-rac isomer. Thus, the relat ive geometry of the indenyl rings is not retained entirely during the trans fer of the ligand framework from calcium to iron. A complete scrambling of the indenyl ring geometry appears to occur upon transfer of the ligand fram ework from calcium to zirconium. The results of X-ray crystal structure det erminations of 1-E-benzylidene-4,7-dimethylindene, trans-Ph2C2H2-rac-(eta(5 )-4,7-Me2C9H4)(2)Ca(THF)(2), and trans-Ph2C2H2-rac-(eta 5-4,7-Me-2-C9H4)(2) Fe are described.