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 -Ph 2 C 2 H 2 - rac -(η 5 -4,7-Me 2 −C 9 H 4 ) 2 Ca(THF) 2 ( trans-rac - 2 ) and cis- Ph 2 C 2 H 2 - meso -(η 5 -4,7-Me 2 −C 9 H 4 ) 2 Ca(THF) 2 ( cis-meso - 2 ) in an approximately 1:1 ratio. Reaction of the calcium species with FeCl 2 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 -Ph 2 C 2 H 2 - rac -(η 5 -4,7-Me 2 −C 9 H 4 ) 2 Ca(THF) 2, and trans -Ph 2 C 2 H 2 - rac -(η 5 -4,7-Me 2 −C 9 H 4 ) 2 Fe are described.