The molecular structures of [(t)BucpFe(CO)(2)](2) (1) and [(t)Bu(2)cpF
e(CO)(2)](2) (2) have been determined by single-crystal X-ray diffract
ion studies. In the solid state, 1 exists solely as the trans-carbonyl
bridged isomer, whereas 2, containing the bulkier (t)Bu(2)cp ligand,
is unexpectedly found to adopt the cis configuration. The Fe-Fe bonds
are approximately equal (2.551(1) Angstrom for 1 and 2.5544(7) Angstro
m for 2).