Reaction of the (pentamethylcyclopentadienyl)silicon cation with the (pentamethylcyclopentadienyl)dicarbonylferrate anion leads to the formation of the crystalline, thermolabile silicon(II) compound [(η5-pentamethylcyclopentadienyl)dicarbonylferrio](η3-pentamethylcyclopentadienyl)silicon. The singlet−triplet energy difference ΔEST is calculated to be 25.4 kcal/mol.