The bond dissociation energy for loss of C2H4 from Fe(CO)(3)(C2H4)(2), produced by the reaction of C2H4 + Fe(CO)(3)(C2H4), has been determined as 21.3 +/- 2.0 kcal/mol. An estimate is made for a lower limit for the bond dissociation energy of Fe(CO)(4)(C2H4), which can be formed by reaction of CO + Fe(CO)(3)(C2H4) or Fe(CO)(4) + C2H4 with rate constants of (4.3 +/- 0.8) x 10(-12) and (1.7 +/- 0.2) x 10(-13) cm(3)/(molecule s) at 24 degrees C, respectively. The values for these bond dissociation energies are compared with those determined in prior studies of these systems. A new compound with infrared absorptions at 2147, 2091, and 2068 cm(-1) is best assigned as Fe(CO)(3)(C2F4)(2). A rate constant of (5.4 +/- 1.7) x 10(-12) cm(3)/(molecule s) at 24 degrees C is reported for the reaction of C2F4 with Fe(CO)(3)(C2F4) to form Fe(CO)(3)(C2F4)(2). Fe(CO)(4)(C2F4) can be formed by reaction of C2F4 and Fe(CO)(4), with a rate constant of (1.8 +/- 0.4) x 10(-14) cm(3)/(molecule s) at 24 degrees C. Infrared absorptions observed at 2135, 2074, and 2043 cm(-1) are assigned to this species. The relative stabilities of the mono- and bisethylene and perfluoroethylene compounds of iron are compared. Where possible, they are also compared to the corresponding chromium compounds and are discussed in the context of current concepts regarding metal-olefin bonding.