Migration reactivities of sigma-bonded organo-iron and -cobalt porphyrins were examined as a function of the compound oxidation state. Migration rates were determined for both the one-electron and two-electron oxidized species produced in the electron-transfer oxidation with different oxidants in acetonitrile at 298 K. The investigated compounds are represented as [(OETPP)Fe(R)](n+), where n = 1 or 2, OETPP = the dianion of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin and R = C6H5, 3,5-C6F2H3, or C6F5, and as [(TPP)Co(R)](n+), where n = 1 or 2, TPP = the dianion of 5,10,15,20-tetraphenylporphyrin, and R = CH3 or C6H5 The rapid two-electron oxidation of (OETPP)Fe-III(R) occurs with [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine) to produce [(OETPP)Fe-IV(R)](2+). The formation of this species is followed by a slow migration of the sigma-bonded R group to a nitrogen of the porphyrin ring to give [(N-ROETPP)Fe-II](2+) and then by a rapid electron-transfer oxidation of the migrated product with [Ru(bpy)(3)](3+) to yield [(N-ROETPP)Fe-III](3+) as a final product. When [Ru(bpy)(3)](3+) is replaced by a much weaker oxidant such as ferricenium ion, only the one-electron oxidation of (OETPP)Fe(R) occurs to produce [(OETPP)Fe-IV(R)(+). A migration of the R group also occurs in the one-electron oxidized porphyrin species, [(OETPP)Fe-IV(R)](+), to produce [(N-ROETPP)Fe-II](+), which is rapidly oxidized by ferricenium ion to yield [(N-ROETPP)Fe-III](2+). The migration rate of the R group in [(OETPP)Fe-IV(R)](+) is about 10(4) times slower than the migration rate of the corresponding two-electron oxidized species, [(OETPP)Fe-IV(R)](2+). The migration rate of the a-bonded ligand of [(TPP)Co-IV(R)](+), produced by the one-electron oxidation of (TPP)Co-III(R) with [Fe(phen)(3)](3+) (phen = 1,10-phenanthroline) is also about 10(4) times slower than the migration rate of the R group in the corresponding two-electron oxidized species, [(TPP)Co-IV(R)](2+), which is produced by the two-electron oxidation with [Ru(bpy)(3)](3+). A comparison of the migration rates with the oxidation states of the porphyrins indicates that the migration occurs via an intramolecular electron transfer from the R group to the Fe(IV) or Co(IV) metal of the organometallic porphyrin.