Theoretical studies on the cyclopentadienyliron chlorides Cp2Fe2Cl (n) (n = 6 -aEuro parts per thousand 1) with iron in the formal oxidation states from +1 to +4 indicate that all the high-spin species are predicted to be the lowest energy structures and they are paramagnetic complexes with magnetic moments between 2.8 mu (B) and 5.9 mu (B). The mixed oxidation state derivatives with odd number of chloride atoms have larger magnetic moments than other species. In addition to Cp2Fe2Cl, which has the largest magnetic moment, these high-spin species have terminal Cp rings and bridging Cl atoms up to a maximum of two bridges. The Cp2Fe2Cl4, Cp2Fe2Cl3 and Cp2Fe2Cl2 derivatives are predicted to be thermodynamically stable molecules with respect to exothermic reactions for the loss of one Cl atom from Cp2Fe2Cl (n) . Moreover, the lowest energy Cp2Fe2Cl (n) (n = 3, 4) derivatives can be derived by the oxidative addition reactions of Cp2Fe2Cl (n-2) + Cl-2 -> Cp2Fe2Cl (n) .