Reactions of Ru-2(O2CMe)(4)Cl with two formamidines, HDXyl(2,6)F = N,N'-di(2,6-xylyl)formamidine and HDAniF = N,N'-di(p-anisyl)formamidine, have been investigated with the idea of synthesizing compounds with a mixed set of ligands having different labilities to be used as precursors of paramagnetic, higher-order assemblies. Depending on the formamidine and the reaction conditions, several Ru-2(5+) compounds of the type Ru-2(O2CMe)(4-n)(DArF)(n)Cl (DArF = anion of an N,N'-diarylformamidine) have been isolated. With the bulky formamidine HXyl(2,6)F, the compounds Ru-2(O2CMe)(3)(DXyl(2,6)F)Cl (1) and trans-Ru-2(O2CMe)(2)(DXyl(2,6)F)(2)Cl (2) were obtained. From reactions with appropriate amounts of HDAniF in THF and in the presence of NEt3 and LiCl, complexes of the general type Ru-2(O2CMe)(4-n)(DArF)(n)Cl (n = 1-4) were selectively obtained. For n = 2, only the cis isomer was obtained. The choice of solvent in reactions of Ru-2(O2CMe)(4)Cl and HDAniF is of great importance. Toluene favored the formation of the fully substituted Ru-2(5+) complex Ru-2(DAniF)(4)Cl (3), whereas MeOH resulted in a disproportionation reaction that gave the edge-sharing bioctahedral Ru3+Ru3+ complex [trans-Ru-2(mu-OMe)(2)(mu-O2CMe)(2)(HDAniF)(4)]Cl-2 (6) and the Ru-2(4+) complex Ru-2(DAniF)(4) (7). Complexes 6 and 7 with an Ru-2(6+) and Ru-2(4+) core, respectively, are diamagnetic, whereas all Ru-2(5+) complexes are paramagnetic with sigma(2)pi(4)delta(2)(pi*delta*)(3) ground-state electronic configurations and large zero-field splitting contributions. All compounds show rich and complex electrochemical behavior.