Filling a Gap: Electrochemical Property Comparison of the Completed Compound Series [Mo2(DArF)n(O2C‑Fc)4–n] (DArF = N,N′‑Diarylformamidinate; O2C‑Fc = Ferrocenecarboxylate)

The reaction of cis-[Mo2(O2C-Fc)2(NCCH3)4]­[BF4]2 (cis-1) with two electronically different N,N′-diarylformamidinate (DArF) ligands (DArF = N,N′-bis­(p-trifluoromethylphenyl)­formamidinate (DTfmpF), N,N′-bis­(p-anisyl)­formamidinate (DAniF)) results in the isolation of the tris- and monosubstituted complexes [Mo2(DTfmpF)3(O2C-Fc)] (2a) and [Mo2(DAniF)­(O2C-Fc)3] (2b). These complexes complete the series of [Mo2(DArF)n(O2C-Fc)4–n] (n = 4–0) type compounds, thus allowing for a comprehensive study. On the basis of the oxidation potential E1/2([Mo2]4+/[Mo2]5+) of all Mo2 complexes, ligand basicity is found to decrease in the order DAniF– > DTfmpF– > Fc–CO2– ≫ CH3CN. In addition, no direct electronic interaction between the trans-positioned Fc units in complex 2b is detected, which is attributed to the full overlap of all Fc oxidation processes. Furthermore, the low-energy absorption bands of compounds 2a,b are located at different positions in their respective UV–vis spectra.