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 E_1/2([Mo₂]⁴⁺/[Mo₂]⁵⁺) of all Mo₂ complexes, ligand basicity is found to decrease in the order DAniF^- > DTfmpF^- > Fc-CO₂^- 蠑 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.