Invariant Oxidation State of Copper but not of Ruthenium in Complexes with Noninnocent N‐(2‐Methyl‐5,8‐dioxo‐5,8‐dihydroquinolin‐7‐yl)acetamide: A Combined Structural, Electrochemical and Spectroelectrochemical Investigation

The compounds [(dppf)Cu(L)](BF4) (1[BF4]) [dppf = 1,1′‐bis(diphenylphosphanylferrocene), L = N‐(2‐methyl‐5,8‐dioxo‐5,8‐dihydroquinolin‐7‐yl)acetamide] and [(acac)2Ru(L)] (2) (acac = acetylacetonato) were prepared from the reactions of [Cu(dppf)(CH3CN)2](BF4) or [Ru(acac)2(CH3CN)2], respectively with L. Structural characterization of 1[BF4] shows a distorted tetrahedral coordinated copper center. Both complexes show one‐electron reversible oxidation as well as reduction processes in their cyclic voltammogram. The first oxidation process of 1[BF4] leads to absorptions at around 900 nm in the UV/Vis/NIR spectrum and results in an EPR silent species up to 110 K thus indicating a dppf‐centered oxidation. The reduction processes of 1[BF4] show features in the UV/Vis/NIR, IR as well as EPR spectrum that are compatible with L‐centered redox processes. In contrast to this, the ruthenium complex 2 shows metal‐centered spin in both the one‐electron oxidized as well as reduced forms. These results show that the copper center does not participate in the redox processes in 1[BF4] whereas the ruthenium center participates strongly in the electron‐transfer processes in 2. Results obtained from electrochemistry as well as from UV/Vis/NIR, IR, and EPR spectroelectrochemistry are invoked to show the noninnocent nature of L in these complexes as well as the more relative importance of metal–L covalency in 2 as compared to 1[BF4].