Complexes of Metal Halides with Unreduced o-(Imino)quinones

Abstract

A series of complexes of metal halides with unreduced quinone-type ligands have been synthesized and characterized in detail. The 3,6-di-tert-butyl-obenzoquinone (1) and 4,6-di-tert-butyl-N-aryl-substituted o-iminobenzoquinones (2−5) (aryl is 2,6-dimethylphenyl in 2, 2-methyl-6-ethylphenyl in 3, 2,6-diethylphenyl in 4, and 2,6-diisopropylphenyl in 5) were used to obtain the molecular complexes with metal 12 group halides as well as with indium(III) iodide. The molecular structures of five complexes, bearing an unreduced form of redox-active ligand, have been established by single-crystal X-ray analysis. The spectral data, electrochemical measurements, and DFT calculations indicate the significant transformations of the molecular orbitals of 1−5 upon complexation with Lewis acids. The reduction potentials of o-(imino)quinones in complexes with metal halides shift into the anodic region versus uncoordinated ones. The choice of metal halide allows varying the shift magnitude up to 1.7 V in 2•CdI 2 . The change of the oxidizing ability of the 1−5 upon coordination with Lewis acids enables the oxidation of mercury and ferrocene, infeasible for free ligands.

α-Diimine Cisplatin Derivatives: Synthesis, Structure, Cyclic Voltammetry and Cytotoxicity

“…A similar effect is observed for the reduction peaks of free ligands: −2.07 V (dpp-DAD(Me) 2 ) [ 44 ], −1.74 V ( Mes -DAD(Me) 2 ) ( Figure S10 ); dpp -DAD [ 44 ]. As in the case of the previously discussed complexes of o -(imino)benzoquinones with metal halides [ 45 ], the coordination of diazadiene ligands with PtCl 2 increased in the reduction potential and, consequently, the electron acceptor ability of the 1,4-diaza-1,3-butadiene ligands. The complex formation favors not only to a shift in the reduction potential of the bound ligand but also hinders the oxidation stage.…”

Magnetically bistable cobalt-dioxolene complexes with a tetradentate N-donor base

“…38 In contrast, our case is exceptional and the formation of a trimethoxy-derivative completes within a few hours. We suppose that it is due to the reduced 39 redox potential of the 36-DBCat fragment coordinated to the metal center as compared to the free ligand. All the results mentioned above, together with the possibility of the RIET rearrangements in the Co-dioxolene pair, favor the discussed chemical transformations.…”