The electrochemical (platinum and glassy carbon electrodes, cyclic and rotating disk electrode voltammetry, bulk electrolysis, voltammetric simulation) and chemical oxidation (NO ϩ ) of the organoamidoplatinum() complex, [Pt{((p-HC 6 F 4 )NCH 2 ) 2 }(py) 2 ], has been studied in acetonitrile and acetone. The initial process is a complicated function of concentration, temperature, and method of oxidation. The products formed have been probed by in situ spectroelectrochemical techniques (UV/Visible and EPR spectroscopy), and ex situ by 1 H, 19 F and 195 Pt NMR spectroscopy and electrospray mass spectrometry. Under conditions of cyclic voltammetry, the initial oxidation process (at high concentration) is an overall irreversible one-electron process, complicated by crossover of current on the reverse scan. This and many (but not all) features are simulated by a sequence of electron transfer steps and coupled chemical reactions which requires the formation of two structurally different dinuclear intermediates. Regeneration of [Pt{((p-HC 6 F 4 )NCH 2 ) 2 }(py) 2 ] by reduction is possible under short timescale conditions, but not long timescale conditions, implying that the finally observed product from long timescale experiments may be oligomeric. The observation of moderately stable diamagnetic diplatinum() compounds is attributed to the formation of bridged complexes containing Pt-Pt bonds. Oxidation of all platinum() intermediates gives rise to the same or very closely related platinum() complexes. Features of the organoamide ligand that enable the formation of moderately stable platinum() complexes are considered.

No abstract

Characterization of the anticancer active compound trans‐[PtII{(p‐BrC6F4)NCH2CH2NEt2}Cl(py)] is described along with identification of electrochemical conditions that favor formation of a monomeric one‐electron‐oxidized PtIII derivative. The square‐planar organoamidoplatinum(II) compound was synthesized through a carbon dioxide elimination reaction. Structural characterization by using single‐crystal X‐Ray diffraction reveals a trans configuration with respect to donor atoms of like charges. As PtIII intermediates have been implicated in the reactions of platinum anticancer agents, electrochemical conditions favoring the formation of one‐electron‐oxidized species were sought. Transient cyclic voltammetry at fast scan rates or steady‐state rotating disc and microelectrode techniques in a range of molecular solvents and an ionic liquid confirm the existence of a well‐defined, chemically and electrochemically reversible one‐electron oxidation process that, under suitable conditions, generates a PtIII complex, which is proposed to be monomeric [PtIII{(p‐BrC6F4)NCH2CH2NEt2}Cl(py)]+. Electron paramagnetic resonance spectra obtained from highly non‐coordinating dichloromethane/([Bu4N][B(C6F5)4]) solutions, frozen to liquid nitrogen temperature immediately after bulk electrolysis in a glove box, support the PtIII assignment rather than formation of a PtII cation radical. However, the voltammetric behavior is highly dependent on the timescale of the experiments, temperature, concentration of trans‐[PtII{(p‐BrC6F4)NCH2CH2NEt2}‐ Cl(py)], and the solvent/electrolyte. In the low‐polarity solvent CH2Cl2 containing the very weakly coordinating electrolyte [Bu4N][B(C6F5)4], a well‐defined reversible one‐electron oxidation process is observed on relatively long timescales, which is consistent with the stabilization of the cationic platinum(III) complex in non‐coordinating media. Bulk electrolysis of low concentrations of [Pt{(p‐BrC6F4)NCH2CH2NEt2}Cl(py)] favors the formation of monomeric [PtIII{(p‐BrC6F4)NCH2CH2NEt2}Cl(py)]+. Simulations allow the reversible potential of the PtII/PtIII process and the diffusion coefficient of [PtIII{(p‐BrC6F4)‐ NCH2CH2NEt2}Cl(py)]+ to be calculated. Reversible electrochemical behavior, giving rise to monomeric platinum(III) derivatives, is rare in the field of platinum chemistry.

No abstract

No abstract