Hydrolysis of (Me3SiCH2)PhSnCl2. Isomerisation of the dimeric tetraorganodistannoxane [(Me3SiCH2)Ph(Cl)SnOSn(Cl)-Ph(CH2SiMe3)]2

The hydrolysis of (Me₃SiCH₂)PhSnCl₂( 1) was studied under two different reaction conditions (i) by using an excess of aqueous NaOH in toluene at reflux temperature and (ii) by using small amounts of NEt₃ and water in CH₂Cl₂ at room temperature. For (i) the products  (Me₃SiCH₂)Ph₂SnOSnPh₂(CH₂SiMe₃)( 2) and [(Me₃SiCH₂Sn)₁₂O₁₄(OH)₆](OH)₂( 3) were isolated indicating that a phenyl group migration took place. For (ii) the dimeric tetraorganodistannoxane [(Me₃SiCH₂)Ph(Cl)SnOSn(Cl)Ph(CH₂SiMe₃)]₂( 4) was obtained. In solution, 4 exists as an equilibrium mixture of all five possible isomers 4a–4e; in the solid state two of these isomers 4d and 4e co-crystallized in the same crystal modification. The observation of interconvertible isomers of 4 was attributed to the kinetic lability of the ladder-like Sn4O2Cl4 structural motif. Compounds 1 and 4 were investigated by X-ray crystallography.

Observation of Te···π and X···X Bonding in para-Substituted Diphenyltellurium Dihalides, (p-Me2NC6H4)(p-YC6H4)TeX2(X=Cl, Br, I; Y=H, EtO, Me2N)-

The supramolecular association of the previously described para-dimethylaminophenyl-substituted diorganotellurium dihalides (p-Me₂NC₆H₄)₂TeX₂ (X = Cl (1), Br (2), I (3)) and (p-Me₂NC₆H₄)RTeCl₂ (R = Ph (4), p-EtOC₆H₄ (5)), was investigated by X-ray crystallography. Unlike almost all other structurally characterized diorganotellurium dihalides, (p-Me₂NC₆H₄)₂TeX₂ (X = Cl (1), Br (2), I (3)) reveal no secondary Te∙∙∙X interactions, but X∙∙∙X interactions. The structure of (p-Me₂NC₆H₄)PhTeCl₂ (4) resembles that of Ph₂TeCl₂ and shows one secondary Te∙∙∙Cl contact, whereas (p-Me₂NC₆H₄)(p-EtOC₆H₄)TeCl₂ (5) exhibits neither secondary Te∙∙∙Cl nor Cl∙∙∙Cl interactions. The unusual structural characteristics of 1–5 are attributed to the occurrence of intermolecular Te∙∙∙π and π∙∙∙π contacts associated with quinoid π-electron delocalization across the para-dimethylaminophenyl (1–5) and para-ethoxyphenyl (5) groups.

Conditions favoring the formation of monomeric Pt(III) derivatives in the electrochemical oxidation of trans-[Pt(II){(p-BrC6F4)NCH2CH2NEt2}Cl(py)]

Characterization of the anticancer active compound trans-[Pt^II{(p-BrC6F4)NCH2CH2NEt2}Cl(py)] is described along with identification of electrochemical conditions that favor formation of a monomeric one-electron-oxidized Pt^III 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 Pt^III 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 Pt^III complex, which is proposed to be monomeric [Pt^III{(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 Pt^III assignment rather than formation of a Pt^II cation radical. However, the voltammetric behavior is highly dependent on the timescale of the experiments, temperature, concentration of trans-[Pt^II{(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 [Pt^III{(p-BrC6F4)NCH2CH2NEt2}Cl(py)]⁺. Simulations allow the reversible potential of the Pt^II/Pt^III process and the diffusion coefficient of [Pt^III{(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.