Platin in seiner ungewöhnlichen Oxidationsstufe + III: Diplatin(III)-Komplexe der Modellnukleobase 1-Methyluracil / Platinum in its Unusual Oxidation State + III: Diplatinum(III) Complexes with the Model Nucleobase 1-Methyluracil

Abstract

Oxidation of the head-tail dimer cis-[(NH3)2Pt(1-MeU)]2(NO3)2 (1-MeU = 1-methyl - uracilato anion, C5H5N2O2) with a mixture of nitrous and nitric acid yields three crystalline species, [(NO2)(NH3)2Pt(C5H5N2O2)2Pt(]SrH3)2(NO2)](NO3)2 · 3 H2O (1), [(H2O)(NH3)2Pt(C5H5N2O2)2Pt(]SrH3)2(NO2)](NO3)2 · 5 H2O (2) and [(NO3)(NH3)2Pt(C5H5N2O2)2Pt(]SrH3)2(NO3)](NO3)2 · 4.5 H2O (3). The crystal structure of 2 has been determined. 2 crystallizes in the triclinic space group P1̄ with cell dimensions a= 11.959(4), b= 11.560(3), c= 11.261(2) Å, α = 89.16(2), β= 104.36(2), γ = 99.61(2)° and Z = 2. The structure was refined to R = 0.056, Rw = 0.061 on 4311 reflections. The Pt-Pt distance within the dinuclear cation of 2 is 2.574(1) Å and cor­responds to a Pt-Pt single bond. The axial ligands are N̲O2 (Ptl) and O̲H2 (Pt2), the equatorial ligands two NH3 groups, N 3 and O4 of 1-MeU for both Pt atoms. The oxidation state of Pt in 2 is +III. 1H NMR and IR spectra of 1, 2, and 3 reveal a close structural similarity of the three compounds.