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Issue 15, 2010
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Synthesis and structures of novel 1-methylcytosinato-bridged (ethylenediamine)platinum(II) and platinum(III) dinuclear complexes

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Abstract

The reaction of [Pt(en)(H2O)2]2+ with 1 equivalent of 1-methylcytosine at an initial pH of 6 ultimately led to the 1-methylcytosinato-bridged (ethylenediamine)platinum(II) dimer, [(en)Pt(MetCyt-H)2Pt(en)](NO3)2 (1). The species during the reactions prior to formation of 1 have been investigated by using 195Pt NMR spectroscopy. From the reaction mixture the [Pt(en)(MetCyt)2](NO3)2 complex (3) could be isolated and structurally characterized. A rational synthesis of 1 was also achieved by dimerization of [Pt(en)(MetCyt)(H2O)](NO3)2. According to X-ray structure analysis, the Pt–Pt distance of 2.9816(3) Å in 1 is well comparable with the corresponding value found in the cis-diammineplatinum(II) analog (2.981(2) Å). Oxidation of 1 with K2S2O8 led to the symmetrically sulfate-capped diplatinum(III) complex with two ethylenediamine ligands equatorially bound to the two Pt atoms ht-[(SO4)(en)Pt(MeCyt-H)2Pt(en)(SO4)] (5), as established by X-ray crystallography. When the oxidation was carried out in the presence of HClO4, the formation of the hydroxido/aqua ht-1-methylcytosinato bridged (en)Pt(III) dimer ht-[H2O(en)Pt(MetCyt-H)2Pt(en)OH](ClO4)3 (6) was observed, as supported by elemental and X-ray structure analysis. In the structure of 6, two ethylenediamine ligands are differently bound to the two Pt centers: one of them equatorially while the second one caps the opposite axial site of the diplatinum(III) core. The Pt–Pt distances in the platinum(III) dimers are 2.5982(4) in 5 and 2.5569(3) Å in 6.

Graphical abstract: Synthesis and structures of novel 1-methylcytosinato-bridged (ethylenediamine)platinum(ii) and platinum(iii) dinuclear complexes

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Publication details

The article was received on 10 Dec 2009, accepted on 23 Jan 2010 and first published on 04 Mar 2010


Article type: Paper
DOI: 10.1039/B926133H
Citation: Dalton Trans., 2010,39, 3633-3643
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    Synthesis and structures of novel 1-methylcytosinato-bridged (ethylenediamine)platinum(II) and platinum(III) dinuclear complexes

    V. M. Djinovic, M. Galanski, V. B. Arion and B. K. Keppler, Dalton Trans., 2010, 39, 3633
    DOI: 10.1039/B926133H

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