title: Synthesis and structures of novel 1-methylcytosinato-bridged (ethylenediamine)platinum(II) and platinum(III) dinuclear complexes.
abstract: The reaction of [Pt(en)(H(2)O)(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)(2)Pt(en)](NO(3))(2) (1). The species during the reactions prior to formation of 1 have been investigated by using (195)Pt NMR spectroscopy. From the reaction mixture the [Pt(en)(MetCyt)(2)](NO(3))(2) complex (3) could be isolated and structurally characterized. A rational synthesis of 1 was also achieved by dimerization of [Pt(en)(MetCyt)(H(2)O)](NO(3))(2). According to X-ray structure analysis, the Pt-Pt distance of 2.9816(3) A in 1 is well comparable with the corresponding value found in the cis-diammineplatinum(II) analog (2.981(2) A). Oxidation of 1 with K(2)S(2)O(8) led to the symmetrically sulfate-capped diplatinum(III) complex with two ethylenediamine ligands equatorially bound to the two Pt atoms ht-[(SO(4))(en)Pt(MeCyt-H)(2)Pt(en)(SO(4))] (5), as established by X-ray crystallography. When the oxidation was carried out in the presence of HClO(4), the formation of the hydroxido/aqua ht-1-methylcytosinato bridged (en)Pt(III) dimer ht-[H(2)O(en)Pt(MetCyt-H)(2)Pt(en)OH](ClO(4))(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) A in 6.
authors.affiliation: University of Vienna, Institute of Inorganic Chemistry, Währinger Strasse 42, A-1090, Vienna, Austria.
authors.forename: Vesna M
authors.initials: VM
authors.lastname: Djinovic
authors.forename: Mathea
authors.initials: S
authors.lastname: Galanski
authors.forename: Vladimir B
authors.initials: VB
authors.lastname: Arion
authors.forename: Bernhard K
authors.initials: BK
authors.lastname: Keppler
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D003596:Cytosine / Q000031:analogs & derivatives* / Q000737:chemistry; D005029:Ethylenediamines / Q000737:chemistry*; D008968:Molecular Conformation; D010984:Platinum / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D056831:Coordination Complexes; D005029:Ethylenediamines; C031532:1-methylcytosine; D010984:Platinum; C031234:ethylenediamine; D003596:Cytosine