Coordination chemistry of 7,9-disubstituted 6-oxopurine metal compounds. 4. Platinum(II) coordination at N(1). Molecular and crystal structure of [(ethylenediamine)bis(7,9-dimethylhypoxanthine)platinum(II)] hexafluorophosphate |
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Authors: | Thomas J Kistenmacher Baltazar de Castro Kenneth Wilkowski Luigi G Marzilli |
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Institution: | Department of Chemistry, The Johns Hopkins University, Baltimore and Emory University, Atlanta, GA, USA |
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Abstract: | The preparation and molecular and crystal structure of the complex (ethylenediamine)bis(7,9,-dimethylhypoxanthine)platinum(II)] hexafluorophosphate, Pt(C2H8N2)(C7H8N4O)2] (PF6)2, are reported. The complex crystallizes in the monoclinic system, space group C2/c, with a = 12.334(2)Å, b = 10.256(2)Å, c = 22.339(3)Å, β = 101.31(1)°, V = 2771.0Å3, Z = 4, Dmeasd = 2.087(3) g cm?3, Dcalc = 2.094 g cm?3. Intensities for 3992 symmetry-averaged reflections were collected in the θ-2o scan mode on an automated diffractometer employing graphite-monochromatized MoKα radiation. The structure was solved by standard heavy-atom Patterson and Fourier methods. Full matrix least-squares refinement led to a final R value of 0.051. Both the ethylenediamine chelate and the PF6? anion are disordered. The primary coordination sphere about the Pt(II) center is approximately square planar with the bidentate ethylenediamine ligand and the N(1) atoms Pt(II) ? N(1) = 2.020(5)Å] of two 7,9-dimethylhypoxanthine bases (related by a crystallographic twofold axis of symmetry) occupying the four coordination sites. The exocyclic O(6) carbonyl oxygen atoms of the two 7,9-dimethylhypoxanthine ligands participate in intracomplex hydrogen bonding with the amino groups of the ethylenediamine chelate N(ethylenediamine) ? O(6) = 2.89( )Å]. The observed Pt ? O(6) intramolecular distances of 3.074(6)Å are similar to those found in other Pt(II) N(1)-bound 6-oxopurine complexes and in several Pt(II) N(3)-bound cytosine systems. |
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Keywords: | Address reprint requests to Dr Thomas J Kistenmacher Department of Chemistry The Johns Hopkins University Baltimore MD 21218 |
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