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

Abstract

The preparation and molecular and crystal structure of the complex [(ethylenediamine)bis(7,9,-dimethylhypoxanthine)platinum(II)] hexafluorophosphate, [Pt(C 2H 8N 2)(C 7H 8N 4O) 2] (PF 6) 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 = 2771.0Å 3, Z = 4, D measd = 2.087(3) g cm −3, D calc = 2.094 g cm −3. Intensities for 3992 symmetry-averaged reflections were collected in the θ-2 o 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 PF 6 − 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.