Kenneth. Wilkowski

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 2 H 8 N 2 )(C 7 H 8 N 4 O) 2 ] (PF 6 ) 2 , are reported. The complex crystallizes in the monoclinic system, space group C2/c, with a = 12.334(2)A, b = 10.256(2)A, c = 22.339(3)A, β = 101.31(1)°, V = 2771.0A 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)A] 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( )A]. The observed Pt ⋯ O(6) intramolecular distances of 3.074(6)A 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.

Structures of two N(1)-bound platinum(II)-6-oxopurine complexes. Comparisons with complexes derived from platinum(II) anti-tumor agents

Abstract The preparation and molecular structure of [(diethylenetriamine) (7,9-dimethylhypoxanthine) platinum(II)] (PF 6 ) 2 ·1.5H 2 O and [(ethylenediamine) (7,9-dimethylhypoxanthine) 2 platinum(II)] (PF 6 ) 2 , are reported. These complexes represent the first structurally characterized N(1)-bound Pt(II) 6-oxopurine complexes. In each case, the Pt(II)N(1) bond length [2.051(6)A in the diethylenetriamine complex and 2.021(8)A in the ethylenediamine complex] indicates a strong metal-to-base binding. Both complexes contain interligand hydrogen bonds, with the ammine ligand acting as the donor and the O(6) atom of the base acting as the acceptor. These N(1)-bound complexes are compared with N(7)-bound 6-oxopurine and N(3)-bound cytosine complexes of Pt(II) anti-tumor agents.