COORDINATION CHEMISTRY OF 7,9-DISUBSTITUTED 6-OXOPURINE METAL-COMPOUNDS .3. PLATINUM(II) COORDINATION AT N - MOLECULAR AND CRYSTAL-STRUCTURE OF (DIETHYLENETRIAMINE)(7,9-DIMETHYLGUANINE)PLATINUM(II) HEXAFLUOROPHOSPHATE AND (DIETHYLENETRIAMINE)(7,9-DIMETHYLHYPOXANTHINE)PLATINUM(II) HEXAFLUOROPHOSPHATE SESQUIHYDRATE

• Type: Article in International Scientific Journal
• Date: 1981

Authors

DECASTRO, B (Author) FCUP; CHIANG, CC (Author) Other; WILKOWSKI, K (Author) Other; MARZILLI, LG (Author) Other; KISTENMACHER, TJ (Author) Other

Journal

Title: Inorganic Chemistry

Vol. 20

Pages: 1835-1844

ISSN: 0020-1669

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 28 Citations

Scopus - 18 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-005-6GR

DOI: 10.1021/ic50220a045

Abstract (EN): The preparation and molecular and crystal structure of the complexes (dien)(7,9-dimethylguanine)platinum(II) hexafluorophosphate, Pt(C4H13N3)(C7H9N 5O)(PF6)2, and (dien)(7,9-dimethylhypoxanthine)platinum(II) hexafluorophosphate sesquihydrate, Pt(C4H13N3)(C7H8N 4O)(PF6)2(H2O)1.5, are reported (dien = diethylenetriamine). The 7,9-dimethylguanine complex crystallizes in the triclinic system, of space group P1, with a = 11.111 (3) Å, b = 11.940 (3) Å, c = 9.440 (3) Å, ¿ = 103.54 (2)°, ß = 102.39 (2)°, ¿ = 70.34 (2)°, V = 1133.8 A3, Z = 2, Dmeasd = 2.30 (4) g cm-3, and Dcalcd = 2.24 g cm-3. The 7,9-dimethylhypoxanthine complex crystallizes in the monoclinic system, of space group C2/c, with a = 15.754 (5) Å, b = 19.162 (7) Å, c = 18.108 (4) Å, ß = 119.02 (2)°, V = 4780.1 A3, Z = 8, Dmeasd; = 2.137 (3) g cm-3, and Dcalcd = 2.166 g cm-3. Intensities for 6632 (7,9-dimethylguanine complex) and 4889 (7,9-dimethylhypoxanthine complex) symmetry-averaged reflections were collected in the ¿-2¿ scan mode on an automated diffractometer employing graphite-monochromatized Mo K¿ radiation. Both structures were solved by standard heavy-atom Patterson and Fourier methods. Full-matrix least-squares refinement has led to final R values of 0.049 and 0.057 for the 7,9-dimethylguanine and the 7,9-dimethylhypoxanthine structures, respectively. The primary coordination sphere about the platinum(II) center is approximately square planar in both complex cations, with the tridentate dien chelate, its terminal amino groups in trans positions, and N(1) of the 7,9-dimethylated purine base [Pt-N(1) = 2.044 (5) Å for the guanine base and Pt-N(1) = 2.051 (6) Å for the hypoxanthine base] occupying the four coordination sites. In both complexes, the exocyclic carbonyl oxygen atom O(6) participates in inter- and intracomplex hydrogen-bonding interactions with the amino protons of the dien chelate. For the 7,9-dimethylguanine system, this latter interaction is weak [N(dien)¿O(6) = 3.039 (6) Å], but the observed Pt¿O(6) intramolecular distance of 3.021 (6) Å suggests some O(6) participation in the metal binding scheme. In contrast, the interligand, intramolecular hydrogen bonding to O(6) in the 7,9-dimethylhypoxanthine complex is stronger [N(dien)¿O(6) = 2.946 (6) Å] but there is little indication of O(6) participation [Pt¿O(6) = 3.145 (5) Å] in the metal binding. The dihedral angle between the coordination plane and that of the purine base is a sensitive indicator of the relative degree of Pt¿O(6) interaction and N(dien)¿O(6) interligand hydrogen bonding, and the respective values for this angle for the guanine and hypoxanthine complexes are 62.4 (3) and 47.7 (3)°. The difference in the molecular geometry of the two complex cations can be ascribed to the additional intracomplex steric interactions in the 7,9-dimethylguanine system owing to the presence of the exocyclic amino group at position 2 of the purine ring. Qualitatively, the molecular properties of these N(1)-bound Pt-6-oxopurine complexes are similar to those displayed by N(3)-bound Pt-cytosine complexes. Both crystal structures are characterized by extensive intercomplex hydrogen bonding (direct in the 7,9-dimethylguanine complex and both direct and water mediated in the 7,9-dimethylhypoxanthine complex) and numerous interactions between the PF6 anions and the cationic coordination complexes. © 1981 American Chemical Society.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10