STRUCTURAL-PROPERTIES OF A NEARLY STOICHIOMETRIC DIAMINEPLATINUM(II) COMPLEX WITH INOSINE 5'-MONOPHOSPHATE

A nonstoichiometric compound, [Na2(5ʹ-IMPH)2•16H2O]0.14 [Na2((NH3)2Pt(5ʹ-IMP2)•15-16H2O]0.86, has been prepared and investigated by single-crystal X-ray methods (5ʹ-IMP = the dianion of inosine 5ʹ-monophosphate). The compound is isomorphous with the monosodium salt of 5ʹ-IMP and several Pt11-5ʹ-IMP complexes previously reported to be nonstoichiometric. The coordination geometry about the Pt(II) is essentially square planar with the N(7) atom of the hypoxanthine base and the ammonia ligand and their twofold related symmetry mates occupying the four coordination sites. Analysis of the structural parameters in these complexes [N(7) to N(7) distance, dihedral angle between hypoxanthine bases] and a detailed study of the crystal packing of the title compound further verify our earlier proposal that the nonstoichiometry of the Pt(II) compounds may result from a competition between the crystal packing forces operative in the sodium salts of 5ʹ-IMP and the coordination-induced distortions in this basic 5ʹ-IMP structural motif. The present study also adds further support to our earlier suggestion that the crystal structure analysis of Na2[(NH3)2Pt(5ʹ-IMP)2]•15-16H2O, reported by others previously, was probably performed on a stoichiometric compound. © 1979, American Chemical Society. All rights reserved.