SYNTHESIS AND STRUCTURAL-PROPERTIES OF DIAMINEPLATINUM(II) AND DIAMINEPLATINUM(IV) COMPLEXES OF ALKYLIDENEMALONIC ACIDS

New diamineplatinum(II) complexes of alkylidenemalonate ligands, A(2)P t(OOC)(2)C=CR(2) [A(2) = ethylenediamine (en), propylenediamine (pn); R(2) = 2CH(3), (CH2)(5)] have been prepared. Subsequent oxidation of t he complexes with H2O2 leads tothe corresponding dihydroxyplatinum(IV) complexes, cis,cis,trans-A(2)Pt((OOC)(2)C=CR(2)) (OH)(2). Among the o ctahedral complexes, cis,cis,trans-(pn)Pt((OOC)(2)C=C(CH3)(2))(OH)(2) and is,cis,trans-(pn)Pt((OOC)(2)C=C(CH2)(4)CH2)(OH)(2) have been chara cterized by X-ray crystallographic analysis. The local geometry of the platinum(IV) atoms is approximately octahedral with hydroxide groups in trans positions. The boat conformation of the chelated dicarboxylat e ring in platinum(IV) complexes is less bent than that of the corresp onding platinum(II) analogues. Carboxylation of the hydroxide of A(2)P t((OOC)(2)C=C(CH3)(2))(OH)(2) with acetic anhydride affords A(2)Pt((OO C)(2)C=C(CH3)(2)) (OAc)(2) (A(2) = en, pn), whereas the reaction of A( 2)Pt((OOC)(2)C=C(CH2)(4)CH2)(OH)(2) under the same conditions does not produce the corresponding analogue. NMR spectra indicate that the str uctures of the title complexes are retained in aqueous solution.