Multinuclear (¹⁹⁵Pt, ¹⁵N, ¹³C) NMR studies of the reactions between cis-diaminediaquaplatinum(ii) complexes and aminomalonate

The reactions between cis-PtAm₂(H₂O)₂²⁺ (Am = RNH₂, aziridine; Am₂ = ethylenediamine, 1,2-diaminocyclohexane) and aminomalonate (amal) show that initially the O,O chelate with the 1,1-dicarboxylic group is formed and that subsequently the kinetic product isomerizes to yield the thermodynamically stable N,O chelate. The identity of the thermodynamic product was established by ¹⁹⁵Pt, ¹⁵N, and ¹³C NMR spectroscopy. The formation of the unidentate intermediate adduct [PtAm₂(H₂O)-(amal-0)]⁺ could not be observed by ¹⁵N NMR spectroscopy due to the fast transformation to give the [PtAm₂(amal-O,O)]⁺ chelate. ¹⁹⁵Pt NMR studies also show that 22-h reactions in DMF between cis-PtAm₂LL (L = DMF, NOj₃j⁻ and amidomalonates resulted in isomeric mixtures in which the O,O:N,O ratio ranged between 3:2 and 5:1.