The electrospray mass spectrometric (ESI-MS) behavior of the complexes trans-dichloro(ethylenediamine-N, N'-di-3-propionato) platinum(IV), trans-dibromo(ethylenediamine-N, N'-di-3-propionato) platinum( IV), dichloro (ethylenediamine-N,N'-di-3-propionic acid) platinum(II), tetrachloro(O,O'-di-n-butyl-ethylenediamine-N,N'-di-3-propanoate) platinum(IV), chlorotribromo(O,O'-di-n-butylethylenediamine-N,N'-di-3-propanoate) platinum(IV), and dichloro(O,O'-di-n-butyl-ethylenediamine-N,N'-di-3-propanoate) platinum( II), with the formulae trans-[PtCl2 (eddp)] (1), trans-[PtBr2(eddp)] (2), [PtCl2(H(2)eddp)] (3), [PtCl4(Bu(2)eddp)] (4), [PtBr3Cl(Bu(2)eddp)] (5), and [PtCl2(Bu(2)eddp)]center dot H2O (6), is reported. The deprotonated molecular ions or halide adducts are usually observed. ESI-MS data demonstrate the usefulness of the method for efficient characterization of metal complexes in solution.