PLATINUM(II) AND PALLADIUM(II) COMPLEXES WITH 2-AMINO-4-METHYLSULFANYLBUTANOL AND 2-(ETHYLSULFANYL)ETHYLAMINE

The reaction of K2[PtX4] (X = Cl or Br) with 2-(ethylsulfanyl)ethylamine (esea) (molar ratio 1:1) in aqueous solution yielded ionic [Pt(esea)2][PtX4] complexes which undergo thermal rearrangement to [PtX2(esea)]. By treating [PtCl2(esea)] or [PtX2(ambo)] (ambo = L-2-amino-4-methylsulfanylbutanol; X = Cl or Br) with an excess of the corresponding [PtX4]2- in water the binuclear complexes K[Pt2Cl5(esea)] and K[Pt2X5(ambo)] have been obtained. The crystal structure of K[Pt2Cl5(ambo)] was determined by X-ray crystallography and refined to R = 0.034, based on 1685 observed reflections. This binuclear complex, in which the ambo ligand is chelated to Pt(1) through the N and S donor atoms and also co-ordinated to Pt(2) through the S atom, is the first example of a chelated methionine derivative with S acting as bridging donor. The Pt atoms are four-co-ordinate in a slightly distorted square-planar geometry. Selected bond distances are Pt-Cl 2.30 (mean of five values), Pt-S 2.26 (mean), and Pt-N 2.05(1) angstrom; the Pt(1)-S-Pt(2) angle is 116.8(2)-degrees. Proton NMR spectra support rupture of the sulfur bridge of the binuclear complexes in dimethyl sulfoxide to form the corresponding [PtX2L] species. The presence of equilibria between ionic and neutral species in the same solvent is also discussed.