Platinum(II) and palladium(II) complexes with 2-amino-4-methylsulfanylbutanol and 2-(ethylsulfanyl)ethylamine

Abstract

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)Å the Pt(1)–S–Pt(2) angle is 116.8(2)°. 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.