Platinum(II) complexes with tris(2-carboxyethyl)phosphine, X-ray structure and reactions with polar solvents and glutathione

•Cis and trans Pt(II) complexes with P(C2H4COOH)3 (TCEP), reductant of S–S bond.•Trans-[PtCl2(TCEP)2] is square planar and cis-[PtCl2(TCEP)2] is distorted square planar.•Trans-[PtCl2(TCEP)2] in H2O isomerizes to cis complexes with TCEP-κO,κP ligands.•PtCl2(TCEP)2 complexes react with glutathione forming Pt–S and Pt–NH cysteinyl bonds.•PtCl2(TCEP)2 are good model complexes for investigation reactions with biomolecules.

It has recently been found that P(C2H4COOH)3 (TCEP), used in the reduction of S–S bonds, promoted reaction of cisplatin with Sp1 zinc finger protein and Cu(I) transporters. However Pt complexes with TCEP were not investigated. New platinum(II) complexes with (TCEP): trans-[PtCl2(TCEP)2] (1) and cis-[PtCl2(TCEP)2]·1.25H2O (2) were fully characterized by IR, 1H, 13C, 31P, 195Pt NMR and ESI-MS spectroscopic techniques. Structures of trans-[PtCl2{P(C2H4COOD)3}2] (1a) and cis-[PtCl2(TCEP)2]·1.25H2O (2) have been determined by X-ray crystallography. Complexes are stable in non-aqueous DMSO and DMF. In aqueous solutions Cl ligands are substituted by COO groups of phosphines. In the mixtures DMSO + H2O and DMF + H2O coordination of COO groups proceeds to a lesser extent and 1 partly isomerizes forming cis-[PtCl2(TCEP)2] and cis-[PtCl{P(C2H4COOH)3-κP}{P(C2H4COOH)2(C2H4COO)-κO,κP}]. The latter complex is also formed in solution of 2 in DMSO + H2O and DMF + H2O. The degrees of isomerization and substitution of Cl ligands in aqueous solutions are higher. NMR data indicate that complexes interact with reduced glutathione (GSH). Compound 2 in D2O forms complex with GS ligand coordinated to platinum via S atom and NH cysteinyl group.

Graphical abstractStructures and reactivity of Pt(II) complexes with P(C2H4COOH)3 (TCEP), reductant of S–S bonds and promoter of reaction of cisplatin with Zn finger protein and Cu(I) transporters, were investigated. TCEP in nonaqueous solvent is coordinated via P atom but in water through P and O atoms. Complexes coordinate glutathione (GSH) via S atom and NHcys group.Figure optionsDownload full-size imageDownload as PowerPoint slide