Five-coordinate aminophosphine platinum(II) complexes containing cysteine derivatives as ligands

• Published in: Inorganica Chimica Acta 2002-06, Vol.335, p.52-60
• Main Authors: Garcı́a-Seijo, M.Inés, Habtemariam, Abraha, del Socorro Murdoch, Piedad, Gould, Robert O, Garcı́a-Fernández, M.Esther
• Format: Article
• Language: English
• Subjects: 31P NMR spectroscopy; Aminophosphines; Crystallography of five-coordinate Pt(II); Phosphine oxide group; Pt(II) complexes; Sulfur-containing biomolecules
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(02)00813-7

The platinum(II) complex, [Pt(NP 3)Cl]Cl ( 1) [NP 3=N(CH 2CH 2PPh 2) 3] reacts with thiol-containing biomolecules such as N-acetyl- l-cysteine ( N-Ac- l-CysH) and the tripeptide reduced glutathione (γ- l-Glu- l-Cys-Gly, GSH) to afford the intensely-coloured five-coordinate complexes, [Pt(NP 3)( N-Ac- l-Cys- S)] ( 2) and [Pt(NP 3)(GS- S)] ( 3), respectively. Complex 2 was shown by X-ray crystallography to be trigonal bipyramidal and contained an axial PtS bond trans to N, the first example of such a complex. Coordination to Pt(II) protected the thiol from oxidation: reactions of complexes 2 and 3 with H 2O 2 gave the four-coordinate complexes [Pt(NP(O)P 2)(SR- S)] ( 4, SR= N-Ac- l-Cys; 5, SR=GS) which possess a dangling arm phosphine oxide group. The thiolate adducts 2 and 3 exhibited low toxicity to cells. [Pt(N(CH 2CH 2PPh 2) 3)Cl]Cl reacts with thiols (RSH) such as N-acetyl- l-cysteine and the tripeptide glutathione to form intensely-coloured adducts [Pt(N(CH 2CH 2PPh 2) 3)(SR-S)] whose biological activity was investigated. The trigonal bipyramidal structure of the N-acetyl- l-cysteine complex was established by X-ray crystallography. Hydrogen peroxide selectively oxidised one of the coordinated phosphine arms.