Substitution of chlorides by l-methionine in the dinuclear [Pt2(8NNpy)Cl4] complex in DMF–water solution

• Each PtII center in the complex can be treated separately during substitution.
• Only one chloride per one PtII center is substituted.
• The reaction rate depends mostly on the nucleophile donor atom accessibility.

Reaction between dinuclear [Pt2(8NNpy)Cl4] complex and l-methionine (Met) has been studied spectrophotometrically in DMF–water (1:1 by volume) medium (DMF = N,N-dimethylformamide). Such medium results from the complex insolubility at purely aqueous solutions. Only one step of the reaction can be observed in an hour-timescale. Rate constants for the reversible first step of the reaction (k1 (forward) and k2[Cl−] (backward)) and activation parameters have been determined. A negative ΔS≠ confirms the associative character of the process. The results show a huge influence of the incoming nucleophile size and structure on the reaction rate. A qualitative extrapolation of the results into ‘pure’ aqueous conditions suggests that the chlorides in the complex can be substituted at aqueous medium faster than in the case of cisplatin, which results from the presence of the π-acceptor ligands in the coordination sphere of [Pt2(8NNpy)Cl4] complex.

Reaction between dinuclear [Pt2(8NNpy)Cl4] complex and l-methionine has been studied spectrophotometrically in DMF–water (1:1 by volume) medium. Rate constants for the reversible first step of the reaction (k1 (forward) and k2[Cl−] (backward)) and activation parameters have been determined. The results show a huge influence of the incoming nucleophile size and structure on the reaction rate.Figure optionsDownload as PowerPoint slide