Crystallographic evidence of anion?π interactions in the pyrazine bridged {[Pt(en)Cl]_2(μ-pz)}Cl_2 complex and a comparative study of the catalytic ability of mononuclear and binuclear platinum(II) complexes in the hydrolysis of N-acetylated l-methionylglycine

摘要

This paper reports on the synthesis and the X-ray characteristics of the binuclear {[Pt(en)Cl]_2(μ-pz)}Cl_2 complex (en is ethylenediamine, acting as a bidentate ligand; pz is a bridging pyrazine ligand). This complex was converted into the corresponding aqua complex, {[Pt(en)(H_2O)]_2(μ-pz)}4+, and ~1H NMR spectroscopy was applied for a comparison of its catalytic activities in the hydrolysis of N-acetylated l-methionylglycine (Ac-l-Met-Gly) dipeptide with those for the mononuclear [Pt(en)(H_2O)_2]~(2+) complex. The peptide and the corresponding platinum(II) complex were reacted in different molar ratios and all reactions were performed at 2.0 < pH < 2.5 in D_2O solvent at 37 °C. The course of these hydrolytic reactions is discussed and the difference in the catalytic ability between the mononuclear and binuclear Pt(II) complexes was correlated with the presence of the different hydrolytically active platinum(II)-peptide complexes formed during their reactions with the Ac-l-Met-Gly dipeptide.