Preparation, X-ray crystal structure, and 195Pt NMR spectra of platinum(II) with dipeptides and dipeptide methyl esters

Three dipeptide complexes of the form K[M(dipeptide)Cl] (H 2dipeptide=glycylβ-alanine, β-alanylglycine, β-alanylβ-alanine) and four dipeptide methyl ester complexes of the form K[M(dipeptideOMe)Cl 2] (HdipeptideOMe=glycylα-alanine methyl ester, α-alanylglycine methyl ester, diα-alanine methyl ester) were newly prepared. The K[Pt(glyβ-ala)Cl] complex crystallizes in the monoclinic space group C2/c with unit cell dimensions of a=25.77(1) Å, b=4.09(2) Å, c=16.432(9) Å, β=103.74(4)°, and Z=8. The K[Pt(glyα-alaOMe)Cl 2] complex crystallizes in the monoclinic space group P 1 ̄ with unit cell dimensions of a=7.195(2) Å, b=7.977(5) Å, c=10.326(3) Å, α=72.49(3)°, β=103.74(4)°, γ=88.27(4)° and Z=2. The 195Pt NMR peaks of the complexes containing the β-alanine moiety appeared significantly more upfield than those of the complexes containing diglycine. The ratios of the species of the platinum complexes containing the dipeptide ester in neutral solution were significantly different from those in alkaline solution at 40°C for a short time.