PT(II) COMPLEXES OF AMINO ACIDS AND PEPTIDES. II. STRUCTURAL ANALYSIS OF TRANS-[CL2-PT-(H-AIB-OH)2] AND TRANS-[PT-(H-AIB-O-)2

The trans-[Cl2-Pt-(H-Aib-OH)2] and trans-[Pt-(H-Aib-O−)2] complexes have been synthesized and characterized in solution and in the solid state. Their crystal and molecular structures have been determined by X-ray diffraction analyses. The complexes show a distorted planar coordination around the heavy atom. The organic moiety in the twocomplexes shows different conformations: in trans-[Pt-(H-Aib-O−)2] the aminoacid residue, acting as a bidentate, is forced to assume an unusual conformation. On the other hand, in trans-[Cl2-Pt-(H-Aib-OH)2], in which the aminoacid acts as a monodentate ligand, the α-aminoisobutyric acid assumes an extended conformation, which in general for α-monosubstituted aminoacid residues coordinated to the platinum should be the preferred conformation. In both crystal structures hydrogen bonds are formed between the donor and acceptor groups with further stabilization deriving from van der Waals interactions between hydrophobic moieties.