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Palladium and Platinum Phosphine Bio-conjugates

Transition metal complexes that incorporate amino acids or short peptides have been extensively studied with focus on structural diversity of the complexes or selectivity towards metal ions. Despite the vast literature work with almost all transition metals up to now, the crystal structures of oligopeptide complexes are scarce, probably due to the high flexibility and many coordination modes of peptide molecules. In expanding our research on Rh bioconjugates to other transition metals, herein, we report novel Pd(II) and Pt(II) complexes with triphenylphosphine ligands bearing different amino acids. Structure of the complexes was studied in detail by means of spectroscopic methods and X-ray crystallography. NMR measurements in chloroform indicate predominant formation of cis and trans isomers for Pt and Pd complexes, respectively. Upon changing the solvent to acetonitrile, a significant increase in cis isomer is observed for Pd. Only trans Pd bioconjugates were found in the crystal structures of Gly and Phe derivatives.

oligopeptide complexes ; crystal structure ; NMR

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