Strong Cytotoxicity of Organometallic Platinum Complexes with Alkynyl Ligands

The synthesis, spectroscopy, structures,
and chemical reactivity
of the organometallic complexes [(COD)­Pt­(CCR)2]
and [(COD)­Pt­(CCR)­(R′)] (COD = 1,5-cyclooctadiene, R
= Ph, (Me)­Ph (2Me, 3Me, or 4Me), (NO2)­Ph (2NO2, 3NO2, or 4NO2), (4F)­Ph, (4OMe)­Ph, 2Py (2-pyridyl);
R′ = Me (methyl), Neop (neopentyl = 2,2-dimethyl-1-methyl),
NeoSi (neosilyl = trimethylsilylmethyl), Bz (benzyl)) has been explored.
The crystal structures reveal square-planar surroundings of the Pt
atoms with short Pt–C­(alkynyl) bonds (<2 Å) and almost
perpendicular orientation of the CC–aryl group to the
Pt coordination plane. Nonattractive π–π stacking
and C–H···F intermolecular interactions were
observed in the crystal structures. Multinuclear (1H, 13C, 195Pt, and 19F) NMR spectroscopy
reveals structures in solution and Pt–ligand bond strength.
The thermal stability in organic solvents, the electrochemical stability,
and the reactivity of the complexes in organic or aquatic (water-containing)
solution toward the physiologically relevant species glutathione,
chloride, and protons was tested, revealing remarkable stability or
inertness of the complexes. Cytotoxicity experiments in HT-29 colon
carcinoma and MCF-7 breast adenocarcinoma cell lines revealed highly
promising activities for selected platinum alkynyl COD complexes.