Nucleophilic substitution reactions of [(η5-Cp*)Ru(η6-C6H5CO2H)]+: Synthesis, characterization and cytotoxicity of organoruthenium ester and amide complexes

•Efficient synthesis of a labile organoruthenium cyclopentadienyl carboxylic acid.•Organoruthenium carboxylic acid reactivity studied under nucleophilic conditions.•Study yielded conversion of carboxylic acid to a range of esters and amides.•[(η5-Cp*)Ru]+ group enhanced reactivity of carbonyl carbon towards nucleophiles.•Complexes display in vitro cytotoxic activity towards tumour cells.

This article outlines the synthesis of an electrophilic organoruthenium carboxylic acid of the structure [(η5-Cp*)Ru(η6-C6H5CO2H)]+ and explores the behavior of this molecule under a variety of nucleophilic substitution conditions using a range of oxygen and nitrogen based nucleophiles including alcohols, primary and secondary amines and aromatic sulfonamides. The resulting organoruthenium ester [(η5-Cp*)Ru(η6-C6H5COOR)]+ and amide [(η5-Cp*)Ru(η6-C6H5CONHR)]+ or [(η5-Cp*)Ru(η6-C6H5CONR)]+ complexes are additionally reported. All prepared complexes have been fully characterized using Fourier-transform IR and NMR spectroscopy and electrospray mass spectrometry with single-crystal X-ray structural determinations reported for three complexes: 3[(η5-Cp*)Ru(η6-C6H5CO2H)]B(C6H5)4.[(η5-Cp*)Ru(η6-C6H5CO2)].H2O, [(η5-Cp*)Ru(η6-C6H5CONHCH2Ph)]PF6 and [(η5-Cp*)Ru(η6-C6H5CONHSO2C6H4COMe)]PF6. Complexes were also evaluated for in vitro cytotoxic activity against the MCF7 (hormone-dependant breast cancer), MDA-MD-231 (hormone-independent breast cancer), MM96L (human melanoma) tumourigenic cell lines and the normal NFF (neonatal foreskin fibroblasts) human cell line.

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