Tricarbonylrhenium(I) complexes of phosphine-derivatized amines, amino acids and a model peptide: structures, solution behavior and cytotoxicity

Modified Mannich reactions of amines, amino acids and a model peptide with Ph2PH and CH2O gave bis(diphenylphosphinomethyl)amines (Ph2PCH2)2NR [R=Ph (1), CH2CH2OH (2), CH2COOCH2Ph (3), CH2CONHCH2COOCH2Ph (4), CH2COOH (5)] and (Ph2PCH2)2NCH2CH2N(CH2PPh2)2 (6). Reaction with [ReBr3(CO)3]2− under mild conditions led to [ReBr(CO)3]{(Ph2PCH2)2NR} [R=Ph (7), CH2CH2OH (8), CH2COOCH2Ph (9), CH2CONHCH2COOCH2Ph (10), CH2COOH (11)] and [ReBr(CO)3(Ph2PCH2)2NCH2]2 (12). All new complexes have been characterized by NMR and IR spectroscopy and for 7, 9 and 10, single-crystal X-ray diffraction analyses. Electrospray mass spectrometric studies show that the rhenium–phosphine chelates are very stable, especially in neutral methanolic solution. Hydrolysis of the ester and amide linkages slowly occur in acidic and basic solutions over several weeks; displacement of the bromide ligand also occurs in basic medium. Cytotoxicity testing of 7–10 and 12 showed that all the complexes are active against specific tumor cell lines, especially MCF-7 breast cancer and HeLa-S3 suspended uterine carcinoma.