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)3Ph2PCH2)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. Stability studies by Electrospray Mass Spectrometry, showed that other than solvolysis, the complexes are fairly stable in neutral and acidic methanol. Cytotoxicity testing of 7-10 and 12 showed that all the complexes are active against specific tumour cell lines