Synthesis and characterization of ruthenium(II) complexes of 2′-hydroxychalcones

Reaction of cis-RuCl2(DMSO)4 with the potassium salts of 2′-hydroxychalcones L leads to the stable complexes RuL2(DMSO)2. For each ligand L three isomers of each bis(dimethyl sulfoxide)bis(chalconato)ruthenium(II) complex were found; in two of them the two chalconates and the two DMSO ligands are equivalent, while in the third one the chalconates and DMSO ligands are inequivalent. Only two isomers of the RuL2(DMSO)2 complex were obtained by the reaction of cis-RuCl2(DMSO)4 with the potassium salt of the 2′-hydroxy-3,4,4′,5,6′-pentamethoxydihydrochalcone. One of these isomers was also obtained by the reduction of the appropriate bis(dimethyl sulfoxide)bis(chalconato)ruthenium(II) complex. All these complexes were fully characterized by extensive NMR studies, mass spectrometry and elemental analysis. The unequivocal stereochemistry of each RuL2(DMSO)2 complex was established by NOESY experiments.