Syntheses, Crystal structures and magnetic properties the tetrahedral [FeX₄] ^- (X=Cl, Br) in the Os-based chelating diphosphine anticancer compounds

Compound 1, trans-[O-sII(dppe)(2)Cl-2], was obtained by refluxing Os-II(PPh3)(3)Cl-2 with dppe (dppe = bis (diphe-nylphosphino) ethane). Based on the oxidation potential of 1, Cp2FeIII(PF6) was chosen as oxidant for the preparation of its one-electron product, trans-[Os-III(dppe)Cl-2](PF6) (2, Cp = cyclopentadienyl anion). Com-pounds trans-[O-sIII(dppe)(2)Cl-2](FeIIIX4) (X = Cl, 3; X = Br, 4) were achieved in a straightforward way by reaction of compound 1 with FeX3 (X = Cl, Br), respectively. Compounds 1-4 were characterized by IR, electronic ab-sorption spectra and elemental analysis, respectively. Single-crystal X-ray diffraction studies indicate that the osmium atoms in compounds 1-4 all define a slightly distorted octahedron with a [OsP4Cl2] coordination core, and the iron atoms in anion FeX4 (-) of compounds 3 and 4 displays the expected tetrahedron with a [Fe1X4] co-ordination core. The electronic absorption spectra exhibit metal-to-ligand charge-transfer (MLCT) transitions in compound 1, and both MLCT and ligand-to-metal charge-transfer (LMCT) transitions in compounds 2-4. Also the magnetic properties of compounds 3 and 4 have been investigated. The relative cell viability of compounds 1-4 on HeLa cancer cells is in the order of 3>1>4 >2 by CCK-8 method. Compound 1 and 3 have better activity than that of cisplatin in higher concentration.