Synthesis and characterization of disubstituted arylcyanoximes and their several metal complexes

A series of new disubstituted halogenated arylcyanoximes was synthesized using nitrosation reaction of the respective phenylacetonitriles by CH3–ONO at room temperature in isopropanol. Six synthesized colorless arylcyanoximes containing two F and/or Cl atoms at 2-, 4-, 5- and 6-positions were characterized by means of NMR, IR, UV–Vis spectroscopy and pKa studies. Crystal structures were determined for four cyanoximes and revealed the presence of only the syn-isomers for fluorinated compounds in a solid state, while the chlorinated arylcyanoxime exists as anti-isomer in the crystal. However, five out of the six protonated arylcyanoximes HL exist as a mixture of syn- and anti-isomers in solutions. Deprotonation of HL with NaOC2H5 in ether solutions leads to yellow NaL which were used as precursors for the synthesis of a series of monovalent Ag, Tl and bivalent Pd, Pt complexes. Seven palladium and platinum arylcyanoximates of [M(HL)2Cl2] composition were synthesized and characterized. Obtained colored compounds are non-electrolytes in solution. However, in EtOH and DMSO solutions Pt(II) cyanoximates undergo two consecutive solvolysis reactions. First order rate constants were measured at 294 K for complexes in both solvents. Binding modes of the cyanoxime ligands and the possible solid state structures of the obtained coordination compounds are suggested on a basis of their IR spectra and MM-2 calculations. Because of their structural resemblance to the cisplatin family of anticancer drugs, synthesized Pd/Pt arylcyanoximates were tested in vitro against human colon carcinoma WiDr cell line using cis-[Pt(NH3)2Cl2] as positive control. Results showed that two Pd(II) and Pt(II) cyanoximates containing oximino(2,4-dichlorophenyl)acetonitrile exhibit cytotoxicity at 0.25 mM concentrations.