Probing CO Generation through Metal-Assisted Alcohol Dehydrogenation in Metal-2-(arylazo)phenol Complexes Using Isotopic Labeling (Metal = Ru, Ir): Synthesis, Characterization, and Cytotoxicity Studies.

The reaction of 2-{2-(benzo[1,3]dioxol-5-yl)- diazo}-4-methylphenol (HL) with [Ru(PPh)Cl] in ethanol resulted in the carbonylated ruthenium complex [RuL(PPh)(CO)] (), wherein metal-assisted decarbonylation via in situ ethanol dehydrogenation is observed. When the reaction was performed in acetonitrile, however, the complex [RuL(PPh)(CHCN)] () was obtained as the main product, probably by trapping of a common intermediate through coordination of CHCN to the Ru(II) center. The analogous reaction of HL with [Ir(PPh)Cl] in ethanol did not result in ethanol decarbonylation and instead gave the organoiridium hydride complex [IrL(PPh)(H)] (). Unambiguous evidence for the generation of CO via ruthenium-assisted ethanol oxidation is provided by the synthesis of the C-labeled complex, [Ru(PPh)L(CO)] () using isotopically labeled ethanol, CHCHOH. To summarize all the evidence, a ruthenium-assisted mechanistic pathway for the decarbonylation and generation of alkane via alcohol dehydrogenation is proposed. In addition, the in vitro antiproliferative activity of complexes - was tested against human cervical (HeLa) and human colorectal adenocarcinoma (HT-29) cell lines. Complexes - showed impressive cytotoxicity against both HeLa (half-maximal inhibitory concentration (IC) value of 3.84-4.22 μM) and HT-29 cancer cells (IC values between 3.3 and 4.5 μM). Moreover, the complexes were comparatively less toxic to noncancerous NIH-3T3 cells.