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Here in, we report a rollover iridacycle complex cis-[Ir(κ2-C–N-L1)(κ2-N–N-L1)Cl2], which can be easily obtained as yellow solid, through the reaction of two equivalents of new 2-(6-bromopyridin-2-yl)imidazo[1,2-a]pyridine (L1) type ligand and IrCl3 in dimethylformamide at 70 °C for a week. Rollover complex have an unusual κ2-C–N-cyclometallated ligand fragment, which involves the C–H bond activation reaction in remote position on bromo-pyridine, with a second one in classic κ2-N–N-donor mode. The structure of both compounds was studied by NMR, IR, and high-resolution mass spectrometry. Rollover complex UV/Vis absorption spectrum showed a dominating π–π* absorption band at 350 nm. Excitation at 385 nm gave a narrow emission band with maximum at 541 nm, which was associated to ligand-centred emission. The ligand shows antiproliferative activities against breast cancer lines. Density Functional Theory (DFT) calculations suggest that the rollover C–H bond activation occurs after a first κ2-N–N coordination during the complexation of the second ligand and is supported by DMF molecules. [ABSTRACT FROM AUTHOR]

The article discusses the study about the rearrangement of pyridine to 2-carbene tautomer mediated by iridium through nuclear magnetic resonance (NMR). Findings reveal that the activation is identical to the rate of bond cleavage control and N-heterocyclic complex. It indicates that the reaction allows the isomerization of pyridine through activation chemistry bound with chelate structure.

The article reports on the transformation of 2-substituted pyridines into carbene tautomers in an iridium mediated process that involves a 1,2-H shift from carbon to nitrogen. It offers an overview of the synthesis and characterization of copmplexes 2-4 and an analysis of the crystallographic data for 2-Me and 2-Ph.