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The article explains the mechanisms of the iridium mediated isomerization of pyridine to form its 2-carbene tautomer.

A study describes the transformation of 2-substituted pyridines into the respective carbene tautomers in an iridium mediated process that involves formally a 1,2-H shift from carbon to nitrogen. The increased bulkiness of the 2-substituted pyridines destabilizes the N-adduct by F-strain, while the isomeric carbene structures do not suffer from this kind of steric repulsion.

Thereaction of dinuclear complex [IrCl(COD)]2(COD =1,5-cyclooctadiene) with 1 equiv of 1,3-dimesitylpropane-1,3-dione(H-AcacBiMs) and an excessof triethylamine in benzene or dichloromethane at room temperatureresults in the formation of β-diketonate complex [Ir(AcacBiMs)(COD)], 1. Further, compound 1reacts with an equivalentof H-AcacBiMsin dichloromethaneunder atmospheric conditions to give the new complex with the formula[cis-Ir(AcacBiMs)2(COE-OH)], 2(COE-OH = σ,π-hydroxyenediyl),through a formal insertion of a hydroxyl group into a COD ring. Allcompounds were characterized by melting point, analytical data, andIR and NMR spectroscopy. Additionally, an X-ray crystallographic studywas undertaken to corroborate the structure of both complexes. [ABSTRACT FROM AUTHOR]

Gallium (Ga) ion-doped TiO 2 (Ga-TiO 2 ) nanocomposite with small particle size (9-10 nm) and high surface area (104 m 2 /g) has been easily synthesized via sol-gel method at low temperature by using low-valent GaI as a doping precursor. The structural and morphological characterization of Ga-TiO 2 was carried out with standard analytical and spectroscopic techniques. Ga doping into the TiO 2 matrix inhibited a phase transformation from anatase to rutile (photocatalytically inactive) form, even at a higher temperature of 750 °C. Finally, Ga-TiO 2 nanocomposite showed high photocatalytic activity and exhibited 97% degradation of acid violet 63 dye within 60 min. The dye degradation rate constant was calculated as 1.6 × 10 -1 and 1.4 × 10 -1 min -1 under UV and white light irradiation, respectively, which is higher, as compared to the previously reported Ga-TiO 2 composites to date.