Reactivity of TpMe2Ir(C2H4)(DMAD) with carboxylic acids. A DFT study on geometrical isomers and structural characterization

The thermally unstable adduct TpMe2Ir(C2H4)(DMAD), which was generated in situ by the reaction of DMAD with TpMe2Ir(C2H4)2 (1) at low temperature, reacted with different carboxylic acids to produce the following compounds: TpMe2Ir(E-C(CO2Me)CH(CO2Me))(H2O)(OC(O)C6H4R), (R = H, 2a; o-OH, 2b; o-Cl, 2c; m-Cl, 2d; o-NO2, 2e; m-NO2, 2f;o-Me, 2g;p-Me, 2h) and TpMe2Ir(E-C(CO2Me)CH(CO2Me))(H2O)(OC(O)Me) 3. In the reaction of derivative 2a with Lewis bases, TpMe2Ir(E-C(CO2Me)CH(CO2Me))(L)(OC(O)C6H5), (L = Py, 4a; m-BrPy, 4b; m-ClPy, 4c; NCMe, 5) were obtained, of which 4b and 4c were isolated as a mixture of two isomers in which the substituted pyridine ring was present at different rotational orientations. All new compounds prepared were characterized by 1H and 13C{1H} NMR spectroscopy, the structure of compounds 2d, 2h and 4a being determined by X-ray diffraction analysis. DFT was used to analyze the relative stability and the structural orientation of the isomers.