Characterisation and mechanistic study of the oxidative addition reactions of [Ir(cod)(sacac)]

• Rate of oxidative addition showed little or no change with a solvent variation.
• ΔV# for different solvents ranging between +10.2(9) and −18(1) cm3 mol−1.
• Kirkwood equation obeyed with an intrinsic volume of activation of −21(3) cm3.
• DFT analysis confirmed that trans addition product is energetically more stable.

[Ir(cod)(sacac)] (sacac = thioacetyl acetonato) complexes were successfully synthesized and characterised using 1H and 13C NMR, IR and micro elemental analyses. The formation of isosbestic points in different solvents clearly indicate the formation of only one product, while the kinetic results for all of the complexes (except for chlorobenzene) showed simple second order kinetics with a zero intercept (within experimental error). The rate of oxidative addition showed little or no change with a solvent variation even with a large difference in polarity for the selected solvents, varying between 1.78 × 10−3 and 5.2(3) M−1 s−1 for chlorobenzene and acetonitrile respectively. Activation volumes were determined in four of the solvents, which varied between +10.2(9) for chloroform to −18(1) cm3 mol−1 for acetonitrile. This solvent variation obeyed the Kirkwood equation with an intrinsic volume of activation of −21(3) cm3. A DFT analysis of the oxidative addition reaction shows that the trans addition is energetically favoured and that the trans [Ir(cod) (sacac) (CH3) (I)]-alkyl product is more stable than the four possible cis [Ir(cod) (sacac) (CH3) (I)]-alkyl products.

Figure optionsDownload as PowerPoint slide