Reactivity of [Rh(β-diketonato)(cod)] complexes: A DFT approach

The density functional theory calculated energies of the highest molecular orbital of [Rh(R′COCHCOR)(cod)] relate to the electrochemical oxidation potential of rhodium(I) to rhodium(III) in [Rh(R′COCHCOR)(cod)] complexes. They also relate to the experimental second order substitution rate constant of the [Rh(R′COCHCOR)(cod)] + phen → [Rh(phen)(cod)]+ + (R′COCHCOR)− reaction. The results are in close agreement with the electron-donating and -withdrawing properties of the side groups R and R′ on the β-diketonato ligand (RCOCHCOR′)− as described by the Gordy scale group electronegativities, Hammett meta substituent constants, Lever electronic parameters and the pKa of the free β-diketone.