Fundamental electron-transfer and proton-coupled electron-transfer properties of Ru(iv)-oxo complexes.

Isolation and characterisation of Ru(O) complexes were accomplished to investigate their fundamental electron transfer (ET) and proton-coupled ET (PCET) properties. Reorganisation energies (λ) in electron transfer (ET) and proton-coupled ET (PCET) from electron donors to the isolated Ru(O) complexes have been determined for the first time to be in the range of 1.70-1.88 eV (ET) and 1.20-1.26 eV (PCET). It was suggested that the reduction of the λ values of PCET in comparison with those of ET should be due to the smaller structural change in PCET than that in ET on the basis of DFT calculations on 1 and 1e-reduced 1 in the absence and presence of TFA, respectively. In addition, the smaller λ values for the Ru(O) complexes than those reported for Fe(O) and Mn(O) complexes should be due to the lack of participation of d orbitals in the ET and PCET reactions. This is the first example to evaluate fundamental ET and PCET properties of Ru(O) complexes leading to further understanding of their reactivity in oxidation reactions.