The prominent charge-transfer effects of trinuclear complexes with nominally high nickel valences

Abstract

Abstract Recently synthesized Rh-Ni trinuclear complexes hexacoordinated with sulfur ions, 3-aminopropanethiolate (apt) metalloligand [Ni{Rh(apt)3}2](NO3) n (n = 2, 3, 4), are found to be chemically interconvertible between the nominal Ni2+ and Ni4+ states. In order to clarify the origins of their interconvertible nature and the stability of such a high oxidation state as the tetravalency from the physical point of view, we have systematically investigated the local 3d electronic structures of [Ni{Rh(apt)3}2](NO3) n by means of soft x-ray core-level absorption spectroscopy (XAS). The experimental data have been reproduced by the single-site configuration-interaction cluster-model simulations, which indicate that the charge-transferred configurations are more stable than the nominal d-electron-number configuration for n = 3, 4 leading to the prominent charge-transfer effects. These are also supported by S K-edge XAS of [Ni{Rh(apt)3}2](NO3) n . Our results imply that the found charge-transfer effects have a key role to realize the interconvertible nature as well as the stability of the high oxidization state of the Ni ions.