The Prominent Charge-Transfer Effects of Trinuclear Complexes with Nominally High Nickel Valences

Abstract

Recently synthesized Rh-Ni trinuclear complexes hexacoordinated with sulfur ions, 3-aminopropanethiolate (apt) metalloligand [Ni{Rh(apt)${}_3$}${}_2$](NO${}_3$)${}_n$ ($n$ = 2, 3, 4), are found to be chemically interconvertible between the nominal Ni${}^{2+}$ and Ni${}^{4+}$ 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 3$d$ electronic structures of [Ni{Rh(apt)${}_3$}${}_2$](NO${}_3$)${}_n$ 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)${}_3$}${}_2$](NO${}_3$)${}_n$. 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.

arXiv comment16 pages, 4 figures

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