Multiple K-edge XAS for the structural analysis of thiophenolate bridged heterotrinuclear complexes

A multiple K-edge X-ray absorption spectroscopic (XAS) approach to determine the structural parameters of an isostructural series of heterotrinuclear thiophenolate-bridged metal-complexes of the general formula [LFeCrFeL]n+ (with n= 1,2,3) is presented. The analysis focuses on the variation of the metal-metal distances and the metal-sulfur distances with the cluster charge n. XAS measurements on the Fe, Cr, and S-K-edges were performed to allow a fit of these distances from these constituent elements. Results show that 3 S atoms and 3 N atoms coordinate each of the terminal Fe atoms, whereas 6 S atoms coordinate the central Cr atom. This symmetry allows extracting structural information with high accuracy especially when the spectra obtained at different edges are refined at the same time. A decrease of the metal-metal distance with increasing cluster charge is also derived from this multiple-edge analysis.