Synthesis and Structure of an Iron-Doped Copper Selenide Cluster Molecule: [Cu30Fe2Se6(SePh)24(dppm)4]

CuCl and bis(diphenylphosphanyl)methane (dppm) react in the presence of small amounts of FeCl3 with PhSeSiMe3 and Se(SiMe3)(2) to yield [Cu30Fe2Se6(SePh)(24)(dppm)(4)]. The crystal structure of the compound was determined by single-crystal X-ray analysis to give a mixed copper selenide/selenolate cluster molecule of a new structural type incorporating two central iron atoms. The formal oxidation state of the iron atoms was determined by Mossbauer spectroscopy to be +3, in agreement with quantum chemical calculations and modeling of the magnetic data. In addition, Mossbauer studies show no magnetic hyperfine structure in zero field, and the magnetically perturbed spectrum displays a pattern typical for a diamagnetic species in a transverse field, suggesting a singlet ground state. However, the inclusion of the iron atoms has a distinct influence on the optical properties of the compound compared to similar clusters containing only copper and selenium atoms.