High-Spin Superatom Stabilized by Dual Subshell Filling br

Quantum confinement in small symmetric clusters leads to thebunching of electronic states into closely packed shells, enabling the classificationof clusters with well-defined valences as superatoms. Like atoms, superatomicclusters withfilled shells exhibit enhanced electronic stability. Here, we show thatoctahedral transition-metal chalcogenide clusters can achievefilled shellelectronic configurations when they have 100 valence electrons in 50 orbitalsor 114 valence electrons in 57 orbitals. While these stable clusters are intrinsicallydiamagnetic, we use our understanding of their electronic structures totheoretically predict that a cluster with 107 valence electrons would uniquelycombine high stability and high-spin magnetic moment, attained byfilling amajority subshell of 57 electrons and a minority subshell of 50 electrons. Weexperimentally demonstrate this predicted stability, high-spin magnetic moment(S= 7/2), and fully delocalized electronic structure in a new cluster,[NEt4]5[Fe6S8(CN)6]. This work presents thefirst computational and experimental demonstration of the importance of dualsubshellfilling in transition-metal chalcogenide clusters.