Superatomic Stabilization of Dinuclear Platinum(III) through Iodide-Bridged Five-Center Ten-Electron Bonding

Abstract

One of the goals in synthetic chemistry is to obtain compounds featuring unusual valence states that are stable under ambient conditions. At present, stabilizing unusual Pt(III) states is considered difficult, except through direct Pt–Pt bonding such as that in platinum-blues or organometallization using bulky ligands. Pt(III) stabilization is also very difficult in halogen-bridged metal complex chains (MX-Chains). Herein, the iodide-bridged Pt(III) dimer compound [Pt₂(en)₄I₃]I₃ (en = ethylenediamine), which is prepared by the iodine oxidation of [Pt^II(en)₂]I₂, has been successfully synthesized and characterized. This compound is stable and is obtained as diamond-shaped single crystals with a lustrous emerald-green color under reflected light and a red color under transmitted light. The Pt(III) state is stabilized by the five-center ten-electron (5c-10e) bonding in the I–Pt–I–Pt–I core, in addition to the very strong antiferromagnetic state. The stabilization mechanism of Pt(III) through a 5c-10e bonding is considered a superatom complex; thus, this work provides new insight for stabilizing the unusual Pt(III) state.