Chemistry of Tetrasulfur Including Mysterious Rectangular S4 Metal Complexes

Abstract Of eleven possible isomers for neutral S4, rectangular S4 has been proposed theoretically as one of the most stable forms. There has, however, been no consensus as to the S4 ground-state geometric structure despite much effort over recent years, because of the lack of direct structural information from experimental work due to lack of preparation in a pure state. The principal question is whether the ground-state geometry is rectangular D2h or open planar C2v. Our group found first rectangular S4 in coordination compounds of Rh and Ir tetranuclear complexes as a ligand and disclosed mysterious rectangular S4 by X-ray analysis and theoretical studies. Here, the newly developed chemistry of rectangular S4 complexes together with the related tetrasulfur species is introduced both from experimental and theoretical view points. In addition, more accurate argument of the principal question mentioned above is also described using results obtained from recent high-level theoretical calculations.