Solution and Mechanochemical Reactions of a Diphosphene with Elemental Sulfur

The bulky Eind-substituted diphosphene, (Eind)P═P(Eind) (1a), reacted with an excess of elemental sulfur (S8) in solution at elevated temperatures to produce an isolable monomeric P(V) species, dithioxophosphorane, (Eind)P(═S)2 (4a), along with cleavage of the P═P double bond (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl). A three-membered P2S ring compound with formally P(II) centers, thiadiphosphirane, (Eind)P(S)P(Eind) (2a), was isolated as an intermediate in this solution-phase reaction. In contrast, mechanochemical treatment of 1a with S8 by ball milling under solid-state conditions afforded a P(I)/P(III) mixed-valent diphosphorus species, diphosphene sulfide, (Eind)(S═)P═P(Eind) (3a), which gradually isomerized to 2a at room temperature. The sulfurized products 2a, 3a, and 4a were characterized by 31P NMR spectroscopy, and the molecular structures of 2a and 4a were confirmed by single-crystal X-ray diffraction (SC-XRD) analysis. The structural and electronic properties of these sulfurized products were further investigated using density functional theory (DFT) calculations.