New polydentate sulfide ligands: Synthesis, redox properties, and molecular structure of 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione

Abstract

The reaction of p-toluenethiol with 4,5-dichloro-4-cyclopenten-1,3-dione in 1,2-dichloroethane with added DBU affords good yields of the new bidentate sulfide ligand 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione. The title compound was isolated by column chromatography and characterized in solution by IR and NMR spectroscopies. The solid-state structure of RC=CRC(O)CH₂C(O) (where R = p-tolylthio) was solved by X-ray crystallography. 4,5-Bis(p-tolylthio)-4-cyclopenten-1,3-dione crystallizes in the monoclinic space group P2 ₁/c, a = 14.203(3) Å, b = 6.181(1) Å, c = 20.372(4) Å, β = 106.111(3)°, V = 1718.1(6) ų, Z = 4, and d _calc = 1.316 mg/m³; R = 0.0743, R _w = 0.1693 for 3958 reflections with I > 2σ(I). The redox properties of 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione have been examined by cyclic voltammetry in CH₂Cl₂ solution, where a quasireversible reduction wave at −1.10 V was found. The reduction behavior is discussed relative to the nature of the LUMO level, which has been determined by extended Hückel MO calculations. The redox chemistry and the LUMO of our bidentate sulfide ligand are contrasted with the known redox chemistry and the LUMO composition of the corresponding bidentate phosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd).