Cerium(III) Phosphinate and Cerium(IV) Phosphostibonate Acting as Catalysts for Mild, Selective Sulfoxidation

A Ce(III) phosphinate and a Ce(IV) phosphostibonate have been assembled by the reaction of a phosphinic acid and phosphostibonate with Ce(III) salts. Single crystal X-ray diffraction (SCXRD) studies reveal the formation of a rare triangular Ce(III) oxo-cluster [Ce^III₃(Ph₃CHPO₂)]₆Cl₃(CH₃OH)(H₂O)₈] (1) and a fascinating hexanuclear oxo-cluster containing Ce(IV) ions [Ce^IV₆ (p-ClC₆H₄Sb^V)₄(μ₄-O)₄(μ₃-O)₄(t-BuPO₃)₈(μ₂-OCH₃)₈] (2). The molecular architecture of 2 showcased an interesting correlation with platonic solids, wherein the Ce(IV), Sb(V), and P(V) ions were found to be present in vertices of an octahedron, a tetrahedron, and a cube, respectively. Under mild conditions, 1 and 2 exhibited the capability to act as catalysts for sulfoxidation in the presence of hydrogen peroxide, with 1 acting as a homogeneous catalyst and 2 acting as a heterogeneous catalyst. Both 1 and 2 showed high conversion for various substrates, with 1 showing moderate selectivity while 2 showcased high selectivity. Moreover 1 and 2 catalyzed the oxidation of 2-chloroethyl ethyl sulfide (CEES) to nontoxic 2-chloroethyl ethyl sulfoxide (CEESO) with high selectivity.