Phosphinoamido ligand supported heterobimetallic rare-earth metal–palladium complexes: versatile structures and redox reactivities

Abstract

Heterobimetallic Ln(III)–Pd(0) complexes (Ln = Y, Sm, Gd, Yb) featuring tetranuclear structures with COD as bridges were obtained via the metallation of tris(phosphinoamido) rare-earth metal complexes [Ph₂PNAd]₃Ln (Ad = adamantyl) with (COD)Pd(CH₂SiMe₃)₂. Notably, the Sc(III)–Pd(0) complex possesses a C₃-symmetry with a very short Sc–Pd bond length of 2.432(2) Å, while the tetranuclear complexes exhibited versatile structures both in solution and in the solid state. Reduction of the trivalent complex (Ph₂PNAd)₃Yb with one equivalent of KC₈ in the presence of 18-c-6 afforded the divalent complex [(Ph₂PNAd)₃Yb][(18-c-6)K(THF)₂], which was further reacted with (Ph₃P)₄Pd to form the first Yb(II)–Pd(0) complex. The Pd(0) → Yb dative interaction weakened significantly from Yb(III) to Yb(II) based on computational studies, which was attributed to the attenuated Lewis acidity of the Yb(II) center. Reactions of Ln(III)–Pd(0) complexes (Ln = Sc and Yb) with the disulfide PhSSPh showed that the Pd(0) center served as a two-electron donor while the reaction apparently occurred on the Ln(III) centers to form Ln(III)–Pd(0) bis-sulfide complexes.