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

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 [Ph 2 PNAd] 3 Ln (Ad = adamantyl) with (COD)Pd(CH 2 SiMe 3 ) 2 . Notably, the Sc(III)-Pd(0) complex possesses a C 3 -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 (Ph 2 PNAd) 3 Yb with one equivalent of KC 8 in the presence of 18-c-6 afforded the divalent complex [(Ph 2 PNAd) 3 Yb][(18-c-6)K(THF) 2 ], which was further reacted with (Ph 3 P) 4 Pd 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.