Lanthanide(II)−Alkali Sandwich Complexes with Cation−Arene π Interactions: Synthesis, Structure, and Solvent-Mediated Redox Transformations

We successfully prepared and characterized two novel sandwich complexes [(LPh)2LnII{K(Et2O)}2] (Ln = Sm (2), Yb (3), LPh = [Ph2Si(NAr)2]2− (Ar = 2, 6-Pri2C6H3)) with cation−π interactions. The divalent samarium complex reacts with azobenzene and obtain rare dimeric samarium clusters [(LPh)2Sm2(μ-η2:η2-N2Ph2)2{K(THF)2}2] (4) and tetrameric [(LPh)Sm4(μ−η2:η2-N2Ph2)3(μ3-NPh)2(THF)3] (5). On the other hand, the reaction of complex 2 and α-diimines ArNCR−CRNAr (DAD, R = H, Me) produce a polymeric [(LPh)Sm{(ArN)RCCR(NAr)}K]n (R = H (6), Me (7)) assembled from cation−π interactions and a [{(LPh)2Sm}{K(THF)6}] byproduct (8). In particular, crystallographic analyses of 6 and 7 revealed that both complexes are samarium(III) stabilized by the DAD dianionic units in a σ2-enediamide manner. Complexes 2−8 have been fully characterized by elemental analyses and X-ray crystallography.