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 [(L-Ph)(2)Ln(II){K(Et2O)}(2)] (Ln = Sm (2), Yb (3), L-Ph = [Ph2Si(NAr)(2)](2-) (Ar = 2, 6-(Pr2C6H3)-C-i)) with cation-pi interactions. The divalent samarium complex reacts with azobenzene and obtain rare dimeric samarium clusters [(L-Ph)(2)Sm-2(mu-eta(2):eta(2)-N2Ph2)(2){K(THF)(2)}(2)] (4) and tetrameric [(L-Ph)Sm-4(mu-eta(2):eta(2)-N2Ph2)(3)(mu(3)-NPh)(2)(THF)(3)] (5). On the other hand, the reaction of complex 2 and alpha-diimines ArN=CR-CR=NAr (DAD, R = H, Me) produce a polymeric [(L-Ph)Sm{(ArN)RC=CR(NAr)}K](n) (R = H (6), Me (7)) assembled from cation-pi interactions and a [{(L-Ph)(2)Sm}{K(THF)(6)}] byproduct (8). In particular, crystallographic analyses of 6 and 7 revealed that both complexes are sumarium(III) stabilized by the DAD dianionic units in a sigma(2)-enediamide manner. Complexes 2-8 have been fully characterized by elemental analyses and X-ray crystallography.