The First Example of a μ₂-Imido Functionality Bound to a Lanthanide Metal Center: X-ray Crystal Structure and DFT Study of [(μ-ArN)Sm(μ-NHAr)(μ-Me)AlMe₂]₂ (Ar = 2,6-ⁱPr₂C₆H₃)¹

Abstract

Reaction of 3 equiv of 2,6-diisopropylaniline with Sm[N(SiMe3)2]3 affords the dimeric species [Sm(NHAr)3]2 (1). X-ray crystallography illustrates that each metal center in 1 engages in an η6-arene interaction with the aryl ring of an amide ligand attached to an adjacent samarium. IR spectroscopy indicates that the π-arene interactions are maintained in solution. Reaction of 1 with 4 equiv of trimethylaluminum leads to formation of the bis(μ2-imido) complex [(μ-ArN)Sm(μ-NHAr)(μ-Me)AlMe2]2 (2). The molecular structure of 2 contains a unique central Sm2N2 core which displays extremely short bridging Sm−N distances of 2.152(8) and 2.271(7) Å, characteristic of an imido complex. Density functional theory (DFT) calculations have been carried out in order to gain a better understanding of the nature of the bonding interactions within complex 2 and indicate that the 5d metal acceptor orbitals play a significant role in stabilizing π-donation from the imido groups to the samarium centers within the Sm2N2 core.