Varying the Lewis Base Coordination of the Y₂N₂ Core in the Reduced Dinitrogen Complexes {[(Me₃Si)₂N]₂(L)Y}₂(μ-η²:η²-N₂) (L = Benzonitrile, Pyridines, Triphenylphosphine Oxide, and Trimethylamine <i>N</i>-Oxide)

The effect of the neutral donor ligand, L, on the Ln₂N₂ core in the (NN)^2– complexes, [A₂(L)­Ln]₂(μ-η²:η²-N₂) (Ln = Sc, Y, lanthanide; A = monoanion; L = neutral ligand), is unknown since all of the crystallographically characterized examples were obtained with L = tetrahydrofuran (THF). To explore variation in L, displacement reactions between {[(Me₃Si)₂N]₂(THF)­Y}₂(μ-η²:η²-N₂), <b>1</b>, and benzonitrile, pyridine (py), 4-dimethylaminopyridine (DMAP), triphenylphosphine oxide, and trimethylamine <i>N</i>-oxide were investigated. THF is displaced by all of these ligands to form {[(Me₃Si)₂N]₂(L)­Y}₂(μ-η²:η²-N₂) complexes (L = PhCN, <b>2</b>; py, <b>3</b>; DMAP, <b>4</b>; Ph₃PO, <b>5</b>; Me₃NO, <b>6</b>) that were fully characterized by analytical, spectroscopic, density functional theory, and X-ray crystallographic methods. The crystal structures of the Y₂N₂ cores in <b>2</b>–<b>5</b> are similar to that in <b>1</b> with N<i>–</i>N bond distances between 1.255(3) Å and 1.274(3) Å, but X-ray analysis of the N<i>–</i>N distance in <b>6</b> shows it to be shorter: 1.198(3) Å