Sodium and Magnesium Complexes with Dianionic α-Diimine Ligands

A series of sodium and magnesium complexes with α-diimine ligands, [Na₂(L^iPr)(Et₂O)]₂ (1, L^iPr = [(2,6-ⁱPr₂C₆H₃)N(Me)C]₂), [Na₂(L^Mes)(solv)₂]₂ (L^Mes = [(2,4,6-Me₃C₆H₃)N(Me)C]₂, 2a, solv = Et₂O; 2b, solv = THF), [Na₄(L^Et)₂]_n (3, L^Et = [(2,6-Et₂C₆H₃)N(Me)C]₂), and [Mg(L^Mes)(THF)₃] (4), have been synthesized by reduction of the diimine ligands with sodium or magnesium metal. Single-crystal X-ray diffraction analysis revealed that the sodium complexes have a 2:1 [Na₂L] unit that aggregates to dimeric (1, 2a, 2b) or polymeric (3) structures, while the magnesium complex (4) shows a monomeric 1:1 structure. In all compounds 1−4, the ligand is doubly reduced to a dianion. The two Na⁺ ions in 1, 2a, 2b, and 3 show different coordination modes, one of which is chelated by the N donors of a ligand with supplementary Na−C bonds to the phenyl ring of another ligand within the [Na₂L]₂ dimer, while the other is bonded by the central C₂N₂ core of the ligand and solvent molecules (1, 2a, and 2b). Compound 3 displays a novel three-dimensional network. The Mg²⁺ ion in 4 is coordinated by a ligand molecule and three THF molecules. Density functional theory (DFT) computations on the sodium and magnesium complexes 1 and 4 confirmed their electronic structures and the dianionic character of the ligands.