Two-coordinate magnesium(I) dimers stabilized by super bulky amido ligands

A variety of very bulky amido magnesium iodide complexes, LMgI(solvent)_0/1 and [LMg(μ-I)(solvent)_0/1]₂ (L=-N(Ar)(SiR₃); Ar=C₆H₂{C(H)Ph₂}₂R′-2,6,4; R=Me, Prⁱ, Ph, or OBu^t; R′=Prⁱ or Me) have been prepared by three synthetic routes. Structurally characterized examples of these materials include the first unsolvated amido magnesium halide complexes, such as [LMg(μ-I)]2 (R=Me, R′=Prⁱ). Reductions of several such complexes with KC₈ in the absence of coordinating solvents have afforded the first two-coordinate magnesium(I) dimers, LMg−MgL (R=Me, Prⁱ or Ph; R′=Prⁱ, or Me), in low to good yields. Reductions of two of the precursor complexes in the presence of THF have given the related THF adduct complexes, L(THF)Mg−Mg(THF)L (R=Me; R′=Prⁱ) and LMg−Mg(THF)L (R=Prⁱ; R′=Me) in trace yields. The X-ray crystal structures of all magnesium(I) complexes were obtained. DFT calculations on the unsolvated examples reveal their Mg−Mg bonds to be covalent and of high s-character, while Ph⋅⋅⋅Mg bonding interactions in the compounds were found to be weak at best.