Two-Coordinate Magnesium(I) Dimers Stabilized by Super Bulky Amido Ligands

摘要

A variety of very bulky amido magnesium iodide complexes, LMgI(solvent)(0/1) and [LMg(mu-I)(solvent)(0/1)](2) (L=-N(Ar)(SiR3); Ar= C6H2{C(H)Ph-2}(2)R'-2,6,4; R= Me, Pr-i, Ph, or OBut; R'= Pr-i 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(mu-I)](2) (R= Me, R'= Pr-i). 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, Pr-i or Ph; R'= Pr-i, 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'= Pr-i) and LMg-Mg(THF) L (R= Pr-i; 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 center dot center dot center dot Mg bonding interactions in the compounds were found to be weak at best.