Activation of CO by Hydrogenated Magnesium(Ⅰ) Dimers: Sterically Controlled Formation of Ethenediolate and Cyclopropanetriolate Complexes

摘要

This study details the formal hydrogenation of two magnesium(Ⅰ) dimers {(Nacnac)Mg}_2 (Nacnac = [{(C_6H_3R_2-2,6)NCMe}_2CH]~-; R = Pr~i (~(Dip)Nacnac), Et (~(Dep)Nacnac)) using 1,3-cyclohexadiene. These reactions afford the magnesium(Ⅱ) hydride complexes, {(Nacnac)-Mg(μ-H)}_2. Their reactions with excess CO are sterically controlled and lead cleanly to different C-C coupled products, viz. the ethenediolate complex, (~(Dip)Nacnac)Mg-{κ~1-0-[(~(Dip)Nacnac)Mg(κ~2-O,O-O_2C_2H_2)]}, and the first cyclopropanetriolate complex of any metal, cis-{(~(Dep)Nacnac)Mg}_3{μ-C_3(H_3)O_3}. Computational studies imply the CO activation processes proceed via very similar mechanisms to those previously reported for related reactions involving f-block metal hydride compounds. This work highlights the potential magnesium compounds hold for use in the "Fischer-Tropsch-like" transformation of CO/H_2 mixtures to value added oxygenate products.