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

This
study details the formal hydrogenation of two magnesium­(I)
dimers {(Nacnac)­Mg}2 (Nacnac = [{(C6H3R2-2,6)­NCMe}2CH]−; R = Pri (DipNacnac), Et (DepNacnac)) 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, (DipNacnac)­Mg­{κ1-O-[(DipNacnac)­Mg­(κ2-O,O-O2C2H2)]}, and the first
cyclopropanetriolate complex of any metal, cis-{(DepNacnac)­Mg}3{μ-C3(H3)­O3}. 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/H2 mixtures to value added oxygenate products.