Homocoupling of C1 Building Blocks by a Heterometallic Mg–Al Complex

A heterometallic magnesium–aluminium hydride complex is reported for the selective homologation of C1 building blocks (CO and CNXyl, Xyl = 2,6-dimethylphenyl) to form products containing C2 and C3 chains. CO reacts to form known deltate or ethynediolate motifs with different outcomes depending on the steric demands of the ligand on magnesium. In contrast, CNXyl reacts through a combination of carbon–carbon bond formation and hydride migration to form a novel metalated ethene diamidolate ligand [RN1C1=C2(H)N2R]3–. To our knowledge, this is the first example of such reactivity. DFT calculations support a mechanism in which carbon–carbon bonding is rate-limiting and occurs by the nucleophilic attack of a dimetallated imine intermediate on a coordinated isocyanide group followed by carbon–hydrogen bond formation through hydride migration from Al to C.