Reductive coupling of CO with magnesium anthracene complexes: formation of magnesium enediolates

Two β-diketiminato-magnesium anthracene complexes, [{(ArNacnac)Mg}2(μ-C14H10)] (ArNacnac = [HC(MeCNAr)2]−, Ar = mesityl (Mes) or 2,6-diethylphenyl (Dep)) react with 1 atm. CO at room temperature to give tetra-magnesium enediolate complexes [{(ArNacnac)Mg}4(O2C16H10)2] via coupling of two molecules of CO with the anthracenediyl fragment. Similarly, reaction of magnesium anthracene, [Mg(THF)3(C14H10)], with CO afforded a low isolated yield of a tetra-magnesium complex bearing both dianthraceneylenediolate and dibenzocyclohepteneolateyl ligands. The presented reactions represent very rare examples of magnesium alkyl carbonylations that occur under mild conditions, and in the absence of catalysts.