Addition of phenylacetylene to a magnesium complex of monoiminoacenaphtheneone (dpp-mian)

In the presence of formic acid, acenaphthenequinone (AQ) reacts with one molar equivalent of 2,6-diisopropylaniline in toluene to give monoiminoacenaphtheneone (3, dpp-mian) in good yield. Reduction of compound 3 with an excess of magnesium in thf results in green crystalline amido-alcoholate [(dpp-mian)Mg(thf)2]2 (4). Crystallization of complex 4 from toluene affords a blue tetramer [(dpp-mian)Mg(thf)]4 (5). Reactions of compounds 4 and 5 with phenylacetylene proceed with C-C bond formation between the alkyne and the dpp-mian ligand to give the monomeric alkynyl-magnesium derivative [(dpp-mian)(PhC=CH2)Mg(C≡CPh)2(thf)]2 (7). Hydrolysis of complex 5 gives metal-free dpp-mian(PhC=CH2)H (8). Reaction of 7 with acetylacetone yields [{dpp-mian(PhC=CH2)}Mg(acac)]2 (9). Compounds 3-5 and 7-9 have been characterized by IR and NMR spectroscopy; molecular structures of 3, 5, 7, 8 and 9 have been determined by single crystal X-ray analysis.