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

Abstract

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)(PhCCH₂)Mg(CCPh)₂(thf)]₂ (7). Hydrolysis of complex 5 gives metal-free dpp-mian(PhCCH₂)H (8). Reaction of 7 with acetylacetone yields [{dpp-mian(PhCCH₂)}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.