Addition of organometallic radicals to organic substrates. Reaction between manganese decacarbonyl and α-dicarbonyl compounds

Some o-quinones and 1,2-diketones were allowed to react with manganese pentacarbonyl radicals generated in situ and the resulting persistent paramagnetic adducts studied by ESR spectroscopy. The evolution of carbon monoxide during the reaction together with the symmetrical distribution of the spin density in the organic framework (as implied by the spectral data) indicated chelation of a Mn(CO)₄ moiety by the two oxygens of the dicarbonyl substrates.One or more carbon monoxide groups can be replaced by compounds containing nitrogen, phosphorus, arsenic or antimony as binding sites. A conjugative transfer of spin density is proposed for the last three classes of substituents, while a σ mechanism is probably involved in the case of nitrogen-containing ligands.