ESR study on the reactions of iron carbonyls with nitro and nitrosoparaffines. A mechanism of the reductive carbonylation of nitro compounds

Abstract

The interaction of Fe n (CO) m , ( n and m equal 1 and 5, 2 and 9, 3 and 12, respectively) with 2-methyl-2-nitrosopropane and sodium salts of nitromethane and nitrocyclohexane was studied. The initial stages of the process, following the activating complex-formation, involves redox disproportionation to give rise to the radical Fe(I) carbonyl complexes and radical anions Fe 2(CO) 8 − . ( I) Fe 3(CO) 11 − . ( II), Fe 4(CO) 13 − . ( III) and Fe 3(CO) 12 − . ( IV). Also, radical anions I– IV are formed in the interaction of salts of carbonyl ferrate anions Na 2Fe(CO) 4·1.5 diox and PPN 2[Fe n (CO) m−1 ] (where PPN = (PPh 3) 2N +), with nitro- and nitroso-tert-butane. Radical anions I– III act as catalytically active species in the coordination sphere of which the nitro compounds undergo a successive deoxygenation to nitrene radical complexes with their subsequent carbonylation to isocyanates. A scheme of the reductive carbonylation is proposed.