Methyl acrylate reaction with iron carbonyl

Reactions between alkynes and transition metal compounds yield a surprising variety of products (76, 77), indicating nonspecific mechanisms of formation. At least for the reaction of alkynes with metal carbonyls any simple polar mechanism must be excluded, in view of the insensitivity of the reactions to the degree of polarity of the solvents. A radical mechanism would perhaps be better suited for a general description but this has so far been rejected, since inhibition of the reactions with f-butylphenol or hydroquinone proved unsuccessful (78). Likewise, iron carbonyls react with diphenylacetylene, using ethyl acrylate, vinyl methyl ketone or vinyl acetate as the solvent, without polymerization of the vinyl compounds (79). These experiments, however, do not fully eliminate the possibility of a radical mechanism. 

Irradiation of (methyl acrylate)iron tetracarbonyl in the presence of excess methyl acrylate at 20° forms a ferracyclopentane product. Thermal reaction of the metallocyclopentane with carbon monoxide or triphenyl-phosphine affords a cyclopentanone derivative (Grevels et al., 1974). Similar ferracyclopentane complexes may be involved as intermediates in the well-known cyclopentanone formation from iron carbonyls and strained olefins (for example, Grandjean et al., 1974 Mantzaris and Weissberger, 1974). 

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