Iron pentacarbonyl promoted addition of CO and MeOH to 1,4-disubstituted-1,3-butadiyne and formation of vinylallyl and butatriene ligand systems

Photochemical reaction of methanol solution containing 1,4-diferrocenyl- or 1,4-diphenyl-1,3-butadiynes and iron pentacarbonyl into which CO was constantly bubbled, yielded diiron hexacarbonyl complexes of cumulene ligand systems, [η1: η3-{RCHC2CR(COOMe)}Fe2(CO)6] (1; E, R = Fc, 2; Z, R = Fc, 5; E, R = Ph, 6; Z, R = Ph) and [η3: η3-{RCHC2CR(COOMe)}Fe2(CO)6] (3; E, R = Fc, 7; E, R = Ph), formed by 1,4-addition of -COOMe and -H to the butadiynes. Additionally, diferrole, [Fe(CO)4{C(O)CC(Fc)C(O)}2],4 was obtained in minor quantity. Compounds 1, 2, 5 and 6 contain vinylallyl carbon framework which is stabilized by MeOC=O → Fe bond along with η1: η3 coordinated Fe2(CO)6 unit. Compounds 3 and 7 contain butatriene units which are stabilized by η3: η3 coordinated Fe2(CO)6 unit. Characterization of the new compounds was carried out by IR and 1H and 13C NMR spectroscopy and by mass spectrometry. Molecular structures of 2-7 were established by single crystal X-ray diffraction methods