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.
Graphical Abstract
Diiron hexacarbonyl complexes of cumulene ligand systems, [η1: η3 {RCHC2CR(COOMe)}] (1; E, R = Fc, 2; Z, R = Fc, 5; E, R = Ph, 6; Z, R = Ph) and [η3: η3-{RCHC2CR(COOMe)}] (3; E, R = Fc, 7; E, R = Ph) were obtained from photochemical reactions between Fe(CO)5, CO and methanol. Yield of the minor product, the diferrole, 4, was improved when the photoreaction was carried out in hexane in place of methanol