Combined 1H NMR and DFT study of the solvent effects on the iron pentacarbonyl‐catalyzed photo‐assisted isomerization of allyl alcohol

The relative rates of iron pentacarbonyl-catalyzed photo-induced isomerization of allyl alcohol to propanal in various solvents have been measured using 1H NMR spectroscopy. The reactions were run in linear and cyclic alkanes, alcohols, and amines in order to investigate solvent effects on the isomerization mechanism upon ultraviolet irradiation. The isomerization was efficient in nonane, hexane, cyclohexane, and benzene. The isomerization was very slow or completely suppressed in ethanol, propanol, isopropanol, triethylamine, and pyridine. Density functional theory calculations predicted thermodynamically favorable (ΔGo   0) formation in the hydrocarbon solvents. The strong solvent ligation likely prevents formation of Fe(CO)3●(η2-alkene) necessary for isomerization. Copyright © 2013 John Wiley & Sons, Ltd.