Time-resolved infrared absorption spectroscopy is used to investigate the kinetics of the linkage
isomerization reaction M(CO)5(η1-L) → M(CO)5(η2-L), where M = Cr, Mo, or W, and L = 2-methyl-2,3-dihydrofuran or 2,3-dihydropyran. Photolysis of M(CO)6 in cyclohexane in the presence of excess L
produces the η1 (O-bound) isomer as the sole kinetic product. The kinetic product subsequently reacts
intramolecularly to form an equilibrium mixture of the η1 and η2 (CC bound) isomers. Activation and
equilibrium parameters are derived for the reactions and compared with previous results for linkage
isomerization of the M(CO)5(dihydrofuran) complexes. The results of the experimental study, supported
by DFT calculations, indicate that for M = W the kinetics of the η1 → η2 isomerization depend primarily
on how close the double bond is to the metal atom in the η1 isomer, while the thermodynamics of the
η1 ⇄ η2 equilibrium are determined primarily by electronic factors. In contrast, for M = Cr and Mo,
both steric and electronic factors play a role in the isomerization kinetics.