Effect of the Ancillary Ligand on the Mechanism for CO Migratory Insertion in High-Valent Oxorhenium Complexes

Several oxorhenium
complexes bearing an SSS pincer ligand were
isolated and characterized, and their reactivity with carbon monoxide
was explored. The corresponding oxorhenium­(V) acyl derivatives were
also isolated and characterized. Carbonylation reactions required
high pressures (400 psi) and temperatures (50 °C). The mechanism
for carbonylation was explored with DFT (M06) calculations and revealed
that the most likely mechanism for carbonylation involved stepwise
formation of CO adducts followed by migration of the carbonyl ligand
to the alkyl/aryl groups.