Al+ Activates Acetone to Form Pinacolate

The interaction between aluminum cations and acetoneis studiedin the gas phase via photodissociation vibrational spectroscopy from1100 to 2000 cm(-1). Spectra of Al+(acetone)(N-2) and ions with the stoichiometry of Al+(acetone)( n ) (n = 2-5) were measured.The experimental results are compared to DFT calculated vibrationalspectra to determine the structures of the complexes. The spectrashow a red shift of the C=O stretch and a blue shift of the CCC stretch,which decrease as the size of the clusters increases. The calculationspredict that the most stable isomer for n & GE;3 is a pinacolate, in which oxidation of the Al+ enablesreductive C-C coupling between two acetone ligands. Experimentally,pinacolate formation is observed for n = 5, as evidencedby a new peak observed at 1185 cm(-1) characteristicof the pinacolate C-O stretch.

Automated summary

The interaction between aluminum cations and acetone in the gas phase was studied using photodissociation vibrational spectroscopy. The spectra of Al+(acetone)(N-2) and Al+(acetone)( n ) (n = 2-5) ions were measured and compared to DFT calculated vibrational spectra to determine the structures of the complexes. The experiments showed red shift of the C=O stretch and blue shift of the CCC stretch, which decreased as the size of the clusters increased. The calculations predicted that the most stable isomer for n ≥ 3 was pinacolate, where oxidation of Al+ enabled reductive C-C coupling between two acetone ligands. Experimentally, pinacolate formation was observed for n = 5, as evidenced by a new peak at 1185 cm(-1) characteristic of the pinacolate C-O stretch.