Reaction of carbon monoxide with tri-tert-butylgallium: The first example of CO insertion into a gallium–carbon bond

Reactions of tBu3M (M = Al, Ga) with CO have been studied by density functional theory employing the B3PW91 functional. Calculations suggest that CO insertion into a M–C bond of tBu3M is thermodynamically favorable at room temperature, whereas CO coordination to tBu3M to form tBu3M·CO is unfavorable due to an unfavorable entropy change. These results are in agreement with experimental observations. Reaction of carbon monoxide with tBu3Ga at 50 °C and atmospheric pressure yields the dimeric tert-butylacyl complex [tBu2GaC(O)tBu]2 (1). Compound 1 has been characterized by X-ray crystallography and NMR and IR spectroscopy. Isotopic labeling with 13CO confirmed that the acyl carbon of 1 results from the CO starting material. CO insertion into a Ga–C bond does not occur for Me3Ga or nBu3Ga under a range of reaction conditions.