Reversible Insertion of CO into an Aluminium–Carbon Bond

While reversible main-group mediated processes involving H2 and alkenes have been reported and studied for over a decade, no such reversible processes involving CO have been reported. In this paper, we show that a [2.2.1] aluminium metallobicycle is capable of reversibly inserting CO to form a [2.2.2] metallobicycle at 100 °C. Eyring analysis allowed determination of the Gibbs activation energy of the back-reaction, CO elimination reaction with G‡298K = 26.6 ±3.0 kcal mol-1. Computational studies reveal a highly asynchronous, but concerted, transition state for CO insertion. The coordination of CO to aluminium precedes C–C bond formation. The reversible migratory insertion reaction mimics that known for transition-metal and marks an important step forward for main group systems.