σ-Cyclopropyl to π-Allyl Rearrangement at AuIII

The possibility for Au-III sigma-cyclopropyl complexes to undergo ring-opening and give p-allyl complexes was interrogated. The transformation was first evidenced within (P,C)-cyclometalated complexes, it occurs within hours at -50 degrees C. It was then generalized to other ancillary ligands. With (N,C)-cyclometalated complexes, the rearrangement occurs at room temperature while it proceeds already at -80 degrees C with a dicationic (P,N)-chelated complex. Density Functional Theory (DFT) calculations shed light on the mechanism of the transformation, a disrotatory electrocyclic ring-opening. Intrinsic Bond Orbital (IBO) analysis along the reaction profile shows the cleavage of the distal sigma(CC) bond to give a pi-bonded allyl moiety. Careful inspection of the structure and bonding of cationic sigma-cyclopropyl complexes support the possible existence of C-C agostic interactions at Au-III.