σ-Cyclopropyl to π-Allyl Rearrangement at AuIII

Abstract

The possibility for Au^III σ-cyclopropyl complexes to undergo ring-opening and give π-allyl complexes was interrogated. The transformation was first evidenced within (P,C)-cyclometalated complexes, it occurs within hours at -50 °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 °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 σ(CC) bond to give a π-bonded allyl moiety. Careful inspection of the structure and bonding of cationic σ-cyclopropyl complexes support the possible existence of C-C agostic interactions at Au^III .

Keywords: Agostic; Cyclopropyl; Gold; Rearrangement; π-Allyl.