Concurrent Stabilization of π‐Donor and π‐Acceptor Ligands in Aromatized and Dearomatized Pincer [(PNN)Re(CO)(O)₂] Complexes

Abstract

Complexes 1 and 2 are prepared from the reaction of 4 and 3, respectively, with CO or isocyanides. Single-crystal X-ray structures of 1 a and 1 b show the expected trans-dioxo structure, in which the oxo ligands occupy the axial positions and the p-acidic ligand occupies the equatorial plane in an overall octahedral geometry about the rhenium(V) center. DFT studies revealed the stability of complexes 1 and 2 arises from a p-backbonding interaction between the d xy orbital of rhenium, the p orbital of the oxo ligands, and the p* orbital of CO/ isocyanide.