Ligand-Enabled Oxidative Fluorination of Gold(I) and Light-Induced Aryl-F Coupling at Gold(III).

MeDalphos Au(I) complexes featuring aryl, alkynyl, and alkyl groups readily react with electrophilic fluorinating reagents such as -fluorobenzenesulfonimide and Selectfluor. The ensuing [(MeDalphos)Au(R)F] complexes have been isolated and characterized by multinuclear NMR spectroscopy as well as X-ray diffraction. They adopt a square-planar contra-thermodynamic structure, with F to N.

σ-Cyclopropyl to π-Allyl Rearrangement at Au.

The possibility for Au 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.

Carbene Radicals in Transition-Metal-Catalyzed Reactions.

Discovered as organometallic curiosities in the 1970s, carbene radicals have become a staple in modern-day homogeneous catalysis. Carbene radicals exhibit nucleophilic radical-type reactivity orthogonal to classical electrophilic diamagnetic Fischer carbenes. Their successful catalytic application has led to the synthesis of a myriad of carbo- and heterocycles, ranging from simple cyclopropanes to more challenging eight-membered rings.

Combining ligand-enhanced backdonation and steric shielding to stabilize a mono-substituted Au(I) carbene.

A mono-substituted Au(I) carbene was prepared by reacting HC(N)(Dmp) (Dmp = 2,6-dimesitylphenyl) with an (-carboranyl)-diphosphine AuNTf complex. It is stable up to -10 °C and was characterized by NMR spectrocopy. According to DFT calculations, the chelating P^P ligand enhances Au → C backdonation, while the Dmp substituent provides kinetic stabilization but does not bias the electronic structure of the carbene complex.

Gold(I) α-Trifluoromethyl Carbenes: Synthesis, Characterization and Reactivity Studies.

Aryl trifluoromethyl diazomethanes 2-R (R=Ph, OMe, CF ) are readily decomposed by the (o-carboranyl)diphosphine gold(I) complex 1. The resulting α-CF substituted carbene complexes 3-R have been characterized by multi-nuclear NMR spectroscopy as well as X-ray crystallography (for 3-Ph). The bonding situation was thoroughly assessed by computational means, showing stabilization of the electrophilic carbene center by π-donation from the aryl substituent and backdonation from Au, as enhanced by the chelating P^P ligand.