Mechanism of the Aryl-F Bond-Forming Step from Bi(V) Fluorides

In this article, we describe a combined experimental and theoretical mechanistic investigation of the C(sp(2))-F bond formation from neutral and cationic high-valent organobismuth(V) fluorides, featuring a dianionic bis-aryl sulfoximine ligand. An exhaustive assessment of the substitution pattern in the ligand, the sulfoximine, and the reactive aryl on neutral triarylbismuth(V) modeling of reductive elimination from neutral bismuth(V) difluorides agrees with the experimentally determined kinetic and thermodynamic parameters. Moreover, the addition of external fluoride sources leads to inactive octahedral anionic Bi(V) trifluoride salts, which decelerate reductive elimination. On the other hand, a parallel analysis for cationic bismuthonium fluorides revealed the crucial role of tetrafluoroborate anion as fluoride source. Both experimental and theoretical analyses conclude that C-F bond formation occurs through a low-energy five-membered transition-state pathway, where the F anion is delivered to a C(sp(2)) center, from a BF4 anion, reminiscent of the Balz-Schiemann reaction. The knowledge gathered throughout the investigation permitted a rational assessment of the key parameters of several ligands, identifying the simple sulfone-based ligand family as an improved system for the stoichiometric and catalytic fluorination of arylboronic acid derivatives.

Automated summary

This article presents a combined experimental and theoretical investigation of the C(sp(2))-F bond formation from neutral and cationic high-valent organobismuth(V) fluorides. The study reveals the impact of different ligands, sulfoximines, and reactive aryls on the kinetic and thermodynamic parameters of the reaction. The addition of external fluoride sources and the role of tetrafluoroborate anion are also explored. Both experimental and theoretical analyses demonstrate that C-F bond formation occurs through a low-energy five-membered transition-state pathway. The study provides a rational assessment of ligands and identifies a sulfone-based ligand family as an improved system for the fluorination of arylboronic acid derivatives.