Preparation of Pyridine(Diimine) Bismuth Cations and Demonstration of Versatile Lewis Acid Activity

Herein we describe the preparation of a library of cationic bismuth(III) pyridine(diimine) compounds and the assessment of their Lewis acidity measured by their interaction with phosphine oxides, acid halides, ketones, and C-based silyl nucleophiles. These bismuth compounds have acceptor number values ranging between BiCl3 and AlCl3, however their catalytic reactivity for the formation of C-C bonds is distinct from these simple salts. Our studies suggest that Friedel-Crafts-type arene acylation is promoted via acid halide coordination, whereas nucleophilic ketone addition reactions are promoted via silyl nucleophile coordination. This work demonstrates that bismuth(III) pyridine(diimine) cations serve as selective and versatile Lewis acids for the activation of diverse donors to achieve C-C bond formation.