Synthesis, structure, and applications of pyridiniophosphines.

A new family of cationic ligands, N-alkyl/aryl pyridiniophosphines, has been synthesized through a short, scalable, and highly modular route. Evaluation of their electronic properties evidenced weak σ-donor and quite strong π-acceptor character when used as ancillary ligands. These attributes confer a substantially enhanced π-acidity to the Pt(II) and Au(I) complexes thereof derived and, as result, they depict an improved ability to activate alkynes towards nucleophilic attack. This superior performance has been demonstrated along several mechanistically diverse Pt(II)- and Au(I)-catalyzed transformations.