Iminophosphonamido-Supported Plumbyliumylidenes: Structural Effects of Counter Anions and Lewis Acid Catalysis

Two-coordinate plumbyliumylidene ions constitute a rare class of highly electron-deficient cationic Pb(II) species. Herein, we report the synthesis and structural characterization of iminophosphonamido-supported plumbyliumylidene ions bearing two different borate counteranions, {B[(4-tBuMe₂Si)C₆F₄]₄}⁻ and [B(C₆F₅)₄]⁻. Single-crystal X-ray analyses reveal pronounced ion-pairing effects that depend on the counteranion, including secondary Pb···F interactions and solvent coordination, highlighting the high Lewis acidity of the lead center. The [B(C₆F₅)₄]⁻ salt exhibits versatile Lewis acid catalysis, enabling living ring-opening polymerization of ε-caprolactone and L-lactide to afford well-defined polymers and PCL-block-PLA copolymers. In addition, the same cationic Pb(II) species catalyzes the hydroamination of alkynes with distinct chemoselectivity, suppressing double hydroamination relative to three-coordinate analogues. These results establish two-coordinate plumbyliumylidenes as powerful and tunable main group Lewis acid catalysts.