Sb-to-P Metathesis: A Direct Route to Structurally Constrained, Cationic P^III Compound

Structurally constrained, cationic P^III compound [LP][SbCl₄] with an OCO pincer-type ligand (L) having a central carbene donor was directly synthesized via an Sb-to-P metathesis reaction between PCl₃ and LSb-Cl. [LP][SbCl₄] was isolated and its reactivity with small molecules (ROH and RNH₂) was studied, showing that [SbCl₄]⁻ is not an innocent counter anion, but an active participant in these reactions. When the [SbCl₄]⁻ was replaced with the [CB₁₁H₁₂]⁻ ([Cb]⁻) anion, the reactions were redirected to [LP]⁺ cation only. The reactions with alcohols and amines led to the equilibrium between the products of the formal E−H (E=O, N) bond oxidative addition to the P-center and products of the P-center/ligand-assisted bond activation. Remarkably, [LP]⁺ activated the PhO−H and PhN(H)−H bonds in a reversible, thermoneutral fashion.