Frustrated Lewis Pair Stabilized Phosphoryl Nitride (NPO), a Monophosphorus Analogue of Nitrous Oxide (N 2 O).

Phosphoryl nitride (NPO) is a highly reactive intermediate, and its chemistry has only been explored under matrix isolation conditions so far. Here we report the synthesis of an anthracene ( A ) and phosphoryl azide based molecule (N 3 P(O) A ) that acts as a molecular synthon of NPO. Experimentally, N 3 P(O) A dissociates thermally with a first-order kinetic half-life that is associated with an activation enthalpy of Δ H ⧧ = 27.5 ± 0.3 kcal mol -1 and an activation entropy of Δ S ⧧ = 10.6 ± 0.3 cal mol -1 K -1 that are in good agreement with calculated DLPNO-CCSD(T)/cc-pVTZ//PBE0-D3(BJ)/cc-pVTZ energies. In solution N 3 P(O) A undergoes Staudinger reactivity with tricyclohexylphosphine (PCy 3 ) and subsequent complexation with tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 , BCF) to form Cy 3 P-NP( A )O-B(C 6 F 5 ) 3 . Anthracene is cleaved off photochemically to form the frustrated Lewis pair (FLP) stabilized NPO complex Cy 3 P ⊕ -N═P-O-B ⊖ (C 6 F 5 ) 3 . An intrinsic bond orbital (IBO) analysis suggests that the adduct is zwitterionic, with a positive and negative charge localized on the complexing Cy 3 P and BCF, respectively.