Frustrated Lewis Pair Stabilized Phosphoryl Nitride (NPO), a Monophosphorus Analogue of Nitrous Oxide (N₂O)

Abstract

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 (N3P­(O)A) that acts as a molecular synthon of NPO. Experimentally, N3P­(O)A dissociates thermally with a first-order kinetic half-life that is associated with an activation enthalpy of ΔH ⧧ = 27.5 ± 0.3 kcal mol–1 and an activation entropy of ΔS ⧧ = 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 N3P­(O)A undergoes Staudinger reactivity with tricyclohexylphosphine (PCy3) and subsequent complexation with tris­(pentafluorophenyl)­borane (B­(C6F5)3, BCF) to form Cy3P−NP­(A)­O–B­(C6F5)3. Anthracene is cleaved off photochemically to form the frustrated Lewis pair (FLP) stabilized NPO complex Cy3P⊕–NP–O–B⊖(C6F5)3. An intrinsic bond orbital (IBO) analysis suggests that the adduct is zwitterionic, with a positive and negative charge localized on the complexing Cy3P and BCF, respectively.

Phosphenic isocyanate (O2PNCO): gas-phase generation, characterization, and photodecomposition reactions

“…The photochemistry of O 2 PNCO including dissociation to CO, NO, and PO via the possible formation of two elusive phosphorus-containing small molecules O 2 PN and OPNO in the triplet ground state has been disclosed. The first time characterization of O 2 PNCO will stimulate further studies on its reactivity, as demonstrated by the very recently uncovered reactions for OPN 22 and HPO 2 . 15 Financial support of this work by the National Natural Science Foundation of China (22025301) is acknowledged.…”

“…Recently, it has been demonstrated that anthracene-based precursors can be used for generation of novel main-group multiply bonded small molecules such as phosphoryl nitride ( 5 ), 22 phosphaazide, 23 phosphorus sulfide, 24 and sulfur monoxide 25 through thermally initiated elimination of anthracene. Herein, we report the facile generation of the highly elusive phosphenic isocyanate O 2 PNCO ( d ) using a dioxaphospholane-based precursor C 2 H 4 O 2 PNCO ( a ) through thermal elimination of ethylene (Scheme 2).…”

“…The existence of OPN 3 has been proposed in the decomposition of anthracene-based phosphoryl azide. 22 The presence of PN implies an alternative decomposition pathway for O 2 PN (→ PN + O 2 ).…”

Curtius-Type Rearrangement of Sulfinyl Azides: A Matrix Isolation and Computational Study

“…Organic azides are useful reagents that have been widely used in synthesis chemistry, materials science, and biology. − Particularly, the rich chemistry of diverse α-oxo azides such as RC­(O)­N 3 , RS­(O) 2 N 3 , and R 2 P­(O)­N 3 has been extensively explored in the past few decades. − As one of the best known reactions in organic chemistry, the Curtius rearrangement refers to the decomposition of acyl azides RC­(O)­N 3 into isocyanates RNCO with simultaneous loss of molecular nitrogen upon either heat or irradiation (Scheme ). Despite being known for more than a century, the underlying reaction mechanism for the Curtius rearrangement of various carbonyl azides in the ground and also in the photolytically excited states keeps attracting interest. − Two pathways termed as concerted and stepwise routes have been proposed from both aspects of experiment and theory, and a number of the key nitrene intermediates (RC­(O)­N) displaying distinct structural and electronic properties in the stepwise route have been generated and characterized by using either ultrafast spectroscopy in solution , or matrix-isolation spectroscopy in cryogenic matrices. − However, most acylnitrenes are unstable and undergo facile 1,2-R shift in forming isocyanates during the thermal decomposition of the corresponding azides.…”

Staudinger Reactivity and Click Chemistry of Anthracene (A)-Based Azidophosphine N3PA

“…Inspired by Carpino’s hydrazine, the Cummins group developed in the past decade the synthesis of dibenzo-7λ 3 -phosphanorbornadiene derivatives, which serve as molecular precursors for the release of reactive phosphorus species. − In an initial study, Velian and Cummins demonstrated the direct reaction of Mg A ·3THF ( A = C 14 H 10 or anthracene; THF = tetrahydrofuran) with phosphorus dichlorides, RPCl 2 [R = tert -butyl ( t Bu), 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]­hepta-2,5-diene (dbabh), (Me 3 Si) 2 N (HMDS), i Pr 2 N], to afford 7λ 3 -phosphanorbornadiene (RP A ) derivatives . These RP A compounds served as starting materials for the synthesis of further A -based molecular precursors for the mild release of small phosphorus-bearing species, including diphosphorus (P 2 ) and HCP. − …”