Metal-Free σ-Bond Metathesis in Ammonia Activation by a Diazadiphosphapentalene

Abstract

A diazadiphosphapentalene derivative 5 featuring a bent geometry with two phosphorus atoms at the bridgehead has been synthesized. Under mild conditions, compound 5 readily activated ammonia to afford 1-aza-2,3-diphospholene derivative 6 bearing an enamine group. The reaction is therefore viewed as a formal σ-bond metathesis between an N-H bond of ammonia and an endocyclic P-N bond of 5. Details of the reaction mechanism for ammonia activation as well as subsequent isomerization were explored by density functional theory calculations.

Sterically Constrained Bicyclic Phosphines: A Class of Fascinating Compounds Suitable for Application in Small Molecule Activation and Coordination Chemistry

“…Results of quantum chemical calculations confirm that in these compounds, the lone pairs of electrons at the phosphorus atoms are localized in orbitals with relatively high s‐character (approximately 65 % s‐character) . From these results, only weak nucleophilicity was derived in accordance with some experimental observations such as the inertness towards an attack of benzyl bromide .…”

“…The LUMO is delocalized but has important contributions from phosphorus orbitals, which should favor a nucleophilic attack of substrates at this position in accordance with experimental findings. The 31 P NMR resonances of these compounds appear at a low field with chemical shifts in a narrow range at δ =187.0 ( 1 a ), 185.0 ( 1 c ), 168.6 ( 2 ), 159.8 ( 3 a ), 151.7 ( 3 b ) and 173.2 ppm ( 4 ) . In accordance with the bonding of the phosphorus atoms to electronegative oxygen or nitrogen atoms, these 31 P NMR resonances are considerably shifted to a lower field compared to the PS 2 compounds 5 ( δ =62.8 to 65.7 ppm) and the PC 3 compound 6 [ δ ( 31 P)=68.8 ppm] .…”

“…Synthesis of the diphosphorus compound 4 is a more demanding four‐step process . It started with the sterically shielded imine Me 3 C−(Me)C=NAryl (Aryl=2,6‐ i Pr 2 C 6 H 3 ).…”

Digging the Sigma‐Hole of Organoantimony Lewis Acids by Oxidation

“…[1] Antimony derivatives,b ecause of their intrinsically higher Lewis acidity, [2] are also drawing considerable attention both in the areas of small-molecule activation and catalysis, [3] as well as in anion complexation. [1] Antimony derivatives,b ecause of their intrinsically higher Lewis acidity, [2] are also drawing considerable attention both in the areas of small-molecule activation and catalysis, [3] as well as in anion complexation.…”

E–H Bond Activation of Ammonia and Water by a Geometrically Constrained Phosphorus(III) Compound

“…[23,24] Furthermore, A can be used in conjunction with ammonia-borane to facilitate the catalytic reduction of azobenzene. [25] Related studies have since extended this approach to nonplanar phosphorus triamide (B)a nd diazadiphosphapentalene (C), [26,27] both of which activate E À Hb onds through al igand-assisted mechanism.…”