Selective [3+1] Fragmentations of P₄ by “P” Transfer from a Lewis Acid Stabilized [RP₄]⁻ Butterfly Anion

Abstract

Two [3+1] fragmentations of the Lewis acid stabilized bicyclo[1.1.0]tetraphosphabutanide Li[Mes*P ⋅ BPh ] (Mes*=2,4,6-tBu C H ) are reported. The reactions proceed by extrusion of a P fragment, induced by either an imidazolium salt or phenylisocyanate, with release of the transient triphosphirene Mes*P , which was isolated as a dimer and trapped by 1,3-cyclohexadiene as a Diels-Alder adduct. DFT quantum chemical computations were used to delineate the reaction mechanisms. These unprecedented pathways grant access to both P - and P -containing organophosphorus compounds in two simple steps from white phosphorus.

Metalate‐Mediated Functionalization of P4 by Trapping Anionic [Cp*Fe(CO)2(η1‐P4)]− with Lewis Acids

“…The 11 B{ 1 H} NMR spectrum revealed two signals at 27.3 and −8.4 ppm, attributed to the amine–borane adduct Me 3 N⋅BPh 3 in equilibrium with its constituents and Li[BPh 4 ]. The phosphanes decompose within 24 h, owing to a lack of steric protection, which is common for neutral bicyclic tetraphosphanes bearing “small” substituents ,…”

“…The selective protonation at the wing‐tip P atoms of the complexed P 4 anions 1 a and 1 b confirms their P‐nucleophilic character and provides a simple route to hitherto scarce non‐symmetrical neutral TM‐complexed P 4 derivatives. The reactivity is analogous to the organyl‐substituted congeners and should, therefore, be extendable to alkylations and possibly [3+1] fragmentations, on which we reported recently . The present report lies the foundation for the isolation of new TM‐mediated P 4 ‐functionalized products.…”

N‐Heterocyclic Carbene–Phosphinidene Adducts: Synthesis, Properties, and Applications

“…Soon after, Lammertsma, Slootweg, and co‐workers have demonstrated that 6· PH can also be prepared from white phosphorus in two controllable steps. First, P 4 was functionalized with the bulky Mes*Li (Mes* = 2,4,6‐ t Bu 3 C 6 H 2 ) and BPh 3 to give the borane‐stabilized bicyclo[1.1.0]tetraphosphabutane anion Mes*P 4 – , which through selective [3+1] fragmentation using imidazolium chloride [ 6 ‐H][Cl] afforded 6· PH, while the P 3 ‐unit was trapped with 1,3‐cyclohexadiene (Scheme ) …”

Functionalization of P4 through Direct P−C Bond Formation

“…In these cases the anionic [RP 4 ] − core transfers to the stronger Lewis acids to give the doubly coordinated anions 8 a and b , respectively (Scheme ) . Intriguingly, the high reactivity of 4 c also grants access to OPCs containing P 1 and P 3 entities through unprecedented [3+1]‐fragmentation reactions using either phenylisocyanate or imidazolium chloride in the presence of an access of the P 3 ‐trapping reagent 1,3‐cyclohexadiene (1,3‐CHD; Scheme ) . The reactions proceed through “P” transfer from the LA‐stabilized butterfly anions to the reagents to give spiro‐phosphoranide 9 and carbene–phosphinidene adduct 11 , respectively, with concurrent trapping of the liberated diphosphene Mes*P 3 by the organic diene that generates in both cases organotriphosphirane 10 .…”