Phosphanylidenephosphoranes

Abstract

Phosphanylidenephosphoranes of the general formula RP(PR′ 3 ) have emerged as a powerful tool in synthetic inorganic chemistry and have found applications in the formation of phosphaalkenes using the so‐called phospha‐Wittig reaction, as well as valuable phosphinidene‐transfer reagents. In addition, the electron‐rich dicoordinate phosphanylidene P‐atom can be utilized in reactions with electrophiles and in the activation of EH bonds. Theoretical investigations clearly show that these species are best described as ylidic phosphanylidene‐σ 4 ‐phosphoranes with a negatively charged electron‐rich divalent P‐atom bearing two lone pairs of electrons (LP), of which the p‐type LP is delocalized into symmetry‐adapted σ*‐orbitals of the PR′ 3 unit. The PR′ 3 unit has been reported to be readily displaced by stronger nucleophiles in an associative manner, which is akin to classical S N 2‐substitution reactions. This article outlines the synthetic developments in the chemistry of phosphanylidenephosphoranes, provides an overview about the bonding situation, and clearly shows the synthetic versatility of these systems.

Atypical “Masked” Frustrated Lewis Pair Character in a Geminal‐Linked Phosphine‐Borane

“…All hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: P1À C1 1.8982 (10), C1À P2 1.9021 (10), P2À Cl1 2.0685(4); P1À C1À P2 112.95 (5). [14] with thermal ellipsoids plotted at 50 % probability.…”

“…[7][8][9] However, we found that the scope of phosphinidene transfer was quite limited by the high thermal and photolytic stability of the PB-phosphinidene adducts. [9,10] As a result, we sought to modify the FLP chelate bite angle to facilitate the release of main group fragments for productive materials synthesis. Our first efforts in this regard involved preparing FLP ligands with increased bite angles as compared to PB, but these proved to be much less reactive due to a strong intramolecular PÀ B bonding in their uncomplexed forms.…”

On the Reactivity of Mes*P(PMe3) towards Aluminum(I) Compounds – Evidence for the Intermediate Formation of Phosphaalumenes

“…[2] Base-stabilized acyclic boraphosphenes have been studied in detail, [3] and NHCstabilized phosphaborenes with small silyl-substituents (B, Figure 1) have been described, that can engage in metathesis reactions through Me 3 Si-halide elimination. [3d] Our group has used phosphanylidenephosphoranes of the type ArP(PMe 3 ) (Ar = sterically demanding aryl group), [4] so-called phospha-Wittig reagents, [5] as phosphinidene transfer reagents, by substitution of PMe 3 with stronger Lewis bases. [6] The reaction of Ar TerP(PMe 3 ) (Ar=Dip (C), Tip (D) 2,4,6-iPr 3 -C 6 H 2 ; Ar Ter = 2,6-Ar 2 -C 6 H 3 , Figure 1) with (Cp*Al) 4 (Cp* = C 5 (CH 3 ) 5 ) afforded the first examples of phosphaalumenes Ar TerP=AlCp*, as violet compounds with a highly polarized PÀ Al multiple bond.…”

Triphosphiranes as phosphinidene-transfer agents – synthesis of regular and chelating NHC phosphinidene adducts

“…4,5 The presence of N-atoms adjacent to the PvC double bond results in an accumulation of π-electron density at the terminal dicoordinate phosphorus atom, akin to isovalence electronic N-heterocyclic olefins (NHOs), 6,7 N-heterocyclic imines (NHIs) 8 and phosphanylidenephosphoranes. 9 Bertrand and co-workers developed a scale based on the 31 P NMR shift of a series of PhPvNHC derivatives to quantify the π-accepting properties of the NHC bonded to phosphorus. PhPvNHC can be conveniently accessed by the treatment of PhPCl 2 with the respective NHC and subsequent reduction with Mg metal.…”