N‐Heterocyclic Carbenes as Promotors for the Rearrangement of Phosphaketenes to Phosphaheteroallenes: A Case Study for OCP to OPC Constitutional Isomerism

Abstract

The concept of isomerism is essential to chemistry and allows defining molecules with an identical composition but different connectivity (bonds) between their atoms (constitutional isomers) and/or a different arrangement in space (stereoisomers). The reaction of phosphanyl ketenes, (NHP)-P=C=O (NHP=N-heterocyclic phosphenium) with N-heterocyclic carbenes (NHCs) leads to phosphaheteroallenes (NHP)-O-P=C=NHC in which the PCO unit has been isomerized to OPC. Based on the isolation of several intermediates and DFT calculations, a mechanism for this fundamental isomerisation process is proposed.

The Chemistry of the 2‐Phosphaethynolate Anion

“…[60] Primary products are zwitterionic compounds which could be isolated in some cases and which result from the nucleophilic attack of the carbenes on the carbon atom of the P=C=Ounit. [60] Primary products are zwitterionic compounds which could be isolated in some cases and which result from the nucleophilic attack of the carbenes on the carbon atom of the P=C=Ounit.…”

Synthesis and Reactivity of the Phosphorus Analogues of Cyclopentadienone, Tricyclopentanone, and Housene

“…Subsequently,t ransient 6 undergoes at ype I dyotropic rearrangement [26] to alleviate steric strain of the three neighboring tert-butyl groups providing 7 (DE = À23.5 kcal mol À1 , DE°= 30.4 kcal mol À1 ). [28] To access the P 1 -A,w et argeted the metal-mediated valence isomerization of phosphatricyclopentanone 7. [28] To access the P 1 -A,w et argeted the metal-mediated valence isomerization of phosphatricyclopentanone 7.…”

L3C3P3: Tricarbontriphosphide Tricyclic Radicals and Cations Stabilized by Cyclic (alkyl)(amino)carbenes

“…[4] Singlet N-heterocyclic carbenes (NHCs) [5] and cyclic diamidocarbenes (DACs) [6] may stabilize otherwise reactive molecules,a nd recently cyclic and acyclicC 2 P 2 skeletons as possible forms of "dicarbondiphosphide" could be isolated with these as substituents. [7] Herein we report the synthesis of neutral tricarbontriphosphide radicals (L 3 C 3 P 3 )C and their oxidation to the corresponding cations (L 3 C 3 P 3 )…”

“…Phosphaketenes such as 1 are easily prepared from chlorodiazaphospholenes and Na(OCP) [7] and are quantitatively rearranged to phosphaallenes L = C = P[PO(NDipp) 2 -(CH) 2 ]u pon reaction with diisopropylphenyl (Dipp)-substituted NHC or DACa sc arbene L. [7a, 8] These phosphaallenes cleanly react with KC 8 to give the anionic oxydiazaphospholene 3 and cyclic or acyclic dicarbondiphosphide compounds L 2 C 2 P 2 (L = NHC,D AC). [8] Carbene-bound CP radicals L=C=PC 4 may be formed as first intermediates.W ereasoned that with sterically less demanding carbenes higher oligomers of these radicals may be obtained.…”