A Phosphorus‐Based Pacman Dication Generated by Cooperative Self‐Activation of a Pacman Phosphane

Abstract

Formal coordination of phosphorus(III) by a calix[4]pyrrole Schiff base ligand was achieved through the reaction of this ligand with PCl 3 under basic conditions. The reaction product adopts a Pacman conformation with two PÀ Cl moieties, one in exo and one in endo position. It represents the first non-metal compound of calix[4]pyrrole Schiff base ligands and of Pacman ligands in general. The spatial neighborhood of the two phosphorus atoms enables cooperative reactions. As a first example, the chloride abstraction with AgOTf is presented, yielding a macrocyclic dication with two embedded phosphorus(III) monocations, which both undergo a cooperative, internal activation reaction with an adjacent C=N double bond. This intramolecular redox process affords two pentacoordinated phosphorus(V) centers within the Pacman dication. All reaction products were fully characterized and all results are supported by computations.

On the Dynamic Behavior of Pacman Phosphanes─A Case of Cooperativity and Redox Isomerism

“…26 By analogy with 2Cl, these are explained by small donor−acceptor interactions of the lone pairs of the imine nitrogen atoms and the antibonding σ*-orbitals of the opposite P−N bonds, including the pyrrole nitrogen atoms (Table S11). 16 In the single crystals of the isomeric mixture of 2F (Figure 1), two dichloromethane molecules are located inside the pocket of the Pacman ligand, widening the cavity and elongating the P•••P-distance by approx. 0.18 Å (4.835(6) Å compared to 4.653(3) Å in pure endo−exo-2F).…”

“…Nevertheless, the broad linewidth of the signals already hints toward an ongoing dynamic process. As previously reported, heating of an NMR sample of 2Cl to 100 °C leads to the formation of only one broad set of signals (Figure b) . Thus, an acceleration of the dynamic process at higher temperatures results in the loss of the information about the orientation of the two P–Cl bonds, which indicates a formal inversion on the phosphorus centers as shown in Scheme .…”

“…The fifth bonding partner is the remaining imine nitrogen atom in the same molecule half. Although this contact (d(P1−N2) = 1.895(2) Å) cannot be interpreted as a typical covalent bond, 16 the short distance proves a strong interaction. The bromide ions do not interact with the phosphorus atoms, and the closest contact is hydrogen atom H8 with a distance of 26 Iodine.…”

A cyclic thioketone as biradical heterocyclopentane-1,3-diyl: synthesis, structure and activation chemistry

“…[1][2][3][4] The diphosphadiazanediyl, [(μ-NR)P • ] 2 (R = Ter = 2,6-dimesitylphenyl, 1), 5 is a fourmembered heterocycle with a significant biradical character (25%) and is known to readily activate small molecules with single and multiple bonds (Scheme 1). [6][7][8][9][10] Here, the activation of molecules with a triple bond, e.g. CO or isonitrile R′-NC (R′ = tbutyl, diisopropylphenyl), proved to be particularly interesting, 11,12 since in the first step the activation leads to a 1,1-or 1,2-bridged species (2R vs. 4X; X = O, NR′; R, R′ = aryl, alkyl), which further reacts under insertion into the four-mem-bered P 2 N 2 ring of 1 (Scheme 1).…”

Coinage metal complexes of multidentate Pacman phosphane ligands

“…Recently, our group was able to introduce phosphorus( iii ) into a Pacman ligand, which may be regarded as the first non-metal Pacman complex (Chart 1, middle). 9 In this case, a phosphorus–chlorine unit is located in each half of the molecule. One chlorine substituent is directed into the cavity of the molecule and the other points outwards, forming the endo-exo isomer exclusively.…”