Supramolecular Structures of Cyclotriphosphazenes

Steiner, Alexander

doi:10.1002/9780470478882.ch20

Cited by 7 publications

(10 citation statements)

References 97 publications

(72 reference statements)

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“…In particular, Cl 6 P 3 N 3 1 has served as an important starting compound for numerous cyclotriphosphazene derivatives. Its six-membered ring offers a rigid platform for multifunctional molecular arrangements, including multisite ligands for metal complexes, coordination polymers, supramolecular building blocks, core moieties for dendrimers, oligopeptide, and multiporphyrin assemblies, as well as molecular components for inclusion compounds, mesophases, and micelles …”

Section: Introductionmentioning

confidence: 99%

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Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO₂}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)₂O} of These Heterocycles

2010

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Cyclotriphosphazenes have been functionalized with various oxo-groups at one of the ring phosphorus atoms. Starting from geminal dichlorides (A) which are equipped with amino groups at the other two phosphorus atoms {(Z 0 2 P) 2 N 3 PCl 2 (Z 0 = NHCy) and (Z 00 P) 2 N 3 PCl 2 (Z 00 = {EtN(C 3 H 6 )NEt}), respectively}, phosphate (B), pyrophosphate (C), phosphamide (D), and phosphite (E) derivatives have been prepared. The zwitterionic phosphate (Z 0 2 P) 2 N 3 H 2 PO 2 B is obtained via the 4-dimethylamino pyridine (dmap)-catalyzed hydrolysis of A in a biphasic mixture of aqueous KOH and tetrahydrofuran (thf). B contains a PO 2 moiety neighboring two protonated ring nitrogen sites. It crystallizes as the tetrahydrate (Z 0 2 P) 2 N 3 H 2 PO 2 3 4H 2 O, which consists of a double helix: A helical chain of hydrogen bonded zwitterions is intertwined with a helical chain of water molecules. The reaction of A with only dmap in CHCl 3 produces the dication [(Z 0 2 P) 2 N 3 P(dmap) 2 ] 2þ , which binds two dmap ligands at one phosphorus atom. The tetrahydrate dehydrates at 160 °C in vacuo under formation of the pyrophosphate {(Z 0 2 P) 2 N 3 HPO} 2 O C, which contains a OdP-O-PdO residue linking the two phosphazene rings. When heated in a mixture of aqueous KOH, primary amine, and thf, A undergoes a concurrent aminolysis-hydrolysis reaction, which gives the phosphamide (Z 2 P) 2 N 3 HP(O)NHR D featuring a P(=O)NHR residue. The corresponding reaction of A with R,R 0 -diamino-p-xylene in a 2:1 ratio leads to the formation of {(Z 0 2 P) 2 N 3 HP(O)NHCH 2 } 2 C 6 H 4 , in which two phosphamide moieties are linked by a xylylene bridge. Phosphites E containing PHO moieties are obtained via reduction of the dichloride with potassium and subsequent treatment with KOH. The product consists of a hexameric potassium complex, which features a central K 6 O 6 double cube arrangement and contains the anionic ligand [(Z 00 P) 2 N 3 PHO]that offers two bidentate N-P-O coordination sites. Addition of NH 4 Cl yields the neutral phosphite (Z 00 P) 2 N 3 HPHO. The title compounds are amphiphilic featuring hydrophilic NH and PO x moieties and hydrophobic alkyl groups. In addition, they show amphiprotic behavior via protonation/deprotonation at ring N atoms.

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Section: Introductionmentioning

confidence: 99%

“…24) Bickley, J. F.; Bonar-Law, R.; Lawson, G. T.; Richards, P. I.; Rivals, F.;Steiner, A.; Zacchini, S. Dalton Trans. 2003, 1235-1244 (25) (a)Richards, P. I.; Benson, M. A.; Steiner, A. Chem.…”

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Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO₂}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)₂O} of These Heterocycles

2010

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“…Cyclotriphosphazenes, Figure 1 , are water insoluble inorganic bases that have first p K a s spanning the range 4–12 which find application as phase transfer catalysts for reactions in organic solvents 40 and as building blocks for supramolecular assemblies. 41 …”

Section: Resultsmentioning

confidence: 99%

“…Cyclotriphosphazenes, Figure 1, are water insoluble inorganic bases that have first pK a s spanning the range 4−12 which find application as phase transfer catalysts for reactions in organic solvents 40 and as building blocks for supramolecular assemblies. 41 Protonation of cyclotriphosphazenes occurs exclusively at the ring nitrogens. 42 The mono-and diprotonation reactions show distinct chemical shift changes allowing pK a 1 = 11.65 and pK a 2 < 4 of IPPN to be studied.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Efficient pK_a Determination in a Nonaqueous Solvent Using Chemical Shift Imaging

et al. 2022

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p K a is an important property of a molecule which impacts many fields, such as drug design, catalysis, reactivity, and environmental toxicity. It is often necessary to measure p K a in nonaqueous media due to the poor solubility of an analyte in water, for example, many compounds of pharmaceutical interest. Although NMR methods to measure p K a in water are well established, determining p K a in organic solvents is laborious and problematic. We present an efficient one-shot method to determine the p K a of an analyte in an organic solvent in a single measurement. Diffusion of an acid into a basic solution of the analyte and a set of pH indicators establishes a pH gradient in the NMR tube. The chemical shift of a pH sensitive resonance of the analyte and the pH of the solution are then determined simultaneously as a function of position along the pH gradient by recording a chemical shift image of the NMR tube. The p K a of the analyte is then determined using the Henderson–Hasselbalch equation. The method can be implemented in any laboratory with a gradient equipped NMR high-field spectrometer and is demonstrated for a range of pharmaceutical compounds and inorganic phosphazene bases.

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“…This provides them with unique surfactant qualities and makes them versatile building blocks for supramolecular assemblies. [35] Our previous study showed that POM-RPN aggregates have the potentialt os erve as highly efficient catalysts for biphasic oxidations with hydrogen peroxidei ncluding oxidative desulfurisation and olefin epoxidation. [27] Both reactions are of significant practical importance and are the subject of much current interest.…”

Section: Introductionmentioning

confidence: 99%

Alkylaminophosphazenes as Efficient and Tuneable Phase‐Transfer Agents for Polyoxometalate‐Catalysed Biphasic Oxidation with Hydrogen Peroxide

et al. 2015

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Alkylaminophosphazenes (RPN) are efficient and tuneable phase‐transfer agents for environmentally benign biphasic oxidation with hydrogen peroxide catalysed by polyoxometalates (POMs). Substituent groups on the phosphazene ring can be varied to modify the phase‐transfer efficiency of RPN for use in water–organic two‐phase systems. Active phosphazene–polyoxometalate aggregates that self‐assemble in situ from RPN and Keggin POMs, such as PMo12O403− and PW12O403−, were found to be efficient and recyclable catalysts for the oxidation of benzothiophenes and the epoxidation of alkenes with hydrogen peroxide. Lipophilic phosphazene cations present in these aggregates render the POM soluble in organic media. Catalyst activity in the biphasic oxidation with H2O2 varies with the RPN substituent alkylamino groups with respect to the solvent system used. The activity decreases in the series of POMs: PMo12O403−>PW12O403−≫SiW12O404− irrespective of the solvent system used.

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Supramolecular Structures of Cyclotriphosphazenes

Cited by 7 publications

References 97 publications

Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO₂}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)₂O} of These Heterocycles

Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO₂}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)₂O} of These Heterocycles

Efficient pK_a Determination in a Nonaqueous Solvent Using Chemical Shift Imaging

Alkylaminophosphazenes as Efficient and Tuneable Phase‐Transfer Agents for Polyoxometalate‐Catalysed Biphasic Oxidation with Hydrogen Peroxide

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Supramolecular Structures of Cyclotriphosphazenes

Cited by 7 publications

References 97 publications

Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO2}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)2O} of These Heterocycles

Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO2}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)2O} of These Heterocycles

Efficient pKa Determination in a Nonaqueous Solvent Using Chemical Shift Imaging

Alkylaminophosphazenes as Efficient and Tuneable Phase‐Transfer Agents for Polyoxometalate‐Catalysed Biphasic Oxidation with Hydrogen Peroxide

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Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO₂}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)₂O} of These Heterocycles

Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO₂}, Phosphamides {P(O)NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)₂O} of These Heterocycles

Efficient pK_a Determination in a Nonaqueous Solvent Using Chemical Shift Imaging