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Phosphazene-containing porous materials are of a great interest due to their unique properties, caused by the synergetic presence of nitrogen and phosphorus atoms, and have found applications as adsorbents, basic catalysts, etc. On the other hand, cage-like silsesquioxanes are ideal building blocks for the preparation of covalently-linked porous materials. Here two new phosphazene-functionalized organosilsesquioxane cage-based porous polymers were synthesized successively by a Friedel-Crafts reaction of hexapyrrolylcyclotriphosphazene with octavinylsilsesquioxane in the presence of AlCl3 and CF3 SO3 H as catalysts. The nature of acid catalysts barely influenced the character of pores due to the interaction of catalysts with basic nitrogen atoms of phosphazene units. The obtained polymers exhibited high efficiency as metal-free catalysts for the Knoevenagel reaction. This work opens new perspectives in the use of porous polymers based on cage-like organosiloxane compounds as basic catalysts for various reactions.

The shuttling of polysulfides is the most detrimental contribution to degrading the capacity and cycle stability of lithium-sulfur (Li-S) batteries. Adding a carbon interlayer to prevent the polysulfides from migrating is feasible, and a rational design of the structures and surface properties of the carbon layer is essential to increasing its effectiveness. Herein, we report a hierarchical porous carbon (HPC) created by carbonization of bis(phenoxy)phosphazene and in-situ doping of triple heteroatoms into the carbon lattice to fabricate an effective polysulfide-trapping interlayer. The generated carbon integrates the advantages of a hierarchical porous structure, a high specific area and rich dopants (N, O and P), to yield chemisorption and physical confinement for polysulfides and fast ion-transport synergistically. The HPC interlayer significantly improves the electrochemical performance of Li-S batteries, including an exceptional discharge capacity of 1509 mA h/g at 0.06 C and a high capacity retention of 83.7 % after 250 cycles at 0.3 C. This work thus proposes a facile in-situ synthesis of heteroatom-doped carbon with rational porous structures for suppressing the shuttle effect.

In this work, a highly efficient and environmentally friendly method for extracting palladium from hydrochloric acid media was developed. The method uses a magnetic sorbent carrying an organophosphorus extractant, which is not washed from the sorbent into the aqueous phase. The extractant was characterized by 1H, 13C, and 31P NMR spectroscopy and MALDI TOF mass spectrometry, and the palladium complex based on it was characterized by IR spectroscopy. According to an in vitro microbiological study, the extractant was non-toxic to soil microflora. It was established that the water uptake and saturation magnetization of the magnetic sorbent were sufficient for use in sorption processes. The sorption efficiency of palladium(II) with the developed sorbent can reach 71% in one cycle. After treatment of the spent sorbent with 5 M hydrochloric acid, palladium was completely extracted from the sorbent. The new sorbent is proposed for the extraction of palladium from hydrochloric acid media obtained by the leaching of electronic waste.

Base-mediated cyclization and annulation reactions are very useful methods in the heterocyclic synthesis. Different types of conventional bases, i.e., inorganic bases or organometallic bases have been traditionally used for carrying out these reactions in the past. Over the years, the phosphazene organic superbases have emerged as effective alternatives to inorganic and organometallic bases. The phosphazene superbase was first used for alkyne cyclization in 2008, and its use has become quite popular over the last decade. This review is aimed to provide an analysis of the use of phosphazene superbase, especially P4–t-Bu as a robust and highly efficient catalyst/reagent in various intra- or intermolecular reactions of substituted alkynes for the synthesis of O,N-heterocycles such as isoindolin-1-ones, benzofurans, isobenzofurans, proline derivatives, pyrroles, etc.

Phenoxy-phosphazene (PPZ) oligomer (Rabitle® FP100) flame retardant (FR) was successfully incorporated into the colorless and transparent semi-alicyclic polyimide (CPI) film matrix derived from 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) and 4,4′-oxydianiline (ODA) (PI-a, CHDA-ODA). The PPZ FR showed good miscibility with the PI-a matrix with a loading amount of up to 10 wt% in the composite films. PI-b (CHDA-ODA-FP100-5) film maintained good optical properties with the transmittance of 83.9% at the wavelength of 400 nm, the yellow index (b*) of 3.28, and the haze of 2.14%. PI-b film also showed good flame retardancy with the limiting oxygen indices (LOI) of 41.2% and the flammability rating of UL94 VTM-0. In addition, PI-b film exhibited the obviously reduced heat release rate (HRR) and total smoke production (THR) during the cone calorimeter measurement. At last, PI-b showed the glass transition temperature (Tg) and 5% weight loss temperature (T5%) of 325.0 and 404.3 °C, respectively, which was slightly lower than those of the pristine PI-a film (Tg = 346.8 °C; T5% = 431.6 °C). Continuous PI-b films with a length of 1000 m and a width of 1000 mm were successfully obtained on the demonstration production line by optimizing the processing parameters via the modified solvent cast technology. Similar thermal, optical, and flame retardancy properties and obviously improved tensile properties were observed for the mass production of PI-b film.

The condensation polymerisation of Cl3PNSiMe3 at room temperature is one of the best methods for polydichlorophosphazene production. The living cationic nature of the polymerisation mechanism of this material enables unique features such as the preparation of well-defined block and star polymers or organic–inorganic hybrid copolymers. Therefore, a reproducible high yield synthesis of Cl3PNSiMe3 from readily available and cheap chemicals under mild conditions is an important issue to be solved. In this study, PCl5 was reacted with hexamethyldisilazane at 0 °C in various solvents to investigate the formation efficiency of Cl3PNSiMe3. 1H and 31P NMR spectroscopic techniques were used to monitor the reaction progress and detect the available intermediates in the reaction mixture. Nonpolar solvents such as n-pentane highly decreased the formation of the side products such as Cl3PNH and cyclic phosphazene derivatives. Thus, the isolated yield of Cl3PNSiMe3 was increased up to 75%. The purity of Cl3PNSiMe3 was over 97%, which was confirmed using 1H, 31P, 13C and 29Si NMR spectroscopic techniques. Moreover, the reaction carried out in toluene led to the direct fabrication of polydichlorophosphazene in one-pot from PCl5 and hexamethyldisilazane in high yield (∼94%) and without the isolation of any phosphazene intermediate.

Phosphazenes as organocatalysts for the synthesis of polymers have evolved to powerful tools, and their catalytic performances highly depend on the basicity and molecular structure (size and shape). Therefore, designing phosphazenes with tunable basicity and molecular structure is greatly promising for the development of organocatalysts with improved catalytic properties, for example, high activity and selectivity. In this contribution, 2,4,6-tris[tri(dimethylamino)iminophosphorane]-1,3,5-triazine (C

Herein, we have successfully synthesized phosphorus/nitrogen/silicon tri-elements compound phosphazene derivative hexa-[4-( N-(3-(triethoxysilyl)propyl)acetamide)phenoxy]cyclotriphosphazene (HNTPC) from hexachlorotriphosphazenitrile, methyl 4-hydroxybenzoate, and 3-triethoxysilylpropylamine, and it was used as an additive flame retardant in epoxy resin (EP). Then, the thermal stability and flame retardancy of the composite (HNTPC/EP) were tested. Thermogravimetric analysis showed that the presence of HNTPC made EP matrix decompose at a relatively low temperature, thus promoted the formation of a stable coke layer and protected the matrix from fire. Therefore, the amount of carbon residue was markedly increased at 800°C, indicating an outstanding condensed phase flame-retardant effect. Furthermore, various combustion test data manifested that the addition of HNTPC could significantly improve the flame-retardant performance of EP. In addition, the sample could pass the vertical burning tests (UL-94) V-1 grade when the addition amount was 10% and the limiting oxygen index value was 32.6%, the peak heat release rate and total heat release rate decreased by 40.0% and 21.5%, respectively. Besides, the results of scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy also showed that HNTPC can promote the formation of carbon layer and improved the flame-retardant property of EP. Finally, the condensed phase and gas phase synergistic flame-retardant mechanism of HNTPC was proposed.

Development of degradable polyester elastomers plays an important role in the applications of soft mateirals. Noncrystalline polymenthides (PMs) from menthol derived lactone monomers are excellent soft segments for preparing degradable polyester elastomers. By using cyclic trimeric phosphazene base (CTPB) as an organocatalyst, we successfully synthesized PMs with different molecular weights (8.2 kDa to 100.7 kDa) in high yields via ring-opening polymerization (ROP) of menthide. When a CTPB/urea binary catalytic system was adopted, the polymerizations proceeded in a more controlled manner. Using glycerol as initiator, star shaped PMs with well-defined structure were synthesized and subsequently end-capped by acrylate. UV irradiation of the terminal acrylate groups in the star-shaped PMs resulted in formation of chemically cross-linked polyester elastomers without heat or other stimuli. The obtained polyester elastomers exhibit matched modulus (3.8–5.5 MPa), tensile strength (0.56–0.68 MPa), and strain at break (280%–320%) with soft body tissues, displaying great potential in biomedical applications.

Synthetically straightforward conditions have been developed for the preparation of poly(bis 2,2,2-trifluoroethoxy)- phosphazene with low PDI (

Metal-free anionic polymerization of n-hexyl isocyanate (HIC) catalyzed by phosphazene bases in THF at −98 °C under 10−6 Torr was attempted to obtain poly(n-hexyl isocyanate) (PHIC) peptide mimics with a high purity. tert-Butylimino-tris(dimethylamino)phosphorene (t-BuP1), 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2λ5,4λ5-catenadi(phosphazene) (t-BuP2), and 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2λ5,4λ5-catenadi(phosphazene) (t-BuP4) with the characteristic orders of basicity and bulkiness (t-BuP1 < t-BuP2 < t-BuP4) were used as catalysts to activate N-phenethyl-3-phenylpropanamide ((PhEt)2OCNH, PEPPA). Only t-BuP2 and t-BuP4 generated the initiating amidate anions paired with each phosphazenium cation, which produced PHICs with MWs higher than the theoretical ones and characteristic ranges of dispersities. A moderately low dispersity was achieved by t-BuP2. The anionic polymerization of HIC catalyzed by t-BuP2 with molar feed ratios of the monomer to the initiator ([HIC]0/[PEPPA]0) within the range 207–801 produced PHICs with high yields (96.9–98.7%) and high MWs (Mn = 44.1–174 kDa, Đ = 1.37–1.64) that were linearly controlled by the feed ratios, even though no polymers were obtained by t-BuP1, and the products whose production was catalyzed by t-BuP4 had unpredictable MWs and high dispersities (Đ = 1.82–2.20).

Novel insoluble star-shaped hexa-branched polymeric materials based on a cyclotriphosphazene core are prepared by the inverse vulcanization of elemental sulfur with hexakis(styreneoxy)cyclotriphosphazene resulting in various wt% sulfur content copolymers, explicitly poly(S-random-phenoxy)cyclotriphosphazene, [poly-(S-r-p)p], to be used as cathode materials for lithium–sulfur (Li–S) batteries. Their structural characterization studies are carried out via Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and scanning electron microscopy. Since the resulting poly-(S-r-p)p copolymers are not soluble in common solvents, an alternative soluble model compound, namely poly(S-random-phenoxy)pentachlorocyclotriphosphazene is synthesized via the same route of the inverse vulcanization process. Hence, this soluble model compound is able to be tested by means of 31P and 1H nuclear magnetic resonance spectroscopy allowing better understanding of the vulcanization mechanism between sulfur and vinylic groups based on phosphazenes. Later, the electrochemical performances of poly-(S-r-p)p as a Li–S battery cathode material are evaluated and the advantage of the resulting cross-linked polymer network is highlighted by comparison with the bare sulfur cathode. To gain further insight into the lithium storage mechanism, electrochemical impedance spectroscopy measurements are also performed before and after cycling. This work offers valuable design principles for the fabrication of sulfur-based polymers with their promising applicability in future Li–S batteries.

International audience; The organocatalyzed ring-opening polymerization (ROP) of various 4-alkoxymethylene-beta-propiolactones (BPL(OR)s; R = CH2CH=H-2 (All), CH2Ph (Bn), (CH2)(3)CH3 (Bu-n), (SiMe2Bu)-Bu-t (TBDMS)) towards the formation of the corresponding poly(hydroxyalkanoate)s (PHAs; poly(BPLOR)s (PBPL(OR)s)) is investigated under mild operating conditions (neat, 60 degrees C), simply using basic organocatalysts of the guanidine (1,5,7-triazabicyclo [4.4.0]dec-5-ene, TBD), amidine (1,8-diazabicyclo[5.4.0]-undec-7-ene, DBU) or phosphazene (2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2diazaphosphorine, BEMP) type. The polymerization proceeds basically at the same rate as the alike organocatalyzed ROP of related beta-lactones (especially the ubiquitous beta-butyrolactone (BL) and alkyl beta-malolactonates (MLA(R)s)), with BEMP being significantly more active than TBD and DBU. Insights into the polymerization mechanisms are gained through detailed 1D/2D NMR spectroscopy and MALDI-ToF mass spectrometry analyses of the resulting PBPL(OR)s and in particular through the identification of the nature of the end-capping groups. Each of the three organobases promotes the polymerization in its own way, as dictated by either its basic, nucleophilic or dual behavior.

A (thio)hydantoin (HHyd) and organic superbase binary cocatalyst is illustrated as a tunable catalytic tool that enabled the efficient ring-opening polymerization (ROP) of various cyclic ester monomers. A series of designed HHyd molecules with diverse substitutions on the imidazolidine-2,4-dione ring at N1, N3, C5, and C2 allowed the fine tuning of the acidity, steric demand, and nucleophilicity of the (thio)hydantoinate cocatalyst. A partner organic superbase abstracted either the N1–H or N3–H proton of HHyd, leading to a conjugate acid acting as a H-bond donor in electrophilic activations. Commercial Bronsted organic bases, including tertiary amines, amidines, guanidines, and phosphazene, were evaluated for HHyd/base cocatalysis. The amidine DBU and guanidines TMG, TBD, and MTBD were screened as effective bases. Two minimal hydantoins, 1,5,5-trimethylimidazolidine-2,4-dione (HHyd2) and 3,5,5-trimethylimidazolidine-2,4-dione (HHyd3), partnered with DBU showed optimal performances, with near-quantitative conversions and narrow dispersities, in the ROPs of various cyclic ester monomers. HHyd2/DBU obviated the potential for epimerization and/or transesterification in the ROP of L-lactide (LLA). The controlled/living nature of the ROP of trimethylene carbonate (TMC) was validated. ROPs of TMC in solvents at room temperature and in bulk at 90 °C were successful: a short reaction time (6 h vs. 0.5 h), high conversion (92% vs. 97%), and narrow dispersity (1.13 vs. 1.12) were observed (solvent vs. bulk). Homopolymers and diblock copolymers of P(TMC-b-LLA) were prepared. The controlled/living nature of the ROPs was supported through kinetics and chain extension experiments, and MALDI-ToF-MS characterizations. A cooperative activation mechanism was proposed and validated using NMR titrations, in which the hydantoinate activated the chain end and the conjugate acid activated the monomer. The high relative cell viability (>90%) of poly(trimethylene carbonate) samples containing the cocatalyst HHyd2/DBU tested via MTT assays on HaCat cells confirmed the desirable biosafety and biocompatibility.

Most organocatalysts for photo-controlled atom transfer radical polymerization (photo-ATRP) are metal complexes or synthetically elaborate organic dyes, which are toxic and expensive. Herein, we present a combination of 1,1,3,3-tetramethylguanidine (TMG) and sodium iodide (NaI) under white LED irradiation that could catalyze iodine-mediated photo-ATRP. Using a dual initiator and combining with ring-opening polymerization (ROP), well-defined poly(methacrylate)-b-polyester diblock copolymers can be successfully prepared in “one-pot” using a TMG/NaI photoredox catalytic system. Moreover, several superbases such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo [5.4.0]-undec-7-ene (DBU) and a phosphazene superbase (t-Bu-P4) could also be employed with NaI to serve as photoredox catalysts for this polymerization system and block copolymers could be synthesized in “one-pot”.

The alternating copolymer of lactic acid and glycolic acid (PLGA) is a highly promising next generation biodegradable material for biomedical and pharmaceutical applications due to its uniform degradation behaviors in addition to its ability to form stereocomplexes. However, versatile synthetic methods toward the narrowly dispersed alternating PLGAs with controlled molecular weights and desired end functionalities have been largely unexplored. Herein, we report the organocatalytic regioselective ring-opening polymerization (ROP) of optically active methylglycolides (l- andd-MGs) to produce highly alternating PLGAs. The ROP ofl-MG using a phosphazene base P-2-t-Bu/alcohol system in THF at -78 degrees C achieved the highest regioselectivity (P= 0.95) as well as a good control over the molecular weight (M-n= 6.6-15.6 g mol(-1)), with a relatively narrow dispersity (D= 1.21-1.29). Furthermore, alternating PLGA diol as well as azido-, ethynyl-, and poly(ethylene glycol) monomethyl ether-end-functionalized alternating PLGAs was successfully obtained by employing the corresponding functional alcohol initiators. An enantiomeric 1 : 1 blend of PLGAs prepared froml- andd-MGs formed a stereocomplex with a crystallinity and melting point comparable to the reported data for the stereocomplex from the perfectly alternating PLGAs producedviaa polycondensation approach, which implies the high degree of the alternating sequence of the obtained copolymers.

The development of adsorptive materials continues to be an important area of research for removal of heavy metal ions from waste water. The adsorption capacity can be modulated by both physical and chemical modification of the adsorbent. Herein, we combine the unique properties of polyhedral oligomeric silsesquioxane (POSS) and organocyclophosphazene as the building units to synthesize a hybrid porous material, abbreviated as PN-POSS. The synthetic method follows a Heck reaction between hexa(4-bromophenoxy)cyclotriphosphazene and octavinylsilsesquioxane (OVS). The Brunauer-Emmett-Teller (BET) analysis shows that the material possesses micro- and mesopores of 1.5 and 3.8 nm size and a surface area on the order of 500 m2 g-1 . These attributes in combination with the donor ability of the phosphazene units qualify the material for high adsorption of Pb2+ , Hg2+ and Cu2+ ions with maximal adsorption capacities on the order of 1326, 1927 and 2654 mg g-1 , respectively. The adsorbent exhibits a good regeneration performance and can be effectively used for water treatment.

With the synthesis of N, N′, N″, N‴-tetrakis(3- (dimethylamino)propyl)triaminophosphazene (TDMPP, 1), we present the first phosphazene superbase with enhanced basicity through the effect of multiple intramolecular hydrogen bonding (IHB). Due to intramolecular solvation of four NH protons, the proton affinity is even higher than that of second-order phosphazene (dma)P2-tBu. X-ray structural proof, NMR titration experiments, and computational investigations provide a more detailed quantitative description of the IHB influence on the superbasicity of 1 in solid-state, solution, and the gas-phase.

Phosphazene base, t-BuP2, was employed to catalyze the proton transfer polymerization (PTP) of 2-hydroxyethyl acrylate (HEA), and PTP was further combined with ring-opening polymerization (ROP) to exploit a new type of hybrid copolymerization. The studies on homopolymerization showed that t-BuP2 was a particularly efficient catalyst for the polymerization of HEA at room temperature, giving an excellent monomer conversion. Throughout the polymerization, transesterification reactions were unavoidable, which increased the randomness in the structures of the resulting polymers. The studies on copolymerization showed that t-BuP2 could simultaneously catalyze the hybrid copolymerization via the combination of PTP and ROP at 25 °C. During copolymerization, HEA not only provided hydroxyl groups to initiate the ROP of e-caprolactone (CL) but also participated in the polymerization as a monomer for PTP. The copolymer composition was approximately equal to the feed ratio, demonstrating the possibility to adjust the polymeric structure by simply changing the monomer feed ratio. This copolymerization reaction provides a simple method for synthesizing degradable functional copolymers from commercially available materials. Hence, it is important not only in polymer chemistry but also in environmental and biomedical engineering.

We demonstrated that the dimeric 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2Λ5, 4Λ5-catenadi(phosphazene) supported on polystyrene (PS-t-BuP2) was an efficient and recyclable catalyst for the ring-opening polymerization (ROP) of δ-valerolactone (δ-VL). The heterogeneous catalyst PS-t-BuP2 could be recycled and reused for five consecutive cycles without significant decrease of catalytic activity. The monomer conversions maintained between 79% and 85% for five cycles. Using BnOH as initiator, the produced polyvalerolactones (PVLs) had controlled molecular weights (MWs) and narrow MW distributions (Đ), and the products were free of catalyst by simple filtration. The 1H NMR and MALDI-TOF characterizations of the obtained PVLs clearly indicated the presence of the initiator residue at the chain end.

We describe the catalytic amination of β-(hetero)arylethyl ethers with amines using the organic superbase t-Bu-P4 to obtain β-(hetero)arylethylamines. The reaction has a broad substrate scope and a...

Phthalic anhydride and propylene/ethylene oxide are copolymerized at room temperature by a bicomponent metal-free catalyst comprising a mild phosphazene base and triethylborane. Provided with proper loadings of the two catalytic components, block copolymers with strict (AB)

Cu(I)-catalyzed azide–alkyne click polymerization has become a powerful tool for the construction of 1,4-regioregular polytriazoles (PTAs). However, the polymerization toward the synthesis of 1,5-r...

The concept of combining a catalyst and an activated center in one molecule was implemented in Michael donors functionalized with phosphazene units. First, the phosphazene group catalyzes Michael addition and then acts as a reactant in an intramolecular aza-Wittig reaction. The viability of this strategy was demonstrated by our development of a one-pot method for azepane core construction starting from functionalized azides, triphenylphosphine and acrolein.

Hydroamination and hydrothiolation are the most efficient and completely atom-economical process to construct important enamine and vinyl sulfide intermediates in pharmaceutical and organic chemistry. The cyclic trimeric phosphazene base (CTPB) showed great catalytic activity for the anti-Markovnikov stereoselective hydroamination and hydrothiolation of alkynes in good to excellent yields. A broad substrate scope of alkynes and nucleophiles was demonstrated, including aryl and heteroaryl alkynes, terminal and internal alkynes, different N-heterocycles, thiols and thiophenols. This versatile and cost-efficient approach with good stereoselectivity and excellent functional group tolerance provided new opportunity for the organocatalyzed hydrofunctionalization of alkynes.

Phosphazene superbase P4- t-Bu mediated iodoaminocyclization of 2-(1-alkynyl)benzamides is reported. The reaction works under ambient conditions and instantaneously results in the synthesis of isoindolin-1-ones in 65-97% yields, in a regio- and stereoselective manner. The exclusive formation of products with Z-geometry (across the exo C═C bond) has been confirmed through X-ray crystallography. The methodology also provides an easy access to aristolactams, an important class of natural products. This has been successfully demonstrated by synthesizing two aristolactam derivatives (including Cepharanone B).

This work is devoted to the influence of phosphazene modifiers with different substituents on the curing process, thermal properties and flammability of benzoxazine resin. Novel catalysts with m-toluidine substituents were introduced. The catalytic activity of studied phosphazene compounds decreased in the row: hexachlorocyclotriphosphazene (HCP) &gt, tetra m-toluidine substituted phosphazene PN-mt (4) &gt, hexa m-toluidine substituted phosphazene PN-mt (6) &gt, hexaphenoxycyclotriphosphazene (HPP), where HPP is totally inactive. Two types of catalysis: basic and acid were proposed. A brief study of resulting properties of polybenzoxazines was presented. The addition of any studied modifier caused the decrease of glass transition temperature and thermal stability of polymers. The morphology of cured compositions was characterized by matrix-dispersion phase structure. All phosphazene containing polybenzoxazines demonstrated the improved flame resistance.

Despite a significant number of investigations in the field of phosphazene chemistry, the formation mechanism of this class of cyclic compounds is still poorly studied. At the same time, a thorough understanding of this process is necessary, both for the direct production of phosphazene rings of a given size and for the controlled cyclization reaction when it is secondary and undesirable. We synthesized a series of short linear phosphazene oligomers with the general formula Cl[PCl2=N]n–PCl3+PCl6– and studied their tendency to form cyclic structures under the influence of elevated temperatures or in the presence of nitrogen-containing agents, such as hexamethyldisilazane (HMDS) or ammonium chloride. It was established that linear oligophosphazenes are inert when heated in the absence of the mentioned cyclization agents, and the formation of cyclic products occurs only when these agents are involved in the process. The ability to obtain the desired size phosphazene cycle from corresponding linear chains is shown for the first time. Known obstacles, such as side interaction with the PCl6– counterion and a tendency of longer chains to undergo crosslinking elongation instead of cyclization are still relevant, and ways to overcome them are being discussed.

The renaissance of Brønsted superbases is primarily based on their pronounced capacity for a large variety of chemical transformations under mild reaction conditions. Four major set screws are available for the selective tuning of the basicity: the nature of the basic center (N, P, …), the degree of electron donation by substituents to the central atom, the possibility of charge delocalization, and the energy gain by hydrogen bonding. Within the past decades, a plethora of neutral electron‐rich phosphine and phosphazene bases have appeared in the literature. Their outstanding properties and advantages over inorganic or charged bases have now made them indispensable as auxiliary bases in deprotonation processes. Herein, an update of the chemistry of basic phosphines and phosphazenes is given. In addition, due to widespread interest, their use in catalysis or as ligands in coordination chemistry is highlighted., The hunt is still on for the most powerful neutral superbase. The steadily growing scope of applications has resulted in a renaissance of highly electron‐rich phosphorus‐containing Lewis and Brønsted bases. Strongly π‐donating substituents at the center of basicity can be employed to increase the proton affinity and the σ‐donation ability. This minireview highlights recently published achievements focusing especially on the past five years.

In the present work, a series of cyclotriphosphazenes including Schiff bases, {[N3P3(biph)2(R)2] (5), [N3P3(biph)(R)4] (6), and N3P3R6 (7) (biph = 2′,2′′-dioxy-1′,1′′- biphenyl, R = Quinoline-4-aldehyde-p-oxyanil}, were synthesized in high yields via the nucleophilic substitution reactions of quinoline-4-aldehyde-p-hydroxyanil (1) with [N3P3(biph)2Cl2] (2) and [N3P3(biph)Cl4] (3) and N3P3Cl6 (4), respectively. The structures of all products (5, 6, and 7) were defined by elemental analysis, mass spectrometry, FTIR, (1H, 13C, and 31P) NMR spectroscopies. Furthermore, the photophysical properties of these new cyclotriphosphazenes (5, 6, and 7) in different solvents and concentrations were investigated and the results were compared and discussed. The absorption characteristics of novel cyclotriphosphazene-based Schiff bases demonstrated n–π* and π–π* transitions which can be attributed to quinoline side whereas absorbance values were significantly enhanced under the same analytical conditions when the number of quinoline groups attached to the cyclotriphosphazene-core increased. As a result, the molar absorptivity of novel cyclotriphosphazene-based Schiff bases which substituted with two (5) and six quinolines moieties (7) were increased 4.43- and 11.4-fold, respectively, when compared with their precursor (1).

While alkyl-substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C2 F5 )3 ]- , which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron-withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C2 F5 )3 O]- . In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C2 F5 )3 OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C2 F5 )3 SiOSi(C2 F5 )3 . Deprotonation of Si(C2 F5 )3 OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C2 F5 )3 O}2 ]2- , implies Lewis amphoteric character of the monomeric [Si(C2 F5 )3 O]- anion.

The regioselective organocatalytic ring-opening polymerization (ROP) of a 6-membered cyclic carbonate, rac-1-methyl trimethylene carbonate, was studied using phosphazene base (t-BuP2) as the princi...

The organic superbase tBu-P4 catalyzes methoxy-alkoxy exchange reactions on (hetero)arenes with alcohols. The catalytic reaction proceeded efficiently with electron-deficient methoxy(hetero)arenes as well as with a variety of alcohols, including 3-amino-1-propanol, β-citronellol, menthol, and cholesterol. An intramolecular version of this reaction furnished six- and seven-membered ring compounds.

An organocatalytic nucleophilic substitution reaction of gem-difluoroalkenes with ketene silyl acetals was developed. Phosphazene P4- tBu effectively catalyzed the reaction under mild conditions to provide monofluoroalkenes possessing an alkoxycarbonylmethyl group in high yields with high Z selectivities.

In the present work, new di-spiro and tetra-spiro organophosphazene compounds (DPP-Ant-1 and 2, BPP-Ant-1 and 2) were synthesized by interaction with conjugate anthracene-substituted chalcone compounds (Ant-1 and 2) with organocyclotriphosphazene compounds DPP and BPP. All the compounds were fully characterized and confirmed by elemental analysis, spectroscopic and thermal techniques such as DSC, TGA, mass, FT-IR, 1H, 13C-APT, 31P NMR and 2D HETCOR NMR. These organocyclotriphosphazes were designed and synthesized in order to investigate the changes in the conductive properties of graphene-based compounds. The graphene-based materials have a wide range of technological applications such as electronics, optics, thermal and mechanical properties. Graphene-based phosphazenes composites were prepared. The AC and DC conductivity of graphene-based phosphazene composites were measured. Dielectric measurements (dielectric constant, dielectric loss factors and conductivity) of organophosphazene compounds were measured against increasing frequency (range from 100 Hz to 20 kHz at 25 °C) at different temperature (between 298 and 348 K) using means of an impedance analyzer and then and compared with each other. Also, the activation energy profile of graphene/phosphazene composites was revealed by measuring DC conductivity of an individual composite material. The obtained graphene/phosphazene composites have been found that they have a semiconductor property according to the DC conductivity results.

The anionic polymerization of methyl methacrylate (MMA) was carried out using phosphazene base t-BuP4 and ethyl acetate (EA) as the catalyst and the initiator, respectively. Gas chromatography (GC), size exclusion chromatography (SEC) measurements, and nuclear magnetic resonance (NMR) analyses were used to reveal the polymerization mechanism and to confirm the polymer structure. The results confirmed the proposed polymerization mechanism and the polymer structure, while the initiator efficiency was low. Meanwhile, the initiation by methoxy anion coming from hydrolysis of the ester bond in MMA was also observed. As a result, there is a marked deviation between the theoretical molecular weight and the measured molecular weight, and it is essential to carry out the polymerization at excessive dosage of t-BuP4 for preparing polymers with narrow molecular weight distribution.

Transformations of α-EWG-substituted (electron-withdrawing group, EWG) γ-azidobutyronitriles proceeding via unusual aza-Wittig reactions between the phosphazene and nitrile functions and affording pyrrole-derived iminophosphazenes were developed. α-EWGs were found to control chemoselectivity and, depending on their nature, act as CN group activators (e.g., ester, amide, or nitrile) or competitors (e.g., ketone) in aza-Wittig reactions. To demonstrate the synthetic utility of the obtained iminophosphazenes as N, N-binucleophiles, their transformations into pyrrole-fused systems, pyrrolo[1,2- a]imidazoles and pyrrolo[1,2- a][1,3]diazepines, were carried out.

Phosphazenes have attracted considerable attention in the field of ring-opening polymerization (ROP) of cyclic esters. However, the application of phosphazenes as catalyst is subject to a trade-off between activity and selectivity (chain propagation versus transesterification/back-biting reaction, e.g., controlled polymerization). Despite extensive research efforts, the development of a new catalytic system having concurrent high activity and selectivity remains a great challenge. In this work, we report that the binary organocatalytic system comprised of cyclic trimeric phosphazene base (CTPB) and ureas shows both of high activity and selectivity for the ROP of e-caprolactone (e-CL) and δ-valerolactone (δ-VL) in the presence of alcohol as initiator. It is found that the introduction of ureas would significantly increase the catalytic selectivity during ROP without sacrificing the catalytic activity of CTPB. Moreover, the polymerizations catalyzed by the title catalytic system exhibit immortal characteristics and thus thousands equivalent of monomer could be converted to polymer efficiently with desired MWs and microstructures. Linear diblock copolymer AB and star copolymers (AB)3 with three identical diblock arms could be readily synthesized by sequential copolymerization using different alcohols as initiators.

Degradable long-chain aliphatic polyesters are promising alternatives to polyolefins. The ring-opening polymerization (ROP) of ω-pentadecalactone (PDL) enables the synthesis of aliphatic polyesters with melting temperature close to low-density polyethylene (LDPE). However, this ROP reaction is of great challenge because of low ring strain of the PDL monomer. The occurrence of intra- and intermolecular transesterification reactions during ROP made it difficult to prepare well-defined block copolyesters for advanced properties. In this context, cyclic trimeric phosphazene base (CTPB) in combination with benzyl alcohol (BnOH) was proved to be an efficient initiator system for ROP of PDL, showing an excellent polymerization rate (TOF up to 600 h–1) at 80 °C. Well-defined diblock copolyesters, i.e., PPDL-b-PLLA, can be easily synthesized by sequential addition of PDL and l-lactide (L-LA). In contrast, sequential addition of PDL and e-caprolactone (CL) or δ-valerolactone (VL) only led to the random copolyesters...

Polysiloxanes containing phenyl functional groups are a class of promising polymer materials with enhanced low-temperature flexibility, high-temperature stability and great damping properties. In this context, organic cyclic trimeric phosphazene bases (CTPBs) have been proved to be highly efficient for the ring-opening polymerization (ROP) of octamethylcyclotetrasiloxane (D4) and the copolymerization of D4 with octaphenylcyclotetrasiloxane (P4) under mild conditions. The polymerizations are fast and the resulting polymers have high molecular weights (Mn up to 1353 kg mol−1). The molecular structures of the obtained copolysiloxanes were characterized by 1H NMR and 29Si NMR, which demonstrate that as high as 64 mol% diphenyl siloxane units can be incorporated within the copolysiloxane chain. Remarkably, copolysiloxanes with different contents of the diphenyl siloxane group are found free of T-branches and Q-branches based on the 29Si NMR analysis, indicating a good controlled ROP by the current organocatalytic system. DSC analysis shows no crystallization exotherm or melting endotherm in the range of −70 °C to 50 °C for all the copolysiloxanes, confirming that incorporation of diphenyl groups successfully suppresses the undesirable crystallization of polydimethylsiloxane. Moreover, the thermal stability of copolysiloxanes was evaluated by TGA, showing dramatically enhanced thermal stability with the increment of the diphenyl siloxane content.

International audience; N-Modified peptide backbones are promising peptidomimetics which offer several advantages in terms of improved biological activity and stability. They further allow the development of novel functional materials. However, the synthesis of N-substituted peptides is very challenging with the existing methods, particularly the synthesis of peptides with larger N-substituents. In this work, we are introducing a new method to create N-polyether substituted cyclic dipeptides via anionic ring-opening polymerization (AROP). Four different cyclic dipeptides with different hydrophobic functional groups were selected to create N-substituted cyclic dipeptides. Backbone amides –NH– were deprotonated with phosphazene bases to form nucleophilic initiators. Furthermore, the effect of different phosphazene bases (tBuP4 and tBuP2) and of the addition of a Lewis acid (i-Bu3Al) was studied in detail towards creating N-polyether-cyclic dipeptides bearing either hydrophobic poly(butylene oxide) chains, or hydrophilic linear polyglycidol chains, thanks to the polymerization of 1,2-epoxybutane and the polymerization followed by the deprotection of t-butyl glycidyl ether monomers, respectively. Moreover, we have demonstrated the possibility of avoiding the isomerization of cyclic dipeptides during the synthesis of N-substituted analogues depending on the synthetic approach.

The chemosynthesis of bio-renewable poly(γ-butyrolactone) (PγBL) with a high molecular weight via ring opening polymerization (ROP) of non-strained γ-butyrolactone (γBL) remains a big challenge although several catalysts have been developed in the past two years. In this contribution, we reported the efficient ROP of γBL using a strong base/urea binary synergistic catalytic system. Either an alkaline alkoxide or organophosphazene superbase was used as a strong base in this study. The base/urea binary catalyst showed high catalytic activity and high selectivity for ring opening relative to transesterification toward the ROP of γBL, and the organophosphazene superbase in combination with urea showed better catalytic activity compared to an alkaline alkoxide/urea system. The effects of bases, ureas, and reaction conditions on monomer conversions and resultant molecular weights of PγBL were systematically investigated. A PγBL homopolymer with a high molecular weight up to 35.0 kDa was synthesized using a combination of a cyclic trimeric phosphazene superbase (CTPB) and suitable ureas with electron-donating substituents. The thermal stabilities of PγBL improved dramatically with an increase in its molecular weight. The obtained PγBL exhibited unprecedented superior mechanical properties with an elongation at break of 858 ± 79%, which paves the way for its practical applications.

Ring-opening polymerization (ROP) of the bioderived and nonstrained γ-butyrolactone (γ-BL) is an emerging approach to produce recyclable polymers. It remains a big challenge to synthesize high molecular weight linear poly(γ-butyrolactone)s (PγBLs) in a highly active and selective manner. In this report, we developed dual organocatalysts for the ROP of γ-BL, using symmetrical (thio)ureas with electron-donating groups to buffer the growing anions that were generared by the superbase phosphazene (P4). Linear PγBLs were selectively obtained with high apparent rate constant (ca. 39 times than single P4), and high number-average molecular weights of up to 64.3 kg/mol (ca. 3 times than single P4). The turnover frequencies of these P4/(thio)urea pair-catalyzed processes were as high as 125 h–1. High molecular weight PγBLs exhibited dramatically improved mechanical properties.