Phosphorus Valence Research Articles

A discovery for phosphorus valence and unsaturated bonds in polyphosphate/polyphosphonate: Promotion or inhibition for its flame-retardant mode of action in PET

Four polyphosphate/polyphosphonate flame retardants (PAP, POP, PAP-UB and POP-UB) have been designed and synthesized to study the effects of phosphorus valence states and the presence of unsaturated carbon-carbon double bonds on self-cross-linking impacting flame-retardant modes of action. It was found that phosphorus valence states affect the proportion of flame-retardant activity between the gas phase and condensed phase. A phosphonate containing +3-valence phosphorus is primarily effective as a gas-phase flame-retardant, while the one containing +5-valence phosphorus mainly exerted an impact in the condensed phase. The introduction of an unsaturated bond enhances the carbon-forming effect promoted by polyphosphates/polyphosphonates in a degrading polymer matrix and increases the melt viscosity for blends at high temperature. The phosphorus-containing fragments which might have been released into the gas phase are locked in the condensed phase due to CC bonds cross-linking, thus forming more high-quality phosphorus-rich char layers. This effect balances the distribution of gas-phase and condense-phase flame-retardant effects and is especially obvious in PET/polyphosphonate blends containing +3-valence phosphorus, which originally plays mainly the role of a gas-phase flame retardant. PET blends containing unsaturated carbon-carbon double bonds display better carbon formation, flame-retardant activity and anti-dripping behavior than these do without this feature.

Flame-retardant in-situ formed gel polymer electrolyte with different valance states of phosphorus structures for high-performance and fire-safety lithium-ion batteries

Lithium-ion batteries (LIBs) have been widely used today owing to portability, high energy storage, and reusability. However, commercial liquid electrolytes in LIBs possess intensive mobility and terrible flammability. Accordingly, leakage, combusting, and even exploding can frequently occur when LIBs work under abuse conditions. Herein, a novel flame-retardant gel polymer electrolyte (GPE) containing + 3 and + 5 phosphorus valence states of phosphorus structures was designed by in-situ thermal polymerization of tri(acryloyloxyethyl) phosphate (TAEP), diethyl vinylphosphonate (DEVP), and pentaerythritol tetraacrylate in electrolytes. After being ignited by fire, this GPE extinguished quickly with a combusting time of only 0.9 s, showing much lower flammability. Besides, the GPE is compatible with graphite anode, LiFePO4 (LFP), and even LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes. The as-assembled LFP and NCM811-based pouch cells (1 Ah-type) with TD-GPE achieved stable cycling, maintaining 88.52 % and 95.2 % of the initial capacities, respectively after 200 and 190 cycles at 0.5C. Moreover, the as-prepared TD-GPE dramatically reduced the fire hazard of NCM811 batteries without sacrificing the electrochemical performance. The thermal abuse test demonstrates that the leakage and combustion of NCM811||TD-GPE||Graphite pouch cell could be significantly suppressed in the test process, indicating that battery safety improves significantly via the combined use of different phosphorus valence structures. This is because the + 5 phosphorus valence of TAEP promoted the formation of carbon layers, and the + 3 phosphorus structure in DEVP captured free radicals by quenching effect. This work paves a different path for designing safe and high-performance GPEs in LIBs based on gaseous-phase and condensed-phase mechanisms.

How Do Phosphorus Compounds with Different Valence States Affect the Flame Retardancy of PET?

This work investigated the effect of different valence states of phosphorus-containing compounds on thermal decomposition and flame retardancy of polyethylene terephthalate (PET). Three polyphosphates-PBPP with +3-valence P, PBDP with +5-valence P and PBPDP with both +3/+5-valence P-were synthesized. The combustion behaviors of flame-retardant PET were studied and the structure-property relationships between the phosphorus-based structures with different valence states and flame-retardant properties were further explored. It was found that phosphorus valence states significantly affected the flame-retardant modes of action of polyphosphate in PET. For the phosphorus structures with +3-valence, more phosphorus-containing fragments were released in the gas phase, inhibiting polymer chain decomposition reactions; by contrast, those with +5-valence phosphorus retained more P in the condensed phase, promoting the formation of more P-rich char layers. It is worth noting that the polyphosphate containing both +3/+5-valence phosphorous tended to combine the advantage of phosphorus structures with two valence states and balance the flame-retardant effect in the gas phase and condensed phase. These results contribute to guiding the design of specified phosphorus-based structures of flame-retardant compounds in polymer materials.

A facile and green strategy to synthesize N/P co-doped bio-char as VOCs adsorbent: Through efficient biogas slurry treatment and struvite transform

Controllable introduction of active sites on bio-char is certified as an available method to resolve a bottleneck issue of conversion of various greenrenewable bio-char into valuable materials. In this work, the bio-char was modified by air thermal oxidation after the formation of struvite via the facile impregnation in the biogas slurry. The structural and elemental properties of the surface of modified bio-char were analyzed by SEM, BET, XRD, and XPS. XPS analysis of the nitrogen and phosphorus valence states on the carbon surface shows that the N/P elements of struvite were synergically converted into N/P functional groups via air thermal oxidation. Then the modified bio-char was used as VOCs-acetone adsorber and the result shows that the acetone adsorption capacity was 4.8 times higher than that of bio-char. The density functional theory (DFT) proves that the binding force of C-O-P and acetone (-16.882 kcal) is stronger than that of C-P-O and acetone (−7.779 kcal). The results certified that air thermal oxidation coupling eutrophic element recycling is a promising approach for the preparation of N/P co-doped bio-char as value-add materials for improving acetone adsorption performance.

Exploration on structural rules of highly efficient flame retardant unsaturated polyester resins

Owing to the lack of research on structure-activity relationship and interaction mechanism between unsaturated polyester resins (UPR) and flame retardants, it has been a big challenge to prepare high-efficiency flame retardants for UPR in industry. In this research, to explore structural rules of high-efficiency flame retardants, several polymeric flame retardants were synthesized with varied main-chain, side-chain, phosphorus valence states and contents of flame retardant elements. The thermal stabilities of flame retardants and UPR composites were firstly assessed. It has been found the interaction existed between flame retardants and UPR, through transesterification reaction and β scission pathway in polyester and polystyrene chains. With only 15 wt% of PCH3-S, UPR composites can reach V0 rating in UL-94. The PHRR and THR values can be maximumly decreased by 71.66 % and 77.67 %, with 20 wt% of PB-S. It has been found flame retardants with sulfone group and + 3 valence state of phosphorus in molecular backbone can release SO2 and phosphorus containing compounds in gaseous phase, which diluted fuel fragments and catalyzed H⋅ and HO⋅ radical removal. The mechanism for improved flame retardancy of UPR composites with various polymeric flame retardants were discussed in detail. Some general rules for highly efficient flame retardant UPR can be summarized: First, gaseous phase flame retardant mechanism plays the major role in improvement of flame retardant performance of UPR composites; Second, the combination of + 3 valence state of phosphorus structures, higher phosphorus contents and sulfone groups effectively improves the flame retardant efficiency of flame retardants.

Phosphine‐NHC Manganese Hydrogenation Catalyst Exhibiting a Non‐Classical Metal‐Ligand Cooperative H2 Activation Mode

AbstractDeprotonation of the MnI NHC‐phosphine complex fac‐[MnBr(CO)3(κ2P,C‐Ph2PCH2NHC)] (2) under a H2 atmosphere readily gives the hydride fac‐[MnH(CO)3(κ2P,C‐Ph2PCH2NHC)] (3) via the intermediacy of the highly reactive 18‐e NHC‐phosphinomethanide complex fac‐[Mn(CO)3(κ3P,C,C‐Ph2PCHNHC)] (6 a). DFT calculations revealed that the preferred reaction mechanism involves the unsaturated 16‐e mangana‐substituted phosphonium ylide complex fac‐[Mn(CO)3(κ2P,C‐Ph2P=CHNHC)] (6 b) as key intermediate able to activate H2 via a non‐classical mode of metal‐ligand cooperation implying a formal λ5‐P–λ3‐P phosphorus valence change. Complex 2 is shown to be one of the most efficient pre‐catalysts for ketone hydrogenation in the MnI series reported to date (TON up to 6200).

Phosphine-NHC Manganese Hydrogenation Catalyst Exhibiting a Non-Classical Metal-Ligand Cooperative H2 Activation Mode.

Deprotonation of the MnI NHC-phosphine complex fac-[MnBr(CO)3 (κ2 P,C-Ph2 PCH2 NHC)] (2) under a H2 atmosphere readily gives the hydride fac-[MnH(CO)3 (κ2 P,C-Ph2 PCH2 NHC)] (3) via the intermediacy of the highly reactive 18-e NHC-phosphinomethanide complex fac-[Mn(CO)3 (κ3 P,C,C-Ph2 PCHNHC)] (6 a). DFT calculations revealed that the preferred reaction mechanism involves the unsaturated 16-e mangana-substituted phosphonium ylide complex fac-[Mn(CO)3 (κ2 P,C-Ph2 P=CHNHC)] (6 b) as key intermediate able to activate H2 via a non-classical mode of metal-ligand cooperation implying a formal λ5 -P-λ3 -P phosphorus valence change. Complex 2 is shown to be one of the most efficient pre-catalysts for ketone hydrogenation in the MnI series reported to date (TON up to 6200).

Influence of Valence and Structure of Phosphorus-Containing Melamine Salts on the Decomposition and Fire Behaviors of Flexible Polyurethane Foams

In this work, 2-carboxyethyl(phenyl)phosphinic acid melamine salt (CMA, phosphorus valence +1), melamine hypophosphite (MHPA, phosphorus valence +1), melamine phosphite (MPOA, phosphorus valence +3), and melamine pyrophosphate (MPyP, phosphorus valence +5) were respectively used as flame retardants for flexible polyurethane foam (FPUF), and fire performance as well as pyrolysis behaviors of FPUF were investigated systematically. CMA and MHPA were found to have better flame retardance than MPOA and MPyP for FPUF, which mainly played a role in the gas phase due to the release of many phosphorus-containing volatiles and melamine derivatives. The types of phosphorus-containing gaseous pyrolysis products of CMA were much more than that of MHPA due to the different chemical moieties surrounding the phosphorus atom, which made it have the highest flame-retardant efficiency for FPUF. Besides this, the possible thermal degradation mechanisms of CMA and MHPA were proposed.

Comparative study on the flame retarded efficiency of melamine phosphate, melamine phosphite and melamine hypophosphite on poly(butylene succinate) composites

The main aim of this work was to investigate the flame retarded efficiency of melamine phosphate (MP), melamine phosphite (MPi) and melamine hypophosphite (MHP) on poly(butylene succinate) (PBS) composites. The flame retardant, thermal degradation and combustion properties of PBS composites were characterized by limiting oxygen index (LOI) test, vertical burning (UL-94) test, thermogravimetric analysis (TGA) and cone calorimeter (Cone), respectively. The LOI results showed that the LOI values followed the sequence of PBS/MP < PBS/MHP < PBS/MPi at the same additive loadings. TGA results indicated that the initial decomposition temperature of PBS composites decreased with the decrease of phosphorus valence state and the incorporation of all three compounds could promote the char formation. Adding these three compounds into PBS matrix can decrease the peak heat release rate (PHRR) obviously from cone calorimeter results. Scanning electron microscopy (SEM) was employed to characterize the morphology and structure of the char residues. The flame-retardant mechanism in gaseous phase and condensed phase were investigated by thermogravimetric analysis/infrared spectrometry (TG-IR) and in situ Fourier transform infrared spectroscopy (in situ FTIR), respectively, and the possible flame-retardant mechanism was proposed.

Photoelectron Spectra of Trimethylphosphine-Substituted Tungsten Carbonyls: Ligand Field Effects, Ligand Additivity Effects, and Core-Valence Ionization Correlations.

High-resolution broad-scan gas-phase photoelectron spectra using synchrotron radiation (including valence, inner valence, and core levels) are reported for a series of trimethylphosphine-substituted tungsten carbonyls: W(CO)(6), W(CO)(5)PMe(3), cis-W(CO)(4)(PMe(3))(2), trans-W(CO)(4)(PMe(3))(2), and fac-W(CO)(3)(PMe(3))(3). The inner valence and core level spectra are interpreted by comparison with the published spectra of W(CO)(6) and other metal carbonyls. High-resolution valence level spectra of these complexes are also obtained by He I radiation. Fine structure, resulting from spin-orbit splitting, ligand field splittings, and vibrational coupling is resolved in the spectra of both W 5d and W 4f regions. Ligand field splittings on both the W 5d and W 4f levels increase in the order W(CO)(6) approximately fac-W(CO)(3)(PMe(3))(3) < W(CO)(5)PMe(3) </= cis-W(CO)(4)(PMe(3))(2) < trans-W(CO)(4)(PMe(3))(2). For the first time, the phosphorus 2p spin-orbit components of the phosphine complexes have been resolved. The binding energies (or ionization potentials) in the spectra of both W 5d valence level and W 4f core level regions are shifted almost linearly to lower energy with each successive step of ligand substitution. The shift per phosphine substitution is 0.66 +/- 0.03 eV for the W 5d ionizations and 0.76 +/- 0.03 eV for the W 4f ionizations (DeltaE(valence)/DeltaE(core) = 0.86 +/- 0.03). Similar linear shift trends are also found in the phosphorus 2p core level and phosphorus valence "lone-pair" ionizations. These data confirm the ligand additivity model predictions for these complexes.

NMR Spectra and Structure of Phosphorus-Containing Cycles with Acyclic P=Se and Cyclic P-C Bonds

Abstract Using 1H, 13C, 31P, 77Se NMR it has been established that six-membered rings of 5-seleno-5-phenyl-2,2-dimetiiyl-l,3,5-dioxaphosphorinanes, 5-seleno-1,3,5-diazaphosphorinanes and 5-seleno-5-phenyl (alkyl)-2,2-dimethyl-1,3,2,5-dioxa-silaphosphorinanes in the solution are in chair conformation with the equatorial PSe group, whereas the eight-membered ring of 6-seleno-2,2,6-trimethyl-1,3,2,6-dioxa-silaphosphocane is mainly in the chair-chair conformation with the symmetry plane passing through the silicon atom and the axially oriented P=Se group. The selenium nuclear chemical shifts δ77se -266–416 ppm in these compounds depend on the size of the cycle, and on the effect of the substituent of the cycle. The phosphorus nuclear chemical shifts δ31pO-50 ppm depend on the phosphorus valence angle at the cycle and the electron infulence of the closest phosphorus substituents. For the stereoisomer pairs of the six-membered cycles the 31P nuclei in the isomer with the equatorial P=Se group have been shown to...

The band structure, electron density, and heat of formation of scandium monophosphide

The Linear Muffin Tin Orbital (LMTO) method has been used to calculate the band structure, electron density, and the heat of formation of scandium monophosphide. The properties of the phosphide have been obtained by minimizing the total valence energy as a function of the atomic volumes of the scandium and phosphorus atoms. The scandium monophosphide is found to be metallic, but the density of states at the Fermi level is very low. The phosphorus valence electrons are divided into a separate low-lying s band and a high-lying p band. The most important bonding interaction takes place between the scandium d- and the phosphous p-orbitals although almost the same number of electrons are involved in interactions between the s and p bands of the scandium and the phosphorus atoms. There is a preference for the scandium d electrons to occupy the d 7 Orbitals pointing in the directions of the nearest phosphorus atoms. The calculated value of the heat of formation is −339 kJ mol −1 which compares favourably with the experimental value of −343.5 ± 12 kJ mol −1. The calculated value of the unit cell a-axes is 5.233 Å (experimental 5.312 Å).

Molecular structure and conformation of 2-acetyl-5-methyl-1,2,3-diazaphosphole: the use of ab initio calculations in an electron diffraction study

A detailed structural r a analysis is performed using electron diffraction data obtained earlier for 2-acetyl-5-methyl-1,2,3-diazaphosphole. The molecular model being refined is based on our recently published ab initio calculation results for some 1,2,3-diazaphospholes. This model suggests an equilibrium mixture of two planar molecular forms of C s symmetry, P,O- syn and P,O- anti, having equal geometrical parameters part from the angle of rotation of the acetyl group (φ). In agreement with the calculations, it is shown that under experimental conditions (nozzle temperature 100–120°), the P,O- syn conformation predominates (95.7(6.0)%). The following values are obtained for the geometrical parameters (bond lengths r a in Å, angles in degrees): N 2P, 1.729(15); P=C 4, 1.729(15); weighted average (N 1N 2, N 2C 11) av ., 1.413(8); ▪, 1.439(13); C 5=N 1, 1.300(6); C=O, 1.242(5); (CC Me) av., 1.533(4); (CH) av., 1.102(8); C 5=N 1N 2, 107.5(8); N 1N 2P, 116.0(5); N 2P=C 4, 88.8(5); P=C 4C 5, 108.8(6); C 4C 5=N 1, 118.8(9); PN 2C 11, 119.9(12); N 2C 11=O, 119.6(9); N 2C 11C 13, 117.4(14); φ P,O- syn , 5.9(130). (Numbers in parentheses are three times the least squares standard deviation values, 3σ.) The changes in the 2H-1,2,3-diazaphosphole cycle bond lengths caused by introduction of the acyl substituent to the N 2 atom, as predicted by ab initio calculation, are corroborated experimentally. The observed changes are presumably the result of somewhat decreased π-electron delocalization in the ring. The value of the two-coordinate phosphorus valence angle is far smaller than, for example, the angle in acyclic structures, i.e., it largely depends on the geometry of the 5-membered ring. The valence angle at the imino nitrogen atom, N 1, not only decreases to 107.5°, but is also far smaller than the endocyclic angle at the three-coordinate amino nitrogen atom N 2.

STERIC STRUCTURE OF PHOSPHORUS CONTAINING HETEROCYCLES XLV. SPECTRAL1H AND13C NMR CRITERIA FOR CONFORMATIONAL STUDIES OF 1,3,2-DIOXAPHOSPHOCINES

Abstract The 13C and dynamic 1H NMR spectroscopy were employed to derive spectral tests for conformational studies of eight-membered phosphorus (PIII and PIV) containing heterocycles: 4,5; 7,8-dibenzo-(I) and dinaphto-(II) 1,3,2-dioxaphosphocines. Passing from series (I) to (II) causes a dramatic change in the shift difference of methylene protons at C-6. The geminal 2 J(HH) and long-range 5 J(PH) spin-spin couplings are determined by the ring structure. The latter is also influenced by the phosphorus valence state and the orientation of substituents at phosphorus. Fairly definite stereo-chemical assignments can be made using the n J(31P13C) couplings with n of 2 to 5.

Alkyloxy- and silyloxy-derivatives of P V and Sb V

The thermal decompositions of Ph 4POR (R = CH 3, CH(CH 3 2, CH 2Ph) and Ph 4SbOCH 2Ph have been investigated. Previously suggested routes of intramolecular transfer whereby the valence of phosphorus and antimony is reduced, have been confirmed. Ph 5P reacting with Ph 3SiOH produces unstable Ph 3P(OSiPh 3) 2 which decomposes to triphenylphosphine oxide and hexaphenyldisiloxane. A similar reaction of Ph 4POCH 2Ph with Ph 3SiOH (1 2) gave similar results. In the latter reaction a ratio of 1 1 results in unstable Ph 3P(OCH 2Ph)OSiPh 3 which decomposes to Ph 3PO and benzyloxytriphenylsilane. In similar reactions of Ph 5Sb and Ph 4SbOCH 2Ph with Ph 3SiOH stable Ph 4SbOSiPh 3 is produced. Ph 3P reacts with (CH 3) 3SiOOSi(CH 3) 3 and Ph 4SbOOGePh 3 along an oxidizing—reducing route to give Ph 3PO, and [(CH 3) 3Si] 2O and Ph 4SbOGePh 3, respectively. Ph 5P reacting with (CH 3) 3SiOOH, Ph 3GeOOH and Ph 3SiOOH produces peroxides of the type Ph 4POOMR 3, which isomerize to unstable P V compounds of the general formula Ph 3P(OPh)(OMR 3) where M an element of Group IV.

INFLUENCE OF INHIBITORS ON THE BASIS OF DERIVATIVES OF PHOSPHIT TO CHEMILUMINESCENCE AT PHOTO AND THERMOOXIDATION OF DIESEL FUEL

It has been carried out thermo-and photothermal oxidation of diesel fuel by thermochemiluminescence and photothermochemiluminescence with participation of phosphite-based inhibitors with various substituents. The influence of the peculiarities of the structure of inhibitors on the efficiency and degree of quenching of chemiluminescence in the temperature range of 20-220 °C before and after exposure to the photo irradiation using a light filter simulating solar radiation is considered. The main components of diesel fuel with a temperature boiling of 180-360 °C are naphthenic-paraffinic and alkylaromatic hydrocarbons. It has been established that photochemical reactions in diesel fuel take place according to the molecular and radical mechanisms, respectively, in one- and two-photon methods of light absorption. The single-quantum process occurs in aromatic rings with the formation of endoperoxides. The two-quantum process proceeds as a result of intramolecular energy transfer from aromatic rings to alkyl substituents in which alkylaromatic radicals are generated by hydrogen atoms. The latter, because of their high reactivity, do not stabilize and contribute to the continuation of the chain reaction with the formation of radicals (Н+R-АУВ®H2+R·-АУВ). The change in the valence of phosphorus in inhibitors during their interaction with peroxide radicals formed in naphthene-paraffinic and alkylaromatic hydrocarbons is discussed. The minimum and maximum amounts of these radicals reacting with molecules containing fragments with weakly bound C-H bonds and unpaired electrons C • -O •, formed during photo-irradiation of the inhibitor, are considered.

Tervalent phosphorus thioesters

1. Ethylphenylphosphinothious esters react with alkyl halides in accordance with the Arbuzov-rearrangement scheme. In the reaction between benzyl bromide and propyl ethylphenylphosphinothioite benzylethylphenyl(propylthio)phosphonium bromide was isolated and was characterized; it is the intermediate product in the rearrangement, and its thermal decomposition gives benzylethylphenylphosphine sulfide. 2. The reactions of ethylphenylphosphinothious esters with acyl halides go without change in the valence of phosphorus with formation of carbothioic esters and ethylphenylphosphinous halides.

The Molecular Structure of P4O6, P4O8, P4O10 and As4O6 by Electron Diffraction

Molecular structures of P4O6 and As4O6 were determined from electron diffraction data. P4O6 was found to have the symmetry of the point group Td with an angle P–O–P of 128.5±1.5°, and a P–O distance of 1.67±0.03A. In this structure the phosphorus oxygen distances and the phosphorus valence angles were preserved with resulting deformation of the oxygen valence angle. The separation of the arsenic atoms in As4O6 was found to be 3.20±0.05A. Because of the predominant scattering of the arsenic atoms it was difficult to determine the oxygen valence angle, As–O–As. Values of 120°, 127.5° and 140° gave approximate agreement between the observed and calculated positions of maxima. Electron diffraction photographs obtained from P4O10 differ considerably from those found for P4O6. It was not possible to explain all of the features of the P4O10 diffraction pattern by a model having the symmetry of the point group Td and it is thought that the structure might be one of lower symmetry. Data were obtained on P4O8 which indicated that it has approximately the same electron diffraction pattern as P4O10.