Hexamethylphosphotriamide Research Articles

Triboluminescence and crystal structure of the complex [Eu(NО3 )3 (HMPA)3 ]: role of cleavage planes.

The atomic structure of crystals of the [Eu(NО3 )3 (HMPA)3 ] [hexamethylphosphotriamide (HMPA)] complex characterized by an intensive luminescence and triboluminescence was determined using X-ray structural analysis. Noncentrosymmetric crystals have a monoclinic syngony: a=16.0686 (3), b=11.0853 (2), c=20.9655Å (4), β=93.232° (1), space group P21 , Z=4, ρcalc =1.560g/cm3. The crystal structure is represented by individual С18 Н54 EuN12 O12 P3 complexes linked through van der Waals interactions with clearly expressed cleavage planes. The Eu(III) atom coordination polyhedron reflected the state of a distorted square antiprism. Structural aspects of the suggested model, including formation of triboluminescence properties, were considered and the role of the cleavage planes was discussed.

Electronic spectra of uranium tetrachloride clusters with electron-donor ligands

Electronic absorption spectra of nanoclusters of uranium tetrachloride are obtained experimentally and analyzed over a wide spectral range, from the visible to the IR. The structure of the long wavelength electronic absorption spectra is discussed in terms of the structure and electron-donor number of the attached ligand. Molecules of dimethyl sulfoxide (DMSO), hexamethyl phosphotriamide (HMPT), and water were used as ligands. The effect of the symmetry of the surroundings of the U4+ ion on the structure of the electronic spectrum is examined.

Enthalpy and heat capacity parameters of ammonium bromide interaction with hexamethylphosphotriamide in water

Thermal effects of solution of ammonium bromide in hexamethylphosphotriamide (HMPT)-water mixtures at 4° C, 15°C, and 46°C in the region of minor additions of the nonaqueous component were investigated for the first time by calorimetry. Variations of heat capacity in the course of solution were calculated using previous data for 25°C and 40°C. The curves of the heat capacity of solution (transfer) and temperature variation of transfer entropy versus composition have a minimum near the region of the existence of the 1:20 HMPT:water clathrate. The enthalpy, heat capacity, and temperature variations of the entropy coefficients of electrolyte amide pair and three-particle interactions in water were calculated in terms of MacMillan-Mayer theory. Within the framework of the group additivity method it is shown that the heat capacity coefficient of the bromide ion-HMPT pair interaction is negative and dictates temperature variations of enthalpy for ammonium bromide and tetraalkylammonium interactions with HMPT in water.

63Cu Nuclear Magnetic Resonance and Viscosity Studies of Copper (I) Perchlorate in Mixed Solvents Containing Acetonitrile

Abstract 63Cu nuclear magnetic resonance and viscosity studies of 0.064 M copper (I) Perchlorate solutions have been made at 298 K in binary mixtures of acetonitrile (AN) with dimethylsulphoxide (DMSO), hexamethylphosphotriamide (HMPA), N,N-dimethylacetamide (DMA), nitromethane (NM), propylene carbonate (PC) and 3-hydroxypropionitrile (3 HPN) at several compositions of the mixtures using a 500 MHz NMR Spectrometer and Ubbelohde viscometer, respectively. The chemical shift (δ), linewidth (Δ) and line intensity (I) of the 63Cu NMR signal in these mixed solvents have been measured relative to the 63Cu signal in 0.064 M copper (I) Perchlorate (CuClO4) solution in pure AN. The quadrupolar re-laxation rates (1/T2)Q, reorientational correlation times (τR) and quadrupolar coupling constants (QCC) of the copper (I) solvates have also been estimated from the data. The QCC values show a big variation in all solvent systems with the change of solvent composition, indicating the formation of mixed com-plexes. The variation of all NMR parameters with solvent composition shows strong effects of DMSO, HMPA, and DMA on the solvation behaviour of Cu + in the first three mixtures, and relatively much weaker effects of PC, NM and 3HPN in the other three mixtures.

Vibrational study of ionic association in polar aprotic solvents. Isocyanate complexes of non-transition-metal ions

Complexes between alkaline-earth-metal ions M2+ and cyanate OCN− in aprotic solvents are studied by infrared spectrometry in the ν(CN) region (2150–2250 cm−1). In dimethylsulphoxide (DMSO) and hexamethylphosphotriamide (HMPT) isocyanate MNCO ion pairs exhibit a specific ν(CN) band while M(NCO)2 species usually have two ν(CN) bands. Pure alkaline earth cyanates are in part dissociated into MNCO+ and OCN− in DMSO. When they are soluble they are not dissociated in N,N-dimethylformanride (DMF) and in pyridine. The Mg2+-OCN− system in HMPT is the only case where two different ion pairs are observed: p1 at 2205 cm−1 and p2 at 2213 cm−1. The high temperature species p2 is tighter than p1. The reaction p1 → p2 is a desolvation reaction as shown by the large values of ΔH and ΔS (ΔH = 37 kJ.mol−1 and ΔS = 100 J.K−1.mol−1). Similar results are obtained with other non-transition ions (Al3+, Zn2+, Cd2+, Hg2+, Ag+, Tl+). The Δν(CN) wavenumber shift of an ion pair relative to free OCN− (≈ 2137 cm1−) is always positive and roughly proportional to the polarizing power of Mz+. This is in agreement with an isocyanate bonding MNCO. When Mz+ is a soft cation Δν(CN) is smaller than expected. This effect is common to all cases of M…CN bonding. The i.r. spectrum of AgOCN in tetrahydrothiophene (THT) exhibits two bands at 2162 cm' (AgNCO) and 2250 cm−1. The second band is assigned to a bridging group AgOCNAg in (AgNCO)2.

Self-Association of Water and Water−Solute Associations in Chloroform Studied by NMR Shift Titrations

Association constants and the corresponding free energies ΔG were obtained by nonlinear least-square fitting of the water 1H NMR shift changes observed at different concentrations. The only until now available earlier value (Shaw, J.-H. L.; Wang, S. M.; Li, N. C. J. Phys. Chem. 1973, 77, 236) is shown to be based on erraneous evaluations and on inaccurate data. Analysis for the self-association of water in chloroform based on a 1:1 dimer model yields ΔG = −3.5 kJ/mol; based on a trimer model one obtains an almost equally good fit with ΔG = −15.4 kJ/mol. The ΔG value in acetonitrile as solvent is with +9 kJ/mol positive (vide infra) as are all ΔG values observed for water−solute associations in chloroform with DMF, DMSO, diphenyl sulfoxide, and benzene, with the exception of HMPT (hexamethylphosphotriamide) and a special diamide designed to take up water by 2 hydrogen bonds. The complexation induced shifts, determined simultaneously from the NMR titrations, are between 3 and 4.5 ppm. They are similar to those observed with hydroxy compounds and show that the simulations are based on realistic models. No correlation is found between the CIS and the corresponding ΔG values. The only upfield shift with −4.4 ppm is found for the benzene−water complex, in agreement with theoretically derived structures.

Electroreduction of nitrobenzene on the mercury electrode in water + HMPA solutions

The electroreduction of nitrobenzene on the mercury electrode has been studied in water+ hexamethylphosphotriamide (HMPA) mixtures. During this study the influence of HMPA on the electrode reactions occurring in the systems PhNO 2 /PhNO 2 .−, PhNO 2 .−/PhNHOH and PhNHOH/PhNO was investigated. The corresponding kinetic parameters have been calculated. The rates of these processes change in the series PhNO 2/PhNO 2 .− > PhNHOH/PhNO PhNO 2 .−/ PhNHOH. The standard rate constants of the PhNO 2 .−/PhNHOH and PhNHOH/PhNO processes decrease with increasing HMPA concentration. This influence is stronger for the PHNO 2 .−/PhNHOH process. The rate of the PhNO 2/PhNO 2 .− process is practically independent of the solvent composition.

Dimethylpropyleneurea-water mixtures: 1. Physical properties

Densities, refractive indices, viscosities, dielectric constants and the absorptions of several solvatochromic indicators have been determined at 25°C for mixtures of N,N′-dimethyl-N,N′-propyleneurea (DMPU) and water in the complete mole fraction scale. the results are compared with the properties of hexamethylphosphotriamide (HMPT) and its mixtures with water which show a striking similarity to DMPU and its mixtures with water. Since HMPT was found to be carcinogenic in animal tests, DMPU offers a suitable substitute since it may be regarded as safe under laboratory conditions.

Adducts of rare-earth trisacetylacetonates with hexamethylphosphotriamide

1. Adducts have been synthesized for the first time of the trisacetylacetonates of the rare earths (RE) with hexamethylphosphotriamide (HMPA), in which the molecule of the molecular ligand is monodentate and coordinated through the oxygen atom of the phosphoryl group. 2. The adducts of the RE trisacetylacetonates with HMPA are more stable thermally than the corresponding hydrates of the trisacetylacetonates, are capable of being sublimed after detachment of the HMPA, and are similar in properties to the corresponding triphenylphosphine oxide derivatives.

Gas Phase Basicity of Hexamethylphosphotriamide (HMPT) and Phosphinoxide Derivatives

Abstract Gas phase basicities are determined by Ion Cyclotron Resonance (ICR) mass spectrometry for the six organophosphorus compounds OP(NMe2)3-x Me x x=0 to 3, OP(nPr)3 and OP(OEt)3. All values are in the range 209–219.3 kcal · mol−1, and their variation with structure is examined. The site of protonation (O or N?) is briefly discussed, and arguments are presented which favour O-protonation.

Enthalpies of solution of tetra-alkylammonium salts in hexamethylphosphotriamide at 298.15 K

The enthalpies of solution of some tetra-alkylammonium salts and of tetraphenylphosphonium bromide in hexamethylphosphotriamide (HMPT) at 298.15 K have been obtained. Ionic enthalpies of transfer from water to HMPT and from HMPT to propylene carbonate (PC) have been calculated on the basis of the extrathermodynamic assumption ΔH°tr(Ph4As+)=ΔH°tr(BPh–4). The results indicate that this assumption is valid for enthalpies of transfer from HMPT to PC, but not for transfer from water to HMPT. The enthalpies of transfer of tetra-alkylammonium ions from HMPT to PC are discussed in terms of the ability of HMPT to solvate alkyl chains.

Enthalpies of solution of some uni-univalent electrolytes in hexamethylphosphotriamide at 298.15 K

Enthalpies of solution of various uni-univalent electrolytes in hexamethylphosphotriamide (HMPT) have been measured at 298.15 K. Ionic enthalpies of transfer from water to HMPT and from HMPT to propylene carbonate (PC) were calculated on the basis of the assumption that the transfer enthalpy of the tetraphenylboride ion is the same as that of the tetraphenyl-arsonium ion. The results are compared with those of the same ions in other solvent pairs and discussed in terms of specific ion–solvent interactions.

Conductance measurements of some electrolytes in N,N-dimethyformamide and its binary mixtures witth other organic solvents—II

Equivalent conductances of Bu 4NBPh 4, Bu 4NNO 3, Bu 4NI,KClO 4, Kl, NaI, NaBPh 4, Ph 4PCl, LiCl, AgNO 3 and CuClO 4. 4AN have been measured at 25°C in binary mixtures of N,N-dimethylformamide (DMF) containing 1 mol % of 1, 1, 3, 3-tetramethylurea (TMU), dimethylsulphoxide (DMSO) and hexamethylphosphotriamide (HMPT). Such measurements for LiCl, NaI, KClO 4 and CuClO 4. 4AN have also been carried out in DMF and in binary mixtures of DMF containing 1 mol % pyridine (Py), α-picoline (α-Pic), β-picoline (β-Pic), γ-picoline (γ-Pic) and acetonitrile (AN). The conductance data in all the cases have been analyzed by the Shedlovsky equation. Limiting ion conductances have been obtained by the method of Fuoss et al. The actual solvated radii of ions, evaluated using limiting ion conductances show that Ag + and Cu + have strong preferential solvation by all solvents which have been used to prepare the binary mixtures with DMF and the preferential solvation for both Ag + and Cu + with HMPT, DMSO and TMU is relatively stronger than with AN and is practically of similar magnitude as with the organic bases.

NUCLEOPHILIC ASSISTANCE IN THE FORMATION OF PYROPHOSPHONATE: EFFECTIVE SIDE-REACTION OF HALOGENOPHOSPHORUS COMPOUNDS WITH WATER IN APROTIC SOLVENTS

Abstract Aside from racemization and direct solvolysis of halogenophosphonates, nucleophilic assistance by dimethylformamide, hexamethylphosphotriamide, N-methylimidazole, pyridine or triethylphosphite in wet solvents brings about P[sbnd]O[sbnd]P bond formation. The nucleophiles are not directly involved in the chemical reaction. The oxygen atom originates from H2O. The reaction does not nevertheless take place via consecutive coupling reaction between preliminary formed phosphonic acid and a second molecule of phosphonic chloride. As proposed in the case of activated racemization and hydrolysis of halogenophosphonates, the mechanistic pathway envisaged involves nucleophilic assistance to dimerization, prior to hydrolysis. In the course of the dynamic stereochemical study of alkyl chloro phenylphosphonates or alkyl chloro phenylthiophosphonates in the presence of nucleophilic agents (dimethylformamide (DMF), hexamethylphosphotriamide (HMPT), N-methylimidazole (NMI), pyridine or triethylphosphite), we have...

Etude par resonance magnétique multinucléaire d'intermédiaires réactionnels électrophiles. Partie 8. Action des acides de Lewis chlorés COCl2, POCl3, (CH3)2N=CHCl+Cl− et Cl2 sur l'hexaméthylphosphotriamide (HMPT)

The structural study of the electrophilic intermediates obtained from carboxamides and chlorinated Lewis acids is extended to the phosphoric amides. The action of COCl2 and POCl3 on hexamethylphosphotriamide (HMPT) can lead to a chlorophosphonium salt (3a) the structure of which is proved by nmr spectroscopy (1H, 13C, 31P, 15N). The mechanism of formation is comparable to that of the chloroiminium chloride (Vilsmeier reagent) from the corresponding amides. The action of chlorine on HMPT does not lead to a stable salt of the same kind but essentially to the substitution product (2). A new biphosphorylated compound (6) has been identified when an excess of chlorine is reacted with HMPT.

Silicon-phosphorus analogies : Participation of external nucleophiles to activated processes of racemization and hydrolysis of chlorophosphono derivatives

Kinetic and stereochemical studies show nucleophilic assistance by dimethylformamide (DMF), dimethylacetainide (DMA), hexamethylphosphotriamide (HMPT) and N-methylimidazole (NMI) in racemization and solvolysis of menthylchloro(phenyl)phosphonate, 1a, and O-ethylchloro(phenyl)thiophosphonate, 2. Similar orders of nucleophilic reactivity (Nu = NMI⪢HMPT>DMF>DMA), and identical rate-laws (v rac=k [M-Cl] [Nu] 2 and v H 2O = k' [M-Cl] [H 2O] [Nu]) are consistent with a common mechanism, governed by entropy (−60 u.e< ΔS ≠<−40u.e). Analogies between reaction mechanisms at silicon and phosphorus are clearly evidenced. A two-step process, involving rate-determining attack on a pentacoordinate complex is discussed.

Electrolyte viscosities in hexamethylphosphotriamide at 25°C

Viscosities of several uni-univalent electrolytes in hexamethylphosphotriamide (HMPT) at 25°C have been measured. Data were analysed by the Jones–Dole equation, and the B-coefficients discussed on the basis of Einstein's equation and in terms of a transition state treatment.

Etude des mobilités ioniques dans les mélanges eau–hexaméthylphosphotriamide. I. Cas du HMPT pur à 25 °C

Ionic mobilities have been measured in hexamethylphosphotriamide (HMPT) and in water–HMPT mixtures in order to investigate the solvation of ions. In view of the large number of studies of conductivities in pure HMPT, we felt it would be interesting to give a general analysis of these data. Our results in pure HMPT will be presented in the course of this analysis.

ChemInform Abstract: ELECTROCHEMILUMINESCENCE OF INORGANIC SALT SOLUTIONS IN HEXAMETHYLPHOSPHOTRIAMIDE

AbstractElektrolyse von LiClO4‐, NaClO4‐, KClO4‐, NaBF4‐, LiCl‐ und KJ‐Lösungen in HMPA liefert kathodisch solvatisierte Elektronen und an der Anode Pseudo‐Phosphoniumionen, die nach Vermischen mit den solvatisierten Elektronen unter Lichtemission reagieren.

Electrochemiluminescence of inorganic salt solutions in hexamethylphosphotriamide

Electrolysis of solutions with the solvent hexamethylphosphotriamide (HMPA) and the solutes LiClO 4, NaClO 4, KClO 4, NaBF 4, LiCl and KI yielded cathodically solvated electrons and, at the anode, species which reacted after mixing with the solvated electrons with emission of light. Electrochemical as well as spectral investigations using some well defined derivatives of HMPA indicated that pseudo-phosphonium ions react with the solvated electrons to form as the excited species the unstable neutral pseudo-phosphonium radicals. It was shown that after addition of anodic products to the solution light emission occurred at the cathode directly upon application of the voltage. The relatively slow rise of intensity of the emitted light in this case was explained by the fact that only the homogeneous reaction could lead to luminescence while the initially direct reduction of the phosphonium ions at the electrode lead to the products without light emission because of quenching.