Prescott, Hillary A.: The Crystal Structures and Thermal Behavior of Hydrogen Monofluorophosphates and Basic Monofluorophosphates with Alkali Metal and N-containing Cations

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Kapitel 2. Experimental Section

The compounds synthesized (Sect. 2.3) were characterized by the following methods.

2.1 Methods

Freeze drying

Freeze drying is a widely used method of sublimation drying, in which a frozen material is dried in high vacuum by subliming the solvent. The method is advantageous for the mild drying and conservation of sensitive products. Originally, the method was used in the manufacturing of instant products: foods, pharmaceuticals, biological and medical materials (blood plasma, serums, viruses). However, freeze drying is also being carried out in the laboratory to isolate unstable compounds, for example, in the synthesis of free radicals in concentrated form. In this case, the solid solvent acts as a stabilizer during freeze drying. A recombination does not take place after freeze drying, because of the absence of the reaction medium [55].

The eluate solutions (200-500 mL) of partially neutralized H2PO3F were evaporated completely by a Christ Alpha 2-4 freeze dryer (LDC-1M control system). The solutions were freezed by liquid N2 prior to freeze drying. The chamber was then evacuated and the


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freeze drying started. Freeze drying was carried out at 0.04 mbar until the product had a constant temperature between 379-388 K. The dried powder/oil was then removed and recrystallized. Sublimation was observed for the amine salts, but did not affect the later compositions of the crystallized salts.

Fluoride Analysis

Fluoride analysis included two types of sample preparation and the measurement of the fluoride contents by a fluoride-sensitive electrode. In the first case, the sample was decomposed according to the Seel method [56] enabling the measurement of fluoride from F- and PO3F2- in the sample. The aqueous solution of the decomposed sample was then measured for its total fluoride content. In a second analysis, a sample of the same compound was simply dissolved in 50 mL. In this case, only the free fluoride in the sample was measured and not the fluoride bonded to phosphorus. The use of these two sample preparations proved to be an excellent method for checking product purity. In cases where enough sample was available, both variations were carried out and compared. The measured fluoride contents are given in Sect. 2.3, where the method of sample preparation is indicated by Seel or H2O.

31P and 19F NMR Spectroscopy

Samples for NMR measurements were dissolved in H2O/D2O and measured in FEP NMR tubes. The spectra were recorded on a Bruker DPX 300 spectrometer at frequencies of 121.5 and 282.4 MHz for 31P and 19F, respectively, with internal standards of 85% H3PO4 and Freon-11. The amount of phosphate (%H2PO4-) was estimated by the signal ratio of the integrated phosphate and monofluorophosphate signals in the 31P-NMR spectrum.

19F, 31P, and 1H MAS NMR Spectroscopy

The 19F, 31P, and 1H MAS NMR spectra (Appendix A.4) of the powdered sample were recorded on a Bruker Solid State ASX 400 spectrometer equipped with a Bruker MAS 4 mm probe head at frequencies of 376.46, 161.9, and 400.13 MHz, respectively, with a rotation of 12 kHz. The following pulse programs were used: pulse time 2 µs with a relaxation time of 60 s for 31P (32 scans), pulse time 1 µs with a relaxation time of 30 s for 19F (80 scans), and pulse time 2 µs with a relaxation time of 30 s for 1H (40 scans).


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Single Crystal X-ray Diffraction

Measured single crystals were selected under paraffin oil using a polarization microscope. The crystals were mounted on glass fibers and measured at a specific temperature (Appendix A.1) on either the four-circle Stoe STADI-4 diffractometer or the Stoe Imaging Plate Diffraction System (IPDS) area detector. In both cases, Mo-Kalpha radiation was employed with a graphite monochromator (lambda = 0.71073 Å). The four-circle diffractometer was used to measure larger crystals of high quality with smaller cells. The measurement method was a 2theta/omega-scan with a ratio of 1.0 or 0.5. Smaller crystals with larger lattice parameters and/or poorer quality were measured on the IPDS with rotation and oscillation about the phi-axis. During the measurements, the crystal were cooled to lower temperatures by a Oxford CRYOSTREAM using liquid nitrogen. An absorption correction was applied to the data by one of the following methods: Psi scan, numerical, or X-Shape [57]. The structures were solved with direct methods using SHELXS-86 [58] or SHELXS-97 [59] and refined with SHELXL-93 [60] or SHELXL-97 [61]. Non-hydrogen atoms were refined anisotropically. Distinction between oxygen and fluorine was accomplished by first refining the structure to a low R1-factor with oxygen occupying all of the atoms on phosphorus. One position on phosphorus was then assigned to fluorine based on typical P-O/F bond lengths and the location of hydrogen bonds. The assignment was confirmed by a decrease in the R1 and wR2-factors after a final refinement of the structure. The hydrogen atoms were found with difference Fourier syntheses and refined isotropically. Experimental data for the measurements can be found in Appendix A.1 and in the corresponding crystal structure sections.

Bond Valence Calculations

The bond valence model [62, 63] was used to calculate valency of fluorine, check bonding, and verify the correctness of the structure. The model is derived from the concept of bond strength suggested by Pauling [64]. The bond valency, í, is calculated from the bond length, dij, between the ion, i, and its coordination partner, j, by the following formula:

íij = exp[(Rij - dij)/b].

Rij is referred to as the bond valence parameter, which has been averaged for each type of bond [62]. The difference, Rij - dij, is normalized with a constant, b [Å], which varies depending on i and j. The total valency, Vi, of the ion, i, is then calculated by drawing the sum of all bond valencies for that ion: Sigmajíij = Vi.


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X-ray Powder Diffraction

X-ray powder diffraction patterns were measured by a XRD 7 Seiffert-FPM diffractometer (Cu-Ká radiation, Ni-filter, 5-65°, 0.05 step, 10s/step). The patterns were then compared with data from the PDF databank [65] for known compounds or with the generated pattern from the single crystal data for new compounds.

Differential Thermal Analysis

The conventional STA graphs (T, DTA, TG, DTG) were obtained by a Netzsch STA 429 thermoanalyzer. MS-coupled investigations (TG-MS) were performed using a Netzsch STA 409 C skimmer-coupled system. In the case of the STA 429 thermoanalyzer, the sample (10-20 mg) was measured by a mini-sample carrier system featuring a Pt/PtRh10-thermocouple, Pt crucible, and alpha-Al2O3 as reference. A purge gas of air or N2 (100 mL/min) and a heating rate of 5 K/min were used. A DTA/TG-sample carrier system (Pt/PtRh10-thermocouple, Pt crucible, sample mass of about 15 mg against an empty crucible, purge gas, air or N2, 30 mL/min, and a heating rate of 10 K/min) was integrated into the STA 409 C skimmer-coupled system.

The sample was pulverized in an agate mortar before measurement. The raw data obtained by the STA 429 and STA 409 C were interpreted with the Netzsch-Software (Version SW/STA/531.123_2) and Netzsch Proteus v. 4.0+, respectively, without further data processing. The determination and assignment of the characteristic temperatures in the STA graphs (Ti - initial, Te - extrapolated onset, Tp - peak temperature) was carried out by following international recommendations [66]. The precision of the measurement was checked regularly by measuring recommendation standards, such as Sn, Li2SO4, Al [67, 68]. The enthalpimetric analysis of the DTA graphs (maximum accuracy of 10-15%) were calibrated by an appropriate standard following the recommendations in [68, 69].

IR Spectroscopy

IR spectra were recorded as KBr disks (tablets) in the range of 450-4000 cm-1 on a Perkin-Elmer 1600 FT-IR spectrometer.


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2.2 Chemicals

Solids

Amberlite IR-120+ ion-exchange resin

Aldrich

Ammonium hydrogen difluoride

Fluka, 98.5%

Cesium carbonate

Aldrich, 99%

Guanidinium carbonate

Riedel-de-Haën, 98%

Monofluorophosphoric acid

ABCR/Avocado, 95%

Potassium carbonate

Fluka, 99%

Phosphorus pentoxide

Merck, 98%

Piperazine

Aldrich, 99%

Rubidium carbonate

Merck, 98%

Sodium monofluorophosphate

BK Giulini Chemie GmbH. & Co.

Uronium phosphate

Fluka, 98%

N, N´-Dimethyl urea

Merck, 98%

Liquids

Diethylamine

Fluka, 99.5%

Diethylether

Fluka, ge 99%

Ethanol, abs.

Bundesmonopolverwaltung f. Branntwein, 99.8%

Fluoric acid

Fluka, 100%

Methanol

Aldrich, 99+%

Tetramethylammonium hydroxide

Aldrich, 25wt% in H2O

Tetramethylammonium hydroxide

Aldrich, 25wt% in MeOH

Triethylamine

Fluka, 98%

2.3 Preparation

The compounds introduced here were synthesized by cation exchange, in which the eluant, an aqueous solution of Na2PO3F (see Sect. 2.2 Chemicals) or (NH4)2PO3F (synthesized according to [70]), was passed through a chromotography column of 150-200 g Amberlite IR 120+ ion-exchange resin. Cation exchange was carried out in H2O despite the risk of hydrolysis of H2PO3F because of the insolubility of the basic monofluorophosphates in other solvents. The rate of cation exchange was adjusted for an effective, but accelerated exchange to avoid extended hydrolysis of the acid in the column. The acidic eluate of H2PO3F was collected after its detection with Litmus paper. An aqueous solution of the corresponding base (carbonate, amine, monofluorophosphate, see Sect. 2.2 Chemicals) was added to the acidic eluate dropwise after collection of the first few drops. The rate of


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neutralization was regulated to achieve a pH between 3-5 in the eluate-base solution to impede hydrolysis. Cation exchange was over when the pH of the solution remained constant and the drops coming off the column were neutral. After cation exchange, the partially neutralized, dilute, aqueous solution was evaporated completely by freeze drying, unless otherwise indicated. This method of sublimation drying was carried out to avoid the escape of HF and consequent condensation of phosphate. Yields were calculated after freeze drying for powders that were easy to handle. Oils obtained were recrystallized directly from the tray without being weighed.

Characterization

The compounds were characterized by elemental analysis and 31P and 19F NMR spectroscopy (Sect. 2.1). The NMR data and elemental analyses are given below for the different compounds. Analyses could not be carried out for compounds that were difficult to obtain in crystalline form. Deviations were also observed in the elemental analyses of compounds. These discrepancies were based on product impurity due to partial hydrolysis of the HPO3F- anion and difficulties with product isolation and recrystallization (Sect. 3.1). The measured fluoride contents, in particular, tend to deviate from calculated values and a complete fluoride analysis with the two types of sample preparation (H2O and Seel) was not always possible. The type of sample preparation used for the fluoride analysis is indicated by H2O and/or Seel (Sect. 2.3 Fluoride analysis).

31P and 19F NMR spectroscopy enabled an estimate of the amount of the phosphate impurity in the eluate solution before freeze drying or in the recrystallized product after dissolution in H2O. Once again, whether the eluate solution or the solution of the recrystallized product were measured, depended on product purity and the ease and success of recrystallization. The 31P and 19F NMR spectra could be recorded for almost all of the compounds as an eluate solution or the dissolved freeze dried product. In fewer cases, spectra of crystals were measured. Therefore, the type of sample used for the NMR measurement is given (neut. eluate, crystals, residue from tray, MeOH solution, or freeze dried powder) with the NMR data. Singulets in 31P and 19F NMR spectra at about 0.7 and -125 ppm confirmed the presence of phosphate and fluoride impurities, respectively, based on the partial hydrolysis of the PO3F anion. Other signals are discussed when appropriate.


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The system of Na / PO3F

NaHPO3F·2.5H2O (M = 167.01 g/mol)

After cation exchange of the eluant of sodium monofluorophosphate (15.8 g, 110 mmol), the eluate was partially neutralized with Na2PO3F (15.8 g, 110 mmol). The final pH was 2.5. Ten grams of the freeze-dried, white powder of NaHPO3F [26, 71] (91% yield) were dissolved in about 5 mL H2O. Recrystallization was carried out by the addition of portions of EtOH (1mL). The cloudy solution was refrigerated overnight. Slightly hygroscopic crystals of NaHPO3F·2.5H2O (58% yield) were filtered, dried, and characterized.

31P-NMR (121.5 MHz, crystals in H2O/D2O, ä): -3.7 (d, J(P,F) = 909 Hz, HPO3F-), 0.7 (s, H2PO4-), 11% H2PO4-.

19F-NMR (282.4 MHz, crystals in H2O/D2O, ä): -74.7 (d, J(P,F) = 909 Hz, HPO3F-).

Anal. Found (Calcd): H 3.30 (3.59), F 0.3 (H2O)/ 9.2 (Seel) (11.38)%.

Na2PO3F·10H2O (M = 324.11 g/mol)

The decahydrate of Na2PO3F was synthesized by (a) cation exchange and (b) direct recrystallization of Na2PO3F.

(a) In the first, Na2PO3F (5 g, 35 mmol) was passed through the cation exchange column and neutralized by a second portion (7.5 g, 52 mmol) reaching a pH of 4.90. The freeze dried powder was isolated in high yield. The raw product (2.13 g) was dissolved in H2O-acetone and placed in the freezer. The partially frozen solution was then moved to the refrigerator and acetone (2 mL) was added. A frozen sludge was found on the bottom of the flask. On examination of this sludge under the microscope, single crystals were found, which melted at room temperature. A single crystal of Na2PO3F·10H2O was then picked out under a cold stream of N2 for measurement. Crystals of NaHPO3F·2.5H2O were also found in the sludge.

31P-NMR (121.5 MHz, freeze dried powder in H2O/D2O, ä): 0.1 (d, J(P,F) = 881 Hz, PO3F2-), 0.8 (s, H2PO4-), 9% H2PO4-.

19F-NMR (282.4 MHz, freeze dried powder in H2O/D2O, ä): -74.2 (d, J(P,F) = 881 Hz, PO3F2-), -120.8 (s, F-).

(b) The decahydrate was also isolated by crystallization of Na2PO3F from aqueous


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solution. Na2PO3F (8.4 g, 58 mmol) was dissolved in H2O (10 mL) under stirring. A fine white precipitate formed and the mixture was left to stand overnight. The solution was then decanted and refrigerated. After five days without crystal formation, a crystal of Na2SO4·10H2O was added to the solution. Single crystals of Na2PO3F·10H2O were obtained after the solution was left to stand overnight.

The thermal stability of the Na2PO3F·10H2O crystals was investigated directly on the IPDS diffractometer between 230 and 285 K. The same unit cell was determined by exposures taken up to 280 K. The exposure at 285 K showed the crystal had broken down to a powder. Powder rings at higher d-values were too diffuse to interpret; however, the d-values observed in the range of 2.00 - 1.356 Å could be assigned to Na2PO3F [72]. The crystals had an incongruent melting point of 283±2 K.

Na5[N(CH3)4](PO3F)3·18H2O (M = 807.3 g/mol)

Long, hygroscopic needles of Na5[N(CH3)4](PO3F)3·18H2O were crystallized from H2O by slow evaporation on a tray or by the additon of EtOH to an aqueous solution and refrigeration. The white, hygroscopic powder was obtained by freeze drying after partial cation exchange of Na2PO3F (10g, 69 mmol) and the addition of N(CH3)4OH in MeOH (29.2 ml, 69 mmol).

31P-NMR (121.5 MHz, crystals in H2O/D2O, ä): 1.3 (d, J(P,F) = 871 Hz, PO3F2-).

19F-NMR (282.4 MHz, crystals in H2O/D2O, ä): -74.3 (d, J(P,F) = 871 Hz, PO3F2-).

Anal. Found (Calcd): F 0.0 (H2O)/6.5 (Seel) (7.06)%.

The system of K / PO3F

KHPO3F (M = 138.08 g/mol) [26]

The KHPO3F salt was obtained with Na2PO3F (8.5 g, 59 mmol) and K2CO3 (4.1 g, 29 mmol) with a final pH 4.14 after cation exchange and partial neutralization. Slow evaporation was not successful in obtaining single crystals from the freeze dried, powder. Branched clusters of crystals of the freeze dried powder were instead formed from concentrated, aqueous solution by slowly adding MeOH (1 mL); the solution was then refrigerated. High amounts of phosphate and low yields of the KHPO3F crystals as the minor phase pervented phase analysis.


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K3[H(PO3F)2] (M = 314.24 g/mol)

The 3:1 potassium hydrogen monofluorophosphate was synthesized by cation exchange of (NH4)2PO3F (1.5 g, 11 mmol) and the addition of K2CO3 (0.8 g, 6 mmol). The eluate solution (50 mL) was concentrated in vacuum at a bath temperature of 20-25°C to 25 mL. Crystals in the solution were filtered and the solution was hung on the freeze dryer. The dried product was dissolved in a mixture of H2O/MeOH (2:1) at 50°C. After refrigeration, MeOH (3 mL) was added. No crystals were formed. Single crystals were then obtained by recrystallization from aqueous solution. The solution was evaporated in a desiccator. These several block crystals characterized as K3[H(PO3F)2] formed had a pH of 4.86 in aqueous solution.

31P-NMR (121.5 MHz, neut. eluate in H2O/D2O, ä): -0.9 (d, J(P,F) = 888 Hz,

H(PO3F)23-), 0.8 (s, H2PO4-), 15% H2PO4-.

19F-NMR (282.4 MHz, neut. eluate in H2O/D2O, ä): -74.4 (dd, J(P,F) = 888 Hz, J(H,F) = 8 Hz, H(PO3F)23-).

Anal. Found (Calcd): F 11.9 (H2O) (6.05)%.

The system of Rb / PO3F

alpha-RbHPO3F (M = 184.45 g/mol)

alpha-RbHPO3F was obtained using Na2PO3F (7.5 g, 52 mmol) and Rb2CO3 (7.4 g, 32 mmol) with cation exchange. The neutralized eluate had pH 4.01 after cation exchange and was then back titrated with H2PO3F to pH 3.5. The solution (300 mL) was freeze dried obtaining a product in high yield. Crystals were obtained from an aqueous solution (1 mL) of the raw product (1.3 g).

31P-NMR (121.5 MHz, freeze dried powder in H2O/D2O, ä): -3.3 (d, J(P,F) = 905 Hz, HPO3F-), 0.8 (s, H2PO4-), 13% H2PO4-.

19F-NMR (282.4 MHz, freeze dried powder in H2O/D2O, ä): -74.7 (d, J(P,F) = 906 Hz, HPO3F-).

Anal. Found (Calcd): F 1.1 (H2O)/ 9.4 (Seel) (10.30)%.


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beta-RbHPO3F (M = 184.45 g/mol)

The beta-modification of RbHPO3F was synthesized using Na2PO3F (13.8 g, 96 mmol) and Rb2CO3 (10.8 g, 47 mmol). The pH was kept between 3 and 5 during cation exchange and neutralization with a final pH of 4.43. The freeze dried powder was obtained in 90% yield. Recrystallization involved the dissolution of the raw product (7 g) in H2O (2 mL). The saturated solution was then filtered and left to stand. After three days, block crystals were found, removed from the solution, and dried on a tile (8.5% yield).

31P-NMR (121.5 MHz, neut. eluate in H2O/D2O, ä): -2.2 (d, J(P,F) = 897 Hz, HPO3F-), 0.8 (s, H2PO4-), 12% H2PO4-.

19F-NMR (282.4 MHz, neut. eluate H2O/D2O, ä): -74.5 (dd, J(P,F) = 897 Hz, J(H,F) = 3.5 Hz, HPO3F-).

Anal. Found (Calcd): H 0.53 (0.53), F 0.5 (H2O)/9.2 (Seel) (10.30)%.

The system of Cs / PO3F

CsHPO3F (M = 231.89 g/mol)

After cation exchange of an eluant of Na2PO3F (5 g, 35 mmol), the eluate was partially neutralized with Cs2CO3 (5.7 g, 17 mmol) to a pH 3.8. The freeze dried, hygroscopic, white powder (81% yield) was recrystallized from H2O by pipetting EtOH slowly along the walls of the PE flask. Crystals formed on the walls. The H2O/EtOH solution was refrigerated overnight. Hygroscopic crystals were measured and characterized.

31P-NMR (121.5 MHz, neut. eluate in H2O/D2O, ä): -3.3 (d, J(P,F) = 905 Hz, HPO3F-), 0.8 (s, H2PO4-), 12% H2PO4-.

19F-NMR (282.4 MHz, neut. eluate in H2O/D2O, ä): -74.4 (d, J(P,F) = 905 Hz, HPO3F-).

Anal. Found (Calcd): H 0.48 (0.43), F 8.1 (Seel) (8.19)%.

Cs3(NH4)2(HPO3F)3(PO3F) (M = 829.72 g/mol)

Cs3(NH4)2(HPO3F)3(PO3F) was prepared using (NH4)2PO3F (1.6 g, 12 mmol) and Cs2CO3 (2.0 g, 6 mmol) in combination with partial cation exchange. The eluate (pH 4.31) was evaporated to 20 mL. The solution was then freeze dried to give a 4.5% yield of a hygroscopic, white powder. The substance was placed in a desiccator overnight.


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Recrystallization was carried out from a mixture of H2O/MeOH of 2:1 at 323 K. The solution was then evaporated in air forming crystals of (NH4)2PO3F·H2O [73]. The crystals were kept in a desiccator and rechecked after one month. Rectangular and block crystals for two phases were observed. The rectangular crystals were again (NH4)2PO3F·H2O; the block crystals were characterized as Cs3(NH4)2(HPO3F)3(PO3F).

31P-NMR (121.5 MHz, freeze dried powder in H2O/D2O, ä): -1.5 (d, J(P,F) = 891 Hz, HPO3F-/PO3F2-), 0.8 (s, H2PO4-), 17% H2PO4-.

19F-NMR (282.4 MHz, freeze dried powder in H2O/D2O, ä): -74.5 (d, J(P,F) = 891 Hz, HPO3F-/PO3F2-).

Anal. Found (Calcd): F 8.2 (H2O) (9.16)%.

The system of NH4 / PO3F [26]

alpha-NH4HPO3F (M = 117.02 g/mol)

á-Ammonium hydrogen monofluorophosphate was obtained by two different methods.

(a) The á-modification was first prepared from (NH4)2PO3F synthesized according to [70]. (NH4)2PO3F (1.5 g, 11 mmol) was protonated by grinding it together with NH4HSO4 (1.3 g, 11 mmol) in MeOH. The NH4HPO3F formed was separated from the byproduct, (NH4)2SO4, by filtration. The (NH4)2SO4 was washed several times with MeOH until more or less neutral. The NH4HPO3F/MeOH solution (pH 2.8) and the washings were collected and concentrated slightly. NH4HPO3F was precipitated by the addition of ether, filtered, and recrystallized from MeOH.

31P-NMR (121.5 MHz, MeOH solution with D2O, ä): -4.3 (d, J(P,F) = 909 Hz, HPO3F-), 0.7 (s, H2PO4-), 62% H2PO4-.

19F-NMR (282.4 MHz, MeOH solution with D2O, ä): -75.9 (d, J(P,F) = 908 Hz, HPO3F-).

Anal. Found (Calcd): F 14.2 (H2O) (16.24)%.

(b) á-NH4HPO3F was also obtained by cation exchange using a H2PO3F/(NH4)2PO3F ratio of 1:1. Recrystallization from aqueous solution at room temperature yielded á- NH4HPO3F.


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â-NH4HPO3F (M = 117.02 g/mol)

Two syntheses were used to obtain the â-modification of ammonium hydrogen monofluorophosphate.

(a) The H2PO3F/(NH4)2PO3F molar ratio was decreased from 1:1 to 2:3. Cation exchange was done with an aqueous solution of Na2PO3F (7 g, 49 mmol). The eluate was neutralized with (NH4)2PO3F (9.8 g, 73 mmol) placed in the beaker prior to cation exchange. After cation exchange, a final pH of 3.4 was reached by adding a second portion of (NH4)2PO3F (0.65 g, 5 mmol). After freeze drying, the white powder was dissolved in H2O-MeOH. The saturated solution was left to stand and after two days, crystals were formed.

31P-NMR (121.5 MHz, crystals in H2O/D2O, ä): -3.6 (d, J(P,F) = 908 Hz, HPO3F-).

19F-NMR (282.4 MHz, crystals in H2O/D2O, ä): -74.8 (d, J(P,F) = 908 Hz, HPO3F-).

Anal. Found (Calcd): N 12.08 (11.96), H 3.96 (4.28), F 0.4 (H2O)/15.7 (Seel) (16.24)%.

(b) â-NH4HPO3F was also obtained by recrystallizing the raw product of a 1:1 H2PO3F/(NH4)2PO3F synthesis from H2O at 333 K.

The system of [N(CH3)4] / PO3F

[N(CH3)4]HPO3F·H2O (M = 191.14 g/mol)

Tetramethylammonium hydrogen monofluorophosphate monohydrate was synthesized via cation exchange with the reagents, Na2PO3F (7.95 g, 55 mmol) and N(CH3)4OH in H2O (21.78 g, 60 mmol). The final 300 mL solution had a pH 3.80. The solution was freeze dried to obtain an oil, which was diluted with H2O and slowly evaporated in an evacuated desiccator. The concentrated thick solution was then placed in the refrigerator. Measured crystals formed from the residue on the freeze drying dish and in solution were [N(CH3)4]H2PO4·H2O [74]. After five months, cubic crystals of [N(CH3)4]HPO3F·H2O were found in the refrigerated solution. Crystals were dried and characterized.

31P-NMR (121.5 MHz, crystals in H2O/D2O, ä): -3.7 (d, J(P,F) = 908 Hz, HPO3F-), 0.8 (s, H2PO4-), 2% H2PO4-.

19F-NMR (282.4 MHz, crystals in H2O/D2O, ä): -74.8 (d, J(P,F) = 908 Hz, HPO3F-).

Anal. Found (Calcd): C 24.81 (25.11), H 7.42 (7.85), N 7.23 (7.32), F 0.2 (H2O)/9.5 (Seel) (9.94)%.


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The system of [NR4] / PO3F (R = H, CH2CH3)

[NH2(CH2CH3)2]HPO3F (M = 173.12 g/mol)

Diethylammonium hydrogen monofluorophosphate was prepared from Na2PO3F (9.5 g, 66 mmol) and NH(CH2CH3)2 (4.8 g, 66 mmol) in 83% yield. Crystals were obtained from EtOH with slow addition of Et2O and refrigeration.

31P-NMR (121.5 MHz, crystals in H2O/D2O, ä): -3.7 (d, J(P,F) = 908 Hz, HPO3F-).

19F-NMR (282.4 MHz, crystals in H2O/D2O, ä): -74.8 (d, J(P,F) = 908 Hz, HPO3F-).

Anal. Found (Calcd): C 27.22 (27.73), N 7.95 (8.09), H 6.72 (7.51), F 0.03 (H2O)/11.65 (Seel) (10.97)%.

[NH(CH2CH3)3]HPO3F (M = 201.18 g/mol)

Triethylammonium hydrogen monofluorophosphate was obtained using Na2PO3F (10 g, 70 mmol) and triethylamine (7.0 g, 69 mmol). The hygroscopic oil was dissolved in EtOH. The saturated solution was stored in the refrigerator. The mixture was then recrystallized from EtOH by adding Et2O. Beautiful plates were filtered and saved (21% yield).

31P-NMR (121.5 MHz, neut. eluate in H2O/D2O, ä): -3.3 (d, J(P,F) = 904 Hz, HPO3F-), 0.7 (s, H2PO4-), 11% H2PO4-.

19F-NMR (282.4 MHz, neut. eluate in H2O/D2O, ä): -74.7 (dd, J(P,F) = 904 Hz, J(H,F) = 7 Hz, HPO3F-), -126.3 (s, F-).

Anal. Found (Calcd): C 35.04 (35.79), N 6.83 (6.96), H 7.79 (8.45), F 0.1 (H2O)/9.2 (Seel) (9.44)%.

The system of [NH2(CH2CH2)2NH2] / PO3F

[NH2(CH2CH2)2NH2][HPO3F]2 (M = 286.11 g/mol)

Piperazinium hydrogen monofluorophosphate was synthesized from Na2PO3F (11 g, 76 mmol) and piperazine (3.0 g, 35 mmol). During neutralization of the dilute H2PO3F, the pH was held between 3-4 with a final pH of 2.86. The freeze dried oil was recrystallized from about 5 mL H2O. Ethanol, 1 mL, was added and a fine precipitate of single crystals for the


20

piperazonium dihydrogen phosphate, already measured, was obtained. Block crystals of a minor phase found along with crystals of the dihydrogen phosphate were characterized as [PpizH2][HPO3F]2.

31P-NMR (121.5 MHz, neut. eluate in H2O/D2O, ä): -3.8 (d, J(P,F) = 909 Hz, HPO3F-), 0.7 (s, H2PO4-), 23% H2PO4-.

19F-NMR (282.4 MHz, neut. eluate in H2O/D2O, ä): -75.2 (d, J(P,F) = 909 Hz, HPO3F-).

The system of [C(NH2)3] / PO3F

[C(NH2)3]HPO3F (M = 159.07 g/mol)

Guanidinium hydrogen monofluorophosphate was synthesized using Na2PO3F (10 g, 69 mmol) and [C(NH2)3]2CO3 (6.3 g, 35 mmol). The aqueous solution had a pH of <2.6 after cation exchange and complete addition of the carbonate. The freeze dried product (60% yield) was recrystallized in two separate batches. Measured crystals of [C(NH2)3]2SiF6 [75] were obtained from the crystallized residue on the tray. The bulk product was then recrystallized from H2O (4 mL) with addition of EtOH. The solution was placed in the refrigerator. Crystals did not appear. Crystals of [C(NH2)3]HPO3F were isolated by the evaporation of a drop of the solution on a glass slide.

31P-NMR (121.5 MHz, residue from tray in H2O/D2O, ä): -4.0 (d, J(P,F) = 909 Hz,

HPO3F-), 0.5 (s, H2PO4-), 28% H2PO4-.

19F-NMR (282.4 MHz, residue from tray in H2O/D2O, ä): -74.5 (dd, J(P,F) = 909 Hz, HPO3F-), -127.5 (s, F-).

Anal. Found (Calcd): C 7.48 (7.54), N 26.24 (26.40), H 4.03 (4.40), F 0.8 (H2O)/11.1 (Seel) (11.94)%.

[C(NH2)3]2PO3F (M = 218.15 g/mol)

Guanidinium monofluorophosphate was synthesized by cation exchange using Na2PO3F (10.1 g, 70 mmol) and [C(NH2)3]2CO3 (11.9 g, 66 mmol). The neutralized eluate had a pH of 6.21. The freeze dried raw product (90% yield) was dissolved in 5 mL H2O and the solution filtered. Crystals were isolated by decanting the thick, cloudy solution onto a tile. The dried crystals were characterized.

31P-NMR (121.5 MHz, neut. eluate in H2O/D2O, ä): 1.4 (d, J(P,F) = 870 Hz, PO3F2-), 1.3


21

(s, H2PO4-), 20% H2PO4-.

19F-NMR (282.4 MHz, neut. eluate H2O/D2O, ä): -73.7 (d, J(P,F) = 870 Hz, PO3F2-).

Anal. Found (Calcd): C 8.97 (11.00), H 4.36 (5.50), N 31.69 (38.51), F 3.5 (H2O)/10.7 (Seel) (8.71)%.

The system of {OC[NH(CH3)]2} / PO3F

{HOC[NH(CH3)]2}HPO3F (M = 188.10 g/mol)

The dilute, aqueous solution of monofluorophosphoric acid (eluant: 10 g, 69 mmol of Na2PO3F) was mixed with N,N´-dimethyl urea (6.1 g, 69 mmol). The pH sank to 0.8 and then rose slightly to 1.5. After freeze drying, the tray of moist raw product was washed with EtOH. The EtOH solution was filtered and left to stand. The tray residue was added to the solution later and crystals were formed and characterized.

31P-NMR (121.5 MHz, neut. eluate in H2O/D2O, ä): -4.1 (d, J(P,F) = 909 Hz, HPO3F-), 0.5 (s, H2PO4-), 62% H2PO4-.

19F-NMR (282.4 MHz, neut. eluate in H2O/D2O, ä): -75.0 (d, J(P,F) = 909 Hz, HPO3F-),

-127.5 (s, F-).

Anal. Found (Calcd): C 17.80 (19.14), N 13.80 (14.89), H 5.01 (4.78), F 0.5 (H2O)/9.4 (Seel) (10.10)%.


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