Difluorophosphate or difluorodioxophosphate or phosphorodifluoridate is an anion with formula PO2F2. It has a single negative charge and resembles perchlorate (ClO4) and monofluorosulfonate (SO3F) in shape and compounds.[2] These ions are isoelectronic, along with tetrafluoroaluminate, phosphate, orthosilicate, and sulfate.[2][3] It forms a series of compounds. The ion is toxic to mammals as it causes blockage to iodine uptake in the thyroid. However it is degraded in the body over several hours.[2]

Difluorophosphate
Structure of difluorophosphate ion
Ball-and-stick model of the difluorophosphate ion
Ball-and-stick model of the difluorophosphate ion
Spacefill model of difluorophosphate
Spacefill model of difluorophosphate
Names
Systematic IUPAC name
Difluorophosphate[1]
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/F2HO2P/c1-5(2,3)4/h(H,3,4)/p-1
    Key: DGTVXEHQMSJRPE-UHFFFAOYSA-M
  • InChI=1/F2HO2P/c1-5(2,3)4/h(H,3,4)/p-1
    Key: DGTVXEHQMSJRPE-REWHXWOFAH
  • [O-]P(=O)(F)F
Properties
PO2F2
Molar mass 100.97 g mol−1
Structure
Tetracoordinated at phosphorus atom
Tetrahedral at phosphorus atom
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N (what is checkY☒N ?)

Compounds containing difluorophosphate may have it as a simple uninegative ion, it may function as a difluorophosphato ligand where it is covalently bound to one or two metal atoms, or go on to form a networked solid.[4] It may be covalently bound to a non metal or an organic moiety to make an ester or an amide.

Formation

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Ammonium difluorophosphate ([NH4]PO2F2) is formed from treating phosphorus pentoxide with ammonium fluoride.[2] This was how the ion was first made by its discoverer, Willy Lange, in 1929.[3][5]

Alkali metal chlorides can react with dry difluorophosphoric acid to form alkali metal salts.[6]

NaCl + HPO2F2 → NaPO2F2 + HCl(g)

Fluorination of dichlorophosphates can produce difluorophosphates.[7] Another method is fluorination of phosphates or polyphosphates.[5]

Trimethylsilyl difluorophosphate ((CH3)3Si−O−P(=O)F2) reacts with metal chlorides to give difluorophosphates.[8]

The anhydride of difluorophosphoric acid (HPO2F2), phosphoryl difluoride oxide (P2O3F4) reacts with oxides such as UO3 to yield difuorophosphates.[9] Phosphoryl difluoride oxide also reacts with alkali metal fluorides to yield difluorophosphates.[10]

Properties

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The difluorophosphate ion in ammonium difluorophosphate and potassium difluorophosphate has these interatomic dimensions:[11]

Difluorophosphate salt P–O length P–F length O–P–O angle F–P–O angle F–P–F angle
Ammonium difluorophosphate 1.457 Å 1.541 Å 118.7° 109.4° 98.6°
Potassium difluorophosphate 1.470 Å 1.575 Å 122.4° 108.6° 97.1°

Hydrogen bonding from ammonium ion to oxygen atoms causes a change to the difluorophosphate ion in the ammonium salt.[11]

On heating the salts that are not of alkali metals or alkaline earth metals, difluorophosphates decompose firstly by giving off POF3 forming a monofluorophosphate (PO3F2−) compound, and then this in turn decomposes to an orthophosphate PO3−4 compound.[12][13]

Difluorophosphate salts are normally soluble and stable in water. However, in acidic or alkaline conditions they can be hydrolyzed to monofluorophosphates and hydrofluoric acid.[14] The caesium and potassium salts are the least soluble.[14]

Irradiating potassium difluorophosphate with gamma rays can make the free radicals •PO2F, •PO3F and •PO2F2.[15][16]

Compounds

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Formula Name Structure Infrared spectrum Melting point Comments Reference
LiPO2F2 Lithium difluorophosphate 360 °C [5][6]
Be(PO2F2)2 Beryllium difluorophosphate >400 °C d prepared from BeCl2 and acid [17]
CH3CH2−O−P(=O)F2 Ethyl difluorophosphate [18]
[NH4]+PO2F2 Ammonium difluorophosphate orthorhombic: a = 8.13 Å, b = 6.43 Å, c = 7·86 Å, Z = 4 space group Pnma P–F stretching 842 and 860 cm−1; P–O stretching 1138 and 1292 cm−1 213 °C
[NO2]+PO2F2 Nitronium difluorophosphate 515, 530, 550, 560, 575, 845, 880, 1145, 1300, 2390, 3760 cm−1 nitronium formed from anhydride and N2O5 [19]
[NO]+PO2F2 Nitrosonium difluorophosphate 500, 840, 880, 1130, 1272, 1315, 2278 cm−1 nitrosonium formed from anhydride and N2O3 [19]
NaPO2F2 Sodium difluorophosphate 210 °C [6]
Mg(PO2F2)2 Magnesium difluorophosphate 200 °C [5]
[NH4]+Mg2+(PO2F2)3 Ammonium magnesium difluorophosphate Cmcm a=5.411 b=15.20 c=12.68 [20]
Al(PO2F2)3 Aluminium difluorophosphate polymeric[4] 505, 541, 582, 642, 918, 971, 1200, 1290 cm−1 (with 355 cm−1 impurity) formed from Al(CH2CH3)3 and acid; colourless insoluble powder[4] [7][8]
Si(−O−P(=O)F2)4 Silicon(IV) difluorophosphate formed from SiCl4 and anhydride [18]
(CH3)3Si−O−P(=O)F2 Trimethylsilyl difluorophosphate formed from anhydride and [(CH3)3Si]2O [4][18]
KPO2F2 Potassium difluorophosphate orthorhombic: a = 8.03 Å, b = 6.205 Å, c = 7.633 Å, Z = 4, V=380.9 Å3, density = 2.44 g/cm3 510, 525, 570, 835, 880, 1145, 1320, 1340 cm−1 263 °C colourless elongated prisms [6][11][19][21][22]
(K+)4(PO2F2)2(S2O2−7) Tetrapotassium difluorophosphate pyrosulfate C2/c: a = 13.00 Å, b = 7.543 Å, c = 19.01 Å, β = 130.07°, Z = 4 [23]
Ca(PO2F2)2·CH3COOCH2CH3 Calcium difluorophosphate - ethyl acetate 1:1 solvate [24]
Ca(PO2F2)2 Calcium difluorophosphate >345 °C d [5]
[VO2]+PO2F2 Pervanadyl difluorophosphate [9]
CrO2(PO2F2)2 Chromyl difluorophosphate formed from anhydride; red-brown [25]
Cr(PO2F2)3 Chromium(III) difluorophosphate 320, 385, 490, 575, 905, 955, 1165, 1255 cm−1 formed from excess anhydride, green [25]
Mn(CO)5PO2F2[clarification needed] 184 °C [26]
HMn(PO2F2)3[clarification needed] dissolve manganese in acid; white [27]
[NH+4](Mn2+)3(PO2F2)(PO3F2−)2(F)2 [28]
Fe(PO2F2)2 Iron(II) difluorophosphate 463, 496, 668 (weak), 869 (double), 1139, 1290 cm−1 180 °C d colour blue green, hygroscopic, melts 250 °C, above 300 °C starts decomposing to Fe3(PO4)2 [12]
Fe(PO2F2)3 Iron(III) difluorophosphate 262, 493, 528, 570, 914, 965, 1173, 1242 cm−1 >400 °C decomposes at 230 °C yielding FeF3; dissolve iron in acid in presence of oxygen [7]
K+(Fe2+)3(PO2F2)(PO3F2−)2(F)2 [28]
Co(PO2F2)2 Cobalt(II) difluorophosphate 173 °C prepared from CoCl2 and acid; pink or blue; blue formed by heating pink to 140 °C [17]
HCo(PO2F2)3[clarification needed] dissolve cobalt in acid; red-purple [27]
Co(PO2F2)2·2CH3CN Cobalt(II) difluorophosphate - methyl cyanide solvate 1:2 orthorhombic: a = 9.227 Å, b = 13.871 Å, c = 9.471 Å, V = 1212 Å3, Z = 4, density = 1.88 g/cm3 treat HCo(PO2F2)3 with CH3CN for a few weeks; red crystals [29]
[NH+4](Co2+)3(PO2F2)(PO3F2−)2(F)2 [28]
Ni(PO2F2)2 Nickel(II) difluorophosphate 255 °C d slowly prepared from NiCl2 and acid; yellow [17]
HNi(PO2F2)3[clarification needed] dissolve nickel in acid; yellow [27]
Cu(PO2F2)2 Copper(II) difluorophosphate orthorhombic Fddd: a = 10.134 Å, b = 24.49 Å, c = 34.06 Å, Z = 48, V = 8454.3 Å3, density = 2.50 g/cm3 265 °C d pale blue needles [5][29]
CuI(xantphos)2(μ-PO2F2) polymeric; monoclinic: a = 12.435 Å, b = 10.887 Å, c = 25.682 Å, β = 100.220°, V = 3421 Å3 colourless [30]
Zn(PO2F2)2 Zinc(II) difluorophosphate c. 25 °C? glassy [5]
H2[Zn(PO2F2)4] Tetra(difluorophosphato)zincic(II) acid
Ga(PO2F2)3 Gallium(III) difluorophosphate
[(CH3)2GaPO2F2]2 Dimethylgallium(III) difluorophosphate dimeric 380, 492, 520, 551, 616, 709, 750, 899, 949, 1171, 1218, 1262, 1295, 1404, 2922, 2982 cm−1 [4][31]
RbPO2F2 Rubidium difluorophosphate orthorhombic: a = 8.15 Å, b = 6.45 Å, c = 7.79 Å, Z = 4, V = 409.5 Å3 density = 3.02 g/cm3 P–F stretching 827 and 946 cm−1; P–O stretching 1145 and 1320 cm−1 160 °C white [6][11][21]
Sr(PO2F2)2 Strontium difluorophosphate 250 °C d prepared from SrCl2 and acid [17]
[NH4]Sr(PO2F2)3 Ammonium strontium difluorophosphate Triclinic P1 a=7.370 b=11.054 c=13.645 α=88.861 β=87.435° γ=89.323° [20]
AgPO2F2 Silver(I) difluorophosphate [32]
Ag9(PO2F2)14[clarification needed] [28]
Ag(1-methyl-2-alkylthiomethyl-1H-benzimidazole)PO2F2 [32]
Ag(2,6-bis-[(2-methylthiophenyl)-2-azaethenyl]pyridine)PO2F2 Triclinic P1: a = 7.687 Å, b = 10.740 Å, c = 13.568 Å, α = 99.52°, β = 96.83°, γ = 99.83°, Z = 2, V = 1076 Å3, density = 1.81 g/cm3 [33]
Ag(4,4′-dicyanodiphenylacetylene)PO2F2
Cd(PO2F2)2 Cadmium(II) difluorophosphate 245 °C d [5]
In(PO2F2)3 Indium(III) difluorophosphate 269, 492, 528, 567, 910, 962, 1179, 1269 cm−1 white, decomposes at 260 °C yielding InF3 [7]
[(CH3)2InPO2F2]2 Dimethylindium(III) difluorophosphate dimeric 373, 490, 500, 535, 559, 735, 878, 925, 1128, 1179, 1275, 1435, 2928, 3000 cm−1 [31]
SnCl2(PO2F2)2 Tin(IV) dichloride difluorophosphate [34]
(CH3)2Sn(PO2F2)2 Dimethyltin(IV) difluorophosphate 204 °C d prepared from (CH3)2SnCl2 and acid; yellow [17]
(CH3CH2)2Sn(PO2F2)2 Diethyltin(IV) difluorophosphate 262 °C d prepared from (CH3CH2)2SnCl2 and acid; yellow [17]
(CH3CH2CH2)2Sn(PO2F2)2 Dipropyltin(IV) difluorophosphate 245 °C d prepared from (CH3CH2CH2)2SnCl2 and acid; yellow [17]
(CH3(CH2)3)2Sn(PO2F2)2 Dibutyltin(IV) difluorophosphate 235 °C d prepared from (CH3(CH2)7)2SnCl2 and acid; yellow [17]
(CH3(CH2)7)2Sn(PO2F2)2 Dioctyltin(IV) difluorophosphate 114 °C prepared from (CH3(CH2)7)2SnCl2 and acid; yellow [17]
SbCl4PO2F2 Antimony(V) tetrachloride difluorophosphate [34]
SbF4PO2F2 Antimony(V) tetrafluoride difluorophosphate [34]
(2,2-dipyradyl)2Re(CO)2PO2F2[clarification needed] [35]
Au[bis(triphenylphosphine sulfide-S)]PO2F2[clarification needed] [36]
IO2PO2F2[clarification needed] Raman: 130, 163, 191, 219, 295, 323, 329, 378, 637, 713, 737, 781, 799, 839, 918, 1163 cm−1 yellowish colour, produced from IO3, decomposed by water [37]
IO3PO2F2[clarification needed] Raman: 217, 247, 269, 305, 343, 367, 395, 473, 569, 643, 671, 717, 797, 891, 1123 cm−1 yellowish colour, produced from H5IO6, decomposed by water [37]
FXePO2F2 Xenon(II) fluoride difluorophosphate [38]
Xe(PO2F2)2 Xenon(II) difluorophosphate [38]
CsPO2F2 Caesium difluorophosphate orthorhombic: a = 8.437 Å, b = 6.796 Å, c = 8.06 Å, Z = 4, V = 462.1 Å3, density = 3.36 g/cm3 286 °C [6][11][21]
(Cs+)2(Fe3+)2(PO2F2)(PO3F2−)2(F)3 [28]
Ba(PO2F2)2 Barium difluorophosphate orthorhombic I42d a =10.4935 b =10.4935 c =26.030 >400 °C [5][20]
[NH4]2Ba(PO2F2)4 Diammonium barium difluorophosphate P2/n a=14.285 b=5.472 c=19.474 β=97.607° [20]
Re(CO)5PO2F2 [35]
Hg(PO2F2)2 Mercury(II) difluorophosphate [5]
Hg2(PO2F2)2 Mercury(I) difluorophosphate or di(difluorophosphato)dimercurane Raman: 220 cm−1 produced from anhydride [5]
TlPO2F2 Thallium(I) difluorophosphate produced from anhydride, or acid on TlCl [5]
[(CH3)2TlPO2F2]2 Dimethylthallium(III) difluorophosphate dimeric 360, 374, 500, 505, 520, 559, 850, 880, 1120, 1140, 1195, 1250, 1285, 2932, 3020 cm−1 [31]
Pb(PO2F2)2 Lead(II) difluorophosphate 189 °C d [5]
UO2(PO2F2)2 Uranyl difluorophosphate 260, 498, 854, 924, 980, 1124 cm−1 IR spectrum due to UO2+2 [9]
[(CH3CH2)4N]+PO2F2 Tetraethylammonium difluorophosphate [39]
1-ethyl-3-methylimidazolium difluorophosphate ionic liquid [40]
1-butyl-3-methylimidazolium difluorophosphate ionic liquid [40]
1-butyl-1-methylpyrrolidinium difluorophosphate ionic liquid [40]
1-butyl-1-methylpiperidinium difluorophosphate ionic liquid [40]
di(3,3′,4,4′-tetramethyl-2,2′,5,5′-tetraselenafulvalenium)difluorophosphate Transitions to a metallic state below 137 K (−136 °C) [41]
1,4-diphenyl-3,5-enanilo-4,5-dihydro-1,2,4-triazole (nitron) monoclinic P21/n: a = 7.3811 Å, b = 14.9963 Å, c = 16.922 Å, β = 102.138°, V = 1361.2 Å3, Z = 4 insoluble; yellow-brown [2][28]
Strychnine PO2F2 [3]
Cocaine PO2F2 [3]
Brucine PO2F2 [3]
Morphine PO2F2 [3]
[N(CH3)4]+PO2F2 Tetramethylammonium difluorophosphate [3]
H[B(PO2F2)4] Tetra(difluorophosphato)boric acid 469, 502, 552, 647, 836, 940, 994, 1093, 1348, 1567 cm−1 formed from BBr3 and acid; liquid [4]
Li[B(PO2F2)4] Lithium tetra(difluorophosphato)borate monoclinic P21/c: a=7.9074 Å, b = 14.00602 Å, c = 13.7851 Å, β = 121.913°, Z = 4 479, 502, 568, 833, 945, 1002, 1080, 1334 cm−1 formed from HB(PO2F2)4 and butyllithium; colourless [4]
[HS(CH3)2]+[B(PO2F2)4] Dimethylsulfonium tetra(difluorophosphato)borate 472, 511, 555, 648, 832, 933, 993, 1082, 1337, 1436, 2851, 2921, 3042 cm−1 formed from BH3·S(CH3)2 and acid; ionic liquid [4]
[Li((CH3CH2)2O)+]3[Al(PO2F2)6] (Diethyl ether)lithium hexa(difluorophosphato)aluminate trigonal R3: a = 17.4058 Å, b = 17.4058 Å, c = 21.4947 Å, γ = 120°, Z = 6 417, 503, 536, 624, 723, 891, 922, 964, 1174, 1204, 1283 cm−1 formed from butyllithium and triethylaluminium and the acid; white [4]
K2CrO2(PO2F2)4 305, 370, 485, 550, 870, 920, 1050, 1130, 1250 cm−1 145 °C d formed from anhydride and K2CrO4; brown [25]
Na2MoO2(PO2F2)4 amorphous 280, 490, 620, 880, 915, 950, 1020, 1070, 1140, 1280 cm−1 125 °C d formed from anhydride and K2MoO4; white [25]
Na2WO2(PO2F2)4 amorphous 280, 474, 620, 930, 1030, 1130, 1230 cm−1 109 °C d formed from anhydride and K2WO4; white [25]
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Difluorphosphoric acid

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Difluorophosphoric acid (HPO2F2) is one of the fluorophosphoric acids. It is produced when phosphoryl fluoride reacts with water:

POF3 + H2O → HPO2F2 + HF

This in turn is hydrolysed more to give monofluorophosphoric acid (H2PO3F), and a trace of hexafluorophosphoric acid (HPF6). HPO2F2 also is produced when HF reacts with phosphorus pentoxide. Yet another method involves making difluorphosphoric acid as a side product of calcium fluoride being heated with damp phosphorus pentoxide. A method to make pure difluorphosphoric acid involves heating phosphoryl fluoride with monofluorophosphoric acid and separating the product by distillation:[42]

POF3 + H2PO3F → 2 HPO2F2

Difluorophosphoric acid can also be produced by fluorinating phosphorus oxychlorides. P2O3Cl4 and POCl3 react with hydrogen fluoride solution to yield HPO2Cl2 and then HPO2F2.[43] Yet another way is to treat orthophosphate (PO3−4) with fluorosulfuric acid (HSO3F).[44]

Difluorphosphoric acid is a colorless liquid. It melts at −96.5 °C (−141.7 °F) and boils at 115.9 °C (240.6 °F). Its density at 25 °C is 1.583 g/cm3.[14]

Phosphoryl difluoride oxide

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Difluorophosphoric acid anhydride also known as phosphoryl difluoride oxide or diphosphoryl tetrafluoride (F2(O=)P−O−P(=O)F2 or P2O3F4) is an anhydride of difluorphosphoric acid. It crystallises in the orthorhombic system, with space group Pcca and Z = 4.[45] P2O3F4 can be made by refluxing difluorophosphoric acid with phosphorus pentoxide. P2O3F4 boils at 71 °C.[46]

Substitution

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In addition to the isoelectronic series, ions related by substituting fluorine or oxygen by other elements include monofluorophosphate, difluorothiophosphate, dichlorothiophosphate, dichlorophosphate, chlorofluorothiophosphate, chlorofluorophosphate, dibromophosphate, and bromofluorophosphate.[47]

Adducts

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Difluorophosphate can form adducts with PF5 and AsF5. In these the oxygen atoms form a donor-acceptor link between the P and As (or P) atoms, linking the difluorides to the pentafluorides. Example salts include KPO2F2·2AsF5, KPO2F2·AsF5, KPO2F2·2PF5 and KPO2F2·PF5.[48]

Amines can react with phosphoryl fluoride to make substances with a formula RR′N−P(=O)F2. The amines shown to do this include ethylamine, isopropylamine, n-butylamine, t-butylamine, dimethylamine, and diethylamine. The monoamines can further react to yield an alkyliminophosphoric fluoride (R−N=P(=O)F).[49]

References

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  1. ^ Toy, Arthur D. F. (22 Oct 2013). The Chemistry of Phosphorus. Pergamon Texts in Inorganic Chemistry. Vol. 3. Pergamon Press. pp. 536–537. ISBN 9781483147413. Retrieved 19 June 2015.
  2. ^ a b c d e Anbar, M.; Guttmann, S.; Lewitus, Z. (30 May 1959). "Effect of Monofluorosulphonate, Difluorophosphate and Fluoroborate Ions on the Iodine Uptake of the Thyroid Gland". Nature. 183 (4674): 1517–1518. Bibcode:1959Natur.183.1517A. doi:10.1038/1831517a0. PMID 13666792. S2CID 4291858.
  3. ^ a b c d e f g Lange, Willy (3 April 1929). "Über die Difluorphosphorsäure und ihre der Perchlorsäure ähnliche Salzbildung" [On difluorophosphoric acid and its perchlorate-like salt formation]. Berichte der Deutschen Chemischen Gesellschaft (A and B Series). 62 (4): 786–792. doi:10.1002/cber.19290620408.
  4. ^ a b c d e f g h i Schulz, Christoph; Eiden, Philipp; Klose, Petra; Ermantraut, Andreas; Schmidt, Michael; Garsuch, Arnd; Krossing, Ingo (2015). "Homoleptic borates and aluminates containing the difluorophosphato ligand – [M(O2PF2)x]y – synthesis and characterization". Dalton Trans. 44 (15): 7048–7057. doi:10.1039/c5dt00469a. PMID 25785817.
  5. ^ a b c d e f g h i j k l m Vast, P.; Semmoud, A.; Addou, A.; Palavit, G. (March 1988). "Étude méthodologique de la synthèse des difluorodioxophosphates métalliques à partir de l'oxyde difluorure de phosphoryle" [Methodical study of the synthesis of metal difluorodioxophosphates from phosphoryl difluoride oxide]. Journal of Fluorine Chemistry. 38 (3): 297–302. doi:10.1016/S0022-1139(00)81065-9.
  6. ^ a b c d e f Thompson, R.C.; Reed, W. (July 1969). "Preparation and infrared spectra of alkali metal difluorophosphates". Inorganic and Nuclear Chemistry Letters. 5 (7): 581–585. doi:10.1016/0020-1650(69)80034-6.
  7. ^ a b c d Weidlein, J. (April 1968). "Darstellung, Eigenschaften und IR-Spektren von OTi(O2PCl2)2, Fe(O2PF2)3 und In(O2PF2)3" [Description, properties and IR spectra of...]. Zeitschrift für anorganische und allgemeine Chemie. 358 (1–2): 13–20. doi:10.1002/zaac.19683580103.
  8. ^ a b Shihada, Abdel-Fattah; Mohammed, Abdulalah T. (1 January 1980). "Zur Reaktion von Trimethylsilyl-difluorophosphat, Trimethylsilyl-dimethylphosphinat und Difluorophosphorsäureanhydrid mit TiCl4 bzw. SbCl5" [On the Reactions of Trimethylsilyl Difluorophosphate, Trimethylsilyl Dimethylphosphinate and Difluorophosphoric Acid Anhydride with TiCl4 and SbCl5]. Zeitschrift für Naturforschung B. 35 (1): 60–63. doi:10.1515/znb-1980-0114. S2CID 96302051.
  9. ^ a b c Vast, P.; Semmoud, A. (January 1985). "Préparation de nouveaux difluorodioxophosphates à partir de l'oxyde de difluorure de phosphoryle. Partie V. Réactions sur le trioxyde d'uranium" [Preparation of new difluorodioxophosphates from phosphoryl difluorideoxide. Part V. Reactions with uranium dioxide]. Journal of Fluorine Chemistry. 27 (1): 47–52. doi:10.1016/S0022-1139(00)80896-9.
  10. ^ Addou, A.; Vast, P.; Legrand, P. (January 1982). "Champ de forces de symetrie locale des composés oxyfluorés du phosphore(V). I. Les difluorodioxophosphates (DFP) alcalins" [Local symmetry force-field of oxyfluorine compounds of phosphorus(V). I. Alkali difluorodioxophosphates (DFP)]. Spectrochimica Acta Part A: Molecular Spectroscopy. 38 (7): 785–790. Bibcode:1982AcSpA..38..785A. doi:10.1016/0584-8539(82)80068-8.
  11. ^ a b c d e Harrison, R. W.; Trotter, James (1969). "Structure of ammonium difluorophosphate". Journal of the Chemical Society A: Inorganic, Physical, Theoretical: 1783. doi:10.1039/J19690001783.
  12. ^ a b Vast, P.; Semmoud, A. (June 1994). "Comportement thermique du difluorodioxophosphate ferreux" [Thermal behaviour of ferrous difluorodioxophosphate]. Journal of Thermal Analysis. 41 (6): 1489–1493. doi:10.1007/bf02549945. S2CID 95079191.
  13. ^ Vast, P.; Semmoud, A.; Palavit, G. (December 1986). "Préparation de l'acide monofluorotrioxophosphorique H2PO3F à partir de l'acide difluorodioxophosphorique HPO2F2" [Preparation of monofluorotrioxophosphoricacid H2PO3F from difluorodioxophosphoric acid HPO2F2]. Journal of Fluorine Chemistry. 34 (2): 229–232. doi:10.1016/s0022-1139(00)85072-1.
  14. ^ a b c Reed, William (September 1965). Studies of Difluorophosphoric Acid and its Alkali Metal Salts (Thesis). Retrieved 23 April 2023.
  15. ^ Begum, Afrozi; Subramanian, S.; Symons, M. C. R. (1970). "Unstable intermediates. Part LXVIII. Electron spin resonance studies of the radicals O3PF and O2PF2". Journal of the Chemical Society A: Inorganic, Physical, Theoretical: 1323. doi:10.1039/J19700001323.
  16. ^ Begum, A.; Subramanian, S.; Symons, M. C. R. (1971). "Unstable intermediates. Part LXXXVI. Electron spin resonance studies of the effect of γ-rays on potassium difluorophosphate: the radical PO2F?". Journal of the Chemical Society A: Inorganic, Physical, Theoretical: 700–702. doi:10.1039/J19710000700.
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