Difluorophosphate
Difluorophosphate or difluorodioxophosphate or phosphorodifluoridate is an anion with formula. It has a single negative charge and resembles perchlorate and monofluorosulfonate in shape and compounds. These ions are isoelectronic, along with tetrafluoroaluminate, phosphate, orthosilicate, and sulfate. 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.
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. It may be covalently bound to a non metal or an organic moiety to make an ester or an amide.
Formation
Ammonium difluorophosphate is formed from treating phosphorus pentoxide with ammonium fluoride. This was how the ion was first made by its discoverer, Willy Lange, in 1929.Alkali metal chlorides can react with dry difluorophosphoric acid to form alkali metal salts.
Fluorination of dichlorophosphates can produce difluorophosphates. Another method is fluorination of phosphates or polyphosphates.
Trimethylsilyl difluorophosphate reacts with metal chlorides to give difluorophosphates.
The anhydride of difluorophosphoric acid, phosphoryl difluoride oxide reacts with oxides such as [uranium trioxide|] to yield difluorophosphates. Phosphoryl difluoride oxide also reacts with alkali metal fluorides to yield difluorophosphates.
Properties
The difluorophosphate ion in ammonium difluorophosphate and potassium difluorophosphate has these interatomic dimensions:| 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.
On heating the salts that are not of alkali metals or alkaline earth metals, difluorophosphates decompose firstly by giving off [phosphoryl fluoride|] forming a monofluorophosphate compound, and then this in turn decomposes to an orthophosphate compound.
Difluorophosphate salts are normally soluble and stable in water. However, in acidic or alkaline conditions they can be hydrolyzed to monofluorophosphates and hydrofluoric acid. The caesium and potassium salts are the least soluble.
Irradiating potassium difluorophosphate with gamma rays can make the free radicals, and.
Compounds
| Formula | Name | Structure | Infrared spectrum | Melting point | Comments | Reference |
| Lithium difluorophosphate | 360 °C | |||||
| Beryllium difluorophosphate | >400 °C | prepared from [beryllium chloride|] and acid | ||||
| Ethyl difluorophosphate | ||||||
| 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 | |||
| Nitronium difluorophosphate | 515, 530, 550, 560, 575, 845, 880, 1145, 1300, 2390, 3760 cm−1 | nitronium formed from anhydride and | ||||
| Nitrosonium difluorophosphate | 500, 840, 880, 1130, 1272, 1315, 2278 cm−1 | nitrosonium formed from anhydride and | ||||
| Sodium difluorophosphate | 210 °C | |||||
| Magnesium difluorophosphate | 200 °C | |||||
| Ammonium magnesium difluorophosphate | Cmcm a=5.411 b=15.20 c=12.68 | |||||
| Aluminium difluorophosphate | polymeric | 505, 541, 582, 642, 918, 971, 1200, 1290 cm−1 | formed from [Triethylaluminium|] and acid; colourless insoluble powder | |||
| Silicon difluorophosphate | formed from [silicon tetrachloride|] and anhydride | |||||
| Trimethylsilyl difluorophosphate | formed from anhydride and | |||||
| 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 | ||
| Tetrapotassium difluorophosphate pyrosulfate | C2/c: a = 13.00 Å, b = 7.543 Å, c = 19.01 Å, β = 130.07°, Z = 4 | |||||
| Calcium difluorophosphate - ethyl acetate 1:1 solvate | ||||||
| Calcium difluorophosphate | >345 °C | |||||
| Pervanadyl difluorophosphate | ||||||
| Chromyl difluorophosphate | formed from anhydride; red-brown | |||||
| Chromium difluorophosphate | 320, 385, 490, 575, 905, 955, 1165, 1255 cm−1 | formed from excess anhydride, green | ||||
| 184 °C | ||||||
| dissolve manganese in acid; white | ||||||
| Iron difluorophosphate | 463, 496, 668, 869, 1139, 1290 cm−1 | 180 °C | colour blue green, hygroscopic, melts 250 °C, above 300 °C starts decomposing to [iron(II) phosphate|] | |||
| Iron difluorophosphate | 262, 493, 528, 570, 914, 965, 1173, 1242 cm−1 | >400 °C | decomposes at 230 °C yielding [iron(III) fluoride|]; dissolve iron in acid in presence of oxygen | |||
| Cobalt difluorophosphate | 173 °C | prepared from [Cobalt(II) chloride|] and acid; pink or blue; blue formed by heating pink to 140 °C | ||||
| dissolve cobalt in acid; red-purple | ||||||
| Cobalt 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 with [Acetonitrile|] for a few weeks; red crystals | ||||
| Nickel difluorophosphate | 255 °C | slowly prepared from [Nickel(II) chloride|] and acid; yellow | ||||
| dissolve nickel in acid; yellow | ||||||
| Copper 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 | pale blue needles | |||
| polymeric; monoclinic: a = 12.435 Å, b = 10.887 Å, c = 25.682 Å, β = 100.220°, V = 3421 Å3 | colourless | |||||
| Zinc difluorophosphate | °C? | glassy | ||||
| Tetrazincic acid | ||||||
| Gallium difluorophosphate | ||||||
| Dimethylgallium difluorophosphate | dimeric | 380, 492, 520, 551, 616, 709, 750, 899, 949, 1171, 1218, 1262, 1295, 1404, 2922, 2982 cm−1 | ||||
| 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 | ||
| Strontium difluorophosphate | 250 °C | prepared from [strontium chloride|] and acid | ||||
| Ammonium strontium difluorophosphate | Triclinic P ''a=7.370 b''=11.054 c=13.645 α=88.861 β=87.435° γ=89.323° | |||||
| Silver difluorophosphate | ||||||
| Ag | ||||||
| Ag | 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 | |||||
| Ag | ||||||
| Cadmium difluorophosphate | 245 °C | |||||
| Indium difluorophosphate | 269, 492, 528, 567, 910, 962, 1179, 1269 cm−1 | white, decomposes at 260 °C yielding [indium trifluoride|] | ||||
| Dimethylindium difluorophosphate | dimeric | 373, 490, 500, 535, 559, 735, 878, 925, 1128, 1179, 1275, 1435, 2928, 3000 cm−1 | ||||
| Tin dichloride difluorophosphate | ||||||
| Dimethyltin difluorophosphate | 204 °C | prepared from and acid; yellow | ||||
| Diethyltin difluorophosphate | 262 °C | prepared from and acid; yellow | ||||
| Dipropyltin difluorophosphate | 245 °C | prepared from and acid; yellow | ||||
| Dibutyltin difluorophosphate | 235 °C | prepared from and acid; yellow | ||||
| Dioctyltin difluorophosphate | 114 °C | prepared from and acid; yellow | ||||
| Antimony tetrachloride difluorophosphate | ||||||
| Antimony tetrafluoride difluorophosphate | ||||||
| Au | ||||||
| Raman: 130, 163, 191, 219, 295, 323, 329, 378, 637, 713, 737, 781, 799, 839, 918, 1163 cm−1 | yellowish colour, produced from [iodine trioxide|], decomposed by water | |||||
| Raman: 217, 247, 269, 305, 343, 367, 395, 473, 569, 643, 671, 717, 797, 891, 1123 cm−1 | yellowish colour, produced from [periodic acid|], decomposed by water | |||||
| Xenon fluoride difluorophosphate | ||||||
| Xenon difluorophosphate | ||||||
| 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 | ||||
| Barium difluorophosphate | orthorhombic I2''d a =10.4935 b =10.4935 c =26.030 | >400 °C | ||||
| Diammonium barium difluorophosphate | P''2/n a=14.285 b=5.472 c=19.474 β=97.607° | |||||
| Mercury difluorophosphate | ||||||
| Mercury difluorophosphate or didimercurane | Raman: 220 cm−1 | produced from anhydride | - | |||
| Thallium difluorophosphate | produced from anhydride, or acid on TlCl | |||||
| Dimethylthallium difluorophosphate | dimeric | 360, 374, 500, 505, 520, 559, 850, 880, 1120, 1140, 1195, 1250, 1285, 2932, 3020 cm−1 | ||||
| Lead difluorophosphate | 189 °C | |||||
| Uranyl difluorophosphate | 260, 498, 854, 924, 980, 1124 cm−1 | IR spectrum due to [uranyl|] | ||||
| Tetraethylammonium difluorophosphate | ||||||
| 1-ethyl-3-methylimidazolium difluorophosphate | ionic liquid | |||||
| 1-butyl-3-methylimidazolium difluorophosphate | ionic liquid | |||||
| 1-butyl-1-methylpyrrolidinium difluorophosphate | ionic liquid | |||||
| 1-butyl-1-methylpiperidinium difluorophosphate | ionic liquid | |||||
| didifluorophosphate | Transitions to a metallic state below | |||||
| 1,4-diphenyl-3,5-enanilo-4,5-dihydro-1,2,4-triazole | 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 | ||||
| Strychnine | ||||||
| Cocaine | ||||||
| Brucine | ||||||
| Morphine | ||||||
| Tetramethylammonium difluorophosphate | ||||||
| Tetraboric acid | 469, 502, 552, 647, 836, 940, 994, 1093, 1348, 1567 cm−1 | formed from [Boron tribromide|] and acid; liquid | ||||
| Lithium tetraborate | 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 and butyllithium; colourless | |||
| Dimethylsulfonium tetraborate | 472, 511, 555, 648, 832, 933, 993, 1082, 1337, 1436, 2851, 2921, 3042 cm−1 | formed from and acid; ionic liquid | ||||
| lithium hexaaluminate | trigonal R: 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 | |||
| 305, 370, 485, 550, 870, 920, 1050, 1130, 1250 cm−1 | 145 °C | formed from anhydride and [potassium chromate|]; brown | ||||
| amorphous | 280, 490, 620, 880, 915, 950, 1020, 1070, 1140, 1280 cm−1 | 125 °C | formed from anhydride and [potassium molybdate|]; white | |||
| amorphous | 280, 474, 620, 930, 1030, 1130, 1230 cm−1 | 109 °C | formed from anhydride and [potassium tungstate|]; white |
Related substances
Difluorophosphoric acid
Difluorophosphoric acid is one of the fluorophosphoric acids. It is produced when phosphoryl fluoride reacts with water:This in turn is hydrolysed more to give monofluorophosphoric acid, and a trace of hexafluorophosphoric acid. also is produced when HF reacts with phosphorus pentoxide. Yet another method involves making difluorophosphoric acid as a side product of calcium fluoride being heated with damp phosphorus pentoxide. A method to make pure difluorophosphoric acid involves heating phosphoryl fluoride with monofluorophosphoric acid and separating the product by distillation:
Difluorophosphoric acid can also be produced by fluorinating phosphorus oxychlorides. and [phosphoryl chloride|] react with hydrogen fluoride solution to yield and then. Yet another way is to treat orthophosphate with fluorosulfuric acid.
Difluorophosphoric acid is a colorless liquid. It melts at and boils at. Its density at 25 °C is 1.583 g/cm3.
Phosphoryl difluoride oxide
Difluorophosphoric acid anhydride also known as phosphoryl difluoride oxide or diphosphoryl tetrafluoride is an anhydride of difluorophosphoric acid. It crystallises in the orthorhombic system, with space group Pcca and Z = 4. can be made by refluxing difluorophosphoric acid with phosphorus pentoxide. boils at 71 °C.Substitution
In addition to the isoelectronic series, ions related by substituting fluorine or oxygen by other elements include monofluorophosphate, difluorothiophosphate, dichlorothiophosphate, dichlorophosphate,,,, and.Adducts
Difluorophosphate can form adducts with and. In these the oxygen atoms form a donor-acceptor link between the P and As atoms, linking the difluorides to the pentafluorides. Example salts include,, and.Amines can react with phosphoryl fluoride to make substances with a formula. The amines shown to do this include ethylamine, isopropylamine, n-butylamine, t-butylamine, dimethylamine, and diethylamine. The monoamines can further react to yield an .