Trimetaphosphimic acid

H. N. Stokes prepared diimidotriphosphoric add, PO(OH)2.NH.PO(OH). NH.PO(OH)2, by heating trimetaphosphimic acid for about seven minutes with nitric acid. The soln. was then treated with an excess of ammonia, and a magnesium salt, and filtered. The acid in question appeared in the filtrate. The silver salt was precipitated by the addition of silver nitrate. Diimidotriphosphoric acid forms two series of salts—an acid salt with three, and a normal salt with five atoms of hydrogen replaced by the metal. For example, trisodium diimidotriphosphate,... 

H. N. Stokes prepared salts of triimidotetraphosphoric add, HN PO(OH).NH. PO(OH)2 2, by the hydrolysis of salts of pentametaphosphimic acid—e.g. a hot acetic acid soln. of sodium pentametaphosphate furnishes sodium triimidotetra-phosphate, NH PO(OH).NH.PO(ONa)2 2 and the addition of silver nitrate to the soln. furnishes the silver triimidotetraphosphate, HN PO(OH).NH.PO(OAg)2 2. The acid is so unstable that it cannot be made by heating tetrametaphosphimate as might have been anticipated by the formation of diimidotriphosphoric acid by the action of heat on trimetaphosphimic acid. 

When an aq. soln. of trimetaphosphimic acid, or of one of its salts, acidified with one of the stronger mineral acids, is heated or kept for a long time, decomposition occurs—slowly if cold, rapidly if heated. Orthophosphoric acid and ammonia (ammonium phosphate) are the ultimate products of the decomposition. Several intermediate products have been detected in addition to pyrophosphoric acid, what H. N. Stokes calls diimidotriphosphoric acid, and imidodiphosphoric acid have been found, and he represents the different stages of the decomposition ... 

While the hydrolysis of triphosphonitrilic chloride furnishes trimetaphosphimic acid, the hydrolysis of tetraphosphonitrilic chloride, P4N4018, furnishes tetrameta-phosphimic acid, P4N4H808, which, by analogy with trimetaphosphic acid, has the ring formula ... 

While the hydrolysis of triphosphonitrilic chloride with sodium acetate furnishes trimetaphosphimic acid and the hydrolysis of tetraphosphonitrilic chloride with water furnishes tetrametaphosphimic acid, the hydrolysis of pentaphosphonitrilic chloride, P5N5C1i0, with sodium hydroxide in ethereal soln. furnishes sodium pentametaphosphimic acid, PsNsHloO10, or rather the alkali pentameta-phosphimate—sufficient alkali must be present to maintain the alkalinity of the soln. The sodium salts are amorphous, and are precipitated in a gelatinous form by the addition of alcohol to the alkaline soln., or to the soln. neutralized with acetic... 

Trimetaphosphimic acid, as the 2-hydrate, crystallizes as rectangular platelets which melt at 105 to 110° by a rapid determination. The solubility in water is approximately 111 g./lOO g. of water at 35°, and 48 g./lOO g. of water at 25°. The transition from 2-hydrate to anhydrous acid occurs at 33°. In the anhydrous form the acid crystallizes in characteristic rhombs which do not melt at 110° but decompose at higher temperatures. The crystals are not noticeably hygroscopic. Both forms are practically insoluble in alcohols, ethyl acetate, ether, or hexane. The x-ray diffraction patterns have been reported.1... 

Trimetaphosphimic acid, 6 79 Trimethylamine, coordination compounds with boron fluoride and chloride, 5 26, 27 purification of, 2 159 Trimethylamine-sulfur dioxide, 2 159... 

Pentametaphosphimic Acid and Hexametaphosphimic Acid were similarly obtained by hydrolysis in ethereal solution of the corresponding nitrilo-chlorides. Like the lower polymers they gave crystalline sodium salts containing water of crystallisation, and anhydrous penta- and hexa-silver salts by the use of ammoniacal silver nitrate. The free acids can be regenerated by the action of H2S on the silver salts. The acids are more stable towards hydrolysing agents than is trimetaphosphimic acid. 

A unique tridentate trianionic ligand derived from trimetaphosphimic acid has been reported. Reaction with M0C12(H20)8 (M = Zr, Hf) gave the isotypic complexes Na4[M4(/i4-0) (/i-0H)6(P02M I)3]4 (M = Zr (104), Hf). These clusters adopted an adamantanoid M—O cage where the trimetaphosphimato ligand chelated each of the metal centers of the [M4(/r4-0) (/r-OH)6]8+ core.564... 

PaOs(NH)2(NH2)8 Diimidotri-phosphoric pentamide, 6 110 Ps06(NH)3H, Trimetaphosphimic acid, 6 79... 

The reaction of P3N3CI3 with formamide in ether solution is known to release hydrogen chloride and hydrogen cyanide, giving trimetaphosphimic acid the analogous reaction with thioformamide is slower but the addition of pyridine speeds the process to give trimetathiophosphimic acid (89). 

Figure 3 The structure of trimetaphosphimic acid dihydrate, H3(P02NH)3,2H20 (Reproduced by permission from Z. anorg. Chem., 1976, 419, 139)...

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