Tetrametaphosphimic acid

The dihydrate of the tetramer is particularly stable and is, in fact, the bishydroxonium salt of tetrametaphosphimic acid [H30]J[(NH)4P4-06(0H)2] the anion of which has a boat configuration and is linked by short H bonds (246 pm) into a two-dimensional sheet (Fig. 12.29). The related salts M4[NHP02)4].- H20 show considerable variation in conformation of the tetrametaphosphimate anion, as do the 8-membered heterocyclic tetraphosphazenes (NPX2)4 (p. 537), e.g. 

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... 

H. N. Stokes mentioned henametaphosphimic acid, formed by hydrolysis from an oily liquid obtained in the preparation of the chloronitrides, with the composition 1,11N11022. The acid readily decomposes into diimidotriphosphoric, t riimidotetraphosphorie, and tetrametaphosphimic acids. 

The silver salts of trimeta and tetrametaphosphimic acids appear to exist in several forms, including doubly basic varieties such as Agg(P02NH)3 and Agg(P02NH)4. These red hexa and octa silver salts probably contain covalently linked silver atoms as in the simple amido salts (7.61). 

Examples of phosphate stractures containing hydroxonium H3O+ cations are provided by hypo-phosphoric acid dihydrate, tetrametaphosphimic acid (13.23) and hydrogen uranyl phosphate tetra-hydrate, all of which possess complex systems of H bonds in the solid state [28-30]. 

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. 

H. N. Stokes also made sodium amidoheximidoheptaphosphatea salt of amidoheximidoheptaphosphoric arid, PO(OH)(NH2).NH. PO(OH)NH 5.PO(OH)2— by the hydrolysis of heptaphosphoric nitrilochloride with sodium hydroxide in an ethereal soln. He expected to obtain heptametaphosphimic acid. The sodium salt is decomposed by acids, forming tetrametaphosphimate. 

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