Dimetaphosphimic acid

It has been supposed that the angle of least strain of the rings or polyhedra is 135°, which is most closely realised in the tetra-compound, which is also the most stable of the series. The structure assigned will determine that of the corresponding metaphosphimic acid which is produced by hydrolysis. Dimetaphosphimic acid, if its existence is admitted, could not be cyclic according to formula (a). Formula (b) is adopted in describing these compounds. 

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