(NH4)6P6O18.NH4X.H2O (X=CL, BR, I) - THE 1ST EXAMPLES OF CYCLOHEXAPHOSPHATE-HALIDES

Chemical preparations and crystal data for a series of three cyclohexa phosphates-halides of general formula (NH4)6P6O18.NH4X.H2O for X = Cl, Br and I, are reported. They belong to two different structure types. The first one common to the two compounds corresponding to X = Cl and Br has been determined using the chlorine derivative. This salt is tr iclinic with the following unit-cell dimensions: a = 6.738(3), b = 10. 101(8), c = 19.33(1) angstrom alpha = 101.48(2), beta = 90.84(3), gamm a = 107.31(2)-degrees. Space group is P1BAR and Z = 2. The iodine deri vative is monoclinic, P2(1)/n with a tetramolecular unit-cell: a = 14. 96(1), b = 24.82(1), c = 6.710(6) angstrom, beta = 91.86(5)-degrees. V ery strong structural analogies exist between the two arrangements and are discussed.