Synthesis and crystal structure of [2-NH2-5-CH3C5H4N]4P4O12·6H2O

Chemical preparation, crystal structure, IR absorption and thermal analysis of a new cyclotetraphosphate [2-NH₂-5-CH₃C₅H₄N]₄P₄O₁₂·6H₂O are reported. This compound is triclinic P-1 with unit-cell parameters: a = 10.206(5), b = 11.778(1), c = 9.991(4) Å,  = 110.40(6), β = 117.74(6), γ = 86.41(3)°, V = 989.1(8) Å³, Z = 1, D_x = 1.445 g cm⁻³. The structure has been determined and refined to R = 0.034 and R_w = 0.044, using 3663 independent reflections. The ring anions and water molecules form layers spreading around (a, b + c) planes via OHO hydrogen bonds. Between them are anchored 2-amino-5-methylpyridium cations, which establish H-bonds to interconnect the different adjacent layers and so contribute to the cohesion of the three-dimensional network. Tautomerization of (C₆H₉N₂)⁺ groups was evidenced in the present structure.