Anion and cation disorder in [CN3H6]⋅(TaF6)

A new guanidinium fluoride tantalate, [CN3H6]⋅(TaF6), crystallises at 50 °C from a solution of Ta2O5 in 40% aqueous HF and of guanidinium chloride. The structure is rhombohedral, R 3 ¯ m space group, with the equivalent hexagonal cell a H = 8.647 ( 1 ) A , c H = 8.507 ( 2 ) A , Z = 3 and R = 0.029 , R w = 0.077 for 312 reflections. The three-dimensional network is built up from parallel (0001)H layers ∞([CN3H6]F6)5− between which tantalum atoms are inserted. These tantalum atoms, in 3a sites, adopt an octahedral coordination with 〈 d Ta F 〉 = 1.894 ( 7 ) A . (TaF6)− anions are disordered over (0001)H mirror plane related positions while guanidinium cations are disordered over centrosymmetric positions; site occupancy of fluoride and nitrogen sites is fifty per cent.