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, R3¯m space group, with the equivalent hexagonal cell aH=8.647(1)Å, cH=8.507(2)Å, Z=3 and R=0.029, Rw=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 〈dTaF〉=1.894(7)Å. (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.