Abstract
A crystal of dodecasil 3C (ZSM-49, 136 SiO2) was prepared and heat treated to expel the enclathrated guest species. The structure of this sample was refined [space group Fd[unk]m, a = 19.369(6) Å] to Rw = 0.057 from 1068 reflections collected at 573 K with synchrotron radiation at λ = 0.593 Å. Anisotropic refinement and subsequent Fourier analysis revealed split positions for three of the four oxygen atoms in the asymmetric unit. The split positions were refined using bond length constraints. The mean values of Si – O bond lengths and Si – O – Si angles changed from 1.546 to 1.581 Å and from 175.6 to 163.5° after this refinement. The refined structure of disordered dodecasil 3C is compared with distance least squares simulations in several subgroups of Fd[unk]m.
