Structural systematics of rare earth complexes. XX. (Maximally) hydrated rare earth sulfates and the double sulfates

Room-temperature single-crystal X-ray studies carried out on trivalent rare earth sulfate hydrates, Ln(2)(SO4)(3).xH(2)O, crystallized at local ambience suggest the following arrays to be prevalent. For Ln = La, the nonahydrate is found, hexagonal P 6(3)/m, with conventional R on \F\ 0.023 for N-o 1159 'observed' (I >3 sigma(I)) diffractometer reflections (redetermination). Although for Ln = Ce a similar structure has been previously recorded, we have obtained that adduct as the monoclinic C 2/c, Z = 4, octahydrate, a phase also found for Ln = Lu and diverse representative intermediate lanthanoids: a approximate to 13.6, b approximate to 6.6, c approximate to 18.2 Angstrom, beta approximate to 102 degrees; for Ln = Ce (redetermination), Dy, Yb (redetermination), Lu, R was 0.022, 0.035, 0.031, 0.024 for N-o 3279, 2127, 3008, 3325 respectively. The structures of two lower hydrates adventitiously obtained are also recorded: the pentahydrate for Ln = Ce, monoclinic C 2/c, a 15.741(3), b 9.632(3), c 10.358(3) Angstrom, beta 119.72(2)degrees, Z = 4, R 0.030 for N-o 3372 (a redetermination), and the trihydrate for Ln = Lu, orthorhombic Cmc2(1), a 13.527(5), b 18.415(5), c 9.242(7) Angstrom, Z = 8, R 0.040 for N-o 1743. All structures are infinite polymeric arrays, the lanthanoid atoms being bridged by sulfate ions. Studies are also recorded for the ammonium/trivalent rare earth double sulfate tetrahydrate salts, (NH4)Ln(SO4)(2).4H(2)O, for the (hitherto) extremal members Ln = La, Tb, which are isomorphous with the previously studied Ln = Sm monoclinic P 2(1)/c, Z = 4 array, a approximate to 6.6, b approximate to 19, c approximate to 8.8 Angstrom, beta 97 degrees; R 0.035, 0.037 for N-o 3631, 3337. The array is a two-dimensional polymer, parallel to the ac plane.