Room-temperature single-crystal X-ray structure determinations of the 1 : 3 adducts of the trivalent lanthanoid perchlorates with 2,2':6',2 "-terpyridine ('tpy') as crystallized from acetonitrile are recorded. The Ln = La complex is the only one of its structural type, being modelled as La(ClO4)(3)/tpy/MeCN/H2O (1 : 3 : 2 :2/3), trigonal P 3c1, Z = 6, a 13.063(7), c 53.04(4) Angstrom, recorded on an interim basis, with conventional R on \F\ 0.081 for N-o 2889 'observed' (I >3 sigma(I)) reflections. For Ln = Ce, (Pr, Sm,) Eu and, by presumption, other intermediate members, a monosolvate is found, monoclinic P 2(1)/n, a approximate to 9.3, b approximate to 21.1, c approximate to 24.7 Angstrom, beta approximate to 91 degrees, Z = 4, R being 0.045, (0.060, 0.049,) 0.047 for N-o 4420, (4199, 3931,) 3713. The Ln = Eu adduct has also been obtained unsolvated in a form representative of Ln = Eu, Lu and, by presumption, intermediate members, as well as Y, which is monoclinic C 2/c, Z = 4, R being 0.051, 0.044, 0.061 for N-o 4386, 4407, 3713. All monoclinic systems are of the form [Ln(tpy)(3)] (ClO4)(3)(.S), Ln being nine-coordinate, and in the case of the C 2/c phase lying on a crystallographic 2 axis. The Ln = La adduct was modelled with three independent cations, all with crystallographic 3 symmetry, two with their coordination number augmented by the approach of solvent along the 3 axis.
