Author:
Semenova Lioubov I.,Junk Peter C.,Skelton Brian W.,White Allan H.
Abstract
Room-temperature single-crystal X-ray structure determinations carried out on
rare earth bromides crystallized from water at room temperature define three
series of hydrates LnBr3.nH2O. For
Ln = La, Ce, a heptahydrate phase (n = 7)
is defined, triclinic P 1, a ≈
8·6, b ≈ 9·4, c
≈ 8·3 Å, α ≈ 108, β ≈ 99, γ ≈ 72°,
isomorphous with the array described for the ‘early’ (Ln =
La-Pr) rare earth chlorides, being binuclear
[(H2O)7Ln(-Br)2Ln(OH2)7]
Br4, Z = 1 dimer;
conventional R on
|F| were 0·051, 0·042 for
2323, 3451 independent ‘observed’ (I >
3σ(I)) diffractometer reflections respectively.
For Ln = Pr(-)Dy, a hexahydrate phase is defined, monoclinic
P 2/n, a
≈ 10·0, b ≈ 6·8,
c ≈ 8·2 Å, β ≈ 93·5°,
Z = 2 f.u., isomorphous with the array defined
for the heavier (Ln = Nd, Lu, Y) rare earth chlorides, being
[(H2O)6LnBr2]
Br, with R 0·029, 0·034 for
No 1590, 1388 respectively. For Ln
= Ho(-)Lu, Y, an octahydrate is defined for the first time, monoclinic
P 21/n,
a ≈ 8·1, b ≈
16·0, c ≈ 10·1 Å,
b ≈ 94·0°, Z
= 4 f.u., a new array of the form
[Ln(OH2)8]
Br3 emerging, with R 0·061,
0·048, 0·042 for No
1191, 2402, 1674 respectively, the metal environment being square
antiprismatic.