Anhydrous lanthanoid metal chlorides
LnCl3(thf)n (Ln = La, Ce,
Nd, Sm, n = 2; Ln = Tb, Ho,
n = 2·5; Ln = Dy, Tm,
n= 2·7; Ln = Gd, Yb, Lu,
n = 3; Ln = Er, n
= 3·5) have been prepared in excellent yield by the direct
reaction of the lanthanoid metal powders with hexachloroethane in
tetrahydrofuran (thf), and (Ln = Eu, n =
0·8; Ln = La, n = 1·7; Ln
= Pr, n = 2; Ln = Gd,
n = 2·5; Ln = Er,
n = 3) in good yield except for
EuCl3(thf)0·8 from bulk metal.
[YbCl3(thf)2]2
was prepared by prolonged treatment of solid
YbCl3(thf)3 with pentane. The
X-ray crystal structures of
[LnC3(thf)2] (Ln
= La, Ce or Pr),
[LnCl3(thf)3.5] (Ln
= Gd or Er),
[YbCl3(thf)3] and
[LaCl3(thf)(H2O)] have
been determined. For
[LaCl3(thf)2], a square
antiprismatic single-stranded polymer, ...
La(-Cl)3(thf)3La(-Cl)3(thf)2
..., is the first eight-coordinate
LnCl3(thf)n complex. The metal is
surrounded by two sets of three bridging chlorines and cis thf oxygens.
[LnCl3(thf)2] (Ln
= Ce, Pr) have seven-coordinate structures with doubly chloride-bridged
linear chains, ...
LnCl(µ-Cl)3(thf)2LnCl(µ-Cl)2(thf)2
... where the lanthanoid atom exists in a pentagonal bipyramidal environment,
the pentagonal bipyramidal plane being defined by four chloride atoms and one
oxygen atom of the thf ligand, and the axial positions being occupied by a
chloride and a thf oxygen atom.
[LnCl3(thf)3.5] (Ln
= Gd, Er) crystallize as discrete ion pairs,
[LnCl2(thf)5]+
[LnCl4(thf)2]¯. The
lanthanoid atom in the cation displays pentagonal bipyramidal geometry with
two apical chloride atoms and five equatorial thf ligands while the anion has
quasi-regular octahedral stereochemistry with trans thf ligands.
[LaCl3(thf)(H2O)]
displays an eight-coordinate two-dimensional polymeric array with six bridging
chlorides per lanthanum atom. Far-infrared spectra have been recorded for a
number of products and used as a basis for structural proposals, particularly
for products with fractional thf.