metal-organic compounds
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of 2.300 (3) and 2.62 (2) A, respectively, two chloride ions,
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with a mean GdÐCl distance of 2.68 (1) A, and two pyridine
Acta Crystallographica Section C
Crystal Structure
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molecules, with a mean GdÐN distance of 2.615 (8) A. This
Communications
ISSN 0108-2701
complex molecule possesses a pseudo (non-crystallographic)
binary axis. The gadolinium ion is thus eight-coordinate, with
two bidentate and four monodentate ligands. The coordina-
tion polyhedron geometry is closer to that of a very distorted
An ion pair uniting a gadolinium(III)±
Schiff base complex and uranyl tetra-
chloride
Â
Olivier Pons y Moll, Thierry Le Borgne, Pierre Thuery*
and Michel Ephritikhine²
Ã
CEA/Saclay, SCM (CNRS URA 331), Batiment 125, 91191 Gif-sur-Yvette, France
Correspondence e-mail: thuery@drecam.cea.fr
Received 19 October 2000
Accepted 18 January 2001
cube than to the most frequently observed square antipris-
matic geometry (Kepert, 1982). The plane containing the
gadolinium cation and the two Cl atoms is nearly perpendi-
cular to that containing Gd and the N atoms of the pyridine
molecules, with a dihedral angle of 89.52 (9)ꢁ between them,
whereas the dihedral angle between the plane containing Gd,
O1 and O3 and that containing Gd, O2 and O4 is 79.89 (9)ꢁ.
Considering the whole coordination sphere, the ®ve atoms Gd,
N3, N4, O2 and O4 are roughly coplanar, with a maximum
The Schiff base N-(tert-butyl)-3-methoxysalicylaldimine (LH)
forms a complex with gadolinium(III) chloride, [GdCl2-
(LH)2(C5H5N)2]+, in which the two O atoms of each ligand
are coordinated (the phenolic O atom being deprotonated)
and the imine N atom is protonated and involved in a
hydrogen bond with the phenoxide group. This complex
crystallizes as an ion pair with uranyl tetrachloride,
i.e. bis{bis[2-(tert-butyliminiomethyl)-6-methoxyphenolato-
O,O0]dichlorobis(pyridine-N)gadolinium(III)} tetrachlorodi-
oxouranium(VI) tetrapyridine solvate [GdCl2(C12H17NO2)2-
(C5H5N)2]2[UCl4O2]Á4C5H5N. The U atom of the UCl4O2
anion lies on an inversion centre.
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deviation of 0.177 (5) A, but the ®ve atoms Gd, Cl1, Cl2, O1
and O3 present a stronger departure from planarity, with
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maximum deviations of 0.417 (4) and 0.479 (4) A for O1 and
O3, respectively. The dihedral angle between these two ®ve-
atom mean planes is 84.68 (5)ꢁ, which con®rms the distorted
cube geometry of the coordination environment (the small
`bite' of the Schiff base ligand does not enable a closer
approach to the cube geometry). The two Schiff base mol-
ecules are planar (maximum deviations from the mean plane
Comment
In the course of our studies on the synthesis, structure and
magnetic properties of heterobimetallic complexes containing
uranium, we have prepared, by reaction of L2UCl2 with GdCl3
[LH is N-(tert-butyl)-3-methoxysalicylaldimine], the U±Gd
compound L2UGdCl5, in which the metal ions are associated
with two Schiff base molecules L. Attempted crystallization of
this compound from pyridine afforded crystals of a new
complex, (I), in which uranium is found in the form of a
dissociated uranyl ion; this certainly results from the presence
of adventitious traces of water in the solvent used. This is the
®rst report of the crystal structure of a complex involving the
Schiff base L.
The asymmetric unit in (I) is composed of one gadolin-
ium(III) complex, half a uranyl tetrachloride moiety (with the
U atom located on a symmetry centre), a non-bonding pyri-
dine molecule and two half pyridine molecules (disordered
around symmetry centres). The uranyl-containing group
presents usual features (see Table 1), with a mean UÐCl bond
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are 0.0181 and 0.0633 A with the methyl and tert-butyl groups
omitted) and the dihedral angle between them is 54.29 (8)ꢁ.
The bulky NH+±C(CH3)3 groups are directed away from one
another.
The uranyl moiety provides one negative charge per
gadolinium complex. The electroneutrality results from the
Schiff base molecules being formally neutral, since the charge
on the phenoxide O atom is compensated for by that on the
protonated N atom. The Schiff base ligand can thus be viewed
as a zwitterionic species. Strong hydrogen bonds are present
between the protonated N and phenoxide O atoms (see
Table 2), resulting in an unprecedented arrangement of a
Schiff base coordinated to a metallic cation. The non-bonding
pyridine molecules occupy intermolecular voids in the crystal
packing and present some distant contacts with the Schiff base
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molecules (as short as 3.33 A), most likely indicating feeble
interactions.
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length of 2.67 (2) A and a nearly perfect square-planar
equatorial environment. The gadolinium ion is surrounded by
two Schiff base molecules, each of them bound through a
phenoxide and an ether O atom, with mean GdÐO distances
A search of the April 2000 release of the Cambridge
Structural Database (Allen & Kennard, 1993) found only one
other crystal structure of a molecular compound containing
both actinide and lanthanide ions. This compound is also an
² Additional correspondence author; email: ephri@drecam.cea.fr.
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392 # 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved
Acta Cryst. (2001). C57, 392±393