collected on a Nonius Kappa CCD diffractometer with Mo-Ka radiation (l
The same reaction in thf afforded [UO2I2(thf)3] (3), which was
isolated as a red powder in 80% yield after extraction in toluene. In
contrast to [UO2Cl2(thf)3], which readily loses one thf molecule to
give the chloro-bridged dimer [UO2Cl2(thf)2]2,9 compound 3, as
with its triflate analogue, is stable under vacuum. Complexes 1–3
gave satisfactory elemental analyses.†
= 0.71073 Å), absorption effects were empirically corrected. CCDC
graphic data in CIF or other electronic format.
§ The melting points of 2 and 3 were measured with an electrothermal
melting point apparatus from samples placed in glass capillaries under
argon. The thermal decomposition range of 1 was estimated by observing
the release of iodine.
The IR spectrum of 1 as a Nujol mull exhibits a strong band with
two major peaks at 988 and 982 cm21 assigned to the asymmetric
UO2 stretching mode. Identical nasym(UO) frequencies are ob-
served for UO2(OTf)2, whereas the corresponding band is de-
scribed at 1000 cm21 for UO2F2.14 The splitting of the band can be
ascribed to interactions between the UO22+ groups via the oxygen
1 M.-J. Crawford, A. Ellern, H. Nöth and M. Suter, J. Am. Chem. Soc.,
2003, 125, 11 778.
2 C. Keller, in Gmelin Handbuch der Anorganischen Chemie, Uranium
Supplement Volume C9, Springer-Verlag, Berlin, 1979, pp. 164–185
and references therein; J. J. Katz and E. Rabinowitch, The Chemistry of
Uranium. The Element, its Binary and Related Compounds, Dover, New
York, 1951, p. 595; J. J. Katz, G. T. Seaborg and L. R. Morss, The
Chemistry of Actinide Elements, Chapman and Hall, London, 2nd edn.,
1986, vol. 1, pp. 332–335; K. W. Bagnall, Coord. Chem. Rev., 1967, 2,
145.
atoms, similarly to the assignment in UO2Cl2 (958 and 946 cm21
)
from the crystal structure.15 In accordance with the greater electron
richness of the adducts, the nasym(UO) frequencies of 2 and 3 are
shifted to the lower values of 927 and 928 cm21 respectively; these
can be compared with those of [UO2Cl2(py)3] (925 cm21),
[UO2(OTf)2(py)3] (943 cm21) or [UO2Cl2(thf)2]2 (921 cm21).9,16
Complexes 1–3 were found to be stable for several days under
argon at room temperature, both in solution and the solid state. This
stability is comparable to that of the few adducts of UO2I2 which
are stabilized with bulky and strongly coordinating ligands.17
Compound 1 decomposes with liberation of iodine above 150 °C;
melting of 2 and 3, at 165 and 115 °C, respectively, is presumably
related to the dissociation of pyridine or thf ligands, as formation of
I2 was not detected at these temperatures.§ That traces of water are
detrimental to the stability of the UO2I2 complexes was confirmed
by carrying out reaction 2 with hydrated UO2(OTf)2 or by adding
H2O to a solution of 1 in diethyl ether. In these experiments, after
48 h at room temperature, evaporation of the solvent afforded a
brown–black residue with concomitant release of iodine. This
material, presumably some uranium oxide, was insoluble in diethyl
ether. These observations are in agreement with previous reports on
the formation of brown–black decomposition products upon
concentration and drying of aqueous solutions of UO2I2.2,4
3 J. Aloy, Ann. Chim. Phys., 1901, 24, 412.
4 L. Lynds, J. Inorg. Nucl. Chem., 1962, 24, 1007.
5 L. R. Avens, D. M. Barnhart, C. J. Burns and S. D. McKee, Inorg.
Chem., 1996, 35, 537; J. Collin, A. Pires de Matos and I. Santos, J.
Organomet. Chem., 1993, 463, 103.
6 L. R. Avens, S. G. Bott, D. L. Clark, A. P. Sattelberger, J. G. Watkin and
B. D. Zwick, Inorg. Chem., 1994, 33, 2248.
7 G. J. Leigh, J. R. Sanders, P. B. Hitchcock, J. S. Fernandes and M.
Togrou, Inorg. Chim. Acta, 2002, 330, 197.
8 J.-C. Berthet, M. Lance, M. Nierlich and M. Ephritikhine, Eur. J. Inorg.
Chem., 2000, 1969.
9 M. P. Wilkerson, C. J. Burns, R. T. Paine and B. L. Scott, Inorg. Chem.,
1999, 38, 4156 and references therein.
10 J. Rebizant, G. Van Den Bossche, M. R. Spirlet and J. Goffart, Acta
Crystallogr., Sect. C, 1987, 43, 1298.
11 M. Pennington, N. W. Alcock and D. J. Flander, Acta Crystallogr., Sect
C, 1988, 44, 1664.
12 N. W. Alcock, D. J. Flanders, M. Pennington and D. Brown, Acta
Crystallogr., Sect. C, 1987, 43, 1476.
13 M. Lamisse and R. Rohmer, Bull. Soc. Chim. Fr., 1963, 24.
14 H. R. Hoekstra, in Gmelin Handbuch der Anorganischen Chemie,
Uranium Supplement Volume A5, Springer-Verlag, Berlin, 1982, p.
217.
15 Gmelin Handbuch der Anorganischen Chemie, Uranium Supplement
Volume C9, Springer-Verlag, Berlin, 1979, p. 75.
The convenient synthesis of 1 which, contrary to previous
assumptions, exhibits good thermal stability, provides a further
demonstration that uranyl chemistry will witness important pro-
gress with the use of anhydrous experimental conditions. While
studies of the UO2X2 species (X = halide, NO3, ClO4, …) in
aqueous solutions have so far afforded limited information on the
chemical reactivity of the uranyl ion, spectacular developments
have been recently observed by using [UO2Cl2(thf)2]2 and
UO2(OTf)2 as starting materials in anhydrous organic media.
Formation of highly reactive uranyl complexes,16,18 the discovery
16 M. J. Sarsfield, M. Helliwell and D. Collison, Chem. Commun., 2002,
2264.
17 J. P. Day and L. M. Venanzi, J. Chem. Soc. A, 1966, 1363; V. A.
Golovnya and G. T. Bolotova, Russ. J. Inorg. Chem., 1966, 11, 1419; N.
Kumar and D. G. Tuck, Inorg. Chim. Acta, 1984, 95, 211; J. G. H. Du
Preez and B. Zeeli, Inorg. Chim. Acta, 1989, 161, 187; K. C. Rout, R. R.
Mohanty, S. Jena and K. C. Dash, Polyhedron, 1996, 15, 1023.
18 C. J. Burns, D. L. Clark, R. J. Donohoe, P. B. Duval, B. L. Scott and C.
D. Tait, Inorg. Chem., 2000, 39, 5464; M. P. Wilkerson, C. J. Burns, H.
J. Dewey, J. M. Martin, D. E. Morris, R. T. Paine and B. L. Scott, Inorg.
Chem., 2000, 39, 5277; W. J. Oldham, S. M. Oldham, B. L. Scott, K. D.
Abney, W. H. Smith and D. A. Costa, Chem. Commun., 2001, 1348.
19 J.-C. Berthet, M. Nierlich and M. Ephritikhine, Chem. Commun., 2003,
166; P. Thuéry, M. Nierlich, B. Masci, Z. Asfari and J. Vicens, J. Chem.
Soc., Dalton Trans., 1999, 3151.
2+
of a novel coordination geometry for the UO2 ion,19 the first
crystallographic characterization of a pentavalent UO2+ ion,20 and
2+
transformation of UO2 into new U(VI) or lower valent species21
have considerably enlarged the area of uranyl chemistry. In view of
the specific features of the U–I bond, UO2I2 and its adducts 2 and
3 are potentially useful precursors for the synthesis of new uranium
compounds.
20 J.-C. Berthet, M. Nierlich and M. Ephritikhine, Angew. Chem., Int. Ed.,
2003, 42, 1952.
Notes and references
‡ Crystal data for 2: C15H15I2N3O2U, M = 761.13, orthorhombic, a =
14.968(3), b = 15.662(3), c = 17.193(3) Å, V = 4030.5(14) Å3, space
group Pbca, Z = 8, Dc = 2.509 g cm23, m(Mo-Ka) = 11.128 mm21, T =
123(2) K, 25 092 measured reflections, 3364 independent, 2616 [I > 2s(I)],
208 parameters, R1 = 0.0339, wR2 = 0.0676, GOF = 0.884; the data were
21 C. J. Burns and A. P. Sattelberger, Inorg. Chem., 1988, 27, 3692; H.
Greiwing, B. Krebs and A. A. Pinkerton, Inorg. Chim. Acta, 1995, 234,
127; P. B. Duval, C. J. Burns, W. E. Buschmann, D. L. Clark, D. E.
Morris and B. L. Scott, Inorg. Chem., 2001, 40, 5491; P. C. Leverd, D.
Rinaldo and M. Nierlich, J. Chem. Soc., Dalton Trans., 2002, 829.
C h e m . C o m m u n . , 2 0 0 4 , 8 7 0 – 8 7 1
871