´
2760
F.J. Arnaiz et al. / Polyhedron 21 (2002) 2755ꢂ
/2760
istence of two pairs of slightly different distances in 1
may be due only to packing forces. Indeed, several
uranyl complexes of composition UO2L4 as for example
mail: deposit@ccdc.cam.ac.uk or www: http://
[UO2Br4]2ꢅ
in
[UO2(HMPA)4]2ꢃ in [UO2(HMPA)4](ClO4)2 [10] dis-
play two and four different UÃL distances, respectively,
despite the counterions possess high symmetry. It is to
note that the mean UÃO(P) distance in 2, 2.305, is
(NMe4)2[UO2Br4]
[16]
and
Acknowledgements
/
This work was supported by the Junta de Castilla y
Leon (Grant BU14/98).
/
slightly superior to that in the closely related [UO2(HM-
PA)4](I3)2, 2.292 [8], as expected from the lower basicity
of OPPh3 with regard to HMPA.
References
The angles O(oxo)Ã
and O(P,As)ÃUÃO(P,As) are close to 1808, 908 and 908,
respectively, in both cations. In 1 the angles UÃOÃAs,
/
UÃ
/
O(oxo), O(oxo)Ã
/
UÃ
/
O(P,As)
[1] C.J. Burns, D.C. Smith, A.P. Sattelberger, H.B. Gray, Inorg.
Chem. 31 (1992) 3724.
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[2] D.M. Barnhart, C.J. Burns, N.N. Sauer, J.G. Watkin, Inorg.
Chem. 34 (1995) 4079.
154.28 and 140.48, are identical for each pair of trans-
ligands, both within the wide range of values found in
[3] M.P. Wilkerson, C.J. Burns, R.T. Paine, B.L. Scott, Inorg. Chem.
38 (1999) 4156.
UO2Ã
able to the angles UÃ
in the range of other UO2Ã
/
OAsPh3 complexes [4,17ꢂ
OÃP in 2, 146.08 and 159.28, also
OPPh3 complexes (for
/
19]. The same is applic-
[4] F.J. Arna´iz, M.J. Miranda, R. Aguado, J. Mah´ıa, M.A. Maestro,
Polyhedron 20 (2001) 3295.
/
/
/
[5] J.H. Burns, in: J.J. Katz, G.T. Seaborg, L.R. Mors (Eds.), The
Chemistry of the Actinide Elements, Chapman and Hall, New
York, 1986.
example in [UO2(NCS)2(OPPh3)2(Me2CO)] the angles
are 143.38 and 163.38 [20]).
Finally, the orientation of the equatorial ligands is
similar in both complexes. The cations are centrosym-
[6] L. Deshayes, N. Keller, M. Lance, M. Nierlich, D. Vigner, Acta
Crystallogr., Sect. C 48 (1992) 1660.
[7] L. Deshayes, N. Keller, M. Lance, M. Nierlich, D. Vigner, Acta
Crystallogr., Sect. C 48 (1992) 2209.
metric with regard to the UO2(OX)4 (Xꢁ
Two of opposite X atoms are oriented toward the
bisection of adjacent O(oxo)ÃUÃO(X) angles while the
other two X atoms lye close to the equatorial plane
(dihedral angles for As(2)ÃO(2)ÃU(1)ÃO(3)ꢁ42.928,
for As(1)ÃO(1)ÃU(1)ÃO(2)ꢁ5.578, for P(1)ÃO(2)Ã
U(1)ÃO(1)ꢁ43.138, for P(2)ÃO(3)ÃU(1)ÃO(2)ꢁ
/P, As) group.
[8] M.R. Caira, J.F. De Wet, J.G.H. Du Preez, B. Busch, H.E.
Rohwer, Inorg. Chim. Acta 77 (1983) L73.
[9] Y.K. Gusev, Radiokhim 27 (1985) 412.
/
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[10] L.R. Nassimbeni, A.L. Rodgers, Cryst. Struct. Commun. 5 (1976)
301.
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/
/
/
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/
/
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[11] See e.g.: (a) K.F. Tebbe, I. Dombrowski, Z. Anorg. Allg. Che. 625
(1999) 167.(b) M.W. Renner, K.M. Barkigia, Y. Zhang, C.J.
Medforth, K.M. Smith, J. Fajer, J. Am. Chem. Soc. 116 (1994)
8582.(c) P.C. Junk, L.R. MacGillivray, M.T. May, K.D. Robin-
son, J.L. Atwood, Inorg. Chem. 34 (1995) 5395.
[12] J. Leciejewicz, N.W. Alcock, T.J. Kemp, Struct. Bonding 82
(1995) 43.
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/
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/
/
/
7.298). We believe there are several possible conforma-
tions of similar energy for the group U(OX)4 (square
planar UO4, non-linear UÃ
/
OÃ/X). The adoption of a
particular conformation is likely determined by packing
forces. However, the steric demand of these ligands may
lead to restraints in free rotation and consequently to
the existence of stable conformers for these cations no
only as solid salts but also in solution. Studies to get
further insight on this possibility are in progress with
salts involving anions more stable than polyhalides.
[13] See, e.g.: K. Nakamoto, Infrared and Raman Spectra of
Inorganic and Coordination Compounds, 5th ed., Wiley, New
York, 1997.
[14] S.B. Akona, J. Fawcett, J.H. Holloway, D.R. Russel, I. Leban,
Acta Crystallogr., Sect. C 47 (1991) 45.
[15] K.W. Bagnal, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty
(Eds.), Comprehensive Coordination Chemistry, vol. 3, Pergamon
Press, Oxford, 1987.
[16] (a) G. Ingletto, L. Di Sipio, E. Tondello, G. Pelizzi, A. Montero,
Cryst. Struct. Commun. 3 (1974) 297;
4. Supplementary material
(b) W. Jensen, D. Dickerson, Q. Johnson, Acta Crystallogr., Sect.
B 30 (1974) 840.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 186697 and 186698 for
[UO2(OAsPh3)4][Br3]2 and [UO2(OPPh3)4][I3]2, respec-
tively. Copies of this information may be obtained free
of charge from The Director, CCDC, 12 Union Road,
[17] C. Panattoni, R. Graziani, U. Croatto, B. Zarli, G. Bombieri,
Inorg. Chim. Acta 2 (1968) 43.
[18] R. Graziani, B. Zarli, A. Cassol, G. Bombieri, E. Forsellini, E.
Tondello, Inorg. Chem. 9 (1970) 2116.
[19] B. Zarli, R. Graziani, U. Croatto, G. Bombieri, E. Forsellini,
Chem. Commun. (1971) 1501.
[20] G. Bombieri, E. Forsellini, G. De Paoli, D. Brown, T.C. Tso, J.
Chem. Soc., Dalton Trans. 26 (1979) 2042.
Cambridge, CB2 1EZ, UK (fax: ꢃ44-1223-336033; e-
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