The presence of water in the common CeCl3/RLi alkylation system

Article abstract of DOI:10.1021/ja954276w

Dehydration of CeCl₃(H₂O)₇ following standard procedures for making the commonly-used CeCl₃/RLi reagent forms a material containing water and not anhydrous CeCl₃. Heating CeCl₃(H₂O)₇ at 150 °C and 0.03 Torr for 12 h forms a material which has an elemental composition of [CeCl₃(H₂O)](n), contains water by Karl Fischer analysis, reacts with MeLi to form methane, and crystallizes from THF as [Ce(μ-Cl)₃(THF)(H₂O)](n) in space group PI? with a = 6.691 (2) A?, b = 7.433(2) A?, c = 10.092(2) A?, α = 84.46(2)°, β = 76.72(2)°, γ = 74.76(3)°, V = 471.0(2) A?³, ρ(calcd) = 2.37 g/cm³, and Z = 2 at T = 158 K. [Ce(μ-Cl)₃(THF)(H₂O)](n) crystallizes in a layered structure in which eight-coordinate cerium atoms are ligated to terminal water and THF ligands and six bridging chlorides in a distorted square antiprismatic geometry. The THF ligands extend above and below the layers which contain the water molecules. Reactions of 'CeCl₃/RLi' must take into account the presence of 1 equiv of water.

Full text of DOI:10.1021/ja954276w

J. Am. Chem. Soc. 1996, 118, 4581-4584
4581
The Presence of Water in the Common CeCl3/RLi Alkylation
System
William J. Evans,* Jay D. Feldman, and Joseph W. Ziller
Contribution from the Department of Chemistry, UniVersity of California, IrVine,
IrVine, California 92717
ReceiVed December 22, 1995X
Abstract: Dehydration of CeCl3(H2O)7 following standard procedures for making the commonly-used CeCl3/RLi
reagent forms a material containing water and not anhydrous CeCl3. Heating CeCl3(H2O)7 at 150 °C and 0.03 Torr
for 12 h forms a material which has an elemental composition of [CeCl3(H2O)]n, contains water by Karl Fischer
analysis, reacts with MeLi to form methane, and crystallizes from THF as [Ce(µ-Cl)3(THF)(H2O)]n in space group
P1h with a ) 6.691(2) Å, b ) 7.433(2) Å, c ) 10.092(2) Å, R ) 84.46(2)°, â ) 76.72(2)°, γ ) 74.76(3)°, V )
471.0(2) Å3, Fcalcd ) 2.37 g/cm3, and Z ) 2 at T ) 158 K. [Ce(µ-Cl)3(THF)(H2O)]n crystallizes in a layered structure
in which eight-coordinate cerium atoms are ligated to terminal water and THF ligands and six bridging chlorides in
a distorted square antiprismatic geometry. The THF ligands extend above and below the layers which contain the
water molecules. Reactions of “CeCl3/RLi” must take into account the presence of 1 equiv of water.
Introduction
for making this reagent involves heating commercially-available
hydrated CeCl3(H2O)7 under reduced pressure and adding RLi
to what is presumed to be anhydrous CeCl3. Several precise
recipes for dehydrating CeCl3(H2O)7 to make CeCl3/RLi have
been given in the literature and range from heating the hydrate
at 140 °C at 0.1 Torr for 2 h6 to heating it for over 12 h at 150
°C and 0.1 Torr.7 The procedures to make this reagent have
evolved to include special details like gradual heating to the
specified temperatures and intermediate grinding. Excess RLi
is typically used in the subsequent reaction, and in some cases,
it is recommended to add excess RLi in case the dehydration
was not optimum.7
An important recent development in organic synthesis has
been the extension of metal-based reagents from the main group
and transition metals to the lanthanide metals.1,2 The three most
common lanthanide reagents in organic synthesis are ceric
ammonium nitrate (CAN), (NH4)2Ce(NO3)6, samarium diiodide,
SmI2(THF)x, and a reagent written as CeCl3/RLi.
The first two of these reagents are well-defined. Ceric
ammonium nitrate has long been used for oxidations and there
is little question about its identity and purity. It has been
crystallographically characterized3 and is neither oxygen nor
moisture sensitive. Recently, samarium diiodide has been fully
characterized by X-ray diffraction and shown to be SmI2(THF)5
in the crystalline state.4 Elemental analyses have established
that as a powder this reagent is SmI2(THF)2.4,5 The preparation
of samarium diiodide in pure form is straightforward since it
can be made from the elemental metal and diiodoethane.
On the other hand, the identity and purity of the reagent
written as CeCl3/RLi6,7 is not well established. The procedure
Prior studies of the dehydration of lanthanide halides suggest
that these dehydration procedures would not make CeCl3, but
instead a material that would contain some oxygen either as
water, hydroxide, or oxide.8-10 Hence, truly anhydrous samples
of LnCl3 are typically made under more forcing conditions, e.g.
heating a mixture of LnCl3(H2O)x and excess NH4Cl to 150 °C
under high vacuum (10-3 Torr) for 24 h followed by heating at
260 °C and sublimation of NH4Cl.8 One role of the NH4Cl is
to react with any OH formed to make H2O and NH3 (which are
removed under vacuum) and leave Cl in the place of OH.10
Furthermore, a detailed fluorescence study of the several steps
in the dehydration of EuCl3(H2O)6 at 10 Torr showed that under
these conditions the first three water molecules of hydration
were lost at 124 °C, the fourth at 151 °C, and the fifth at 165
°C. Further heating failed to remove the final water of
hydration, but instead led to the formation of Eu(OH)Cl2 at 215
°C and EuOCl at 342 °C.9
X Abstract published in AdVance ACS Abstracts, May 1, 1996.
(1) Kagan, H. B.; Namy, J. L. In Handbook on the Physics and Chemistry
of Rare Earths; Gschneider, K. A., Jr., Eyring, L., Eds.; Elsevier:
Amsterdam, 1984; Vol. 6, Chapter 50. Kagan, H. B.; Namy, J. L.
Tetrahedron 1986, 42, 6573-6614. Soderquist, J. A. Aldrichim. Acta 1991,
24, 15-23. Molander, G. A. Chem. ReV. 1992, 92, 29-68.
(2) ComprehensiVe Organic Synthesis; Trost, B. M., Fleming, I., Eds.;
Pergamon Press: Oxford, 1991.
(3) Beineke, T. A.; Delgaudio, J. Inorg. Chem. 1968, 7, 715-721.
(4) Evans, W. J.; Gummersheimer, T. S.; Ziller, J. W. J. Am. Chem.
Soc. 1995, 117, 8999-9002.
(5) Watson, P. L.; Tulip, T. H.; Williams, I. Organometallics 1990, 9,
1999-2009.
We report here that “CeCl3”, prepared following the standard
procedures for making CeCl3/RLi, gives a material which
contains water as determined by IR spectroscopy, Karl Fischer
(6) Imamoto, T. In ComprehensiVe Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon: Oxford, 1991; Chapter 1.8 and references
therein. Imamoto, T. Pure Appl. Chem. 1990, 62, 747-752. Imamoto, T.;
Takiyama, N.; Nakamura, K.; Hatajima, T.; Kamiya, Y. J. Am. Chem. Soc.
1989, 111, 4392-4398. Denmark, S. E.; Weber, T.; Piotrowski, D. W. J.
Am. Chem. Soc. 1987, 109, 2224-2225. Paquette, L. A.; Learn, K. S.;
Romine, J. L.; Lin, H.-S. J. Am. Chem. Soc. 1988, 110, 879-890. Guo,
B.-S.; Doubleday, W.; Cohen, T. J. Am. Chem. Soc. 1987, 109, 4710-
4711. Garigipati, R. S.; Tschaen, D. M.; Weinreb, S. M. J. Am. Chem. Soc.
1990, 112, 3475-3482. Jasperse, C. P.; Curran, D. P. J. Am. Chem. Soc.
1990, 112, 5601-5609. Abraham, W. D.; Cohen, T. J. Am. Chem. Soc.
1991, 113, 2313-2314. Paquette, L. A.; DeRussy, D. T.; Vandenheste, T.;
Rogers, R. D. J. Am. Chem. Soc. 1990, 112, 5562-5573. Suzuki, M.;
Kimura, Y.; Terashima, S. Chem. Lett. 1984, 1543-1546.
(7) Encyclopedia of Reagents for Organic Synthesis; Paquette, L. A.,
Ed.; Wiley: Chichester, England, 1995; pp 1031-1034.
(8) Taylor, M. D.; Carter, C. P. J. Inorg. Nucl. Chem. 1962, 24, 387-
391. Taylor, M. D. Chem. ReV. 1962, 62, 503-511. Burgess, J.; Kijowski,
J. AdV. Inorg. Chem. Radiochem. 1981, 24, 57-114. Brown, D. Halides of
the Lanthanides and Actinides; Wiley-Interscience: New York, 1968;
Chapter 3.
(9) Stump, N. A.; Schweitzer, G. K.; Gibson, J. K.; Haire, R. G.; Peterson,
J. R. App. Spectrosc. 1994, 48, 937-944.
(10) Meyer, G. Inorg. Synth. 1989, 25, 146-150.
S0002-7863(95)04276-4 CCC: $12.00 © 1996 American Chemical Society

4582 J. Am. Chem. Soc., Vol. 118, No. 19, 1996
EVans et al.
Table 1. Crystal Data and Structure Refinement Information on
analysis, elemental analysis, chemical analysis, and X-ray crys-
tallography.
[Ce(µ-Cl)3(THF)(H2O)]n
empirical formula
formula weight
temperature
wavelength
crystal system
space group
C4H10CeCl3O2
336.59
158 K
0.710 73 Å
triclinic
P1h
Experimental Section
General. CeCl3(H2O)7 was obtained from Research Chemicals, Inc.
Elemental analysis was obtained from Analytische Laboratorien,
Gummersbach, Germany. Karl Fischer analysis was conducted on a
Fisher Scientific Accumet 150. Infrared spectra were obtained on a
Mattson Galaxy FTIR 5000.
unit cell dimens
a ) 6.691(2) Å; R ) 84.46(2)°
b ) 7.433(2) Å; â ) 76.72(2)°
c ) 10.092(2) Å; γ ) 74.76(3)°
471.0(2) Å, 2
[CeCl3(H2O)]n (1). CeCl3(H2O)7 (10 g, 26.8 mmol) was placed into
a 500-mL Schlenk flask containing a magnetic stir bar. The flask was
attached to a vacuum manifold connected to a liquid nitrogen trap and
a mechanical pump. Following a literature procedure,7 but at a lower
pressure, the flask was evacuated to 0.03 Torr, slowly heated to 150
°C over 3 h with an oil bath, and agitated at this temperature for 12
additional hours to give 1 as a colorless solid. The vessel was moved
from the vacuum line to a nitrogen-containing glovebox in which
samples of 1 were taken for analysis. Anal. Calcd for [CeCl3(H2O)]n:
Ce, 53.00; Cl, 40.21; H, 0.76; O, 6.05. Found: Ce, 53.20; Cl, 40.07;
H, 0.72; O (by difference), 6.01. A saturated solution of 1 in THF
was prepared and found by Karl Fischer analysis to contain 0.22-
0.23 mg of H2O/mL which corresponds to 90-95% of the water
expected from the formula [CeCl3(H2O)]n based on a measured
solubility of 3.5 mg/mL. Compound 1 (277 mg, 1.05 mmol) was placed
in a tube fitted with two greaseless high-vacuum stopcock adapters,
one attached to a 24/40 joint and the other to a septum-capped sidearm.
Excess MeLi (2.9 mmol) obtained by removing Et2O from a commercial
solution (Aldrich) was added to the tube and the apparatus was attached
to a high-vacuum line connected to a Toepler pump. THF was added
by syringe through the sidearm and gas evolution was observed when
it contacted the solids. The gas was collected by Toepler pump and
identified as methane by mass spectrometry (10.5 mL, 0.43 mmol).
Recrystallization at 25 °C from a THF solution which had been saturated
by stirring 1 in boiling THF followed by removal of excess solid via
centrifugation gave crystals of [Ce(µ-Cl)3(H2O)(THF)]n.
X-ray Data Collection, Structure Determination, and Refinement
for [Ce(µ-Cl)3(H2O)(THF)]n. A colorless crystal of approximate
dimensions 0.20 × 0.20 × 0.21 mm was mounted on a Siemens P4
diffractometer. Determination of Laue symmetry, crystal class, unit
cell parameters, and the crystal’s orientation matrix was carried out
according to standard procedures.11 Low-temperature (158 K) intensity
data were collected via a 2θ-omega scan technique with Mo KR
radiation. All 1807 data were corrected for absorption12 and for Lorentz
and polarization effects and placed on an approximately absolute scale.
The crystal class is triclinic and the space group is centrosymmetric
P1h. Details appear in Table 1.
volume, Z
density (calcd)
abs coeff
F(000)
crystal size
θ range for data collection
limiting indices
reflcns collected
independent reflcns
abs corr
max and min transmission
refinement method
data/restraints/parameters
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole
2.374 g/cm3
5.627 mm-1
318
0.21 × 0.20 × 0.20 mm
2.07-25.00°
-2 e h e 7, -8 e k e 8, -12 e l e 11
1807
1650 (Rint ) 0.0248)
semiempirical from ψ scans
0.4904 and 0.3882
full-matrix least-squares on F2
1650/0/100
1.085
R1 ) 0.0206, wR2 ) 0.0499a
R1 ) 0.0224, wR2 ) 0.0507a
0.859 and -1.306 eÅ-3
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) [∑[w(Fo2 - Fc2)2/∑[w(Fo )2]]1/2
.
2
The infrared spectrum of 1 contained a strong absorption at 3440
cm-1, which is consistent with an OH stretch. The presence of
water in 1 was detected by dissolving a sample in THF and
analyzing the solution by the Karl Fischer technique. On the
basis of the measured solubility of 1, the analyses detected 90-
95% of the amount of water expected for the stoichiometry
[CeCl3(H2O)]n. When THF was added to a mixture of 1 and
MeLi in a Toepler pump system, gas was immediately evolved
which proved to be methane by mass spectroscopy. The amount
of methane obtained accounted for a 40% yield according to
the stoichiometry of eq 1.
(1/n)[CeCl3(H2O)]n + CH3Li f
(1/n)[CeCl3]n + LiOH + CH4 (1)
The low yield may be due to incomplete dissolution of 1 under
the reaction conditions.
All crystallographic calculations were carried out using the UCI
modified version of the UCLA Crystallographic Computing Package13
and the SHELXTL14 program. The analytical scattering factors15 for
neutral atoms were used throughout the analysis. The structure was
solved by direct methods and refined by full-matrix least-squares
techniques (SHELXTL). Refinement of the model led to convergence
with wR2 ) 0.0507 and GOF ) 1.09 for 100 parameters refined against
all 1650 unique data (R1 ) 0.021 for those 1584 data with Fo > 4.0σ-
(Fo)).
X-ray Crystal Structure of [CeCl3(H2O)(THF)]n. Crystal-
lization of 1 from THF gave single crystals which were analyzed
by X-ray diffraction as [Ce(µ-Cl)3(H2O)(THF)]n (Figure 1). This
experiment unequivocally established the presence of water in
this system.
The complex crystallizes in an interesting polymeric layered
structure in which all of the chloride ligands are bridging, i.e.
the monomeric unit is Ce(µ-Cl)3(THF)(H2O). As a result, each
cerium is eight coordinate due to ligation by six bridging
chlorides and the two oxygen donor groups. The eight donor
atoms describe a distorted square antiprism in which the oxygen
atoms are adjacent, but reside on different square faces (Figure
2). The two square faces are defined by the atoms O(1), Cl(2),
Cl(2A), and Cl(1A), which are coplanar to within 0.1 Å, and
the atoms O(2), Cl(1), Cl(3), and Cl(3A), which are coplanar
to within 0.08 Å. The dihedral angle between these two squares
is 3.2°. The δ angles used to evaluate distortions from idealized
structures in 8-coordinate geometries16 are 7.9, 9.7, 38.5, and
52.2° compared to 29.5° for a perfect dodecahedron and 0.0
Results and Discussion
Heating CeCl3(H2O)7 at 150 °C for 12 h and 0.03 Torr
following the extremes of literature procedures for preparing
CeCl3/RLi6,7 produces a colorless powder, 1, which has an
elemental analysis consistent with the formula [CeCl3(H2O)]n.
(11) XSCANS Version 2.10; Siemens Analytical X-ray Instruments,
Inc.: Madison, WI 1990-1995.
(12) XPREP program: Sheldrick, G.; SHELXTL PLUS program set;
Siemens Analytical X-Ray Instruments, Inc.: Madison, WI 1990.
(13) UCLA Crystallographic Computing Package, University of Cali-
fornia Los Angeles, 1981, C. Strouse; personal communication.
(14) Sheldrick, G.; SHELXTL PLUS program set; Siemens Analytical
X-Ray Instruments, Inc.: Madison, WI 1990.
(16) Muetterties, E. L.; Guggenberger, L. J. J. Am. Chem. Soc. 1974,
96, 1748-1756. Haddad, S. F.; Raymond, K. N. Inorg. Chim. Acta 1986,
122, 111-118.
(15) International Tables for X-Ray Crystallography; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1992; Vol. C.

Presence of Water in the CeCl3/RLi Alkylation System
J. Am. Chem. Soc., Vol. 118, No. 19, 1996 4583
Figure 1. Part of the extended structure of [Ce(µ-Cl)3(THF)(H2O)]n.
Figure 3. Side view of the layers of [Ce(µ-Cl)3(THF)(H2O)]n showing
the interleaving of THF between layers containing cerium, chloride,
and water.
Table 2. Selected Bond Distances (Å) for [Ce(µ-Cl)3(H2O)(THF)]n
17
with Comparable Values for [CeCl(µ-Cl)2(THF)2]n Listed Side
by Side
[Ce(µ-Cl)3(H2O)(THF)]n
[CeCl(µ-Cl)2(THF)2]n
Ce(1)-Cl(1)
Ce(1)-Cl(2)
Ce(1)-Cl(3)
Ce(1)-Cl(1A)
Ce(1)-Cl(2B)
Ce(1)-Cl(3C)
Ce(1)-O(1)
2.930(1)
Ce(1)-Cl(1)
2.828(1)
2.880(1)
2.825(1)
2.856(1)
2.861(1)
2.823(1)
2.888(1)
2.875(1)
2.846(1)
2.528(3)
Ce(1)-Cl(3)
Ce(1)-Cl(3A)
Ce(1)-Cl(1B)
Figure 2. Diagram of the donor atom coordination geometry around
cerium in [Ce(µ-Cl)3(THF)(H2O)]n.
Ce(1)-O(1)
Ce(1)-O(2)
2.492(3)
2.508(3)
Ce(1)-O(2)
2.492(3)
and 52.4° for a perfect square antiprism. The φ angles are 22.5
and 21.7° compared to 0° for a dodecahedron and 24.5° for an
ideal square antiprism.
hydroxyl Ln-O(OH) bond.21 Nd-O(H2O) distances are typi-
cally 2.46-2.55 Å for 8- to 10-coordinate structures.22 In
comparison, the metal hydroxyl Nd-O(OH) distance in 8-co-
ordinate [(Me3CC5H4)2Nd(µ-OH)]2 is only 2.329(2) Å.23 The
Ce-O(H2O) distance in 1 is identical to the 2.490(4)-Å Nd-
O(H2O) distance in the structurally similar 8-coordinate [Nd(µ-
Cl)2Cl2(H2O)2]- anion in (MeNH3)8(NdCl6)[NdCl4(H2O)2]2Cl3.24
The overall structure of [Ce(µ-Cl)3(THF)(H2O)]n consists of
layers of cerium and chloride atoms linked as shown in Figure
1 with THF groups extending above and below the plane of
the layer. These THF groups interleave between the layers as
shown in Figure 3. Hence, the structure has layers of THF and
layers of cerium and chloride atoms. It is within the cerium
chloride layer that the water molecules are found. Within the
cerium chloride sheets, rectangles are formed by every six
cerium centers as shown in Figure 1. The water molecules
reside inside these rectangles. Next nearest neighbor calcula-
tions show that each hydrogen is located between the oxygen
to which it is bonded and a chloride ion attached to a different
cerium. The shortest hydrogen chloride contacts are the 2.37-Å
The structure differs from that obtained by crystallization of
truly anhydrous CeCl3, which crystallizes from THF with a
seven-coordinate bridged structure of formula [CeCl(µ-Cl)2-
(THF)2]n.17 This seven-coordinate extended structure is com-
mon for solvated lanthanide halides and has been observed in
a number of other solvated lanthanide halide structures.17,18
Each cerium atom in the structure of [Ce(µ-Cl)3(THF)(H2O)]n
forms three bridges to other cerium atoms via chlorine atoms
labeled 1, 2, and 3. Each pair of cerium atoms is linked by a
Ce(µ-Cl)(µ-Cl′)Ce′ unit, each of which is located about an
inversion center such that there are only six independent Ce-
Cl distances. As shown in Table 2, the bond distances in [Ce-
(µ-Cl)3(THF)(H2O)]n are slightly larger than those in [CeCl(µ-
Cl)2(THF)2]n as would be expected for the higher coordinate
structure.19 The Ce-O(THF) distance is 0.02 Å larger and the
Ce-Cl(bridging) average distance is 0.03 Å larger (cf. eight-
coordinate Ce(III) is 0.073 Å larger than seven-coordinate Ce-
(III)19).
The 2.492(3)-Å Ce-O(H2O) distance is quite reasonable
compared to other data on Ln-O(H2O) distances in the
literature20 and is longer than would be expected for a lanthanide
(20) Hart, F. A. In ComprehensiVe Coordination Chemistry; Wilkinson,
G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon: Oxford, UK, 1987;
Chapter 39.
(21) Gilje, J. W.; Roesky, H. W. Chem. ReV. 1994, 94, 895-910.
(22) Rogers, R. D.; Rollins, A. N.; Henry, R. F.; Murdoch, J. S.;
Etzenhouser, R. D.; Huggins, S. E.; Nun˜ez, L. Inorg. Chem. 1991, 30, 4946-
4954.
(23) Herrmann, W. A.; Anwander, R.; Kleine, M.; O¨ fele, K.; Riede, J.;
Scherer, W. Chem. Ber. 1992, 125, 2391-2397.
(24) Runge, P.; Schulze, M.; Urland, W. Z. Anorg. Allg. Chem. 1991,
592, 115-120.
(17) Evans, W. J.; Shreeve, J. L.; Ziller, J. W.; Doedens, R. J. Inorg.
Chem. 1995, 34, 576-585.
(18) Castellani, C. B.; Tazzoli, V. Acta Crystallogr. 1984, C40, 1834-
1836. Castellani, C. B.; Coda A. Acta Crystallogr. 1985, C41, 186-189.
Rogers, R. D.; Voss, E. J.; Etzenhouser, R. D. Inorg. Chem. 1988, 27, 533-
542.
(19) Shannon, R. D. Acta Crystallogr. 1976, A32, 751-767.

4584 J. Am. Chem. Soc., Vol. 118, No. 19, 1996
EVans et al.
H(1C)‚‚‚Cl(2B) and 2.53-Å H(2C)‚‚‚Cl(1D) distances. Due to
the inherent uncertainty in locating hydrogen atoms in the
presence of heavy atoms, it is better to specify the associated
oxygen chloride distances, which are 3.28 Å for O(2A)‚‚‚Cl-
(1D) and 3.13 Å for O(2A)‚‚‚Cl(2B). These distances are in
the range of distances expected for O-H‚‚‚Cl hydrogen
bonding.25 Hence, the water molecules are anchored via the
Ce-O bond and hydrogen bonding inside the rectangles in the
cerium chloride layers and these in turn are sandwiched between
layers of THF.
instead of terminal and this can affect their reactivity.28 The
reagent should not be considered to be RCeCl2 and any
mechanistic interpretations of its chemistry as this discrete
species are too simplistic.
None of these discoveries diminishes the observed effective-
ness of this reagent. Its use should continue to be explored.
However, it is possible that additional exceptional chemistry
could be obtained by using a truly anhydrous CeCl3/RLi or by
using stoichiometric combinations of lithium salts with CeCl3/
RLi. Indeed, the variability of results obtained with this reagent
may be due to variable amounts of lithium salts present
depending on how the drying was done. Precise control of the
amount of LiOH or Li2O present may lead to better reproduc-
ibility and specificity in reactivity.
Conclusion
The usual preparation of the reagent written as “CeCl3/RLi”
does not lead to anhydrous CeCl3 as a precursor, but rather to
the solvated species [CeCl3(H2O)]n. Hence, this reagent is better
written as [CeCl3(H2O)]n/RLi. Use of excess RLi may well lead
to CeCl3/RLi, but it should be realized that LiOH or Li2O may
also be present and these may affect the chemistry. Given the
tendency of the lanthanide metals to form complexes of high
coordination number20,26 as well as the tendency of lithium salts
to bridge lanthanide structures,27 it is likely that this “CeCl3/
RLi” reagent is better considered as [CeClaRb(OH)cOdLie]f. The
complex may well be polymetallic (i.e. f > 1), since this is
typical of lanthanide complexes containing small ligands. The
extended bridged structures of [CeCl3(H2O)(THF)]n and [CeCl3-
(THF)2]n are but two examples. If the complex is polymetallic
or if the structure contains lithium, the ligands could be bridging
Acknowledgment. We thank the Division of Chemical
Sciences of the Office of Basic Energy Sciences of the
Department of Energy for support of this research, the Camille
and Henry Dreyfus Foundation for a Jean Dreyfus Boissevain
Undergraduate Scholarship for J.D.F., and Professor Larry E.
Overman for use of the Karl Fischer apparatus.
Note Added in Proof: The composition CeCl3(H2O) has also
been identified in thermal gravimetric analyses of hydrated
cerium trichlorides (Reuter, G.; Fink, H.; Seifert, H. J. Z. Anorg.
Allg. Chem. 1994, 620, 665-671).
Supporting Information Available: A view of the hydrogen
bonding and tables of crystallographic data (11 pages). Ordering
information is given on any current masthead page.
(25) Cotton, F. A.; Wilkinson, G. AdVances in Inorganic Chemistry, 5th
ed.; Wiley: New York, 1980; p 93.
(26) Moeller, T. In ComprehensiVe Inorganic Chemistry; Bailer, J. C.,
Jr., Ed.; Pergamon Press: Oxford, England, 1973; Vol. 4, Chapter 44. Evans,
W. J.; Foster, S. E. J. Organomet. Chem. 1992, 433, 79-94.
(27) Evans, W. J.; Boyle, T. J.; Ziller, J. W. Inorg. Chem. 1992, 31,
1120-1122. Evans, W. J.; Sollberger, M. S.; Hanusa, T. P. J. Am. Chem.
Soc. 1988, 110, 1841-1850.
JA954276W
(28) For example, see: Evans, W. J. Polyhedron 1987, 6, 803-835 and
references therein. Evans, W. J.; Dominguez, R.; Hanusa, T. P. Organo-
metallics 1986, 5, 263-270.