Alkali Metal Induced Structural Changes in Complexes Containing Anionic Lanthanum Aryloxide Moieties. X-ray Crystal Structures of (THF)La(OAr)2(μ-OAr)2Li(THF), (THF)La(OAr)2(μ-OAr)2Na(THF)2, and CsLa(OAr)4 (Ar = 2,6-i-Pr2C6H3)

Article abstract of DOI:10.1021/ic9510472

Reaction of La₂(OAr)₆ (1, Ar = 2,6-i-Pr₂C₆H₃) with 2 equiv of LiOAr in THF produces the lanthanum tetrakis(aryloxide) salt (THF)La(OAr)₂(μ-OAr)₂Li(THF) (2). A similar reaction employing NaOAr leads to isolation of the analogous sodium salt (THF)La(OAr)₂(μ-OAr)₂Na(THF)₂ (3), 1 reacts with 2 equiv of cesium aryloxide in THF to yield the base-free cesium salt CsLa(OAr)₄ (4). Compounds 2, 3, and 4 have been characterized by ¹H NMR and IR spectroscopy, microanalysis, and single-crystal X-ray diffraction studies. The overall molecular geometry of 2 comprises a five-coordinate La metal center coordinated by four aryloxide ligands and one THF ligand in a somewhat distorted trigonal bipyramidal geometry and a three-coordinate Li cation which is coordinated to the oxygen atoms of two aryloxide ligands as well as a single THF ligand. La - O bond lengths average 2.208(3) and 2.384(3) A? for terminal and bridging aryloxide ligands, respectively, while the average Li-O(aryloxide) bond distance is 1.866(10) A?. The molecular geometry of 3 is similar to that observed in 2, with a five-coordinate La metal center displaying a distorted trigonal bipyramidal geometry in which a THF ligand and an aryloxide ligand occupy axial positions. Two of the aryloxide ligands on the La metal center bridge to a sodium cation, which completes its coordination sphere by coordination of two additional molecules of THF. La - O bond lengths average 2.227(6) and 2.333(5) A? for terminal and bridging aryloxide ligands, respectively, while the average Na - OAr bond distance is 2.350(6) A?. The ipso carbon atom of one of the bridging aryloxide ligands is directed toward the fifth coordination site of the sodium cation at a distance of 3.085(9) A?. The solid state structure of CsLa(OAr)₄ (4) features alternating tetrahedral [La(OAr)₄]^- anions (La-O = 2.241(6) A? (ave.)) and Cs⁺ cations held in an extended structure by means of cesium - μ-arene interactions, resulting in the formation of a quasi one-dimensional infinite chain structure. The cesium environment in 4 consists exclusively of multihapto Cs - C interactions (Cs - C range 3.696(7)-3.847(7) A?), with no Cs - O contacts of less than 4.649 A?. Crystal data for 2 (at -100 °C): orthorhombic space group Pbca, a = 20.091(3) A?, b = 19.983(2) A?, c = 27.288(2) A?, V = 10956 A?³, Z = 8, D_calc = 1.202 g cm^-3. Crystal data for 3 (at -100 °C): orthorhombic space group Pbca, a = 26.035(3) A?, b = 20.771(4) A?, c = 26.441(3) A?, V = 14299 A?³, Z = 8, D_calc = 1.174 g cm^-3. Crystal data for 4 (at -100 °C): monoclinic space group C2/c, a = 21.261(2) A?, b = 22.616(3) A?, c = 20.740(2) A?, β= 108.126(7)°, V = 9478 A?³, Z = 8, D_calc = 1.465 g cm^-3.

Full text of DOI:10.1021/ic9510472

Inorg. Chem. 1996, 35, 667-674
667
Alkali Metal Induced Structural Changes in Complexes Containing Anionic Lanthanum
Aryloxide Moieties. X-ray Crystal Structures of (THF)La(OAr)2(µ-OAr)2Li(THF),
(THF)La(OAr)2(µ-OAr)2Na(THF)2, and CsLa(OAr)4 (Ar ) 2,6-i-Pr2C6H3)
David L. Clark,*,1a Rebecca V. Hollis,1b Brian L. Scott,1b and John G. Watkin*,1b
Chemical Science and Technology (CST) Division, Los Alamos National Laboratory,
Los Alamos, New Mexico 87545
ReceiVed August 9, 1995X
Reaction of La2(OAr)6 (1, Ar ) 2,6-i-Pr2C6H3) with 2 equiv of LiOAr in THF produces the lanthanum tetrakis-
(aryloxide) salt (THF)La(OAr)2(µ-OAr)2Li(THF) (2). A similar reaction employing NaOAr leads to isolation of
the analogous sodium salt (THF)La(OAr)2(µ-OAr)2Na(THF)2 (3). 1 reacts with 2 equiv of cesium aryloxide in
1
THF to yield the base-free cesium salt CsLa(OAr)4 (4). Compounds 2, 3, and 4 have been characterized by H
NMR and IR spectroscopy, microanalysis, and single-crystal X-ray diffraction studies. The overall molecular
geometry of 2 comprises a five-coordinate La metal center coordinated by four aryloxide ligands and one THF
ligand in a somewhat distorted trigonal bipyramidal geometry and a three-coordinate Li cation which is coordinated
to the oxygen atoms of two aryloxide ligands as well as a single THF ligand. La-O bond lengths average
2.208(3) and 2.384(3) Å for terminal and bridging aryloxide ligands, respectively, while the average Li-O(aryloxide)
bond distance is 1.866(10) Å. The molecular geometry of 3 is similar to that observed in 2, with a five-coordinate
La metal center displaying a distorted trigonal bipyramidal geometry in which a THF ligand and an aryloxide
ligand occupy axial positions. Two of the aryloxide ligands on the La metal center bridge to a sodium cation,
which completes its coordination sphere by coordination of two additional molecules of THF. La-O bond lengths
average 2.227(6) and 2.333(5) Å for terminal and bridging aryloxide ligands, respectively, while the average
Na-OAr bond distance is 2.350(6) Å. The ipso carbon atom of one of the bridging aryloxide ligands is directed
toward the fifth coordination site of the sodium cation at a distance of 3.085(9) Å. The solid state structure of
CsLa(OAr)4 (4) features alternating tetrahedral [La(OAr)4]- anions (La-O ) 2.241(6) Å (ave.)) and Cs+ cations
held in an extended structure by means of cesium-π-arene interactions, resulting in the formation of a quasi
one-dimensional infinite chain structure. The cesium environment in 4 consists exclusively of multihapto Cs-C
interactions (Cs-C range 3.696(7)-3.847(7) Å), with no Cs-O contacts of less than 4.649 Å. Crystal data for
2 (at -100 °C): orthorhombic space group Pbca, a ) 20.091(3) Å, b ) 19.983(2) Å, c ) 27.288(2) Å, V )
10956 Å3, Z ) 8, Dcalc ) 1.202 g cm-3. Crystal data for 3 (at -100 °C): orthorhombic space group Pbca, a )
26.035(3) Å, b ) 20.771(4) Å, c ) 26.441(3) Å, V ) 14299 Å3, Z ) 8, Dcalc ) 1.174 g cm-3. Crystal data for
4 (at -100 °C): monoclinic space group C2/c, a ) 21.261(2) Å, b ) 22.616(3) Å, c ) 20.740(2) Å, â )
108.126(7)°, V ) 9478 Å3, Z ) 8, Dcalc ) 1.465 g cm-3
.
Introduction
We have reported previously that the formation of “ate” or
“double alkoxide” salts of the f-elements may be somewhat
mitigated by the use of potassium reagents,9b,c,e purportedly due
to the greater insolubility of KCl in typical organic solvents
The preparation of inorganic and organometallic complexes
of the lanthanide elements Via the addition of an alkali metal
reagent to a lanthanide halide derivative is a cornerstone of
synthetic methodology in this field.2 In many cases, the
reactions proceed in a straightforward manner to produce the
desired target molecule in high yield with no undesirable side
reactions. However, there are a large number of documented
cases, particularly when utilizing reagents containing the smaller
alkali metals (M ) Li, Na), in which the isolated reaction
products contain one, two, or more equivalents of an alkali metal
salt bound within the coordination sphere of the lanthanide
metal, resulting in the formation of salt or “ate” complexes.
This phenomenon has been widely observed during syntheses
of alkyl,3 alkoxide,4 amide,5 thiolate,6 cyclopentadienyl,7 and
related complexes8 of the lanthanide elements.
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Chem. 1984, 263, 29. (b) Huang, Z.; Chen, M.; Qiu, W.; Wu, W.
Inorg. Chim. Acta 1987, 139, 203. (c) Cotton, S. A.; Hart, F. A.;
Hursthouse, M. B.; Welch, A. J. J. Chem. Soc., Chem. Commun. 1972,
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McKeeing, J.; Pearce, R.; Lappert, M. F. J. Chem. Soc., Chem.
Commun. 1978, 140. (e) Taube, R.; Windisch, H.; Gorlitz, F. H.;
Schumann, H. J. Organomet. Chem. 1993, 445, 85. (f) van der Heijden,
H.; Pasman, P.; de Boer, E. J. M.; Schaverien, C. J.; Orpen, A. G.
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Lin, Y. J. Organomet. Chem. 1992, 427, 141.
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3041. (b) Evans, W. J.; Deming, T. J.; Olofson, J. M.; Ziller, J. W.
Inorg. Chem. 1989, 28, 4027. (c) Schumann, H.; Kociok-Kohn, G.;
Loebel, J. Z. Anorg. Allg. Chem. 1990, 581, 69. (d) Evans, W. J.;
Sollberger, M. S.; Hanusa, T. P. J. Am. Chem. Soc. 1988, 110, 1841.
(e) Schumann, H.; Mu¨ller, J.; Brunks, N.; Lauke, H.; Pickardt, J.;
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X Abstract published in AdVance ACS Abstracts, January 1, 1996.
(1) (a) LANL, Mail Stop G739. (b) LANL, Mail Stop C346.
(2) (a) Schaverien, C. J. In AdVances in Organometallic Chemistry;
Academic Press: New York, 1994; Vol. 36, p 283. (b) Caulton, K.
G.; Hubert-Pfalzgraf, L. G. Chem. ReV. 1990, 90, 969. (c) Schumann,
H.; Meese-Marktscheffel, J. A.; Esser, L. Chem. ReV. 1995, 95, 865.
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1287.
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390, 45. (b) Guan, J.; Jin, S.; Lin, Y.; Shen, Q. Organometallics 1992,
11, 2483.
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1985, 24, 985. (b) Schumann, H.; Albrecht, I.; Gallagher, M.; Hahn,
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0020-1669/96/1335-0667$12.00/0 © 1996 American Chemical Society

668 Inorganic Chemistry, Vol. 35, No. 3, 1996
Clark et al.
compared to that of LiCl and NaCl. However, even the use of
heavier alkali metal reagents has not completely eliminated the
problem of salt retention. Thus the room temperature reaction
of anhydrous LnCl3 (Ln ) Nd, Er, Lu) with 3 or 4 equiv of
potassium 2,6-diisopropylphenoxide in THF leads to the forma-
tion of potassium salts of formula KLn(OAr)4, according to the
stoichiometry of eq 1.9a,f
calculations have shown that the larger, more polarizable cations,
potassium through cesium, prefer multihapto interactions with
ring carbons while the smaller alkali metals, particularly lithium,
tend to interact with the center of highest charge.11i,12c Collateral
interactions with additional carbanions were also found to be
energetically favorable for the heavier alkali metals, in contrast
to lithium and sodium cations which favored interactions with
heteroatoms such as nitrogen and oxygen.
LnCl3 + 4KOAr THF8 KLn(OAr)4 + 3KCl
Ln ) Nd, Er, Lu; Ar ) 2,6-i-Pr2C6H3
(1)
On the basis of expected differences in coordination environ-
ment upon moving from lithium to cesium and having noted
recent publications which describe the significant structural and
reactivity effects of varying the alkali metal cation in a series
of anionic cobalt and chromium aryloxide derivatives,13,14 we
undertook an investigation of a series of lanthanum salt
complexes of general formula M[Ln(OAr)4] (M ) Li, Na, Cs;
Ar ) 2,6-i-Pr2C6H3). Together with the known structure of the
potassium analog, the results allow a general picture of the
effects of different alkali metal cations upon the extended solid
state structures of anionic lanthanide aryloxide complexes to
be developed.
These salts exhibit unusual solid state structures involving
multihapto π-arene interactions between the aryloxide ligands
and potassium cations. The presence of K-C interactions
between adjacent [Ln(OAr)4]- units leads to the formation of
pseudo-one-dimensional infinite chains, as shown in I for the
neodymium salt KNd(OAr)4. A similar structural motif has also
been observed in the recently-reported lanthanide aryloxide
10a
complexes {K[(µ-η-C5H5)2Nd(µ-O-2,6-Me2C6H3)2]}n
and
{K[Sm(µ-O-2,6-t-Bu2C6H3)3(THF)]}n,10b and related alkali metal-
π-arene interactions have been documented in a number of
recent publications.11
Results and Discussion
Synthesis and Reactivity. Initial investigations were directed
toward optimization of a suitable synthetic strategy for the
preparation of the desired lanthanum salt complexes of general
formula MLa(OAr)4 (M ) Li, Na, Cs; Ar ) 2,6-i-Pr2C6H3). It
was found that the reaction of anhydrous LaCl3 with 4 equiv of
alkali metal aryloxide in THF produced mixtures of products
which proved difficult to separate. It is postulated that these
mixtures contain both neutral and anionic chloride/aryloxide
species of the type LaClx(OAr)3-x and KLaClx(OAr)4-x. Sub-
sequently, we focused on the reaction of a preformed tris-
(aryloxide) species with an additional 1 equiv of alkali metal
aryloxide. We have previously reported the synthesis of the
homoleptic lanthanide aryloxide complexes Ln2(OAr)6 (Ln )
La, Nd, Sm, Er) Via the synthetic route shown in eq 2.9d,g
Detailed computational studies have recently been performed
concerning the interaction of alkali metal cations with both
neutral arene rings12a,b and delocalized carbanions.11i,12c These
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1988, 7, 2004. (e) Song, S.; Shen, Q.; Jin, S. Polyhedron 1992, 11,
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Helm, D.; Ji, X. Organometallics 1991, 10, 2585. (g) Gornitzka, H.;
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K.-H. J. Organomet. Chem. 1992, 439, C6.
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1985, 4, 52. (b) Schumann, H.; Nickel, S.; Hahn, E.; Heeg, M. J.
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1995, 34, 5.

Anionic Lanthanum Aryloxide Moieties
Inorganic Chemistry, Vol. 35, No. 3, 1996 669
Table 1. Summary of Crystal Dataa
2Ln[N(SiMe3)2]3 + 6HOAr toluene8
2
3
4
Ln2(OAr)6 + 6HN(SiMe3)2 (2)
empirical formula LiLaC56H85O6 NaLaC74H100O7 CsLaC48H68O4
space group
a, Å
b, Å
c, Å
â, deg
T, °C
Pbca
Pbca
C2/c
Ar ) 2,6-i-Pr2C6H3
20.091(3)
19.983(2)
27.288(2)
26.035(3)
20.771(4)
26.441(3)
21.261(2)
22.616(3)
20.740(2)
108.126(7)
-100
8
9478
1.465
0.71069
1044.84
17.1
0.0385
0.0757
It was found that the reaction of THF soluble La2(OAr)6 with
2 equiv of MOAr (M ) Li, Na, Cs) consistently provided a
more reliable and higher-yielding synthetic route to lanthanide
“ate” complexes than did the reaction of the rather insoluble
LaCl3 with 4 equiv of the aryloxide salt. Thus the reaction of
La2(OAr)6 (1) with 2 equiv of lithium 2,6-diisopropylphenoxide
in THF solution at room temperature for 72 h, followed by
crystallization from hexane, produced the lithium “ate” complex
(THF)La(OAr)2(µ-OAr)2Li(THF) (2) in 49% yield as shown in
eq 3. Compound 2 was found to be slightly soluble in hexane
and highly soluble in toluene and benzene. A directly analogous
reaction in which 1 was allowed to react with 2 equiv of sodium
aryloxide resulted in the isolation, following crystallization from
toluene, of the sodium “ate” complex (THF)La(OAr)2(µ-
OAr)2Na(THF)2 (3) (eq 3). The sodium salt 3 was found to be
moderately soluble in toluene and benzene.
-100
8
10956
1.202
0.71069
991.02
8.24
-100
8
14299
1.174
0.71069
1263.44
6.52
Z (mol/unit cell)
V, Å3
D
calcd, g cm-3
λ (Mo KR)
fw
abs coeff, cm-1
R(F)b
0.0457
0.1049
0.0659
0.1207
R2w
a 2 ) (THF)La(OAr)2(µ-OAr)2Li(THF); 3 ) (THF)La(OAr)2(µ-
OAr)2Na(THF)2‚(C7H8)2; 4 ) CsLa(OAr)4. b R(F) ) ∑||Fo| - |Fc||/
∑|Fo|.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
(THF)La(OAr)2(µ-OAr)2Li(THF) (2)
La(1)-O(1)
La(1)-O(2)
La(1)-O(3)
La(1)-O(4)
2.213(3)
2.376(3)
2.204(3)
2.392(3)
La(1)-O(5)
Li(1)-O(2)
Li(1)-O(4)
Li(1)-O(6)
2.608(3)
1.857(10)
1.875(9)
1.871(9)
+ 2MOAr THF8
La2(OAr)6
(1)
Li(1)-O(2)-La(1)
95.7(3)
Li(1)-O(4)-La(1)
94.7(3)
2(THF)La(OAr)2(µ-OAr)2M(THF)x
O(1)-La(1)-O(2) 103.20(12) O(1)-La(1)-O(3) 112.34(13)
(3)
M ) Li (2), x ) 1
M ) Na (3), x ) 2
O(1)-La(1)-O(4) 121.88(12) O(1)-La(1)-O(5)
O(2)-La(1)-O(3) 103.80(13) O(2)-La(1)-O(4)
81.31(12)
71.99(11)
O(2)-La(1)-O(5) 154.50(12) O(3)-La(1)-O(4) 125.24(13)
Ar ) 2,6-i-Pr2C6H3
O(3)-La(1)-O(5)
C(1)-O(1)-La(1)
97.33(13) O(4)-La(1)-O(5)
172.2(3) C(9)-O(2)-La(1)
84.24(11)
130.1(3)
C(17)-O(3)-La(1) 170.8(3)
C(25)-O(4)-La(1) 143.2(3)
O(2)-Li(1)-O(6)
C(9)-O(2)-Li(1)
The reaction of La2(OAr)6 with 2 equiv of cesium 2,6-
diisopropylphenoxide in THF solution at room temperature for
72 h, followed by dissolution into hot toluene and crystallization,
yielded the THF-free cesium salt complex CsLa(OAr)4 (4) (eq
4). Compound 4 was found to be slightly soluble in toluene
and moderately soluble in THF. 1H NMR spectroscopy
confirmed the absence of THF ligands in this complex, and
microanalytical data are consistent with the proposed stoichi-
ometry of CsLa(OAr)4.
O(2)-Li(1)-O(4)
O(4)-Li(1)-O(6)
97.3(4)
131.4(5)
131.3(5)
131.9(4)
C(25)-O(4)-Li(1) 122.0(4)
THF
2CsLa(OAr)
La2(OAr)6
+ 2CsOAr
8
(4)
4
(4)
(1)
Ar ) 2,6-i-Pr2C6H3
Solid State and Molecular Structures. Three heterometallic
2,6-diisopropylphenoxide complexes have been examined by
single-crystal X-ray diffraction techniques during the course of
this work: (THF)La(OAr)2(µ-OAr)2Li(THF) (2), (THF)La-
(OAr)2(µ-OAr)2Na(THF)2‚(C7H8)2 (3), and CsLa(OAr)4 (4). A
summary of data collection and crystallographic parameters is
given in Table 1.
Figure 1. ORTEP plot (50% probability ellipsoids) showing the
molecular structure of (THF)La(OAr)2(µ-OAr)2Li(THF) (2) and giving
the atom-numbering scheme used in the tables. Methyl carbon atoms
of the iso-propyl groups are omitted for clarity.
(THF)La(O-2,6-i-Pr2C6H3)2(µ-O-2,6-i-Pr2C6H3)2Li-
(THF) (2). Crystals of 2 suitable for an X-ray diffraction study
were grown by cooling a concentrated hexane solution to -40
°C. Selected bond lengths and angles are presented in Table
2. An ORTEP drawing giving the atom-numbering scheme used
in the tables is shown in Figure 1. The overall molecular
geometry comprises a five-coordinate lanthanum metal center,
which is coordinated by four aryloxide ligands and one THF
ligand in a somewhat distorted trigonal bipyramidal geometry
and a three-coordinate lithium cation which is coordinated to
the oxygen atoms of two aryloxide ligands as well as a single
THF ligand (Figure 1). The overall molecular structure of 2 is
thus similar to that of the previously-reported vanadium(III) salt
complex V(OAr)2(µ-OAr)2Li(THF) (Ar ) 2,6-i-Pr2C6H3).15a The
THF ligand and the aryloxide ligand containing O(2) are
considered to occupy axial positions within the trigonal bipy-
ramidal geometry about the La metal center, and the O(2)-
La(1)-O(5) angle is distorted away from the idealized 180° to
154.50(12)°, presumably due to steric demands of the bridging
aryloxide ligand. The O-La-O angles within the equatorial
plane sum to 359.5°, indicating near planarity of the equatorial
ligand set.
Terminal La-O bond lengths average 2.208(3) Å, which falls
within the range previously reported for terminal La-O

670 Inorganic Chemistry, Vol. 35, No. 3, 1996
Clark et al.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
(THF)La(OAr)2(µ-OAr)2Na(THF)2‚(C7H8)2 (3)
La(1)-O(1)
La(1)-O(3)
La(1)-O(5)
Na(1)-O(4)
Na(1)-O(8)
2.323(5)
2.229(6)
2.625(5)
2.339(6)
2.280(7)
La(1)-O(2)
La(1)-O(4)
Na(1)-O(1)
Na(1)-O(7)
Na(1)-C(13)
2.224(6)
2.343(5)
2.362(6)
2.291(7)
3.085(9)
La(1)-O(1)-Na(1)
O(1)-La(1)-O(2)
O(1)-La(1)-O(4)
O(2)-La(1)-O(3)
O(2)-La(1)-O(5)
O(3)-La(1)-O(5)
C(13)-O(1)-La(1)
C(1)-O(3)-La(1)
O(1)-Na(1)-O(4)
O(1)-Na(1)-O(8)
O(4)-Na(1)-O(8)
O(1)-Na(1)-C(13)
99.4(2) La(1)-O(4)-Na(1)
106.1(2) O(1)-La(1)-O(3)
79.6(2) O(1)-La(1)-O(5)
112.5(2) O(2)-La(1)-O(4)
89.0(2) O(3)-La(1)-O(4)
81.3(2) O(4)-La(1)-O(5)
151.8(5) C(7)-O(2)-La(1)
171.6(6) C(19)-O(4)-La(1)
78.9(2) O(1)-Na(1)-O(7)
103.0(3) O(4)-Na(1)-O(7)
145.4(3) O(7)-Na(1)-O(8)
99.5(2)
103.4(2)
160.6(2)
124.9(2)
119.3(2)
81.7(2)
171.1(6)
141.3(5)
151.0(3)
104.8(3)
90.1(3)
24.8(2) O(4)-Na(1)-C(13) 103.2(2)
O(7)-Na(1)-C(13) 136.1(3) O(8)-Na(1)-C(13)
85.6(3)
C(13)-O(1)-Na(1) 108.8(5) C(19)-O(4)-Na(1) 115.7(5)
Figure 2. ORTEP plot (50% probability ellipsoids) showing the
molecular structure of (THF)La(OAr)2(µ-OAr)2Na(THF)2 (3) and giving
the atom-numbering scheme used in the tables. Methyl carbon atoms
of the iso-propyl groups are omitted for clarity.
distances of 2.193(5)-2.290(9) Å.4a,9g,16,17 La-O distances to
the bridging ligands are, as expected, somewhat longer at
2.384(3) Å (ave.). The O-La-O bond angle between the two
terminal aryloxide ligands is fairly close to the 120° value
expected for two ligands within the equatorial plane (O(1)-
La(1)-O(3) ) 112.34(13)°), whereas the O(2)-La(1)-O(4)
angle between the two aryloxide ligands which bridge to the
lithium cation is dramatically smaller at 71.99(11)°. The La-
O-C bond angles for the bridging aryloxide ligands are rather
acute at 130.1(3) and 143.2(3)°, reflecting their interaction with
the lithium cation, while the La-O-C bond angles for the
terminal aryloxide ligands are typically more obtuse and average
171.5(3)°.
The coordination geometry of the lithium cation is trigonal
planar, a geometry which has been reported for a number of
other lithium salt complexes. The average Li-O(aryloxide)
bond distance of 1.866(10) Å lies at the lower end of the range
previously reported for Li-OAr bonds of 1.811(17)-1.995(12)
Å and most likely reflects the low coordination number of the
lithium metal center.18 The O-Li-O bond angle between the
bridging aryloxide ligands is 97.3(4)°, while the two O-Li-O
angles between the THF and the bridging aryloxide ligands
average 131.3(5)°. The three O-Li-O angles sum to 360°,
indicating almost perfect planarity of the lithium cation and the
three coordinated oxygen atoms. The nonbonding La-Li
distance within the dimer is 3.158(9) Å.
the atom-numbering scheme used in the tables is shown in
Figure 2. Compound 3 crystallizes in the orthorhombic space
group Pbca, and no unusual intermolecular contacts are seen
in the solid state. The overall molecular geometry is similar to
that observed in the lithium complex 2, with a five-coordinate
lanthanum metal center displaying a distorted trigonal bipyr-
amidal geometry in which a THF ligand and an aryloxide ligand
occupy axial positions. Two of the aryloxide ligands on the
lanthanum metal center bridge to a sodium cation, which
completes its coordination sphere by coordination of two
additional molecules of THF (Figure 2). The axial O(5)-La-
O(1) angle is distorted from 180 to 160.6(2)°, while the
O-La-O angles in the equatorial plane sum to 356.7°. The
La-O bond lengths average 2.227(6) Å for terminal ligands
and 2.333(5) Å for bridging aryloxide ligands and are within
the range of La-O distances reported above. As previously
observed in the structure of 2 (Vide supra), the O-La-O angle
between the bridging aryloxide ligands [O(1)-La-O(4) )
79.6(2)°] is much smaller than that between the two terminal
aryloxide ligands [O(2)-La-O(3) ) 112.5(2)°]. The La-O-C
bond angles for the bridging aryloxide ligands are 141.3(5) and
151.8(5)°, while the La-O-C angles for the terminal aryloxide
ligands average 171.4(6)°.
The sodium cation is bound to the oxygen atoms of two
bridging aryloxide ligands in addition to two terminal THF
ligands. Furthermore, the ipso carbon atom of one of the
bridging aryloxide ligands is directed toward the fifth coordina-
tion site of the sodium cation at a relatively long bond distance
of 3.085(9) Å. This coordination geometry is similar to that
documented previously for [Na(TMEDA)]2[Cr(O-2,6-Me2C6H3)4],
which also contains a long Na-C interaction with one of the
methyl carbons bound to the aromatic ring.13b The average Na-
OAr bond distance of 2.350(6) Å lies within the range previously
reported for Na-OAr distances of 1.811(17)-2.842(5).11j,m,19
The O-Na-O bond angle between the bridging aryloxide
ligands is 78.9(2)° while the O-Na-O angle between the two
THF ligands is 90.1(3)°. The nonbonding La-Na distance
within the dimer is 3.573(3) Å.
(THF)La(O-2,6-i-Pr2C6H3)2(µ-O-2,6-i-Pr2C6H3)2Na-
(THF)2‚(C7H8)2 (3). Single crystals of 3 were grown from a
concentrated toluene solution at -40 °C. Selected bond lengths
and angles are presented in Table 3. An ORTEP drawing giving
(15) (a) Wilisch, W. C. A.; Scott, M. J.; Armstrong, W. H. Inorg. Chem.
1988, 27, 4333. (b) Scott, M. J.; Wilisch, W. C. A.; Armstrong, W.
H. J. Am. Chem. Soc. 1990, 112, 2429. (c) Kociok-Kohn, G.; Pickardt,
J.; Schumann, H. Acta Crystallogr., Sect. C 1991, 47, 2649. (d) Harder,
S.; Lutz, M.; Streitwieser, A. J. Am. Chem. Soc. 1995, 117, 2361.
(16) Schaverien, C. J.; Meijboom, N.; Orpen, A. G. J. Chem. Soc., Chem.
Commun. 1992, 124.
(17) (a) Blech, P.; Floriani, C.; Chiesi-Villa, A.; Gustini, C. J. Chem. Soc.,
Dalton Trans. 1990, 3557. (b) McGeary, M. J.; Coan, P. S.; Folting,
K.; Streib, W. E.; Caulton, K. G. Inorg. Chem. 1989, 28, 3283.
(18) (a) Watson, K. A.; Fortier, S.; Murchie, M. P.; Bovenkamp, J. W.;
Rodrigue, A.; Buchanan, G. W.; Ratcliffe, C. I. Can. J. Chem. 1990,
68, 1201. (b) van der Schaaf, P. A.; Hogerheide, M. P.; Grove, D.
M.; Spek, A. L.; van Koten, G. J. Chem. Soc., Chem. Commun. 1992,
1703. (c) Hundal, M. S.; Sood, G.; Kapoor, P.; Poonia, N. S. J.
Crystallogr. Spectrosc. Res. 1991, 21, 201. (d) Khasnis, D. V.; Burton,
J. M.; Lattman, M.; Zhang, H. J. Chem. Soc., Chem. Commun. 1991,
562. (e) Power, M. B.; Bott, S. G.; Atwood, J. L.; Barron, A. R. J.
Am. Chem. Soc. 1990, 112, 3446.
In complexes 2 and 3 it is notable that the lanthanum metal
center coordinates a molecule of THF in addition to the four
aryloxide ligands to produce a five-coordinate metal center,
rather than the pseudotetrahedral lanthanum metal centers
observed in 4 (Vide infra) and KLa(OAr)4.9f A possible

Anionic Lanthanum Aryloxide Moieties
Inorganic Chemistry, Vol. 35, No. 3, 1996 671
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
CsLa(OAr)4 (4)a
La(1)-O(1)
La(2)-O(3)
Cs(1)-C(8)
Cs(1)-C(10)
Cs(1)-C(17)
Cs(2)-C(2)
Cs(2)-C(4)
Cs(2)-C(27)#1
2.251(4)
2.240(5)
3.809(7)
3.748(7)
3.684(7)
3.807(6)
3.710(7)
3.622(7)
La(1)-O(2)
La(2)-O(4)
Cs(1)-C(9)
Cs(1)-C(16)
Cs(1)-C(18)
Cs(2)-C(3)
Cs(2)-C(26)
Cs(2)-C(28)#1
2.231(5)
2.248(4)
3.696(7)
3.716(7)
3.847(7)
3.651(7)
3.771(7)
3.700(7)
Figure 4. Ball-and-stick drawing of the extended quasi one-
dimensional infinite chain structure of CsLa(OAr)4 (4). Methyl carbon
atoms of the iso-propyl groups are omitted for clarity.
actions. However, these interactions result in the formation of
a quasi one-dimensional infinite chain bridged by cesium-η-
arene interactions (Figure 4), rather than the pseudo-two-
dimensional sheet structure observed in KLa(OAr)4.9f This one-
dimensional chain configuration is very similar to that observed
in the structures of KLn(OAr)4 (Ln ) Nd, Er), which possess
one-dimensional infinite chain structures differing only in the
number of alkali metal interactions which bridge the subunits.9f
The KLn(OAr)4 (Ln ) Nd, Er) complexes also feature potas-
sium interactions with oxygen atoms of the aryloxide ligands
while 4 does not feature any meaningful Cs-O contacts (Vide
infra).
O(1)-La(1)-O(1)#1
O(1)-La(1)-O(2)#1
O(3)-La(2)-O(3)#1
O(3)-La(2)-O(4)#1
C(1)-O(1)-La(1)
110.8(2) O(1)-La(1)-O(2)
108.7(2)
111.4(2) O(2)-La(1)-O(2)#1 105.9(3)
106.5(2) O(3)-La(2)-O(4) 110.5(2)
110.1(2) O(4)-La(2)-O(4)#1 109.0(2)
149.6(4) C(7)-O(2)-La(1)
156.1(5)
150.9(4)
C(25)#2-O(3)-La(2) 154.1(4) C(13)-O(4)-La(2)
a Symmetry transformation used to generate equivalent atoms: #1
-x, y, -z + 1/2, #2 x, y + 1, z.
The lanthanum metal center in 4 displays a pseudotetrahedral
coordination environment with O-La-O angles very close to
ideal, ranging from 105.9(3) to 111.4(2)°. The average La-O
distance of 2.241(6) Å is directly comparable to the distances
found in 2 and 3. The cesium environment in the solid state
structure of 4 consists exclusiVely of multihapto Cs-C inter-
actions, with no Cs-O contacts of less than 4.649 Å being
present within the structure (Figure 4). This coordination
environment bears comparison with that found in [Cs(4-tert-
butylcalix-4-arene)(MeCN)],20a in which the cesium cation
interacts with arene moieties (Cs-C ) 3.545(3)-4.121(4) Å)
but makes no Cs-O contacts shorter than 4.0 Å. The cesium
cation in 4 exhibits four principal η3-arene interactions with
the phenyl rings containing C(16)-C(18) and C(16a)-C(18a)
(Cs-C range 3.716(7)-3.847(7) Å) and C(8)-C(11) and
C(8a)-C(11a) (Cs-C range 3.696(7)-3.809(7) Å). These
Cs-C distances lie within the range of 3.35(4)-4.12(1) Å found
in other structurally characterized complexes containing Cs-
arene interactions.11i,k,20 The shortest nonbonding Cs-La
distance within the structure is 5.637 Å.
Spectroscopic Characterization. 1H NMR spectroscopy.
(THF)La(OAr)2(µ-OAr)2Li(THF) (2). Ambient temperature
1H NMR spectra of 2 in benzene-d6 solution reveal only one
aryloxide and one THF ligand environment, in a 2:1 ratio. At
room temperature the R-THF protons are observed as a broad
resonance at δ 3.14. However, when a toluene-d8 solution of
2 was cooled to -80 °C, this resonance decoalesces into two
broad resonances at δ 3.57 and 2.54. Overlap of the resonance
at 3.57 ppm with a resonance at 3.44 ppm, which is assigned
to the isopropyl methine protons, precluded accurate integration
of the two THF resonances. The resonance at δ 3.57 is assigned
to the R-protons on the THF bound to the lanthanum metal
center, and the chemical shift agrees well with the values for
several other lanthanum-THF adducts.4a,11e,21 The resonance
at δ 2.54 is assigned to the R-protons on the THF bound to the
lithium cation, and integration reveals a ratio of one lithium-
Figure 3. ORTEP plot (50% probability ellipsoids) showing the solid
state structure of CsLa(OAr)4 (4), emphasizing the multihapto interac-
tion between the cesium cation and the arene rings of the aryloxide
ligands. Methyl carbon atoms of the iso-propyl groups are omitted for
clarity.
explanation for this results from a consideration of the oxygen-
bridging configurations of complexes 2 and 3. The O-La-O
bond angles for the bridging aryloxides of (THF)La(OAr)2(µ-
OAr)2Li(THF) (2) and (THF)La(OAr)2(µ-OAr)2Na(THF)2 (3)
are greatly reduced from a typical tetrahedral value down to
71.99(11) and 79.6(2)°, respectively. This significant deforma-
tion of bond angle effectively makes available an additional
coordination site which is filled by the THF ligand.
CsLa(O-2,6-i-Pr2C6H3)4 (4). Crystals of 4 suitable for an
X-ray diffraction study were grown from a concentrated toluene
solution upon slow evaporation under a helium atmosphere.
Selected bond lengths and angles are presented in Table 4. An
ORTEP drawing giving the atom-numbering scheme used in
the tables is shown in Figure 3. The solid state structure of
CsLa(OAr)4 (4) shows an overall similarity to that of the
previously-reported potassium analog KLa(OAr)4,9f in that it
features alternating [La(OAr)4]- anions and Cs+ cations held
in an extended structure by means of cesium-π-arene inter-
(19) (a) Liu, S.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1992, 31, 5400. (b)
Floriani, C.; Mazzanti, M.; Chiesi-Villa, A.; Guastini, C. Angew.
Chem., Int. Ed. Engl. 1988, 27, 576. (c) Liu, S.; Wong, E.; Karunaratne,
V.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1993, 32, 1756. (d)
Gambarotta, S.; Floriani, C.; Villa, A. C.; Guastini, C. J. Chem. Soc.,
Chem. Commun. 1982, 756. (e) Solari, E.; De Angelis, S.; Floriani,
C.; Chiesi-Villa, A.; Rizzoli, C. J. Chem. Soc., Dalton Trans. 1991,
2471. (f) Arena, F.; Floriani, C.; Zanazzi, P. F. J. Chem. Soc., Chem.
Commun. 1987, 183. (g) Floriani, C.; Fiallo, M.; Chiesi-Villa, A.;
Guastini, C. J. Chem. Soc., Dalton Trans. 1987, 1367. (h) Reinhoudt,
D. N.; Dijkstra, P. J.; In’t Veld, P. J. A.; Bugge, K. E.; Harkema, S.;
Ungaro, R.; Ghidini, E. J. Am. Chem. Soc. 1987, 109, 4761.
(20) (a) Harrowfield, J. M.; Ogden, M. I.; Richmond, W. R.; White, A. H.
J. Chem. Soc., Chem. Commun. 1991, 1159. (b) Neumu¨ller, B.;
Gahlmann, F. Chem. Ber. 1993, 126, 1579. (c) Ungaro, R.; Casnati,
A.; Ugozzoli, A. P.; Dozol, J.-F.; Hill, C.; Rouquette, H. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1506. (d) Mallinson, P. R. J. Chem.
Soc., Perkin Trans. 2 1975, 261. (e) Pauer, F.; Stalke, D. J. Organomet.
Chem. 1991, 418, 127. (f) Casnati, A.; Pochini, A.; Ungaro, R.;
Ugozzoli, F.; Arnaud, F.; Fanni, S.; Schwing, M.-J.; Egberink, R. J.
M.; de Jong, F.; Reinhoudt, D. N. J. Am. Chem. Soc. 1995, 117, 2767.

672 Inorganic Chemistry, Vol. 35, No. 3, 1996
Clark et al.
bound THF to four aryloxide ligands. The â-THF resonances
display similar, although less marked, temperature-dependent
behavior. At room temperature the â-THF protons appear as a
broad resonance at 0.95 ppm, whereas at -80 °C this resonance
decoalesces into two separate resonances which show a tem-
perature-dependent shift upfield to 0.681 and 0.58 ppm.
The aromatic proton resonances and the iso-propyl methine
resonance of the aryloxide ligand broaden upon cooling to -80
°C and show more complex splittings, but do not decoalesce
into assignable bridging and terminal resonances. However, at
-80 °C the iso-propyl methyl resonances show the presence of
a broad doublet at 1.33 ppm and a broad singlet at 1.22 ppm.
The close proximity of the resonances for the two types of
methyl group environments, as well as their equivalent integra-
tions, prevents assignment of terminal and bridging aryloxide
ligands, but the 1:1 ratio is consistent with maintenance of the
bridging structure in solution.
present investigation as to the generality of this type of extended
structure as the alkali metal was systematically varied from
lithium to cesium. The work described here has clearly
demonstrated that the nature of the products isolated from
reaction of La2(OAr)6 with alkali metal aryloxide salts is highly
dependent upon the alkali metal employed. In the case of the
smaller alkali metals, lithium and sodium, discrete “double
alkoxide” or “ate” complexes are isolated, in which the aryloxide
ligand forms an oxygen donor bridge to the alkali metal atom
(II). The use of potassium or cesium aryloxide, however, leads
to the formation of complexes with extended one- or two-
dimensional structures bridged by η-arene interactions (III).
(THF)La(OAr)2(µ-OAr)2Na(THF)2 (3). Ambient temper-
1
ature H NMR spectra of 3 in benzene-d6 solution reveal only
one type of aryloxide and one type of THF ligand environment,
in a 4:3 ratio. At -80 °C, however, it is possible to discern
two types of R-THF resonances at 3.50 and 2.52 ppm.
Integration of these resonances support the assignment of the
downfield resonances to the R-protons on the THF coordinated
to the lanthanum and the upfield resonances to the two THF
ligands bound to sodium.
The strong preference of lithium and sodium to interact with
oxygen atoms of the aryloxide ligands rather than the aromatic
π-electron density would appear to be in agreement with simple
electrostatic arguments, which would postulate that the relatively
“hard” lithium and sodium cations (high charge/size ratio) would
preferentially interact with a site of more concentrated electron
density (oxygen lone pairs of aryloxide or THF ligands).
Conversely, the softer potassium and cesium cations interact
exclusively with arene rings of the aryloxide ligands, despite
the fact that the preparative reactions were carried out in a donor
solvent (THF). In fact, the alkali metal environments of the
complexes synthesized in these experiments show striking
similarities with the calculated coordination environments of
the alkali metal benzyl complexes (MCH2Ph, M ) Li-Cs)
reported by Schleyer et al.12c In that work it was found that
the smaller alkali metals favored interactions with the center of
greatest charge and the presence of additional hard donor ligands
to complete their coordination spheres, whereas the larger, softer
alkali metals (potassium-cesium) were found to favor polyhapto
interactions with the aromatic ring.
In 3, the â-THF resonances do not separate out into two
distinct types; however, they do shift significantly upfield upon
cooling. At ambient temperature these protons resonate at 1.21
ppm while at -80 °C they are shifted to 0.86 ppm.
1
CsLa(OAr)4 (4). The ambient temperature H NMR spec-
trum of 4 in benzene-d6 reveals only one type of aryloxide ligand
environment in solution. The aromatic resonances are shifted
upfield from those of complexes 2 and 3. The shielding effect
(and upfield shifting of the aromatic resonances) is found to be
greater in the cesium complex 4 than in the potassium analog
KLa(OAr)4.9f These results are consistent with changes ex-
pected due to shielding of the aromatic rings by the large alkali
metal cations but do not rule out the possibility of separate ion
pairs in solution.
Infrared Spectroscopic Studies. Solid state IR spectra of
the heterometallic complexes (THF)La(OAr)2(µ-OAr)2Li(THF)
(2) and (THF)La(OAr)2(µ-OAr)2Na(THF)2 (3) are rather similar
in appearance, and both exhibit aromatic CdC stretches at 1588
cm-1. In the case of KLa(OAr)4 and CsLa(OAr)4, however,
subtle shifts of the CdC stretch to lower energy (1581 and 1583
cm-1, respectively) are observed. This is suggestive of a slight
decrease in aromatic CdC bond strength due to donation of
electron density from the aromatic π-cloud to the alkali metal
cations.
During the course of this work, it has been found that the
stoichiometry of the preparative reactions may be controlled
much more effectively when a highly-soluble species such as
La2(OAr)6 (1) is used as starting material rather than anhydrous
LaCl3, which is virtually insoluble in THF. This is a phenom-
enon which has been noted on many previous occasions during
the synthesis of f element complexes.9f,23-25 It seems likely
that the limited solubility of LaCl3 in THF leads to a situation
in which the small quantity of LaCl3 in solution is actually
exposed to a large local excess of alkali metal aryloxide (all of
which dissolves readily in THF) and thus the reaction can
proceed beyond the formation of MLa(OAr)4 to produce M2La-
(OAr)5.26 A similar explanation has been proposed for the
unexpected formation of other lanthanide and actinide “double
alkoxide” and “ate” complexes.9f
A band consistent with THF coordination is seen at 855 and
852 cm-1 in the IR spectra of 2 and 3, respectively. This band
can be compared with those seen in UI3(THF)4, UBr3(THF)4,
NpI3(THF)4, and PuI3(THF)4 which show similar bands for
coordinated THF in the region from 856 to 847 cm-1 22
.
The results discussed here are the beginnings of a fundamental
knowledge of a newly emerging class of heterometallic lan-
thanide compounds. The applicability of the calculations of
Concluding Remarks
The initial synthesis of pseudo-one-dimensional chain com-
plexes of the type KLn(OAr)4 (Ln ) Nd, Er, Lu)9a,f led to the
(23) Mehrotra, R. C.; Batwara, J. M. Inorg. Chem. 1970, 9, 2505.
(24) Brown, L. M.; Mazdiyasni, K. S. Inorg. Chem. 1970, 9, 2783.
(25) Mazdiyasni, K. S.; Lynch, C. T.; Smith, J. S. Inorg. Chem. 1966, 5,
342.
(26) The three-dimensional extended structure of Cs2[La(OAr)5] is the
subject of a separate publication: Clark, D. L.; Hollis, R. V.; Scott,
B. L.; Watkin, J. G. Submitted for publication in J. Chem. Soc., Chem.
Commun.
(21) (a) Deacon, G. B.; Gatehouse, B. M.; Shen, Q.; Ward, G. N. Aust. J.
Chem. 1993, 12, 1289. (b) Scholz, A.; Smola, A.; Scholz, J.; Loebel,
J.; Schumann, H.; Thiele, K. Angew. Chem., Int. Ed. Engl. 1991, 30,
435. (c) van der Heijden, H.; Schaverien, C. J.; Orpen, A. G.
Organometallics 1989, 8, 255.
(22) Avens, L. R.; Bott, S. G.; Clark, D. L.; Sattelberger, A. P.; Watkin, J.
G.; Zwick, B. D. Inorg. Chem. 1994, 33, 2248.

Anionic Lanthanum Aryloxide Moieties
Inorganic Chemistry, Vol. 35, No. 3, 1996 673
meta OAr), 6.94 (br, 1 H, para OAr), 3.61 (br, 2 H, CHMe2), 3.50 (br
m, 1 H, R-THF-La), 2.52 (br m, 2 H, R-THF-Na), 1.30 (br, 12 H,
CHMe2), 0.86 (br m, 3 H, â-THF). IR (cm-1): 1588 (m), 1429 (s),
1378 (m), 1359 (w), 1327 (m), 1279 (sh, w), 1262 (s), 1204 (m), 1141
(w), 1108 (w), 1098 (w), 934 (w), 886 (m), 861 (sh, w), 852 (m), 842
(m), 754 (s), 744 (s), 722 (w), 684 (m). Anal. Calcd for C60H92LaNaO7
(lattice solvent lost on standing): C, 66.28; H, 8.53. Found: C, 65.92;
H, 8.73.
Schleyer to anionic lanthanide aryloxide systems and the
possible generality of these observations to other heterometallic
complexes are of great significance. Further studies of the
extended solid state structures of lanthanide aryloxide complexes
containing heavier alkali metal cations are currently underway.
Experimental Section
Cs[La(O-2,6-i-Pr2C6H3)4] (4). La2(OAr)6 (0.101 g, 0.0753 mmol)
was dissolved in toluene (10 mL) in the drybox, and this solution was
added to a 3:1 toluene/THF solution (10 mL) of 0.049 g (0.15 mmol)
of cesium 2,6-diisopropylphenoxide. Vigorous stirring was continued
for 72 h at room temperature. The resulting purple solution was filtered
through Celite, and the volatiles were removed in Vacuo to yield a
purple solid. The solid was then extracted into 50 mL of hot toluene
and filtered again through Celite. The volume of the filtrate was
reduced to 30 mL in Vacuo, and the flask was then cooled to -40 °C.
Overnight a pink powder had deposited. Yield: 0.054 g (37%). 1H
NMR (300 MHz, THF-d8): δ 6.79 (d, J ) 7 Hz, 2 H, meta OAr), 6.36
(t, J ) 7 Hz, 1 H, para OAr), 3.65 (septet, J ) 7 Hz, 2 H, CHMe2),
1.10 (d, J ) 7 Hz, 12 H, CHMe2). IR (cm-1): 1583 (m), 1426 (s),
1377 (m), 1359 (w), 1335 (m), 1276 (s), 1209 (m), 1156 (w), 1138
(w), 1110 (w), 1104 (w), 1060 (w), 1042 (m), 958 (w), 934 (w), 919
(w), 908 (w), 885 (m), 852 (m), 805 (w), 795 (m), 754 (s), 723 (m),
684 (m), 668 (w), 615 (w), 605 (w), 596 (w), 564 (m), 546 (s). Anal.
Calcd for C48H68CsLaO4: C, 58.78; H, 6.99. Found: C, 59.10; H,
7.10.
Crystallographic Studies. (THF)La(O-2,6-i-Pr2C6H3)2(µ-O-2,6-
i-Pr2C6H3)2Li(THF) (2). A light yellow, triangular-shaped slab was
attached to a thin glass fiber using silicone grease. The crystal was
immediately placed under a nitrogen cold-stream on a Siemens P4/PC
diffractometer. The radiation employed was graphite monochromatized
Mo KR radiation (λ ) 0.710 69 Å). The lattice parameters were
optimized from a least-squares calculation on 32 carefully centered
reflections of high Bragg angle. Three check reflections monitored
every 97 reflections showed no systematic variation of intensities.
Lattice determination and data collection were carried out using
XSCANS Version 2.10b software. All data reduction (including
Lorentz and polarization corrections), structure solution, and graphic
procedures used SHELXTL PC Version 4.2/360 software. The structure
refinement was performed using SHELX 93 software.27 No absorption
corrections were performed due to the low (<10 cm-1) absorption
coefficient.
The space group Pbca was uniquely determined by the systematic
absences. Patterson techniques were used to locate the lanthanum atom.
The remaining atoms appeared in subsequent Fourier synthesis. All
hydrogen atoms were refined using the riding model in the HFIX facility
in SHELX 93.27 The final refinement included anisotropic thermal
parameters on all non-hydrogen atoms. Hydrogen atoms had their
isotropic temperature factors fixed at 1.2 (ethyl and phenyl) or 1.5
(methyl) times the equivalent isotropic U of the carbon atom to which
they were bonded. The final refinement converged to R1 ) 0.0457
and R2w ) 0.1049.28
(THF)La(O-2,6-i-Pr2C6H3)2(µ-O-2,6-i-Pr2C6H3)2Na(THF)2‚
(C7H8)2 (3). A colorless, triangular-shaped slab was attached to a thin
glass fiber using silicone grease. The crystal, which was mounted from
a pool of mineral oil bathed in argon, was then immediately placed
under a nitrogen cold stream on a Siemens P4/PC diffractometer. The
radiation used was graphite monochromatized Mo KR radiation (λ )
0.710 69 Å). The lattice parameters were optimized from a least-
squares calculation on 32 carefully centered reflections of high Bragg
angle. Three check reflections monitored every 97 reflections showed
no systematic variation of intensities. Lattice determination and data
collection were carried out using XSCANS Version 2.10b software.
All data reduction (including Lorentz and polarization corrections),
structure solution, and graphic procedures used SHELXTL PC Version
General Procedures and Techniques. All manipulations were
carried out under an inert atmosphere of oxygen-free UHP grade argon
using standard Schlenk techniques, or under oxygen-free helium in a
Vacuum Atmospheres glovebox. 2,6-Diisopropylphenol was purchased
from Aldrich and degassed before use. La2(OAr)6 was prepared as
previously described.9g Cesium 2,6-diisopropylphenoxide was prepared
from reaction of cesium metal (Aldrich) with 2,6-diisopropylphenol in
THF. NaH was obtained as a 60% dispersion in mineral oil, washed
with hexane, filtered, and vacuum dried. Solvents were degassed and
distilled from sodium benzophenone ketyl under nitrogen. Benzene-
d6, THF-d8, and toluene-d8 were degassed, dried over Na-K alloy, and
then trap-to-trap distilled before use.
NMR spectra were recorded at 22 °C on Bru¨ker WM300 or Varian
Unity 300 spectrometers. All 1H NMR chemical shifts are reported in
1
ppm relative to the H impurity in benzene-d6, THF-d8, or toluene-d8
set at δ 7.15, 3.58, or 2.09, respectively. Infrared spectra were recorded
on a Digilab FTS-40 spectrometer. Solid state spectra were taken as
Nujol mulls between KBr plates. Elemental analyses were performed
on a Perkin-Elmer 2400 CHN analyzer. Elemental analysis samples
were prepared and sealed in tin capsules in the glovebox prior to
combustion.
(THF)La(O-2,6-i-Pr2C6H3)2(µ-O-2,6-i-Pr2C6H3)2Li(THF) (2). In
the drybox, a solution of La2(OAr)6 (0.50 g, 0.37 mmol) in toluene
(25 mL) was added to a stirred solution of lithium 2,6-diisopropyl-
phenoxide, prepared by addition of 0.44 mL (0.74 mmol) of 1.7 M
tert-butyllithium to 0.13 g (0.74 mmol) of 2,6-diisopropylphenol in
THF. Vigorous stirring was continued for 72 h at room temperature.
The resulting clear, pale yellow solution was filtered through Celite,
and volatiles were removed in Vacuo to yield an off-white solid. The
solid was extracted with 50 mL of hexane and filtered through Celite.
The volume of the filtrate was reduced to 20 mL in Vacuo, and the
flask was then cooled to -40 °C. Clear colorless crystals were
deposited overnight. Yield: 0.361 g (49%). 1H NMR (300 MHz,
benzene-d6, 298 K): δ 7.14 (d, J ) 8 Hz, 2 H, meta OAr), 6.88 (t, J
) 8 Hz, 1 H, para OAr), 3.56 (septet, J ) 7 Hz, 2 H, CHMe2), 3.14
(br m, 2 H, R-THF), 1.29 (d, J ) 7 Hz, 12 H, CHMe2), 0.95 (br m, 2
H, â-THF). 1H NMR (300 MHz, toluene-d8, 193 K): δ 7.10 (br, 2 H,
meta OAr), 6.94 (br, 1 H, para OAr), 3.57 (br m, 1 H, R-THF-La),
3.44 (br, 2 H, CHMe2), 2.54 (br m, 1 H, R-THF-Li), 1.33 (d, J ) 6
Hz, 6 H, CHMe2), 1.22 (br, 6 H, CHMe2), 0.68 (br m, 1 H, â-THF),
0.58 (br m, 1 H, â-THF). IR (cm-1): 1588 (m), 1429 (s), 1378 (m),
1359 (w), 1325 (m), 1278 (sh, w), 1259 (s), 1199 (m), 1157 (w), 1143
(w), 1109 (w), 1097 (w), 1056 (w), 1040 (m), 1033 (m), 1025 (m),
953 (w), 944 (sh, w), 935 (w), 919 (w), 885 (m), 855 (m), 839 (m),
804 (w), 795 (w), 756 (s), 752 (s), 728 (w), 722 (sh, w), 689 (m), 683
(m), 668 (w), 616 (w), 595 (w), 555 (m), 527 (m), 428 (m). Anal.
Calcd for C56H84LiLaO6: C, 67.32; H, 8.47. Found: C, 66.41; H, 8.34.
(THF)La(O-2,6-i-Pr2C6H3)2(µ-O-2,6-i-Pr2C6H3)2Na(THF)2 (3). In
the drybox, a solution of La2(OAr)6 (0.996 g, 0.74 mmol) in toluene
(30 mL) was added to a solution of sodium 2,6-diisopropylphenoxide,
prepared by addition of 0.036 g (1.50 mmol) of NaH to a solution of
0.237 g (1.33 mmol) of 2,6-diisopropylphenol in 50 mL of THF.
Vigorous stirring was continued for 72 h at room temperature. The
resulting clear, pale yellow solution was filtered through Celite, and
the volatiles were removed in Vacuo to yield an off-white solid. The
solid was washed with 50 mL of hexane, yielding no soluble material.
The solid was then extracted into 50 mL of toluene and filtered through
a Celite pad. The volume of the filtrate was reduced to 20 mL in Vacuo,
and the flask was then cooled to -40 °C. Clear colorless crystals were
deposited overnight. Yield: 1.437 g (99%). 1H NMR (300 MHz,
benzene-d6): δ 7.08 (d, J ) 7 Hz, 2 H, meta OAr), 6.80 (t, J ) 7 Hz,
1 H, para OAr), 3.58 (br septet, J ) 7 Hz, 2 H, CHMe2), 3.25 (br m,
3 H, R-THF), 1.25 (d, J ) 7 Hz, 12 H, CHMe2), 1.20 (br m, 3 H,
â-THF). 1H NMR (300 MHz, toluene-d8, 193 K): δ 7.14 (br, 2 H,
(27) XSCANS, SHELXTL PC, and SHELXL 93 are products of Siemens
Analytical X-ray Instruments, Inc., 6300 Enterprise Lane, Madison,
WI 53719.
2 2
(28) R1 ) σ||Fo| - |Fc||/σ|Fo| and R2w ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo ) ]]1/2
.
The parameter w ) 1/[σ2(Fo ) + (0.0635P)2], with P ) [0.33333-
(maximum of 0 or Fo ) + (0.66667)Fc ].
2
2
2

674 Inorganic Chemistry, Vol. 35, No. 3, 1996
Clark et al.
4.2/360 software. The structure refinement was performed using
SHELX 93 software. No absorption corrections were performed due
to the low (<10 cm-1) absorption coefficient.
SHELX 93 software. All data were corrected for absorption using the
ellipsoid routine in the XEMP facility of SHELXTL PC.
The space groups C2/c and Cc were suggested by systematic
absences. Patterson techniques were used to locate the La and Cs atoms
in space group C2/c. The remaining non-hydrogen atoms appeared in
subsequent Fourier synthesis. All hydrogen atoms were fixed and
refined using the riding model in the HFIX facility in SHELX 93.
Hydrogen atoms had their isotropic temperature factors fixed at 1.2
(aromatic) and 1.5 (methyl) times the equivalent isotropic U of the
carbon atom they were bonded to. The final refinement included
anisotropic thermal parameters on all non-hydrogen atoms and con-
verged to R1 ) 0.0358 and R2w ) 0.0757.30 Attempts to refine the
C2/c Patterson solution in space group Cc failed.
The space group Pbca was uniquely determined by the systematic
absences. Patterson techniques were used to locate the lanthanum atom.
The remaining atoms appeared in subsequent Fourier synthesis. Two
toluene solvent molecules were located in the lattice and refined
anisotropically. All hydrogen atoms were refined using the riding
model in the HFIX facility in SHELX 93. The final refinement
included anisotropic thermal parameters on all non-hydrogen atoms.
Hydrogen atoms had their isotropic temperature factors fixed at 1.2
(ethyl and phenyl) or 1.5 (methyl) times the equivalent isotropic U of
the carbon atom to which they were bonded. The final refinement
converged to R1 ) 0.0659 and R2w ) 0.1207.29
Cs[La(O-2,6-i-Pr2C6H3)4] (4). A colorless slab was attached to a
thin glass fiber using silicone grease. The crystal, which was mounted
from a pool of mineral oil bathed in argon, turned orange upon rapid
transfer to a nitrogen cold stream on a Siemens P4/PC diffractometer.
The radiation used was graphite monochromatized Mo KR radiation
(λ ) 0.710 69 Å). The lattice parameters were optimized from a least-
squares calculation on 32 carefully centered reflections of high Bragg
angle. Three check reflections monitored every 97 reflections showed
no systematic variation of intensities. Lattice determination and data
collection were carried out using XSCANS Version 2.10b software.
All data reduction (including Lorentz and polarization corrections),
structure solution, and graphic procedures used SHELXTL PC Version
4.2/360 software. The structure refinement was performed using
Acknowledgment. This work was performed under the
auspices of the Laboratory Directed Research and Development
Program. Los Alamos National Laboratory is operated by the
University of California for the U.S. Department of Energy
under Contract W-7405-ENG-36.
Supporting Information Available: Tables of fractional atomic
coordinates, bond lengths and angles, anisotropic thermal parameters,
and hydrogen atom coordinates for complexes 2, 3, and 4 (31 pages).
Ordering information is given on any current masthead page.
IC9510472
2 2
2 2
(29) R1 ) σ||Fo| - |Fc||/σ|Fo| and R2w ) [∑[w(Fo2 -Fc2)2]/∑[w(Fo ) ]]1/2
.
(30) R1) σ||Fo| - |Fc||/σ|Fo| and R2w ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo ) ]]1/2
.
The parameter w ) 1/[σ2(Fo ) + (0.0453P)2 + 22.9864P], with P )
The parameter w ) 1/[σ2(Fo ) + (0.0224P)2 + 44.2661P], with P )
2
2
2
2
2
2
(Fo + 2Fc )/3.
(Fo + 2Fc )/3.