Synthesis and structures of scandium and lutetium benzyl complexes

Article abstract of DOI:10.1021/om701171y

Scandium and lutetium benzyl complexes were prepared. Reaction of [ScCl₃(THF)₃] with potassium benzyl afforded [Sc(CH ₂Ph)₃(THF)₃] (1). In the solid state the coordination polyhedron is a distorted octahedron, in which the benzyl groups are located in a facial arrangement on one side of the molecule. One of the coordinated THF molecules could be removed by trituration with toluene and recrystallization of 1 from toluene to give [Sc(CH₂Ph) ₃(THF)₂] (2). A significantly different compound is obtained by starting the transmetalation reaction at -196°C. Under these conditions the reaction of ScCl₃ with KCH₂Ph led to a two-dimensional coordination polymer of composition [Sc(CH₂Ph) ₅K₂(THF)₃]_n (3), in which the scandium atom is surrounded by five benzyl groups in a trigonal bipyramidal fashion. Under the same reaction conditions, but using LuCl₃ as the starting material, the analogue of 1, [Lu(CH₂Ph)₃(THF) ₃] (4), is obtained, which can also be induced to lose a coordinated THF ligand to give [Lu(CH₂Ph)₃(THF)₂] (5).

Full text of DOI:10.1021/om701171y

Organometallics 2008, 27, 1501–1505
1501
Synthesis and Structures of Scandium and Lutetium Benzyl
Complexes
Nils Meyer,† Peter W. Roesky,*,† Sergio Bambirra,‡ Auke Meetsma,‡ Bart Hessen,*,‡
Kuburat Saliu,§ and Josef Takats*,§
Institut für Chemie, Freie UniVersität Berlin, Fabeckstrasse 34-36, 14195 Berlin, Germany, Center for
Catalytic Olefin Polymerization, Stratingh Institute for Chemistry and Chemical Engineering, UniVersity of
Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and Department of Chemistry, UniVersity
of Alberta, Edmonton, Alberta, Canada T6G 2G2
ReceiVed NoVember 22, 2007
Scandium and lutetium benzyl complexes were prepared. Reaction of [ScCl3(THF)3] with potassium
benzyl afforded [Sc(CH2Ph)3(THF)3] (1). In the solid state the coordination polyhedron is a distorted
octahedron, in which the benzyl groups are located in a facial arrangement on one side of the molecule.
One of the coordinated THF molecules could be removed by trituration with toluene and recrystallization
of 1 from toluene to give [Sc(CH2Ph)3(THF)2] (2). A significantly different compound is obtained by
starting the transmetalation reaction at -196 °C. Under these conditions the reaction of ScCl3 with KCH2Ph
led to a two-dimensional coordination polymer of composition [Sc(CH2Ph)5K2(THF)3]n (3), in which the
scandium atom is surrounded by five benzyl groups in a trigonal bipyramidal fashion. Under the same
reaction conditions, but using LuCl3 as the starting material, the analogue of 1, [Lu(CH2Ph)3(THF)3] (4), is
obtained, which can also be induced to lose a coordinated THF ligand to give [Lu(CH2Ph)3(THF)2] (5).
lished as starting material in zirconium chemistry8 we and others
were attracted by homoleptic tribenzyl complexes of the
lanthanides as starting materials for the synthesis of alkyl
complexes.9–11 In this context Manzer12 and Harder10 reported
the synthesis of rare-earth tribenzyl complexes bearing intramo-
lecularly coordinating groups on the aryl moiety, whereas some
of us prepared the salt-free lanthanum tribenzyl complexes of
composition [La(CH2Ph)3(THF)3] and [La(CH2-Ph-4-Me)3-
(THF)3].9 Now, we report here on benzyl complexes of the
smallest rare-earth elements. To our surprise, small differences
in the preparation result in significantly different scandium and
lutetium benzyl complexes.
Introduction
An attractive alternative to the usual salt metathesis reaction
involving lanthanide halides for the synthesis of organometallic
compounds of group 3 metals and the lanthanides is the use of
an amine or alkane elimination route starting from homolepetic
lanthanide amides or alkyls. Thus, in amido chemistry the so-
called “silyl amide route” or “extended silyl amide route”
starting from [Ln{N(SiMe3)2}3] and [Ln{N(SiHMe2)2}3(THF)x],
respectively, was established about a decade ago.1,2 To obtain
the more reactive alkyl complexes the homoleptic trialkyl
complexes of the type [Ln(CH2SiMe3)3(THF)n] (n ) 2, 3)3–6
and [Ln{CH(SiMe3)2}3]7 are proving to be valuable starting
materials. Since homoleptic benzyl complexes are well estab-
Results and Discussion
* Towhomcorrespondenceshouldbeaddressed.E-mail:roesky@chemie.fu-
berlin.de; b.hessen@rug.nl; joe.takats@ualberta.ca.
Scandium Complexes. Transmetalation of [ScCl3(THF)3]
with 3 equiv of potassium benzyl in THF at room temperature,
† Freie Universität Berlin.
‡ University of Groningen.
§ University of Alberta.
(5) (a) Tazelaar, C. G. J.; Bambirra, S.; Van Leusen, D.; Meetsma, A.;
Hessen, B.; Teuben, J. H. Organometallics 2004, 23, 936–939. (b) Bambirra,
S.; Bouwkamp, M. W.; Meetsma, A.; Hessen, B. J. Am. Chem. Soc. 2004,
126, 9183–9184.
(1) Review: Anwander, R. Top. Curr. Chem. 1996, 179, 33–112.
(2) (a) Anwander, R.; Runte, O.; Eppinger, J.; Gerstberger, G.;
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(b) Eppinger, J.; Spiegler, M.; Hieringer, W.; Herrmann, W. A.; Anwander,
R. J. Am. Chem. Soc. 2000, 122, 3080–3096.
(6) (a) Hou, Z. Bull. Chem. Soc. Jpn. 2003, 76, 2253–2266. (b) Nishiura,
M.; Hou, Z.; Wakatsuki, Y.; Yamaki, T.; Miyamoto, T. J. Am. Chem. Soc.
2003, 125, 1184–1185. (c) Tardiff, O.; Nishiura, M.; Hou, Z. Organome-
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2488. (b) Edelmann, F. T.; Freckmann, D. M. M.; Schumann, H. Chem.
ReV. 2002, 102, 1851–1896.
(7) [Ln{CH(SiMe3)2}3] (Ln ) La, Sm): (a) Hitchcock, P. B.; Lappert,
M. F.; Smith, R. G.; Bartlett, R. A.; Power, P. P. J. Chem. Soc., Chem.
Commun. 1988, 1007–1008.[Ln{CH(SiMe3)2}3] (Ln ) Y, Lu): (b) Schav-
erien, C. J.; Orpen, A. G. Inorg. Chem. 1991, 30, 4968–4978.
(8) (a) Samuel, E. Bull. Soc. Chim. Fr. 1966, 11, 3548–3564. (b) Crust,
E. J.; Clarke, A. J.; Deeth, R. J.; Morton, C.; Scott, P. Dalton Trans. 2004,
4050–4058. (c) Munslow, I. J.; Wade, A. R.; Deeth, R. J.; Scott, P. Chem.
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T. K.; Roesky, P. W. Dalton Trans. 2005, 2147–2150.
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126–127. (b) Schumann, H.; Müller, J. J. Organomet. Chem. 1978, 146,
C5–C7. (c) Schumann, H.; Müller, J. J. Organomet. Chem. 1979, 169, C1–
C4. (d) Atwood, J. L.; Hunter, W. E.; Rogers, R. D.; Holton, J.; McMeeking,
J.; Pearce, R.; Lappert, M. F. J. Chem. Soc., Chem. Commun. 1978, 140–
141. (e) Niemeyer, M. Acta Crystallogr. 2001, E57, m553–m555. (f) Evans,
W. J.; Brady, J. C.; Ziller, J. W. J. Am. Chem. Soc. 2001, 123, 7711–7712.
(g) Arndt, S.; Spaniol, T. P.; Okuda, J. Chem. Commun. 2002, 89, 6–897.
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2003, 115, 5229–5233; Angew. Chem., Int. Ed. 2003, 42, 5075–5079. (j)
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Dalton Trans. 2006, 1157–1161.
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3454–3462.
(10) Harder, S. Organometallics 2005, 24, 373–379.
(11) See also for the related Ca compounds: Harder, S.; Müller, S.;
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10.1021/om701171y CCC: $40.75
2008 American Chemical Society
Publication on Web 03/13/2008

1502 Organometallics, Vol. 27, No. 7, 2008
Meyer et al.
Scheme 1
THF-d8 to study the influence of the solvent on the spectra.
Most significant is a downfield shift of the benzyl methylene
signal by changing the solvents (δ(C6D6) 1.83 ppm vs δ(THF-
d8) 2.11 ppm). However, the shape of the signals is not
influenced. The benzyl methylene 13C{1H} NMR resonances
are found at δ(C6D6) 57.2 ppm and δ(THF-d8) 60.0 ppm (1),
δ(C6D6) 57.8 ppm (2), and δ(THF-d8) 56.6 ppm (3).
Compound 1 crystallizes in the monoclinic space group Cc
having four molecules in the unit cell. The structure reveals a
metal center bound to three benzyl groups and three THF
molecules, with Sc-O bond distances of Sc-O1 2.290(2) Å,
Sc-O2 2.267(2) Å, and Sc-O3 2.268(2) Å (Figure 1). The
latter are located in a facial arrangement on one side of the
molecule, with O-Sc-O angles of 79.64(6)-81.74(6)°. Thus,
the coordination polyhedron is a distorted octahedron. In contrast
to the previously reported lanthanum tribenzyl complex
[La(CH2Ph)3(THF)3],9 in which the benzyl groups are η2 bound
to the metal center, an η1 coordination is observed in compound
1, with an average Sc-CH2-C angle of 119.58 (17)°. This is
obviously a result of the smaller ionic radius of scandium.14
The observed Sc-C bond distances of Sc-C13 2.308(3) Å,
Sc-C20 2.309(3) Å, and Sc-C27 2.317(3) Å are slightly longer
than those observed in the only other structurally characterized
neutral scandium benzyl compound, [{(Ar)NC(tBu)CHC(tBu)-
N(Ar)}Sc(CH2Ph)2] (Ar ) 2,6-iPr-C6H3) (2.263 and 2.203
Å).15,16
followed by centrifugation and decantation (to remove the KCl)
and subsequent crystallization from THF/hexane, afforded
[Sc(CH2Ph)3(THF)3] (1) as analytically pure light-orange crys-
tals in 75% yield (Scheme 1). Trituration of 1 with toluene
results in ready loss of one THF ligand. Subsequent crystal-
lization from toluene allows isolation of [Sc(CH2Ph)3(THF)2]
(2) as orange blocks in high yield (Scheme 1). The difference
between compounds 1 and 2 is obviously the number of THF
molecules that are attached to the metal center. Similar
observations were made previously for [Y(CH2SiMe3)3(THF)2]
and [Y(CH2SiMe3)3(THF)3].4f,13A significantly different com-
pound is obtained by using anhydrous scandium trichloride
in THF and starting the reaction at -196 °C. Under these
conditions the reaction with 3 equiv of KCH2Ph leads to a
two-dimensional coordination polymer of composition
[Sc(CH2Ph)5K2(THF)3]n (3), in which the scandium atom is
surrounded by five benzyl groups in a trigonal bipyramidal
fashion. Surprisingly, attempts to generate and isolate 3 in
higher yield, by using the appropriate 5:1 KCH2Ph to ScCl3
stoichiometry, were not successful. In these attempts, ap-
parently not all KCH2Ph was consumed, and an intractable
mixture of products was formed.
The new complexes have been characterized by standard
spectroscopic techniques and the structures were confirmed by
single-crystal X-ray diffraction in the solid state. Data collection
parameters and selected bond lengths and angles are given in
Table 1 and the corresponding figure captions.
Complexes 1 and 2 are soluble in hydrocarbon solvents,
whereas compound 3 is rather poorly soluble. NMR spectra of
the latter compound could be recorded in THF-d8. All complexes
show one singlet in the 1H NMR spectrum for the benzyl
methylene protons. This is in accord with the symmetrical solid
state structures of compounds 1 and 2 (vide infra), but shows
that the polymeric structure of 3 is disrupted in THF solution.
For compound 1 the NMR spectra were recorded in C6D6 and
j
Compound 2 crystallizes in the triclinic space group P1 with
two molecules in the unit cell. The coordination polyhedron,
which is formed by two THF molecules and three benzyl groups,
is a slightly distorted trigonal bipyramid with THF molecules
occupying the axial positions (Figure 2). The O1-Sc-O2 angle
of 173.04(4)° is almost linear and the C-Sc-C angles of the
benzyl group in the plane are close to the expected value of
120° (C9-Sc-C16 120.91(6)°, C9-Sc-C23 123.33(6)°, and
C16-Sc-C23 115.76(6)°). As a result of the lower coordination
number of the scandium center atom the Sc-C bond distances
are shorter (av 2.290(5) Å) and the Sc-CH2-C angles (av
113.64 (11)°) are smaller than those observed in 1.
In contrast to compounds 1 and 2, compound 3 is a two-
dimensional coordination polymer, in which the scandium center
is surrounded by five η1-benzyl groups in a trigonal bipyramidal
fashion (Figure 3). Formally the {Sc(CH2Ph)5}2- subunit can
be considered as an analogue to compound 2, in which the two
axial THF ligands are substituted by benzyl groups. The two
benzyl groups, which are located in the apex of the trigonal
bipyramid,arecoordinatedinanideallinearfashion(C1-Sc-C15
179.38(14)°). As usual for a trigonal bipyramidal geometry, the
Sc-C bond distances (av 2.396(4) Å) to these ligands are longer
than the corresponding equatorial bond lengths (av 2.32(1) Å).
The latter distances are somewhat longer than the values in 1
and 2, a reflection of the dianionic nature of 3. The distances
between potassium ions and carbon atoms of the aromatic benzyl
rings are all less than 3.50 Å, a conservative limit for K-C
interactions.17 By using these criteria, the phenyl rings of all
benzyl groups are η6 coordinated to the potassium atoms. Thus,
K1 is surrounded by two η6-coordinated phenyl rings and two
molecules of THF, whereas K2 is coordinated by three η6-
(15) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.; Knight, L. K.; Parvez,
M.; Elsegood, M. R. J; Clegg, W. Organometallics 2001, 20, 2533–2544.
(16) The cationic Sc benzyl compound [{(Ar)NC(Me)CHC(Me)N(Ar)}-
Sc(CH2Ph)][PhCH2B(C6F5)3] (Sc–C ) 2.229(2) Å) has also been reported
by Piers: Lee, L. W. M.; Piers, W. E.; Elsegood, M. R. J.; Clegg, W.; Parvez,
M. Organometallics 1999, 18, 2947-2949.
(13) The Sc(BzMe2)3(THF)2 complex was recently reported but not
structurally characterized by Diaconescu: Carver, C. T.; Montreal, M. J.;
Diaconescu, P. L. Organometallics 2008, 27, 363-370.
(14) Shannon, R. D.; Prewitt, C. T. Acta Crystallogr. 1969, B25, 925–
945.
(17) Clark, D. L.; Gordon, J. C.; Huffmann, J. C.; Vincent-Hollis, R. L.;
Watkin, J. G.; Zwick, B. D. Inorg. Chem. 1994, 33, 5903–5911.

Scandium and Lutetium Benzyl Complexes
Organometallics, Vol. 27, No. 7, 2008 1503
Table 1. Crystallographic Details of [Sc(CH2Ph)3(THF)3] (1), [Sc(CH2Ph)3(THF)2] (2), [Sc(CH2Ph)5K2(THF)3]n (3), and [Lu(CH2Ph)3(THF)3] (4)a
1
2
3
4
formula
formula weight
space group
a, Å
b, Å
c, Å
C33H45O3Sc
534.67
Cc (no. 9)
17.202(4)
20.759(5)
8.267(2)
C29H37O2Sc
462.57
P1 (no. 2)
C47H59K2O3Sc
795.10
Pna21 (no. 33)
25.471(5)
9.295(2)
18.336(4)
C33H45O3Lu
664.66
Cc (no. 9)
17.3716(9)
20.9550(14)
8.3958(4)
j
7.6779(6)
11.3723(9)
14.824(1)
86.423(1)
82.664(1)
78.332(1)
1256.4(2)
2
R, deg
ꢀ, deg
93.695(4)
93.571(4)
γ, deg
3
V, Å
2946.0(12)
4
1.205
Mo KR (λ ) 0.71073 Å)
0.280
SADABS
12243
5994 [Rint ) 0.0387]
5392
0.03(2)
5994; 514
4341(2)
4
1.216
Mo KR (λ ) 0.71073 Å)
0.399
none
19529
10588 [Rint ) 0.0493]
6643
0.01(4)
10588; 446
0.0568; 0.1427
3050.3(3)
4
1.447
Mo KR (λ ) 0.71073 Å)
3.266
integration (X-shape)
13424
5033 [Rint ) 0.0381]
4745
-0.001(8)
5033; 334
0.0203; 0.0454
Z
density (g/cm3)
Radiation
1.223
Mo KR (λ ) 0.71073 Å)
0.315
SADABS
11481
5968 [Rint ) 0.0164]
5105
µ, mm-1
abs corr
no. of reflns collected
no. of unique reflns
no. of obsd reflns
abs structure parameter (Flack)
data; parameters
R1b); wR2c)
5968; 437
0.0418; 0.1105
0.0399; 0.0852
2
2 2
a All data collected at 100 (1 and 2) or at 200 K (3 and 4). b R1 ) ∑||Fo| - |Fc||/∑|Fo|. c wR2 ) {∑[w(Fo - Fc ) ]/∑[w(Fo2)2]}1/2
.
Figure 2. Perspective ORTEP view of the molecular structure of
2. Thermal ellipsoids are drawn to encompass 50% probability.
Hydrogen atoms are omitted for clarity. Selected bond lengths [Å]
or angles [deg]: Sc-O1 2.1870(11), Sc-O2 2.1868(11), Sc-C9
2.299(2), Sc-C16 2.281(2), Sc-C23 2.289(2) and O1-Sc-O2
173.04(4), O1-Sc-C9 90.75(5), O1-Sc-C16 93.81(5), O1-Sc-
C23 85.31(5), O2-Sc-C9 87.16(5), O2-Sc-C16 92.96(5),
O2-Sc-C23 90.30(5), C9-Sc-C16 120.91(6), C9-Sc-C23
123.33(6), C16-Sc-C23 115.76(6).
Figure 1. Perspective ORTEP view of the molecular structure of
1. Thermal ellipsoids are drawn to encompass 50% probability.
Hydrogen atoms are omitted for clarity. Selected bond lengths [Å]
or angles [deg] (also given for isostructural 4): 1, Sc-O1 2.290(2),
Sc-O2 2.267(2), Sc-O3 2.268(2), Sc-C13 2.308(3), Sc-C20
2.309(3), Sc-C27 2.317(3) and O1-Sc-O2 79.64(6), O1-Sc-O3
81.43(6), O1-Sc-C13 92.72(8), O1-Sc-C20 172.63(8), O1-Sc-
C27 91.43(8), O2-Sc-O3 81.74(6), O2-Sc-C13 94.24(8),
O2-Sc-C20 94.95(8), O2-Sc-C27 170.35(8), O3-Sc-C13
173.39(8), O3-Sc-C20 92.91(7), O3-Sc-C27 93.40(8), C13-Sc-
C20 92.67(9), C13-Sc-C27 89.79(9), C20-Sc-C27 93.61(9); 4,
Lu-O1 2.356(3), Lu-O2 2.387(4), Lu-O3 2.361(3), Lu-C13
2.404(7), Lu-C20 2.408(4), Lu-C27 2.413(5) and O1-Lu-
O2 78.75(13), O1-Lu-O3 80.82(11), O1-Lu-C13 94.2(2),
O1-Lu-C20 168.99(15), O1-Lu-C27 94.8(2), O2-Lu-O3
80.82(13), O2-Lu-C13 92.63(14), O2-Lu-C20 90.98(15),
O2-Lu-C27 171.6(2), O3-Lu-C13 172.4(2), O3-Lu-C20
93.74(15), O3-Lu-C27 92.8(2), C13-Lu-C20 90.2(2), C13-Lu-
C27 93.3(2), C20-Lu-C27 95.0(2).
compound 4 elicits the removal of one THF molecule and gives
[Lu(CH2Ph)3(THF)2] (5).
The structure of 4 in the solid state was confirmed by single-
crystal X-ray diffraction (Figure 1). Unfortunately attempts to
obtain suitable single crystals of 5 for structural work have, so
far, been unsuccessful. Data collection parameters and selected
bond lengths and angles for 4 are given in Table 1 and the
caption of Figure 1. In the solid state compound 4 is isostructural
to the Sc analogue. Thus, the structure reveals a metal center
bound to three molecules of THF and three benzyl groups with
Lu-C bond distances of Lu-C13 2.404(7) Å, Lu-C20 2.408(4)
Å, and Lu-C27 2.413(5) Å and an average Lu-CH2-C angle
of 118.57°. Thus, despite the increased metal size relative to
Sc, the benzyl groups are η1-coordinated. Since, to the best of
our knowledge, this is the first structurally characterized lutetium
benzyl complex the Lu-C bond distances cannot be compared
with other data. The THF molecules of compound 4 are located
in a facial arrangement on one side of the complex, with
O-Lu-O angles of 78.75(13)-80.82(11)°. Thus, the coordina-
tion polyhedron is again a distorted octahedron.
bonded phenyl rings and one molecule of THF. As a result of
these coordination modes the potassium ions are acting as a
knot between [K(THF)Sc(CH2Ph)5K(THF)2] units.
Lutetium Complexes. In contrast to Sc, Lu behaves more
simply. Transmetalation of LuCl3 with 3 equiv of the potas-
sium benzyl in THF under the reaction conditions used for
the preparation of the polymeric compound 3 resulted in
[Lu(CH2Ph)3(THF)3] (4) (Scheme 2). Compound 4, which is
also obtained when a slurry of LuCl3(THF)x is treated with a
THF solution of potassium benzyl at low temperature (see the
Experimental Section), is the lutetium analogue of compound
1. As observed with [Sc(CH2Ph)3(THF)3] (1), trituration of

1504 Organometallics, Vol. 27, No. 7, 2008
Meyer et al.
tion conditions, but using LuCl3 as starting material,
[Lu(CH2Ph)3(THF)3] is obtained, which is the analogue of
the corresponding Sc compound 1. In the solid state both
scandium (1) and lutetium (4) complexes exhibit a six-
coordinate octahedral geometry with facial disposition of the
like ligands.
Experimental Section
General. All manipulations of air-sensitive materials were
performed with the rigorous exclusion of oxygen and moisture in
flame-dried Schlenk-type glassware either on a dual manifold
Schlenk line, interfaced to a high-vacuum (10-4 torr) line, or in an
argon-filled MBraun or nitrogen/helium-filled Vacuum Atmospheres
Company glovebox. Ether solvents (tetrahydrofurane and diethyl
ether) were predried over Na wire and distilled under nitrogen from
K (THF) or Na wire (diethyl ether) benzophenone ketyl prior to
use. Hydrocarbon solvents (toluene and n-pentane) were distilled
under nitrogen from LiAlH4. Deuterated solvents were obtained
from Chemotrade Chemiehandelsgesellschaft mbH or Cambridge
Isotope Laboratories (all g99 atom % D) and were degassed, dried,
and stored in vacuo over Na/K alloy in resealable flasks. NMR
spectra were recorded on a JNM-LA 400 FT-NMR or a Varian
Unity 500 spectrometer. Chemical shifts are referenced to internal
solvent resonances and are reported relative to tetramethylsilane.
Elemental analyses were carried out with an Elementar vario EL
at the FU Berlin or at the Microanalytical Department of H. Kolbe
(Mülheim an der Ruhr), or at the Analytical and Instrumentation
Laboratory, University of Alberta. ScCl3,18 LuCl3,18 and KCH2Ph19
were prepared according to literature procedures.
Figure 3. Perspective ORTEP view of the molecular structure of
3. Thermal ellipsoids are drawn to encompass 50% probability.
Shown is one unit out of the polymeric structure and the atom
labeling scheme, omitting hydrogen atoms. Selected bond lengths
[Å] or angles [deg]: Sc-C1 2.387(4), Sc-C8 2.327(4), Sc-C15
2.404(4), Sc-C22 2.331(4), Sc-C29 2.288(4), K1-O1 2.776(3),
K1-O2 2.664(3), K2-O3 2.726(3) and C1-Sc-C29 92.91(15),
C1-Sc-C15 179.38(14), C1-Sc-C22 89.30(13), C1-Sc-C8
90.62(13), C8-Sc-C15 89.07(13), C8-Sc-C22 127.37(13),
C8-Sc-C29 117.63(2), C15-Sc-C22 90.46(13), C15-Sc-C29
87.71(15), C22-Sc-C29 114.93(2).
Scheme 2
1
[Sc(CH2Ph)3(THF)3] (1). To a mixture of solid K(CH2Ph) (0.87
g, 6.0 mmol) and ScCl3(THF)3 (0.73 g, 2.0 mmol) in a Centrifuge
Schlenk Vessel (CSV-100 mL) was added 100 mL of THF. The
dark red mixture was sonicated (due to the large crystal size of
ScCl3(THF3)) and hand shaken for 15 min (by then the mixture
features an orange color), centrifuged, and then decanted from the
KCl precipitate. The solution was concentrated under reduced
pressure to about 10 mL, during which crystalline solid formed.
Hexane was layered onto the mixture, and cooling to -30 °C
afforded the title compound as light-orange crystals (0.81 g, 1.5
mmol, 75%).
The H NMR spectra of compounds 4 in C6D6 and 5 in
toluene-d8 showed one set of resonances for the three benzyl
ligands, with well-resolved H-H coupling, and one for the THF
ligands, consistent with symmetrical fac-octahedral and trigonal
bipyramidal coordination geometries of complexes 4 and 5,
respectively. Contrary to the scandium complex 1, the room
1
temperature H NMR spectrum of the lutetium complex 4 in
THF-d8 showed broad signals for the benzyl protons, an
indication of dynamic solution behavior. In an effort to slow
down the process and to obtain a well-resolved 1H NMR
spectrum, a VT NMR study in THF-d8 was carried out. To our
surprise, instead of sharpening the peaks broadened and, already
at 0 °C, the benzyl p-H signal resolved into two broad signals.
Lowering the temperature resulted in sharpening of the reso-
nances and, at -80 °C, two sets of well-resolved benzyl aryl-H
and Lu-CH2 signals were observed, with an intensity ratio
greater than 2:1. Two sets of signals were also seen in the 13C
NMR spectrum at low temperature. Curiously, this seems to
indicate the presence of a mixture of 4 and 5 in solution at low
temperature instead of a potential solvent-induced fac-to-mer
isomerization.
3
1H NMR (500 MHz, C6D6, 20 °C): δ 7.14 (t, JHH ) 7.6 Hz,
3
3
6H, m-H), 6.84 (d, JHH ) 7.6 Hz, 6H, o-H), 6.80 (t, JHH ) 7.2
Hz, 3H, p-H), 3.57 (m, 12H, R-THF), 1.83 (s, 6H, ScCH2), 1.17
(m, 12H, ꢀ-THF). 13C{1H} NMR (125.7 MHz, C6D6, 20 °C): δ
151.6 (Ar Cipso), 128.8 (Ar CH), 125.0 (Ar CH), 119.1 (Ar CH),
70.6 (R-THF), 57.2 (br, ScCH2), 25.3 (ꢀ-THF).
1H NMR (300 MHz, THF-d8, 20 °C): δ 6.80 (d, 3JHH ) 7.6 Hz,
3
3
6H, m-H), 6.70 (d, JHH ) 7.6 Hz, 6H, o-H), 6.37 (t, JHH ) 6.7
Hz, 3H, p-H), 2.11 (s, 6H, ScCH2). 13C{1H} NMR (75.4 MHz,
THF-d8, 20 °C): δ 156.8 (Ar Cipso), 129.1 (Ar CH), 125.6 (Ar CH),
118.2 (Ar CH), 60.0 (br, ScCH2). Anal. Calcd for C33H45O3Sc
[534.29]: C, 74.13; H, 8.48. Found: C, 73.70; 8.46.
[Sc(CH2Ph)3(THF)2] (2). A solution of [Sc(CH2Ph)3(THF)3]
(0.25 g, 0.47 mmol) in toluene (5 mL) was evaporated to dryness,
leaving a somewhat sticky crystalline orange residue. Recrystalli-
zation from toluene (3 mL) provides the title compound as orange
blocks (0.15 g, 0.3 mmol, 69%).
Conclusions
We have prepared the first tribenzyl complexes of the
smallest rare-earth elements, scandium and lutetium. It turned
out that small differences in the preparation resulted in
significantly different scandium complexes. Thus, a trans-
metalation of [ScCl3(THF)3] with potassium benzyl afforded
[Sc(CH2Ph)3(THF)3]. One of the coordinated THF molecules
could be removed by recrystallization of 1 from toluene to
give [Sc(CH2Ph)3(THF)2]. A significantly different compound
is obtained by starting the transmetalation reaction at -196
°C. Under these conditions the reaction of ScCl3 with
KCH2Ph led to a two-dimensional coordination polymer of
composition [Sc(CH2Ph)5K2(THF)3]n. Under the same reac-
3
1H NMR (500 MHz, C6D6, 20 °C): δ 7.16 (t, JHH ) 7.1 Hz,
3
3
6H, m-H), 6.87 (d, JHH ) 7.1 Hz, 6H, o-H), 6.83 (t, JHH ) 7.0
Hz, 3H, p-H), 3.55 (m, 8H, R-THF), 1.88 (s, 6H, ScCH2), 1.07 (m,
8H, ꢀ-THF). 13C{1H} NMR (125.7 MHz, C6D6, 20 °C): δ 151.6
(Ar Cipso), 128.7 (Ar CH), 125.0 (Ar CH), 119.0 (Ar CH), 71.4
(18) Taylor, M. D.; Carter, C. P. J. Inorg. Nucl. Chem. 1962, 24, 387–
391.
(19) (a) Schlosser, M.; Hartmann, J. Angew. Chem. 1973, 85, 544–545.
(b) Angew. Chem., Int. Ed. Engl. 1973, 12, 508–509.

Scandium and Lutetium Benzyl Complexes
Organometallics, Vol. 27, No. 7, 2008 1505
(R-THF), 57.8 (br, ScCH2), 25.2 (ꢀ-THF). Anal. Calcd for
C29H37O2Sc [462.23]: C, 75.30; H, 8.06. Found: C, 74.80; H, 7.90.
[Sc(CH2Ph)5K2(THF)3]n (3). THF (20 mL) was condensed at
-196 °C onto a mixture of ScCl3 (0.45 g, 3 mmol) and potassium
benzyl (1.17 g, 9 mmol) and the mixture was stirred for 16 h at
ambient temperature. The dark red solution was then filtered off,
concentrated, and layered with pentane. X-ray quality colorless
crystals were grown overnight. The crystals were isolated and
washed with pentane to give the analytically pure product (0.56 g,
13C{1H} NMR (100.58 MHz, 27 °C, THF-d8): δ 156.9 (Ph Cipso
v br.), 128.0 (Ph o/m-CH), 124.0 (Ph o/m-CH), 115.9 (Ph p-CH v
br), 68.3 (THF), 59.0 (Lu-CH2 v br), 26.3 (THF). 13C{1H} NMR
(100.58 MHz, -80 °C, THF-d8): δ 159.2 (Ph′ Cipso), 156.3 (Ph
Cipso), 128.4 (Ph o/m-CH), 127.8 (Ph′ o/m-CH), 123.9 (Ph o/m-
CH), 122.6 (Ph′ o/m-CH), 116.0 (Ph p-CH), 112.3 (Ph′ p-CH), 70.7
(br, THF), 68.4 (R-THF), 59.3 (Lu-CH2), 53.5 (Lu′-CH2), 26.5 (ꢀ-
THF).
[Lu(CH2Ph)3(THF)2] (5). A suspension of 0.3 g (0.45 mmol)
of Lu(CH2Ph)3(THF)3 in 15 mL of toluene was stirred at room
temperature for 1.5 h. During stirring, the color became slightly
deeper than the original. After 1.5 h, the solvent was stripped under
vacuum to obtain a yellow solid. The above procedure was repeated
once more to obtain a yellow-orange solid after stripping the solvent
in vacuum. The solid was further dried in vacuum for another 2 h
to obtain 0.23 g (0.39 mmol, 85%) of yellow-orange solid. An
attempt to crystallize the compound from a saturated toluene
solution (-30 °C, for several days) gave only powdery solid.
0.7 mmol, 24%).
3
1H NMR (400 MHz, THF-d8, 25 °C): δ 6.62 (t, 10 H, JH,H
)
7.3 Hz, m-H), 6.45 (d, 10 H, 3JH,H ) 7.3, o-H), 6.06 (t, 5 H, 3JH,H
) 7.0 Hz, p-H), 1.82 (s, 10 H, ScCH2). 13C{1H} NMR (100.4 MHz,
THF-d8, 25 °C): δ 156.1 (Ar CH), 128.2 (Ar CH), 123.1 (Ar CH),
113.1 (Ar CH), 56.6 (ScCH2). Anal. Calcd for C47H59K2O3Sc
[795.14]: C, 71.00; H, 7.48. Found: C, 69.89, H, 7.57.
[Lu(CH2Ph)3(THF)3] (4). Method A. THF (10 mL) was
condensed at -196 °C onto a mixture of LuCl3 (0.28 g, 1 mmol)
and potassium benzyl (0.39 g, 3 mmol) and the mixture was stirred
for 16 h at ambient temperature, resulting in a color change from
dark red to yellow. Ten milliliters of toluene was condensed onto
the mixture and the solution was then filtered of, concentrated, and
layered with pentane. X-ray quality light yellow crystals were grown
overnight. The crystals were isolated and washed with pentane to
give the analytically pure product. Yield: 0.57 g (0.8 mmol, 80%).
Anal. Calcd for C33H45O3Lu [664.68]: C, 59.63; H, 6.83. Found:
C, 60.04; 7.15.
1H NMR (400 MHz, C7D8, 25 °C): δ 7.10 (“t”, 3JHH ) 7.6 Hz,
3
3
6H, Ph m-H), 6.74 (d, JHH ) 7.6 Hz, 6H, Ph o-H), 6.71 (t, JHH
) 7.2 Hz, 3H, Ph p-H), 3.43 (m, 8H, R-THF), 1.50 (s, 6H, Lu-
CH2), 1.15 (m, 8H, ꢀ-THF). 13C{1H} NMR (100.58 MHz, C7D8,
25 °C): δ 152.1 (Ph Cipso), 129.0 (Ph o/m-CH), 124.3 (Ph o/m-
CH), 118.3 (Ph p-CH), 71.0 (R-THF), 59.5 (br, Lu-CH2), 25.1 (ꢀ-
THF). Anal. Calcd for C29H37O2Lu (592.58): C, 58.78; H, 6.29.
Found: C, 58.85; H, 6.26.
Method B. A suspension of anhydrous LuCl3 (1.07 g, 3.80
mmol) was stirred overnight in THF (14 h). The suspension was
then cooled to -10 °C with stirring for another 1 h. A cold THF
solution of KCH2Ph (1.48 g, 11.4 mmol) was slowly added to the
suspension over about 10 min. During addition, the bright orange-
red color of the KCH2Ph disappeared immediately and LuCl3
suspension dissolved giving a very pale yellow emulsion-like
mixture, which was stirred at this temperature for a further 2 h.
The mixture was centrifuged to remove KCl and the pale yellow
supernatant was concentrated to about 10 mL, layered with Et2O,
and kept at -30 °C overnight to obtain a pale yellow microcrys-
talline solid, which was dried under vacuum to obtain the title
compound in 60% yield (1.523 g, 2.3 mmol). The compound is
sufficiently pure for spectroscopic characterization and further
reactions. X-ray quality crystals were grown from THF/OEt2
mixture. An analytically pure sample was obtained by careful,
repeated crystallization. Anal. Calcd for C33H45O3Lu [664.68]: C,
59.63; H, 6.83. Found: C, 59.40; H, 6.78.
X-ray Crystallographic Studies of 1–4. All structures were
solved by the Patterson method (SHELXS-9720). The remaining
non-hydrogen atoms were located from successive difference in
Fourier map calculations. The refinements were carried out by using
full-matrix least-squares techniques on F, minimizing the function
(Fo - Fc)2, where the weight is defined as 4Fo /2(Fo ) and Fo and
Fc are the observed and calculated structure factor amplitudes, using
the program SHELXL-97.21 Carbon-bound hydrogen atom positions
were calculated and allowed to ride on the carbon to which they
are bonded assuming a C-H bond length of 0.95 Å. The hydrogen
atom contributions were calculated, but not refined. The final values
of refinement parameters are given in Table 1. The locations of
the largest peaks in the final difference Fourier map calculation as
well as the magnitude of the residual electron densities in each
case were of no chemical significance. Positional parameters,
hydrogen atom parameters, thermal parameters, bond distances, and
angles have been deposited as Supporting Information.
2
2
3
1H NMR (400 MHz, 27 °C, C6D6): δ 7.17 (t, JHH ) 7.6 Hz,
3
3
Acknowledgment. This work was supported by the
Deutsche Forschungsgemeinschaft (DFG Schwerpunktpro-
gramm (SPP 1166): Lanthanoidspezifische Funktionalitäten
in Molekül and Material) and the Fonds der Chemischen
Industrie (P.W.R.), by the Natural Sciences and Engineering
Council of Canada (J.T.), and by the National Research
School Combination Catalysis (NRSC-C) (B.H.).
6H, Ph m-H), 6.85 (d, JHH ) 7.6 Hz, 6H, Ph o-H), 6.78 (t, JHH
) 7.6 Hz, 3H, Ph p-H), 3.48 (s br, 12H, R-THF), 1.62 (s, 6H,
LuCH2), 1.20 (s br, 12H, ꢀ-THF). 13C{1H} NMR (100.58 MHz,
27 °C, C6D6): δ 152.3 (Ph Cipso), 129.0 (Ph o/m-CH), 124.3 (Ph
o/m-CH), 118.3 (Ph p-CH), 69.7 (R-THF), 59.3 (Lu-CH2), 25.3
(ꢀ-THF).
1H NMR (400 MHz, THF-d8, 27 °C): δ 6.78 (s br, 6H, Ph m-H),
6.67 (d, 3JHH ) 7.2 Hz, 6H, Ph o-H), 6.25 (s br, 3H, Ph p-H), 3.62
(m, 12H, R-THF), 1.77 (m, 12H, ꢀ-THF), 1.64 (s, 6H, Lu-CH2).
Supporting Information Available: NMR spectra and tables
of crystallographic data in CIF file format, including bond lengths
and angles of compounds 1-4. This material is available free of
charge via the Internet at http://pubs.acs.org.
3
1H NMR (400 MHz, THF-d8, -80 °C): δ 6.84 (t, JHH ) 7.6 Hz,
3
Ph m-H), 6.73 (d, JHH ) 7.6 Hz, Ph′ o-H), 6.67–6.62 ((doublet
3
overlapping with a triplet and other minor peaks) d, JHH ) 7.6
Hz, Ph o-H; t, 3JHH ) 7.2 Hz, Ph′ m-H), 6.32 (t, 3JHH )7.4 Hz, Ph
3
p-H), 5.98 (t, JHH ) 7.0 Hz, Ph′ p-H), 3.62 (m, 12H, R-THF),
OM701171Y
1.78 (m, 12H, ꢀ-THF), 1.73 (s, (partially buried under THF-d8
solvent peak) Lu-CH2), 1.52 (s br, Lu′-CH2).
The two sets of resonances at LT are in a 2.7:1 ratio, minor
peaks marked with prime. Other minor peaks were also seen. The
intensity ratio of these signals was difficult to ascertain.
(20) Sheldrick, G. M. SHELXS-97, Program of Crystal Structure
Solution; University of Göttingen: Göttingen, Germany, 1997.
(21) Sheldrick, G. M. SHELXL-97, Program of Crystal Structure
Refinement; University of Göttingen: Göttingen, Germany, 1997.