Synthesis, structural characterization, and reactivity of lanthanide complexes containing a new methylene-bridged indenyl-pyrrolyl dianionic ligand

Article abstract of DOI:10.1021/om060610t

A new methylene-bridged ligand incorporating both indenyl and pyrrolyl moieties, (C₉H₇)CH₂(α-C₄H ₃-NH) (1), was prepared. Reaction of LnI₂ with 1 equiv of [(C₉H₆)CH₂(α-C₄H ₃N)]Li₂(THF)_x in THF, followed by recrystallization in DME, gave the organolanthanide(II) complexes {(η⁵-C₉H₆)CH₂[μ- η¹: η⁵-(α-C₄H₃N)] Ln(DME)}₂ (Ln = Sm (2), Yb (3)) in mederate yields. Treatment of SmCl₃ with 1 equiv of [(C₉H₆)CH ₂(α-C₄H₃N)]Li₂(THF) _x in THF gave the trivalent organosamarium chloride {(η⁵-C₉H₆)CH₂-[μ- η¹:η⁵-(α-C₄H₃N)] Sm(μ-Cl)₂Li(THF)₂}₂ (4) in 73% yield, while reaction of ErCl₃ with [(C₉H₆)CH ₂-(α-C₄H₃N)]Li₂(THF), under the same conditions generated [(η⁵-C₉H ₆)CH₂(μ-η¹:η³-C ₄H₃N)Er(μ₃-Cl)(μ-Cl)Li(THF) ₂]₂ (5). Reaction of 4 with 2 equiv of n-butyllithium (ⁿBuLi) and subsequently with N,N′-dicyclohexylcarbodiimide (CyN=C=NCy) gave the carbodiimide insertion into the Sm-C bond product {(η⁵-C₉H₆)CH₂[μ- η¹:η⁵-(α-C₄H₃N)] Sm[CyNC(ⁿBu)NCy]}₂ (6), while treatment of 4 with 2 equiv of NaN-(SiMe₃)₂ in THF followed by reacting with CyN=C=NCy gave the carbodiimide insertion into the Sm-N bond product [(η⁵- C₉H₇)CH₂[μ-η¹: η⁵-(α-C₄H₃N)]Sm{CyNC[N(SiMe ₃)₂]NCy}]₂ (7). These complexes were characterized by IR and ¹H NMR spectra and elemental analyses. Furthermore, the structures of all these compounds were also confirmed by X-ray diffraction analyses.

Full text of DOI:10.1021/om060610t

Organometallics 2006, 25, 5165-5172
5165
Synthesis, Structural Characterization, and Reactivity of Lanthanide
Complexes Containing a New Methylene-Bridged Indenyl-Pyrrolyl
Dianionic Ligand
Chengfu Pi,† Zhengxing Zhang,† Ruiting Liu,† Linhong Weng,† Zhenxia Chen,† and
Xigeng Zhou*,†,‡
Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and InnoVatiVe Material,
Fudan UniVersity, Shanghai 200433, People’s Republic of China, and State Key Laboratory of
Organometallic Chemistry, Shanghai 200032, People’s Republic of China
ReceiVed July 6, 2006
A new methylene-bridged ligand incorporating both indenyl and pyrrolyl moieties, (C9H7)CH2(R-C4H3-
NH) (1), was prepared. Reaction of LnI2 with 1 equiv of [(C9H6)CH2(R-C4H3N)]Li2(THF)x in THF,
followed by recrystallization in DME, gave the organolanthanide(II) complexes {(η5-C9H6)CH2[µ-η1:
η5-(R-C4H3N)]Ln(DME)}2 (Ln ) Sm (2), Yb (3)) in mederate yields. Treatment of SmCl3 with 1 equiv
of [(C9H6)CH2(R-C4H3N)]Li2(THF)x in THF gave the trivalent organosamarium chloride {(η5-C9H6)CH2-
[µ-η1:η5-(R-C4H3N)]Sm(µ-Cl)2Li(THF)2}2 (4) in 73% yield, while reaction of ErCl3 with [(C9H6)CH2-
(R-C4H3N)]Li2(THF)x under the same conditions generated [(η5-C9H6)CH2(µ-η1:η3-C4H3N)Er(µ3-Cl)(µ-
Cl)Li(THF)2]2 (5). Reaction of 4 with 2 equiv of n-butyllithium (nBuLi) and subsequently with N,N′-
dicyclohexylcarbodiimide (CyNdCdNCy) gave the carbodiimide insertion into the Sm-C bond product
{(η5-C9H6)CH2[µ-η1:η5-(R-C4H3N)]Sm[CyNC(nBu)NCy]}2 (6), while treatment of 4 with 2 equiv of NaN-
(SiMe3)2 in THF followed by reacting with CyNdCdNCy gave the carbodiimide insertion into the Sm-N
bond product [(η5-C9H7)CH2[µ-η1:η5-(R-C4H3N)]Sm{CyNC[N(SiMe3)2]NCy}]2 (7). These complexes were
characterized by IR and 1H NMR spectra and elemental analyses. Furthermore, the structures of all these
compounds were also confirmed by X-ray diffraction analyses.
system has a promising feature with the formation of macro-
cyclic lanthanide clusters able to carry out four-electron reduc-
tion of dinitrogen.4 In addition, the bimodal σ/π-bonding
capability of this ligand provides the potential of retaining alkali
cations, which proved to allow for the fine-tuning of the bonding
model of the lanthanide center.5 Despite the great development
of various bridged cyclopentadienyl ligands and the emerging
importance of the replacement of cyclopentadienyl groups with
heterocyclic analogues, few studies have been reported on
organolanthanide complexes containing the bridged hybrid
cyclopentadienyl/heterocycle dianionic ligands.1c
To our knowledge, no example of bridged indenyl/pyrrolyl
complexes has been reported to date. Given the rich chemistry
of ansa-lanthanocene and/or ansa-dipyrrolyl lanthanide com-
plexes and the greater reactivities of indenyl metal complexes
compared to their cyclopentadienyl analogues,6 we are interested
to find out whether ansa-bridged indenyl-pyrrolyl complexes
of lanthanides display the same variety of reactivities. We report
here the synthesis and characterization of a series of organo-
Introduction
The development of new ancillary ligands to support sto-
ichiometric and catalytic reactivity at metal centers is currently
an intensively studied area in organolanthanide chemistry.1
Among strategies for the design of new ligands, ansa carbonous-
bridged cyclopentadienyl ligands have received wide attention
due to the often dramatic effects of the incorporation of the
ansa-bridge on both the stability and the behavior of reactivity
and catalytic activity of lanthanocene complexes.2 Furthermore,
the examination of alternatives to the commonly used cyclo-
pentadienyl groups is also receiving special attention.3 For
example, it has been found that the ansa-dipyrrolyl ligand
* Corresponding author. E-mail: xgzhou@fudan.edu.cn.
† Shanghai Key Laboratory of Molecular Catalysis and Innovative
Material.
‡State Key Laboratory of Organometallic Chemistry.
(1) (a) Schumann, H.; Meese-Marktscheffel, J. A.; Esser, L. Chem. ReV.
1995, 95, 865. (b) Arndt, S.; Okuda, J. Chem. ReV. 2002, 102, 1953. (c)
Xie, Z. W. Acc. Chem. ReV. 2003, 3, 1. (d) Togni, A.; Halterman, R. L.
Metallocenes: Synthesis, ReactiVity, Applications; Wiley-VCH: New York,
1998; Vols. 1 and 2. (e) Arnold, P. L.; Liddle, S. T. Organometallics 2006,
25, 1485. (f) Patel, D.; Liddle, S. T.; Mungur, S. A.; Rodden, M.; Blake,
A. J.; Arnold, P. L. Chem. Commun. 2006, 1124. (g) Arnold, P. L.; Liddle,
S. Chem. Commun. 2005, 5638. (h) Liddle, S.; Arnold, P. L. Organome-
tallics 2005, 24, 2597. (i) Cantat, T.; Jaroschik, F.; Ricard, L.; Le Floch,
P.; Nief, F.; Mezailles, N. Organometallics 2006, 25, 1329. (j) Turcitu, D.;
Nief, F.; Ricard, L. Chem. Eur. J. 2003, 9, 4916. (k) Cui, C.; Shafir, A.;
Reeder, C. L.; Arnold, J. Organometallics 2003, 22, 3357.
(4) (a) Dube, T.; Conoci, T.; Gambarotta, S.; Yap, G. P. A.; Vasapollo,
G. Angew. Chem., Int. Ed. 1999, 38, 3657. (b) Dube, T.; Ganesan, M.;
Conoci, S.; Gambarotta, S.; Yap, G. P. A Organometallics 2000, 19, 3716.
(c) Dube, T.; Gambarotta, S.; Yap, G. P. A. Organometallics 2000, 19,
115. (d) Dube, T.; Conoci, S.; Gambarotta, S.; Yap, G. P. A. Organome-
tallics 2000, 19, 1182. (e) Mani, G.; Lalonde, M. P.; Gambarotta, S.; Yap,
G. P. A. Organometallics 2001, 20, 2443. (f) Ganesan, M.; Gambarotta,
S.; Yap, G. P. A. Angew. Chem., Int. Ed. 2001, 40, 766. (g) Berube C. D.;
Yazdanbakhsh, M.; Gambarotta, S.; Yap, G. P. A. Organometallics 2003,
22, 3742.
(2) (a) Qian, C. T.; Nie, W. L.; Sun, J. J. Organomet. Chem. 2001, 626,
171. (b) Qian, C. T.; Nie, W. L.; Chen, Y. F.; Sun, J. J. Organomet. Chem.
2002, 645, 82. (c) Nie, W. L.; Qian, C. T.; Chen, Y. F.; Sun, J. J. Organomet.
Chem. 2002, 647, 114.
(5) (a) Ganesan, M.; Be´rube´, C. D.; Gambarotta, S.; Yap, G. P. A.
Organometallics 2002, 21, 1707.
(3) (a) Edelmann, F. T.; Freckmann, D. M. M.; Schumann, H. Chem.
ReV. 2002, 102, 1851. (b) Dube, T.; Conoci, T.; Gambarotta, S.; Yap, G.
P. A.; Vasapollo, G. Angew. Chem., Int. Ed. 1999, 38, 3657.
(6) (a) Qian, C. T.; Zou, G.; Jiang, W. H.; Chen, Y. F.; Sun, J.; Li, N.
Organometallics 2004, 23, 4980. (b) Qian, C. T.; Zou, G.; Chen, Y. F.;
Sun, J. Organometallics 2001, 20, 3106.
10.1021/om060610t CCC: $33.50 © 2006 American Chemical Society
Publication on Web 09/06/2006

5166 Organometallics, Vol. 25, No. 21, 2006
Pi et al.
IR (Nujol, cm-1): 3053 (m), 3037 (m), 2995 (m), 2720 (w), 1303
(w), 1209 (w), 1194 (w), 1148 (w), 1117 (w), 1071 (m), 1030 (m),
995 (w), 914 (w), 856 (m), 816 (w), 769 (w), 753 (w), 738 (w),
718 (m).
lanthanide(II) and organolanthanide(III) complexes containing
a new asymmetrically methylene-bridged indenyl and pyrrolyl
ligand. The reactivities of their trivalent alkyl and amide
derivatives toward N,N′-dicyclohexylcarbodiimide are also
described.
Preparation of {(η5-C9H6)CH2[µ-η1:η5-(R-C4H3N)]Yb(DME)}2
(3). Following the procedure described for 2, YbI2 (0.04 M THF
solution, 31.3 mL, 1.25 mmol) reacted with 1 equiv of dilithium
salt of 1 to gave 3 as dark red blocks, yield: 0.24 g (42%). Mp:
128-130 °C (dec). Anal. Calcd for C36H42N2O4Yb2: C, 47.37; H,
4.64; N, 3.07; Yb, 37.91. Found: C, 47.25; H, 4.43; N, 2.92; Yb,
37.70. 1H NMR (pyridine-d5): δ 9.01 (m, 14H), 7.77 (s, 4H), 5.50
(s, 4H), 4.93 (s, 4H), 4.71 (s, 12H), 3.64 (s, 4H). IR (Nujol, cm-1):
3177 (m), 3078 (w), 2714 (w), 1329 (m), 1184 (m), 1146 (w), 1114
(m), 1069 (s), 1028 (m), 991 (w), 948 (m), 867 (s), 755 (m), 739
(s), 704 (w).
Preparation of {(η5-C9H6)CH2[µ-η1:η5-(R-C4H3N)]Sm(µ-
Cl)2Li(THF)2}2 (4). To a THF (30 mL) solution of 1 (0.390 g,
2.00 mmol) held at 0 °C was added dropwise n-butyllithium in
hexane (1.6 M, 2.5 mL, 4.00 mmol). After stirring at room
temperature for 2 h, the resulting orange solution was added slowly
to a suspension of SmCl3 (0.513 g, 2.00 mmol) in THF (45 mL)
with stirring at -78 °C. Then, the mixture was allowed to warm to
room temperature and stirred for 24 h. The solution changed from
colorless to light red during the course of the reaction. The solvent
was evaporated under vacuum, leaving an oily residue that was
washed with hexane (10 mL × 2). The resulting solid was extracted
with THF (15 mL × 2). The solutions were combined and
concentrated to about 10 mL, from which 4 was obtained as red-
orange crystals after this solution stood at room temperature for 2
weeks (0.83 g, 73%). Mp: 121-123 °C (dec). Anal. Calcd for
C44H54Cl4Li2N2O4Sm2: C, 46.71; H, 4.81; N, 2.48. Found: C,
46.47; H, 4.63; N, 2.26. 1H NMR (500 MHz, THF-d8): δ 9.72 (br
s, 2H, C9H7), 7.39 (d, 2H, C9H7), 7.30 (d, 2H, C9H7), 7.16(s, 2H,
C9H7), 7.11(d, 2H, C9H7), 6.15 (d, 2H, C9H7), 6.54 (s, 2H, C4H3N),
5.93 (s, 2H, C4H3N), 5.87 (s, 2H, C4H3N), 3.29 (s, 4H, -CH2-),
3.58 (br s, 16H, THF), 1.73 (br s, 16H, THF). IR (Nujol, cm-1):
3120 (m), 3070 (m), 2900 (m), 1336 (m), 1039 (m), 958 (w), 859
(m), 769 (m), 723 (s).
Preparation of [(η5-C9H6)CH2[µ-η1:η3-(R-C4H3N)]Er(µ3-Cl)-
(µ-Cl)Li(THF)2]2 (5). To a THF (30 mL) solution of 1 (0.390 g,
2.00 mmol) held at 0 °C was added dropwise n-butyllithium in
hexane (1.6 M, 2.50 mL, 4.00 mmol). The reaction mixture was
stirred at room temperature for 2 h. The resulting orange solution
was added slowly to a suspension of ErCl3 (0.547 g, 2.00 mmol)
in THF (40 mL) with stirring at -78 °C, and the mixture was stirred
for 24 h at room temperature. The solution changed from colorless
to dark red. The solvent was evaporated under vacuum, leaving an
oily residue, which was washed with hexane (10 mL × 2). The
resulting solid was extracted with benzene (20 mL × 2). The
solutions were combined and concentrated to about 20 mL. After
standing at room temperature for several days, 5‚C6H6 was obtained
as pink crystals (0.696 g, 56%). Once crystallized, the complex is
nearly insoluble in benzene. Mp: 131-133 °C (dec). Anal. Calcd
for C50H60Cl4Er2Li2N2O4: C, 48.30; H, 4.86; N, 2.25. Found: C,
48.08; H, 4.63; N, 2.11. IR (Nujol, cm-1): 3057 (w), 3035 (m),
2900 (m), 1930 (w), 1604 (m), 1494 (w), 1401 (w), 1348 (w), 1338
(w), 1226 (m), 1166 (m), 1150 (w), 1136 (w), 1094 (m), 1031 (s),
959 (s), 913 (w), 866 (m), 802 (s), 762 (m), 739 (w), 729 (w), 695
(m), 661 (w), 622 (w).
Experimental Section
General Procedures. Except where noted, all manipulations
were conducted in the absence of oxygen and water under an
atmosphere of dinitrogen, either by use of standard Schlenk methods
or within an mBraun glovebox apparatus. All organic solvents
(including deuterated solvents for the NMR measurements) were
7
dried and distilled under dinitrogen prior to use. Anhydrous LnCl3
and LnI2(THF)x (Ln ) Sm, Yb)8 were prepared according to
literature methods. All other chemicals were purchased from Aldrich
Chemical Co. and used as received unless otherwise noted. Melting
points were determined in sealed nitrogen-filled capillaries without
temperature correction. Elemental analyses for C, H, and N were
carried out on a Rapid CHN-O analyzer. Infrared spectra were
obtained on a Nicolet FT-IR 360 spectrometer with samples
prepared as Nujol mulls. 1H NMR data were obtained on a Bruker
DMX-500 NMR spectrometer.
Preparation of (C9H7)CH2(R-C4H3NH) (1). To a CH3OH
solution (50 mL) of pyrrole-2-carboxaldehyde (5.1 g, 53.5 mmol)
and indene (12.4 g, 107 mmol) was added pyrrolidine (7.6 g, 107
mmol) at rt. After stirring for 12 h, glacial AcOH (6.4 g, 107 mmol)
was added to the dark red solution at 0 °C. The reaction mixture
was diluted with ether (50 mL) and water (50 mL). The aqueous
portion was extracted with Et2O (50 mL × 4), and the combined
organic portion was washed with water and brine and dried over
anhydrous MgSO4. Removal of solvent gave a pale yellow solid
of fulvene-type indene compounds (5.0 g, 26.2 mmol, 49%), which
was then added to a suspension of lithium aluminum hydride (0.89
g, 26.2 mmol) in THF (200 mL) in several portions at 0 °C. After
stirring for 20 h, the mixture was quenched with water, then 10%
HCl, extracted with diethyl ether (50 mL × 4), dried (MgSO4),
filtered, and concentrated. Reduced pressure distillation of the
residues afforded 1 as a light yellow liquid, which solidified in a
few days in a refrigerater. Yield: 2.82 g, 27% (based on pyrrole-
2-carboxaldehyde). Mp: 27-28 °C. Anal. Calcd for C14H13N: C,
1
86.12; H, 6.71; N, 7.17. Found: C, 85.98; H, 6.68; N, 7.11. H
NMR (500 MHz, CDCl3, 25 °C): δ 7.95 (br s, NH), 6.65 (d, 1H,
C4H3NH), 6.16 (m, 1H, C4H3NH), 6.07 (s, 1H, C4H3NH), 3.93 (s,
2H, -CH2-), 3.37 (s, CH2, C9H7), 6.27 (s, 1H, C9H7), 7.46 (d,
1H, C9H7), 7.20-7.30 (m, 3H, C9H7). IR (Nujol, cm-1): 3483 (w),
3415 (m), 1605 (m), 1560 (m), 1421(w), 1279 (w), 1261 (m), 1228
(m), 1195 (w), 1158 (w), 1113 (w), 1086 (m), 1028 (m), 962 (m),
914 (m), 880 (m), 799 (m), 775 (s), 721 (s), 648 (w).
Preparation of {(η5-C9H6)CH2[µ-η1:η5-(R-C4H3N)]Sm(DME)}2
(2). To a THF solution of 1 (0.244 g, 1.25 mmol) (40 mL) held at
0 °C was dropwise added n-butyllithium (1.60 M in hexane, 1.56
mL, 2.50 mmol). The reaction mixture was stirred for 5 h at ambient
temperature and turned slowly to orange. Then, a THF solution of
SmI2 (0.04 M, 31.3 mL, 1.25 mmol) was added at -30 °C. The
reaction mixture was allowed to warm to room temperature. After
stirring overnight, all volatiles were removed in vacuo to give a
black, oily product, which was washed with hot toluene (5 mL ×
3). The residue was extracted with DME (30 mL), and the solution
was concentrated to ca. 10 mL and left at -15 °C for 3 days. 2
(0.27 g) was obtained as black crystals. Yield: 50%. Once
crystallized, the complex is nearly insoluble in DME. Mp: 140-
142 °C (dec). Anal. Calcd for C36H42N2O4Sm2: C, 49.85; H, 4.88;
N, 3.23; Sm, 34.67. Found: C, 49.67; H, 4.72; N, 3.09; Sm, 34.51.
Preparation of {(η5-C9H6)CH2[µ-η1:η5-(R-C4H3N)]Sm[CyNC-
(nBu)NCy]}2 (6). To a solution of 4 (1.13 g, 1.00 mmol) in THF
(30 mL) was added n-butyllithium (1.6 M in n-hexane, 1.25 mL)
at -30 °C. After stirring for 4 h, to the mixture was added N,N′-
dicyclohexylcarbodiimide (0.412 g, 2.00 mmol) at -10 °C. The
reaction mixture was then warmed to ambient temperature and
stirred overnight. The solvent was removed by reduced pressure.
The solid was extracted with benzene. The resulting yellow solution
(7) Taylor, M. D.; Carter, C. P. J. Inorg. Nucl. Chem. 1962, 24, 387
(8) Girard, P.; Namy, J. L.; Kagan, H. B. J. Am. Chem. Soc. 1980, 102,
2693.

Lanthanide Complexes with a Methylene-Bridged Ligand
Organometallics, Vol. 25, No. 21, 2006 5167
Table 1. Crystal and Data Collection Parameters of Complexes 1, 2, 3, and 4
1
2
3
4
formula
C14H13N
195.25
colorless
0.25 × 0.25 × 0.20
monoclinic
P21/n
C36H42N2O4Sm2
867.42
black
0.20 × 0.10 × 0.10
orthorhombic
P21212
C36H42N2O4Yb2
912.80
black-red
0.30 × 0.05 × 0.05
orthorhombic
P21212
C44H54Cl4Li2N2O4Sm2
1131.27
red-yellow
molecular weight
cryst color
cryst dimens (mm)
cryst syst
space group
unit cell dimens
a (Å)
0.05 × 0.02 × 0.02
triclinic
P1h
9.144(8)
11.761(10)
10.372(9)
103.654(13)
1084.0(16)
4
1.196
0.070
416
13.719(5)
18.172(6)
8.247(3)
90
2056.1(12)
2
1.401
2.861
856
13.822(5)
18.293(6)
7.949(3)
90
2010.0(12)
2
1.508
4.658
888
10.200(7)
10.495(7)
11.609(8)
93.357(11)
1175.0(13)
1
1.599
2.743
562
b (Å)
c (Å)
â (deg)
V (Å3 )
Z
Dc (g cm-3
)
µ (mm-1
F(000)
)
radiation
Mo KR
Mo KR
Mo KR
Mo KR
(λ ) 0.710730 Å)
temperature (K)
scan type
θ range (deg)
h,k,l range
293.2
ω-2θ
2.66 to 25.00
-10 e h e 5,
-13 e k e 13
-12 e l e 12
4412
293.2
ω-2θ
293.2
ω-2θ
293.2
ω-2θ
1.86 to 25.01
-12 e h e 12
-12 e k e 12
-13 e l e 13
5727
1.86 to 25.00
-16 e h e 15
-21 e k e 20
-9 e l e 6
1.85 to 25.01
-16 e h e 13
-20 e k e 21
-9 e l e 9
no. of reflns measd
7090
8408
no. of unique reflns
completeness to θ
max. and min. transmn
refinement method
1907 [Rint ) 0.0340]
99.8% [θ ) 25.00]
0.9862 and 0.9828
3567 [Rint ) 0.0220]
98.4% [θ ) 25.01]
0.7629 and 0.5985
3529 [Rint ) 0.0417]
99.7% [θ ) 25.01]
0.8005 and 0.3355
5727 [Rint ) 0.0000]
97.2% [θ ) 25.01]
0.9472 and 0.8751
full-matrix least-squares on F2
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
1907/0/136
1.029
3567/0/169
1.065
3529/0/199
1.066
5727/18/267
0.946
R1 ) 0.0473,
wR2 ) 0.1202
R1 ) 0.0751,
wR2 ) 0.1352
0.210 and -0.151
R1 ) 0.0514,
wR2 ) 0.1565
R1 ) 0.0694,
wR2 ) 0.1733
1.548 and -0.531
R1 ) 0.0516,
wR2 ) 0.1347
R1 ) 0.0727,
wR2 ) 0.1458
1.460 and -0.599
R1 ) 0.0906,
wR2 ) 0.1828
R1 ) 0.1307,
wR2 ) 0.2056
3.804 and -2.718
R indices (all data)
largest diff peak and
hole (e‚Å-3
)
was concentrated by reduced pressure to about 5 mL, and a yellow
solid precipitated. The precipitate was resolved by addition of 2
mL of THF. Yellow crystals of 6‚C6H6 (0.96 g, 74%) were obtained
upon standing at room temperature for a few days. Mp: 146-148
°C (dec). Anal. Calcd for C68H90N6Sm2: C, 63.20; H, 7.02; N, 6.50.
Found: C, 63.01; H, 6.84; N, 6.32. 1H NMR (500 MHz, benzene-
d6): 6.29 (s, 2H, C4H3N), 6.22 (s, 2H, C9H7), 6.09 (s, 2H, C4H3N),
5.88 (s, 2H, C4H3N), 3.03 (s, 4H, CH2Ind), many broad, unresolved
resonances. IR (Nujol, cm-1): 3110 (w), 3065 (m), 3012 (m), 1649
(m), 1419 (w), 1361 (w), 1335 (w), 1276 (w), 1189 (m), 1175 (m),
1158 (m), 1088 (w), 1069 (w), 1039 (m), 1027 (m), 952 (s), 886
(m), 850 (m), 778 (m), 751 (s), 729 (s), 696 (s), 645 (v).
Preparation of [(η5-C9H7)CH2[µ-η1:η5-(R-C4H3N)]Sm{CyNC-
[N(SiMe3)2]NCy}]2 (7). To a solution of 4 (1.13 g, 1.00 mmol) in
30 mL of THF was added NaN(SiMe3)2 (0.267 g, 2.00 mmol) at 0
°C. After stirring at this temperature for 2 h, the mixture was
warmed to room temperature and continued to stir for 5 h. The
precipitate (NaCl) was removed by centrifugation. Then, to the clear
solution was added N,N′-dicyclohexylcarbodiimide (0.412 g, 2.00
mmol) at -30 °C. After stirring for 2 h at -30 °C, the mixture
was slowly warmed to ambient temperature and was further stirred
for 24 h. Removal of the solvent left a pale yellow solid. The
resulting solid was extracted with 60 mL of benzene, followed by
filtration. The extract was evaporated to ca. 20 mL. Red-yellow
crystals of 7‚4THF‚C6H6 were slowly formed at room temperature.
Yield: 1.09 g (61%). Mp: 106-108 °C. Anal. Calcd for
C88H140N8O4Si4Sm2: C, 59.14; H, 7.90; N, 6.27. Found: C, 58.95;
H, 7.72; N, 6.13. 1H NMR (500 MHz, benzene-d6): 3.55 (s, 16H,
free THF), 3.04 (s, 4H, CH2Ind), 1.80, 1.60 (2 brm, together, 22H,
C6H11), 1.45 (s, 16H, free THF), 1.24 (m, 22H, C6H11), 0.27, 0.22
(2 s, 36H, SiMe3), plus many broad, unresolved peaks. IR (Nujol,
cm-1): 3080 (w), 3046 (m), 2950 (w), 1629 (m), 1342 (w), 1291
(w), 1173 (m), 1071 (m), 994 (m), 953 (m), 938 (m), 777 (m), 750
(m), 722 (m).
X-ray Structural Determination. Suitable single crystals were
sealed under N2 in thin-walled glass capillaries. Data were collected
at 293.2 K on a Bruker SMART Apex CCD diffractometer using
graphite-monochromated Mo KR (λ ) 0.71073 Å) radiation. During
the intensity data collection, no significant decay was observed.
The intensities were corrected for Lorentz-polarization effects and
empirical absorption with the SADABS program.9 The structures
were solved by direct methods using the SHELXL-97 program.10
All non-hydrogen atoms were found from the difference Fourier
syntheses. The H atoms were included in calculated positions with
isotropic thermal parameters related to those of the supporting
carbon atoms but were not included in the refinement. All
calculations were performed using the Bruker Smart program. The
absolute configuration of 2 was assigned by anomalous dispersion
effects in diffraction measurements on the crystal, while the absolute
structure of 3 has not been established by anomalous dispersion
effects in diffraction measurements on the crystal, for which an
arbitrary choice of enantiomer has been made. Crystal data and
details of data collection and structure refinements are given in
Tables 1 and 2, respectively. Selected bond distances and angles
are compiled in Tables 3-8, respectively. Further details are
included in the Supporting Information.
Results and Discussion
Synthesis of Indenylpyrrolylmethane. [(C9H7)CH2(R-C4H3-
NH)] (1) was readily prepared by the reaction of pyrrole-2-
(9) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction; University of Go¨ttingen: Go¨ttingen, Germany, 1998.

5168 Organometallics, Vol. 25, No. 21, 2006
Pi et al.
Table 2. Crystal and Data Collection Parameters of Complexes 5, 6, and 7
5‚C6H6
6‚C6H6
7‚4THF‚C6H6
formula
C50H60Cl4Er2Li2N2O4
1243.20
pale orange
C68H90N6Sm2
1292.16
yellow
C88H140N8O4Si4Sm2
1787.14
red-yellow
0.20 × 0.10 × 0.10
triclinic
molecular weight
cryst color
cryst dimens (mm)
cryst syst
space group
unit cell dimens
a (Å)
0.15 × 0.10 × 0.10
0.10 × 0.08 × 0.05
monoclinic
triclinic
P21/c
P1h
P1h
11.699(4)
18.752(6)
12.686(4)
110.629(4)
2604.5(14)
2
1.585
3.448
1232
9.215(2)
11.225(3)
15.391(4)
92.436(5)
1563.5(7)
1
1.372
1.903
664
11.566(4)
13.722(5)
15.778(5)
105.602(4)
2281.1(13)
1
1.301
1.378
936
b (Å)
c (Å)
â (deg)
V (Å3 )
Z
Dc (g cm-3
)
µ (mm-1
F(000)
)
radiation
Mo KR
Mo KR
Mo KR
(λ ) 0.710730Å)
temperature (K)
scan type
θ range (deg)
h,k,l range
293.2
ω-2θ
1.86 to 26.01
-14 e h e 10
-23 e k e 22
-5 e l e 15
11 654
293.2
ω-2θ
1.85 to 25.01
-10 e h e 10
-12 e k e 13
-18 e l e 16
6627
293.2
ω-2θ
1.36 to 25.01
-13 e h e 13,
-16 e k e 16
-10 e l e 18
9566
no. of reflns measd
no. of unique reflns
completeness to θ
max. and min. transmn
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
5102 [Rint ) 0.0305]
99.6% [θ ) 26.01]
0.7243 and 0.6258
5441 [Rint ) 0.0631]
98.7% [θ ) 25.01]
0.9108 and 0.8325
full-matrix least-squares on F2
5441/11/343
7893 [Rint ) 0.0163]
98.3% [θ ) 25.01]
0.8745 and 0.7702
5102/10/289
1.135
7893/31/418
1.087
1.025
R1 ) 0.0349,
wR2 ) 0.0809
R1 ) 0.0621,
wR2 ) 0.0976
1.189 and -0.666
R1 ) 0.0742,
wR2 ) 0.1427
R1 ) 0.1257,
wR2 ) 0.1649
1.801 and -0.782
R1 ) 0.0437,
wR2 ) 0.1175
R1 ) 0.0611,
wR2 ) 0.1348
1.000 and -0.711
R indices (all data)
largest diff. peak and
hole (e‚Å-3
)
Table 3. Selected Bond Lengths [Å] and Angles [deg] for Complex 1
N(1)-C(1)
N(1)-C(4)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
1.365(3)
1.366(3)
1.342(3)
1.408(3)
1.356(3)
1.495(3)
C(5)-C(6)
C(6)-C(7)
C(6)-C(10)
C(7)-C(8)
C(8)-C(9)
C(9)-C(10)
1.503(3)
1.339(3)
1.468(3)
1.497(3)
1.503(3)
1.405(3)
N-H‚‚‚centroid(benzene ring)
2.47
C(4)-C(5)-C(6)
C(3)-C(4)-C(5)
115.05(16)
130.74(18)
C(7)-C(6)-C(5)
128.20(19)
Table 4. Selected Bond Lengths [Å] and Angles [deg] for Complexes 2 and 3
2
3
2
3
Ln
Sm
Yb
Ln
Sm
Yb
Ln1-N(1)
Ln1A-N(1A)
Ln1-O(1)
Ln1-O(2)
Ln1-C(1)
Ln1-C(6)
Ln1-C(7)
2.602(11)
2.829(9)
2.456(12)
2.790(11)
2.490(11)
2.460(11)
2.861(17)
2.841(13)
2.743(14)
Ln1-C(8)
2.843(11)
2.816(12)
2.920(12)
2.973(11)
2.914(12)
2.794(13)
4.281
2.686(14)
2.734(14)
2.875(14)
2.865(15)
2.796(15)
2.743(14)
4.166
Ln1-C(9)
2.581(11)
2.578(12)
2.868(12)
2.891(11)
2.855(11)
Ln1A-C(11A)
Ln1A-C(12A)
Ln1A-C(13A)
Ln1A-C(14A)
Ln1‚‚‚Ln1A
N(1)-Ln-O(2)
N(1)-Ln1-O(1)
O(2)-Ln1-O(1)
C(10)-C(7)-Ln1
86.2(3)
151.5(3)
65.4(4)
84.6(4)
149.7(4)
65.1(4)
N(1)-Ln1-N(1A)
C(11)-C(10)-C(7)
Ln1-N(1)-Ln1A
72.7(4)
114.6(11)
103.9(3)
71.4(4)
115.6(13)
104.9(4)
113.3(8)
111.7(9)
carboxaldehyde with indene catalyzed by pyrrolidine (Scheme
1). 1 is soluble in some common organic solvents. The
formulation of 1 was confirmed through a single-crystal X-ray
diffraction study. Figure 1 and Table 3 provide a summary of
these results. No isomers in this solid were detected by 1H NMR
spectrometry.
In the solid state, compound 1 is present as pairs of
enantiomeric molecules with a center of inversion. There is no
intermolecular hydrogen bonding, and aggregation into dimers
is based on parallel head-to-tail stacking with only weak centroid
(10) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.

Lanthanide Complexes with a Methylene-Bridged Ligand
Organometallics, Vol. 25, No. 21, 2006 5169
Table 5. Selected Bond Lengths [Å] and Angles [deg] for
Complex 4
Table 8. Selected Bond Lengths [Å] and Angles [deg] for
Complex 7
Sm(1)-N(1)
Sm(1)-N(1A)
Sm(1)-C(4)
Sm(1)-C(1)
Sm(1)-C(3)
Sm(1)-Cl(1)
Sm(1)-C(5)
Sm(1)-C(2)
Sm(1)-Cl(2)
Sm(1)‚‚‚Sm(1A)
2.468(13) Cl(1)-Li(1)
2.824(12) Cl(2)-Li(1)
2.691(19) N(1)-Sm(1A)
2.36(4)
2.25(4)
Sm(1)-N(3)
Sm(1)-N(2)
Sm(1)-N(1)
Sm(1)-C(6)
N(1)-Sm(1A)
C(1)-Sm(1A)
C(2)-Sm(1A)
N(2)-C(15)
N(2)-C(16)
N(3)-C(15)
2.432(4)
2.444(4)
2.566(4)
2.698(5)
2.840(4)
2.815(5)
2.817(6)
1.307(7)
1.472(7)
1.346(7)
Sm(1)-C(7)
Sm(1)-C(8)
Sm(1)-C(10)
Sm(1)-N(1A)
C(4)-Sm(1A)
C(3)-Sm(1A)
Sm(1)‚‚‚Sm(1A)
N(3)-C(22)
2.739(5)
2.780(6)
2.798(6)
2.840(4)
2.836(6)
2.840(6)
4.570
1.476(7)
1.476(7)
1.456(7)
2.824(12)
2.829(18)
2.834(17)
2.715(15)
2.702(16)
2.02(4)
2.72(2)
2.72(2)
C(11)-Sm(1A)
C(12)-Sm(1A)
2.730(6) C(13)-Sm(1A)
2.733(17) C(14)-Sm(1A)
2.746(19) O(1)-Li(1)
2.795(5) O(2)-Li(1)
4.422
1.87(4)
N(3)-C(22)
N(4)-C(15)
N(1)-Sm(1)-Cl(1)
N(1)-Sm(1)-Cl(2)
Cl(1)-Sm(1)-Cl(2)
N(1)-Sm(1)-N(1A)
C(10)-C(4)-Sm(1)
C(11)-C(10)-C(4)
78.9(4)
157.1(3)
O(2)-Li(1)-O(1) 106.3(18)
O(2)-Li(1)-Cl(2) 120(2)
N(1)-Sm(1)-N(1A)
Sm(1)-N(1)-Sm(1A)
N(1)-Sm(1)-C(6)
N(3)-Sm(1)-N(1)
64.6(2)
N(2)-C(15)-N(3)
N(2)-C(15)-N(4)
N(3)-C(15)-N(4)
N(3)-Sm(1)-N(2)
114.5(5)
123.4(5)
122.1(5)
54.4(2)
115.4(2)
65.0(2)
94.3(1)
79.08(17) O(1)-Li(1)-Cl(2) 113.5(18)
66.8(4)
111.9(13)
110.8(17)
O(2)-Li(1)-Cl(1) 106.5(18)
O(1)-Li(1)-Cl(1) 110.9(19)
Cl(2)-Li(1)-Cl(1) 99.2(14)
Scheme 1
Sm(1)-N(1)-Sm(1A) 113.2(4)
Table 6. Selected Bond Lengths [Å] and Angles [deg] for
Complex 5
Er(1)-O(1)
Er(1)-N(1)
Er(1)-C(3)
Er(1)-C(1)
Er(1)-C(2)
Er(1)-Cl(2)
Er(1)-C(5)
Er(1)-C(4)
Er(1)-Cl(1A)
2.346(4)
2.367(5)
2.627(6)
2.637(6)
2.638(6)
2.657(16)
2.694(6)
2.695(6)
2.718(2)
Er(1)-Cl(1)
2.814(2)
2.715(19)
2.718(2)
2.297(14)
2.153(14)
2.686(15)
2.448(16)
1.908(15)
Cl(1)-Li(1)
Cl(1)-Er(1A)
Cl(2)-Li(1)
Li(1)-N(1A)
Li(1)-C(11A)
Li(1)-C(14A)
O(2)-Li(1)
O(2)-Li(1)-Cl(2)
112.0(6)
O(1)-Er(1)-N(1)
O(1)-Er(1)-Cl(2)
N(1)-Er(1)-Cl(1A)
Cl(2)-Er(1)-Cl(1A)
Cl(2)-Er(1)-Cl(1)
Cl(1A)-Er(1)-Cl(1)
Li(1)-Cl(1)-Er(1)
86.82(17) O(2)-Li(1)-Cl(1)
85.87(12) O(2)-Li(1)-N(1A)
85.43(13) O(2)-Li(1)-Cl(2)
108.2(8)
121.2(7)
112.0(6)
93.10(5)
78.83(5)
73.91(5)
87.2(3)
O(2)-Li(1)-C(14A) 131.6(9)
O(2)-Li(1)-C(11A)
O(2)-Li(1)-Cl(1)
N(1A)-Li(1)-Cl(1)
Cl(2)-Li(1)-Cl(1)
O(2)-Li(1)-Cl(2)
91.3(6)
108.2(8)
89.8(6)
87.4(5)
112.0(6)
Er(1A)-Cl(1)-Er(1) 106.09(5)
Figure 1. ORTEP diagram of 1 with the probability ellipsoids
drawn at the 30% level.
Li(1)-Cl(2)-Er(1)
C(11)-N(1)-Er(1)
100.5(4)
122.1(4)
Table 7. Selected Bond Lengths [Å] and Angles [deg] for
Complex 6
Sm(1)-N(2)
Sm(1)-N(1)
Sm(1)-N(3A)
Sm(1)-C(26)
Sm(1)-C(18)
Sm(1)-C(19)
Sm(1)-C(25)
Sm(1)-N(3)
2.391(9)
2.438(9)
2.592(8)
2.715(10)
2.734(10)
2.766(10)
2.779(10)
2.809(9)
Sm(1)-C(20)
2.816(11)
2.592(8)
2.844(10)
2.831(10)
2.796(11)
2.747(11)
4.507
N(3)-Sm(1A)
C(28)-Sm(1A)
C(29)-Sm(1A)
C(30)-Sm(1A)
C(31)-Sm(1A)
Sm(1)‚‚‚Sm(1A)
N(2)-Sm(1)-N(1)
N(2)-Sm(1)-N(3A)
N(3A)-Sm(1)-C(26)
N(1)-C(13)-N(2)
55.2(3)
96.1(3)
65.0(3)
N(1)-C(13)-C(14)
N(2)-C(13)-C(14)
121.7(10)
122.3(10)
Sm(1A)-N(3)-Sm(1) 113.1(3)
116.1(10) N(3A)-Sm(1)-N(3)
66.9(3)
phenyl embrace interactions between N-H functions and benzene
rings (Figure 2). The two components of these dimeric units
show no π-π stacking (the indene parts are not facing each
other) but each has a H-N bond pointing toward a center of a
benzene ring of a neighboring indene moiety. The H-centroid
(benzene ring) distance is 2.47 Å and is shorter than the
previously observed value of 2.79 Å.11
Synthesis and Characterization of ansa-Bridged Indenyl/
Pyrrolyl Complexes of Lanthanides(II) {(η5-C9H6)CH2[µ-
η1:η5-(R-C4H3N)]Ln(DME)}2 (Ln ) Sm, Yb). Treatment of
C9H7CH2(R-C4H3NH) with 2 equiv of n-butyllithium in THF
followed by reacting with LnI2(THF)x afforded the neutral
Figure 2. Pairs of enantiomeric molecules of 1 in the crystal
(arbitrary radii). Hydrogen atoms on the N atom of the pyrrolyl in
the ligand are in a “phenyl-embraced” orientation.
complexes {(η5-C9H6)CH2[µ-η1:η5-(R-C4H3N)]Ln(DME)}2 [Ln
) Sm (2), Yb (3)] in mederate yields (Scheme 2). In sharp
contrast to ansa-bridged dipyrrolides of divalent rare earths,
which are precursors to dinitrogen reduction,12 exposure of 2
and 3 to nitrogen gas or carrying out the above preparation
(12) (a) Evans, W. J.; Rabe, G. W.; Ziller, J. W. Organometallics 1994,
13, 1641. (b) Edelmann, F. T. Coord. Chem. ReV. 1995, 137, 403. (c)
Minhas, R.; Song, J.; Ma, Y.; Gambarotta, S. Inorg. Chem. 1996, 35, 1866.
(d) Evans, J. W.; Ansari, M. A.; Ziller, J. W. Inorg. Chem. 1996, 35, 5435.
(11) Adams, H.; Harris, K. D. M.; Hembury, G. A.; Hunter, C. A.;
Livingstone, D.; McCabe, J. F. Chem. Commun. 1996, 2531.

5170 Organometallics, Vol. 25, No. 21, 2006
Pi et al.
Scheme 2
Figure 4. ORTEP diagram of 4 with the probability ellipsoids
drawn at the 30% level. Hydrogen atoms are omitted for clarity.
Scheme 3
Figure 3. ORTEP diagram of 2 and 3 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for
clarity.
directly under an N2 atmosphere did not afford any dinitrogen
complex but yielded instead intractable compounds. Complexes
2 and 3 are very air- and moisture-sensitive. 3 is readily
dissolved in THF and DME, but 2 is sparing soluble in these
solvents.
As shown in Figure 3, complexes 2 and 3 are isostructural,
in which the ansa-bridged indenyl/pyrrolyl ligand acts as a
tridentate dianion, with the pyrrolyl being both σ-bonded to one
lanthanide ion and π-bonded to another metal, resulting in a
symmetrical bimetallic structure. Each metal is η1-bonded to
two oxygen atoms of DME and one N atom of the pyrrolyl
moiety and η5-bonded to one indenyl group and the pyrrolyl
group from another ansa-bridged indenyl/pyrrolyl ligand. The
coordination geometry about each Ln2+ ion may be viewed as
a distorted triangle bipyramid, in which one σ-bonded nitrogen
atom and two donating O atoms of DME define the equatorial
plane, while the centroid of the η5-bonded cyclopentadienyl ring
in the indenyl group and that of the η5-bonded pyrrole ring of
the adjacent ligand occupying the axial positions. Obviously,
the bonding mode of the pyrrolyl ring in the present ligand is
similar to those in the ansa-dipyrrolyl lanthanide complexes,4
but is different from the observation in ansa-bridged cyclopen-
tadienyl/pyrrolyl titanium complexes, where the pyrrolyl group
is bound to metal only in a σ-mode through the nitrogen atom.13
Combustion analysis data of 4 and 5 were in good agreement
with the formulation as elucidated by the X-ray crystal structural
analysis.
Yb2+ ion are 2.861(17) and 2.841(13) Å, respectively. The
Yb-C bond distances of an allylic (C7, C8, and C9) fragment
range from 2.686(14) to 2.743(14) Å, with the central carbon
atom (C8) somewhat nearer to the metal than the terminal ones.
These results show that the tendency to slip toward η3- from
η5-mode for the indenyl group increases with “the contraction
effect of lanthanides”. The average Sm-O(DME) distance of
2.58(1) Å in 2 is similar to the corresponding value in meso-
O(CH2CH2C9H6)2Sm(DME), 2.576(5) Å.14 The Sm1-N1 dis-
tance (2.602(11) Å) in 2 is similar to that found in {[Et2C(R-
C4H3N)2]Sm}8(THF)4, 2.617(10) Å.4h All bond parameters for
3 are in normal ranges (Table 4). The bond distances involving
the metal in 3 are similar to the corresponding values in 2, if
the difference in metal radii is considered.15
Synthesis and Characterization of ansa-Bridged Indenyl/
Pyrrolyl Lanthanide(III) Chloride Complexes. Reaction of
SmCl3 with 1 equiv of (C9H6)CH2(R-C4H3N)Li2(THF)x in THF
formed the dimeric organolanthanide complex {(η5-C9H6)CH2-
[µ-η1:η5-(R-C4H3N)]Sm(µ-Cl)2Li(THF)2}2 (4) in 73% yield,
while treatment of ErCl3 with 1 equiv of (C9H6)CH2(R-C4H3N)-
Li2(THF)x under the same reaction conditions gave {(η5-C9H6)-
CH2[µ-η1:η3-(R-C4H3N)]Er(µ3-Cl)(µ-Cl)Li(THF)2}2 (5) in 56%
yield (Scheme 3). They remain air- and moisture-sensitive,
whether in the solid or solution phase. These complexes are
readily dissolved in THF, but nearly insoluble in benzene,
toluene, and hexane at room temperature. The molecular
structures of 4 and 5 were confirmed by X-ray analyses, as
shown in Figures 4 and 5. The paramagnetic erbium complex
5 does not offer useful NMR information. However, the
paramagnetic samarium complex 4 provides interpretable NMR
data.
The indenyl group in 2 shows η5-coordination to the
samarium atom with normal distances ranging from 2.816(12)
to 2.891(11) Å, and the average Sm-C(Ind) distance of 2.855-
(11) Å is similar to those found in meso-O(CH2CH2C9H6)2Sm-
(DME) (average 2.875 Å),14 while in 3 the indenyl group
exhibits a pronounced “slip-fold” distortion relative to a planar
η5-indenyl ligand, so that the Cp part of indenyl moiety tends
to be an η3 + η2 type ligand and bent over the C7 and C9 axis
by 10°; the distances of nodal carbon atoms C1 and C6 to the
(13) Seo, W. S.; Cho, Y. J.; Yoon, S. C.; Park, J. T.; Park, Y. J.
Organomet. Chem. 2001, 640, 79.
(14) Qian, C. T.; Zou G.; Jiang, W. H.; Chen, Y. F.; Sun J.; Li, N.
Organometallics 2004, 23, 4980.
(15) Shannon, R. D. Acta Crystallogr. Sect. A 1976, 38, 75.

Lanthanide Complexes with a Methylene-Bridged Ligand
Organometallics, Vol. 25, No. 21, 2006 5171
Scheme 4
Figure 5. ORTEP diagram of 5 with the probability ellipsoids
drawn at the 30% level. Hydrogen atoms are omitted for clarity.
In the solid, complex 4 is comprised of two samarium atoms
(Sm1‚‚‚Sm1A ) 4.422 Å) held together by two pyrrolyl rings
of different ligands. Each Sm3+ ion is σ-bonded to two bridging
Cl atoms and one N atom from the pyrrolyl ring and η5-bonded
to one five-membered ring of the indenyl group and one pyrrolyl
ring of the adjacent ansa-ligand, which in turn is also both
σ-bonded and π-bonded to the other Sm atom. The samarium
atoms adopt a distorted trigonal-bipyramidal conformation with
two chlorides and one nitrogen atom of the σ-bonded ring
occupying the equatorial positions and one π-bonded pyrrolyl
centroid and one π-bonded five-membered ring of the indenyl
group occupying the axial positions. Two lithium atoms are also
part of the structure. Each Li atom bonded to two THF
molecules [Li1-O1 ) 2.02(4) Å; Li1-O2 ) 1.87(4) Å] is
attached to two bridging chlorines to form a distorted-tetrahedral
geometry.
Figure 5 shows the structure of 5. In sharp contrast to 4, the
ansa-bridged indenyl/pyrrolyl ligand in 5 chelates the Er3+ ion
with one nitrogen atom and one η5-indenyl group and bridges
one Li+ ion in η3-fashion, forming a tetrametallic cluster
structure. Each Er3+ ion is η5-bound to one five-membered ring
of the indenyl group and σ-bound to one N atom of the pyrrolyl
ring, one doubly bridging Cl atom, and two triply bridging Cl
atoms and one O atom of THF in a distorted-octahedral
arrangement. The structure also incorporates two lithium atoms,
and each lithium atom is coordinated to η3-pyrrolyl, one doubly
bridging Cl atom, and one triply bridging Cl atom and one THF
O atom in a distorted-tetrahedral arrangement.
of erbium by pyrrolyl rings is accepted on account of favorable
packing of the cluster.
Reactivity of ansa-Bridged Indenyl/Pyrrolyl Lanthanide-
(III) Alkyl and Amido Complexes toward N,N-Dicyclohexyl-
carbodiimide. Recently, insertions of carbodiimides into the
lanthanide-ligand bonds have attracted considerable attention.18
Complexes 4 and 5 represent rare structurally characterized
examples of organolanthanide compounds bearing both a Ln-
pyrrolyl bond and a Ln-Cl bond, in which the chlorine atoms
can be expected to be replaced by other groups via salt
metathesis reactions.4a,c,19, To further study the effects of the
nature of co-ligands on the carbodiimide insertion reaction and
to examine whether the lanthanide-pyrrolyl bond was reactive
to unsaturated substrates, we synthesized in situ the alkyl
derivative [(C9H6)CH2(R-C4H3N)]Sm(nBu)(THF)x by the treat-
ment of 4 with 2 equiv of LinBu in THF and studied its reaction
with N,N′-dicyclohexylcarbodiimide, as shown in Scheme 4.
Like the corresponding nonbridged lanthanocene alkyl spe-
cies, [(C9H6)CH2(R-C4H3N)]Sm(nBu)(THF)x also exhibits high
reactivity toward unsaturated substrates. It reacts with 1 equiv
of N,N-dicyclohexylcarbodiimide in THF at -10 °C to give the
monoinsertion product (6). But attempts to further insert one
carbodiimide into the Ln-N(pyrrolyl) bond were unsuccessful
even when a large excess of N,N′-dicyclohexylcarbodiimide was
added with a higher reaction temperature and a prolonged
reaction time.
Although Er3+ ions did not π-bond to the pyrrolyl ring, two
lithium atoms are both π-bonded to the pyrrolyl ring and located
toward the exterior of the molecule 5, and one molecule of THF
and two bridging Cl anions complete the coordination sphere
of the each lithium atoms. These bond distances (Li1-N1A
2.153(14) Å; Li1-C14A 2.448(16) Å; Li1-C11A 2.686(16)
Å) are comparable with those in [Ph2C(R-C4H3N)2]2Li4(OEt2)3.16
The structural difference between 4 and 5 gives new insight
into the effect of the lanthanide contraction on the structure.17
It is interesting to note that 5 adopts a eight-coordinated cluster
structure as opposed to the nine-coordinated linear structure of
4. Obviously, it is possible that the steric factor favors the
observed cluster structure over a linear alternative, and the
increased steric effect resulting from the lanthanide contraction
would cause unfavorable contacts between the indenyl group
and the pyrrolyl ring. Therefore the observed low coordination
To obtain additional data on ansa-bridged indenyl/pyrrolyl
lanthanide systems, we then turned to the reactivity of the amide
derivative of 4. The metathesis reaction of 4 with 2 equiv of
NaN(SiMe3)2, followed by treating with N,N′-dicyclohexylcar-
bodiimide, allowed the isolation of the Ln-N bond insertion
product[(η5-C9H7)CH2[µ-η1:η5-(R-C4H3N)]Sm{CyNC[N(SiMe3)2]-
NCy}]2 (7) in 61% yield (Scheme 4).
(18) (a) Zhang, J.; Ruan, R. Y.; Shao, Z. H.; Cai, R. F.; Weng, L. H.;
Zhou, X. G. Organometallics 2002, 21, 1420. (b) Zhang, J.; Cai, R. F.;
Weng, L. H.; Zhou, X. G. J. Organomet. Chem. 2003, 672 (1-2), 94. (c)
Zhang J.; Cai R. F.; Weng L. H.; Zhou X. G. Organometallics 2003, 22,
5385. (d) Zhang, J.; Cai, R. F.; Weng, L. H.; Zhou, X. G. Organometallics
2004, 23, 3303. (e) Zhou, L. Y.; Yao, Y. M.; Zhang, Y, Sheng, H. T.; Xue,
M. Q.; Shen, Q. Appl. Organomet. Chem. 2005, 19, 398. (f) Zhou, L. Y.;
Yao, Y. M.; Zhang, Y.; Xue, M. Q.; Chen, J. L.; Shen, Q. Eur. J. Inorg.
Chem. 2004, 2167. (g) Zhang, W. X.; Nishiura, M. Hou, Z. M. Synlett
2006, 1213. (h) Zhang, W. X.; Nishiura, M.; Hou, Z. M. J. Am. Chem.
Soc. 2005, 127, 16788.
(19) (a) Dube´, T.; Freckmann, D.; Conoci, S.; Gambarotta, S.; Yap, G.
P. A. Organometallics 2000, 19, 209. (b) Dube´, T.; Gambarotta, S.; Yap,
G. P. A. Organometallics 2000, 19, 817. (c) Wang, J.; Dick, A. K. J.;
Gardiner, M. G.; Yates, B. F.; Peacock, E. J.; Skelton, B. W.; White, A. H.
Eur. J. Inorg. Chem. 2004, 10, 1992.
(16) Aharonian, G.; Gambarotta, S.; Yap, G. P. A. Organometallics 2002,
21, 4257.
(17) Study along this line is currently underway in our labs, and the
results will be published later.

5172 Organometallics, Vol. 25, No. 21, 2006
Pi et al.
Si)2NC(C6H11)2]2SmCH(SiMe3)2 (55.1(1)° and 55.6(1)°).21 The
bond angles around C(15) are consistent with sp2 hybridization.
The coordination number of the central Sm3+ is nine. The bond
lengths of Sm-N3 and Sm-N2 in the delocalized chelating
guanidinate ligand are 2.432(4) and 2.444(4) Å, respectively,
consistent with the values found in [(SiMe3)2NC(C6H11)2]2-
21
SmCH(SiMe3)2 and Sm[Ph2N(NCy)2]3.22 The orientation of
the N(SiMe3)2 groups relative to the NCNSm plane is ap-
proximately perpendicular, which is identical to the observations
in other guanidinate lanthanide complexes.23 This disposition
prevents p-overlapping between these two moieties; however,
it increases the steric bulk above and below the planar
guanidinate ligand. As a result, the N4-C15 distance of 1.456-
(7) Å is significantly longer than the values observed in (C5H5)2-
Ln[RNC(NHiPr)NiPr] (R ) tBu, Ln ) Yb, Er, Dy, Y; R ) Ph,
Ln ) Yb) (1.368(8)-1.378(8) Å).19d
Figure 6. ORTEP diagram of 6 with the probability ellipsoids
drawn at the 30% level. Hydrogen atoms are omitted for clarity.
Conclusions
A new methylene-bridged indenyl-pyrrolyl hybrid ligand was
designed and successfully prepared. Several di- and trivalent
organolanthanide complexes derived from this ligand were
synthesized and fully characterized. Furthermore, the reactions
of their trivalent alkyl and amide derivatives with carbodiimide
were also studied. These results show that this ligand possesses
not only the common features of both moieties but also versatile
coordination chemistry. From the data reported in this work, it
seems reasonable to conclude that the bonding mode adopted
by (C9H6)CH2(R-C4H3N) is likely directed by the nature of the
lanthanide metal and the alkali metal. For example, it can
coordinate in µ-η1:η5:η5 or µ-η1:η3:η5 fashion depending on the
nature of the lanthanide metals. Furthermore, these results
suggest that the present ligand in the bonding modes to metals
may be more versatile than the corresponding methylene-bridged
cyclopentadienyl-pyrrolyl hybrid ligand. For the latter, only
the chelating η1:η5-bonding mode is observed.
Figure 7. ORTEP diagram of 7 with the probability ellipsoids
drawn at the 30% level. Hydrogen atoms are omitted for clarity.
Both 6 and 7 were confirmed by spectroscopic data, elemental
analyses, and single-crystal X-ray analyses, which were in good
agreement with the proposed formula. The IR spectra of
compounds 6 and 7 show typical characteristic -N.C.N-
absorptions at 1649 and 1629 cm-1, respectively. Complexes 6
and 7 are soluble in polar organic solvents such as THF, ether,
and toluene but sparely soluble in n-hexane.
An X-ray diffraction study shows that complex 6 is a
centrosymmetric dimer (Figure 6). The structural data listed in
Table 7 indicate that the geometry of the [(C9H6)CH2(R-
C4H3N)]2Sm2 core in 6 is very close to that in 4 with normal
bond parameters. The C13-N1 and C13-N2 distances of the
amidinate group are approximately equivalent and significantly
shorter than the C-N single bond distances, indicating that the
π-electrons of the CdN double bond in the present structure
are delocalized over the N-C-N unit. Consistent with this,
the Sm-N1 and Sm-N2 distances, 2.391(9) and 2.438(9) Å,
are intermediate between the values observed for a Sm-N single
bond distance and a Sm-N donor bond distance.20
Acknowledgment. We thank the NNSF of China, NSF of
Shanghai, the Fund of the New Century Distinguished Scientist
of the Education Ministry of China, and the Research Fund for
the Doctoral Program of Higher Education of China for financial
support.
Supporting Information Available: Tables of atomic coordi-
nates and thermal parameters, all bond distances and angles, and
experimental data for all structurally characterized complexes. This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
Positive structural verification of 7 was also provided by a
single-crystal X-ray analysis (Figure 7). Complex 7 is similar
to complex 6, the main difference being the presence of a
N(SiMe3)2 substituent replacing the butyl. As expected, the
newly formed guanidinate ligand is bound to Sm through two
nitrogen atoms to yield a planar four-membered ring with a bite
angle of 54.4(2)°, which is comparable with those in [(Me3-
OM060610T
(21) Zhou, Y. L.; Yap, G. P. A.; Richeson, D. S. Organometallics 1998,
17, 4387.
(22) Zhou, L. Y.; Yao Y. M.; Zhang, Y.; Xue, M. Q.; Chen, J. L.; Shen,
Q. Eur. J. Inorg. Chem. 2004, 2167.
(23) (a) Lu, Z. P.; Yap, G. P. A.; Richeson, D. S. Organometallics 2001,
20, 706. (b) Giesbrecht, G. R.; Whitener, G. D.; Arnold, J. J. Chem. Soc.,
Dalton Trans. 2001, 923. (c) Luo, Y. J.; Yao, Y. M.; Shen, Q.; Yu, K. B.;
Weng, L. H. Eur. J. Inorg. Chem. 2003, 318.
(20) Wang, J.; Gardiner M. G. Chem. Commun. 2005, 1589. Evans, W.
J.; Forrestal, K. J.; Ziller, J. W. J. Am. Chem. Soc. 1998, 120, 9273. Obora,
Y.; Ohta, T.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 1997, 119, 3745.
Zhou, X. G.; Zhang, L. B.; Zhu, M.; Cai R. F.; Weng, L. H.; Huang, Z. X.;
Wu, Q. J. Organometallics 2001, 20, 5700.