Synthesis and crystal structure of bis(2-dimethylaminoethylindenyl) divalent organolanthanides (Ln=Sm, Yb)

Article abstract of DOI:10.1016/S0022-328X(99)00189-8

First examples of racemic bis(2-dimethylaminoethylindenyl) divalent unsolvated organolanthanide complexes (Me₂NCH₂CH₂C₉H₆) ₂Sm (1) and (Me₂NCH₂CH₂C₉H₆) ₂Yb (2) have been synthesized by the reaction of (Me₂NCH₂CH₂C₉H₆)K with LnI₂ (Ln=Sm, Yb). The two compounds have been characterized by elemental analysis and ¹H-NMR spectrometry. The X-ray crystal structure of 2 has been determined by diffraction study. The crystals are prismatic, space group P2₁/a (≠14), with a=17.342(6) A, b=8.542(7) A, c=17.353(2) A, β=118.70°, V=2254(1) A³, Z=4, D=1.607 g cm^-3.

Full text of DOI:10.1016/S0022-328X(99)00189-8

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Journal of Organometallic Chemistry 585 (1999) 59–62
Synthesis and crystal structure of bis(2-dimethylaminoethylindenyl)
divalent organolanthanides (Ln=Sm, Yb)
Changtao Qian *, Hengfeng Li, Jie Sun, Wanli Nie
Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu,
Shanghai 200032, PR China
Received 19 September 1998; received in revised form 30 March 1999
Abstract
First examples of racemic bis(2-dimethylaminoethylindenyl) divalent unsolvated organolanthanide complexes
(Me2NCH2CH2C9H6)2Sm (1) and (Me2NCH2CH2C9H6)2Yb (2) have been synthesized by the reaction of (Me2NCH2CH2C9H6)K
1
with LnI2 (Ln=Sm, Yb). The two compounds have been characterized by elemental analysis and H-NMR spectrometry. The
X-ray crystal structure of 2 has been determined by diffraction study. The crystals are prismatic, space group P21/a ("14), with
3
a=17.342(6) A, b=8.542(7) A, c=17.353(2) A, i=118.70°, V=2254(1) A , Z=4, D=1.607 g cm−3. © 1999 Elsevier Science
S.A. All rights reserved.
,
,
,
,
Keywords: 2-Dimethylaminoethylindenyl; Organolanthanide; NMR
We started to prepare chiral samarium(II), and ytterbi-
um(II) complexes involving a new donor-functionalized
indenyl ligand and present X-ray structure determina-
tions of representative complexes. Herein, we report the
synthesis of bis(2-Dimethylaminoethylindenyl) divalent
lanthanide complexes (Me2NCH2CH2C9H6)2Ln (Ln=
Sm(1), Yb(2)) and the X-ray structure of (Me2NCH2-
CH2C9H6)2Yb.
1. Introduction:
Over the past several years, cyclopentadienyl ligands
bearing a donor-functionalized side chain have at-
tracted much attention in lanthanide [1] and alkaline-
earth [2] chemistry, because the donating ability of the
terminal functional group in the side chain can stabilize
p-complexes by additional intramolecular coordination
and sidearm participation may play an important role
in catalytic processes. Consequently, the ether- or
amine-substituted cyclopentadienyl ligands have been
used to stabilize bis(cyclopentadienyl) lanthanide com-
plexes [3,4]. A series of lanthanide complexes contain-
ing ether- or amine-substituted cyclopentadienyl ligands
has been prepared by Qian et al. In order to seek better
catalysts for the organic reactions and olefin polymer-
ization, we designed the dimethylaminoethyl indene as
a ligand and found it very useful for coordination to
lanthanide ions; we hope to reveal possible application
of these complexes in stereospecific catalytic reactions.
2. Results and discussion
2.1. Synthesis of metallocenes 1 and 2
(2-Dimethylaminoethyl)indene was synthesized by
the reaction of indenyl lithium and 2-dimethyl-
aminoethylchloride, as shown in Scheme 1. In the sub-
stitution, it may produce two isomers 3 and 3%, but no
isomer 3% was detected by 1H-NMR spectrometry.
Compound (2-dimethylaminoethyl)indene (3) was de-
protonated with potassium hydride to afford the in-
denyl anions (4). Reaction of the indenyl potassium
salts with samarium(II) and ytterbium(II) diiodide in
THF at room temperature (r.t.), cleanly gave the sol-
* Corresponding author. Fax: +86-21-64166128.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00189-8

60
C. Qian et al. / Journal of Organometallic Chemistry 585 (1999) 59–62
Scheme 1.
Scheme 2.
vent-free metallocenes 1 and 2, as shown in Scheme 2.
Crystallization from toluene afforded the complexes in
20–21% isolated yields. The red Sm and Yb com-
pounds are air- and moisture-sensitive and soluble in
polar solvents like THF, and aromatic solvents such as
toluene. The complexes were characterized by elemental
analyses and mass spectrometry. From the thermody-
namics, complexes 1, 2 have the most favorable
configuration, as shown in Fig. 1. By X-ray crystallog-
raphy, we found they are rac-isomer in solid state.
Fig. 1.
2.2. Molecular structure of (Me2NCH2CH2C9H6)2Yb
(2)
A crystal suitable for X-ray diffraction analysis was
obtained by recrystallization from toluene. The struc-
ture of one of the four identical well-separated
molecules in the unit cell of complex 2 is shown in Fig.
2. The crystallographic data are given in Table 1, and
selected structural data are given in Table 2. Nitrogen
atoms of both dimethylaminoethyl group are in-
tramolecularly coordinated to the Yb atom to form an
intramolecular coordination bond. Only one possible
diastereomeric conformation with trans arrangement of
both indenyl rings and coordinated sidearms (Fig. 2) is
present. The compound is unsolvated 8-coordinate
monomeric complex in solid state. Overall, the struc-
ture of 2 closely resembles the distorted-tetrahedral
coordination geometry of [Yb{h5:h1-(Me2NCH2-
CH2C9H6)2}] with N–Yb–N%=103.6°. Two indenyl
groups are bonded to central metal in h5 fashion.
The dihedral angle of the two indenyl rings is
,
47.73°. The Yb–N distances, at 2.58 and 2.608 A, are
very close to those reported for [Yb{(s)-h5:h1-
Fig. 2. ORTEP plot of the molecular structure and numbering scheme
of 2.
C5H4CH2CH(Me)NMe2}2] [4].

C. Qian et al. / Journal of Organometallic Chemistry 585 (1999) 59–62
61
Table 1
out under an inert atmosphere of nitrogen or argon using
standard Schlenk techniques in dry, oxygen-free solvents.
All solvents were distilled under argon from sodium-ben-
zophenone prior to use. LnI2 [5] (Ln=Sm, Yb), and
Me2NCH2CH2Cl [6] were prepared according to pub-
lished procedures. n-Butyllithium and indene were pur-
chased from Aldrich. All chemical shifts are reported in
ppm relative to the residues of the deuteriated solvents.
Mass spectra were recorded on a HP 5989A spectrometer
(50–400°C, 1.3 kV) and 1H-NMR spectra were obtained
on Am-300 (300 MHz) spectrometers. Elemental analysis
wereperformedbytheAnalyticalLaboratoryofShanghai
Institute of Organic Chemistry.
Crystal data and structure refinement for 2
Compound
(Me2NCH2CH2C9H6)2
Yb
Empirical formula
Formula weight
Crystal color
C26H32N2Yb
545.59
Red
0.20×0.20×0.30
17.342(6)
8.452(7)
17.353(2)
118.70(3)
4
2254(1)
1.607
1088.00
41.61
3610
3461
Crystal dimensions (mm)
,
a (A)
,
b (A)
,
c (A)
i (°)
Z value
3
,
V (A )
Dc (g cm−3
F(000)
)
4.2. Preparation of (2-dimethylaminoethyl)indene
v(Mo–Ka) (cm−1
)
n
To a solution of indene (18 ml), THF (150 ml) BuLi
Reflections collected
Independent reflections
Observed data
Parameters
Goodness-of-fit
R, wR
(1.0 M in hexane, 18 ml) was added dropwise with
rigorous stirring at 0°C, the mixture was stirred for 3 h
at r.t. until no gas was given off, then added slowly to
Me2NCH2CH2Cl (22 ml) at 0°C. The resulting yellow
mixture was stirred overnight, allowed to warm to r.t.,
then quenched with water. The organic phase was
separated and the aqueous phase extracted with diethyl
ether (2×100 ml). The combined organic solution was
dried over anhydrous MgSO4 overnight. The solvent was
removedinvacuoandtheresiduewasfractionallydistilled
under reduced pressure to provide 13.13 g (39%) of 3 as
a light yellow liquid. B.p. 75–80°C/20 Pa. 1H-NMR
(CDCl3, 300 MHz):7.45–7.21 (m, 4H), 6.27 (s, 1H), 3.29
(s, 2H), 2.74 (m, 2H), 2,56 (m, 2H), 2.24 (s, 6H). EI mass
spectrum(70 eV), m/z: 187 (2.28 M+) 141 (5.53) 58
(100.00).
2243
262
1.94
0.046, 0.051
Table 2
a
,
Selected bond lengths (A) and bond angles (°) for complex 2
Yb–N(1)
Yb–N(2)
Yb–C(3)
Yb–C(9)
Yb–C(11)
Yb–C(17)
Yb–C(19)
Yb–C(4)
Yb–C(10)
Yb–C(24)
Yb–C(16)
Yb–C(18)
2.58(1)
2.608(10)
2.69(1)
2.77(1)
2.70(1)
2.61(1)
2.78(1)
2.745(9)
2.76(1)
2.79(1)
2.70(1)
2.66(1)
N(1)–Yb–N(2)
N(1)–Yb–C(4)
N(1)–Yb–C(10)
N(1)–Yb–C(11)
N(1)–Yb–C(3)
N(1)–Yb–C(9)
N(2)–Yb–C(16)
N(2)–Yb–C(18)
N(2)–Yb–C(17)
N(2)–Yb–C(24)
N(2)–Yb–C(19)
C(3)–Yb–C(9)
103.6(3)
85.0(3)
117.4(4)
89.8(4)
69.5(4)
114.3(3)
67.8(4)
115.2(4)
85.0(5)
87.5(4)
116.2(4)
48.9(4)
4.3. Preparation of (Me2NCH2CH2C9H6)K
a Dihedal angle of indene planes: 47.73°.
A solution of compound 3 (6.372 g, 0.036 mol in 30
ml THF) was added dropwise to a stirred suspension of
potassium hydride (1.455 g, 0.036 mol) in 70 ml THF at
0°C. The resulting mixture was stirred overnight and
warmed to r.t. After centrifugation, a clear red solution
was obtained. The solvent was removed under vacuum
and the residue washed with hexane (2×30 ml). After
drying under vacuum, the compound 4 was obtained as
yellow solids. Yields: 47%. 1H-NMR (THF-d8, 300 MHz):
7.21–7.17 (m, 2H); 6.37–6.34 (m, 2H); 6.25 (m, 1H); 5.73
(m, 1H); 2.92 (m, 2H); 2.51 (m, 2H); 2.05 (s, 6H).
3. Conclusions
We have prepared two novel chiral metallocenes of
divalent lanthanides samarium(II) and ytterbium(II) in-
volving a new donor functionalized indenyl ligands. The
intramolecular coordination of the donor arm with trans
orientation of both indene rings and sidearms has been
confirmed by X-ray structural analyses carried out for
complex 2. We shall continue to examine these complexes
with respect to their potential use in catalytic reactions.
Supplementary information is available from the authors.
4.4. Preparation of (Me2NCH2CH2C9H6)2Sm (1)
To a solution of (Me2NCH2CH2C9H6)K (1.493 g, 6.6
mmol) in THF (40 ml) was added dropwise SmI2 (0.1 M
THF solution, 30 ml) with rigorous stirring, then warmed
to r.t., and stirred for 48 h. The precipitate was separated
and the clear solution concentrated until a solid appeared.
The product was washed with cool THF (10 ml) and dried
4. Experimental
4.1. General procedures
All operations involving organometallics were carried

62
C. Qian et al. / Journal of Organometallic Chemistry 585 (1999) 59–62
in vacuo at r.t. affording 0.7 g of a red solid, yield: 20%
Anal. Found: C. 59.51; H, 6.04; N.5.37; Sm, 26.68%.
C26H32N2Sm; Calc.: C, 59.71; H, 6.17; N, 5.36; Sm,
28.76%. MS, m/z: 268 (4.74) 141 (29.53) 129 (100.00)
115 (79.98) 44 (94.34).
atoms were refined anisotropically by full-matrix least
squares. All hydrogen atoms were included in calcu-
lated position. All calculations were performed using
the TEXSAN crystallographic software package. Final R
and wR values were 0.046 and 0.051 for 3610 observed
reflections.
4.5. Preparation of (Me2NCH2CH2C9H6)2Yb (2)
A
procedure similar to that for compound
Acknowledgements
(Me2NCH2CH2C9H6)2Sm was adopted using YbI2 (0.06
M THF solution, 48 ml) and afforded 0.7 g of a red
solid, yield: 21%. Anal. Found: C, 56.99; H, 5.82; N,
5.01; Yb, 32.05%. C26H32N2Yb; Calc.: C, 57.23; H,
5.91; N, 5.14; Yb, 31.72%. MS, m/z: 253 (3.38) 141
(10.64) 91 (15.09) 58 (100.00) 44 (63.61). 1H-NMR
(THF-d8, 300 MHz): 7.41–7.32 (m, 4H); 6.82 (m, 4H);
6.12 (m, 2H); 5.38 (m, 2H); 2.92 (m, 4H); 2.71 (m, 4H);
2.10 (s, 12H).
We are grateful to the National Science Foundation
of China for financial support.
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4.6. Crystallography
A suitable crystal with 0.20×0.20×0.30 mm3 di-
mensions was sealed in thin-walled glass capillaries
under argon. Crystal data and details of data collection
and structure refinement are given in Tables 1 and 2,
respectively. Data were collected on a Rigaku AFC7R
diffractomer with graphite-monochromated Mo–Ka ra-
,
dition u=0.71069 A using the ꢀ–2q technique at 20°C.
[5] P.L. Watson, T.H. Tulip, I. Williams, Organometallics 9 (1990)
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[6] H. Gurien, J. Org. Chem. 28 (1963) 878.
[7] TEXSAN, Crystal Structure Analysis package, Molecular Structure
Corporation, Houston, TX, 1985 and 1992.
A total of 3461 unique reflection was collected. The
data were corrected for Lorentz polarization effects;
The structure were solved by direct methods and ex-
panded using Fourier techniques [7]. The non-hydrogen
.
.