Sidearm effects. Synthesis, structural characterization, and reactivity of rare earth complexes incorporating a linked carboranyl-indenyl ligand with a tethered oxygen atom

Article abstract of DOI:10.1021/om0498807

New ether-functionalized carboranyl-indenyl hybrid ligands were prepared. They can prevent lanthanocene chlorides from ligand redistribution reactions and offer samarium(II) complexes unusual reactivities. Treatment of Me ₂SiCl(C₉H₆CH₂CH₂OMe) with 1 equiv of Li₂C₂B₁₀H₁₀ in toluene/Et₂O afforded the monolithium salt [Me₂Si(C ₉H₅CH₂CH₂OMe)-(C₂B ₁₀H₁₁)]Li(OEt₂) (2). Interaction of 2 with 1 equiv of n-BuLi in Et₂O produced the dilithium salt [Me ₂Si(C₉H₅CH₂CH₂OMe)(C ₂B₁₀H₁₀)]Li₂(OEt₂) ₂ (3). Reaction of 3 with 1 equiv of LnCl₃ at room temperature gave the complex salts of general formula [{[η⁵: σ-Me₂Si(C₉H₅CH₂CH ₂-OMe)(C₂B₁₀H₁₀)]Ln(THF)(μ-Cl) ₃Ln[η⁵:η¹:σ-Me ₂Si(C₉H₅CH₂CH₂OMe)(C ₂B₁₀H₁₀)]}2{Li(THF)}]-[Li(THF)₄] (Ln = Y (4), Yb (5)). Upon heating, 5 was converted into [η⁵: η¹:σ-Me₂Si(C₉H₅-CH ₂CH₂OMe)(C₂B₁₀H₁₀)] Yb(THF)(μ-Cl)₂Yb[η⁵:η¹:σ- Me₂Si(C₉H₅CH₂CH₂OMe) (C₂B₁₀H₁₀)] (6) by eliminating LiCl. Treatment of 4 or 5 with 2 equiv of group 1 metal amides gave organo-rare-earth amide complexes [η⁵:η¹:σ-Me₂Si(C ₉H₅CH₂CH₂OMe)(C₂B ₁₀H₁₀)]Y(NHC₆H₃-2,5- ^tBu₂)-(μ-Cl)Li(THF)₃ (8) or [η⁵:η¹:σ-Me₂Si(C ₉H₅CH₂CH₂OMe)(C₂B ₁₀H₁₀)]Yb(NHC₆H₃-2,6- ⁱPr₂)(μ-Cl)Li(THF)₃ (9). An equimolar reaction of SmI₂ with 3 in THF generated, after addition of LiCl, [{[η⁵:σ-Me₂Si(C₉H₅CH ₂CH₂OMe)(C₂B₁₀H₁₀)] ₂Sm}{Li(THF)}]_n (10) and [{η⁵: η¹:σ⁶-Me₂-Si(C₉H ₅CH₂CH₂OMe)(C₂B₁₀H ₁₀)Sm}₂(μ-Cl)][Li(THF)₄] (11). In sharp contrast, a less reactive YbI₂ reacted with 3 in THF, producing only salt metathesis product [η⁵:η¹:σ-Me ₂Si(C₉H₅-CH₂CH₂OMe(C ₂B₁₀H₁₀)]Yb(DME)(THF) (12). 12 reacted with 1 equiv of 3 to give the ionic complex {[(μ-η⁵: η²):η¹:σ-Me₂Si(C ₉H₅CH₂CH₂OMe)(C₂B ₁₀H₁₀)]₂Yb}{Li(THF)₂}₂ (13). All complexes were characterized by various spectroscopic techniques and elemental analyses. The structures of 5, 6, and 8-13 were further confirmed by single-crystal X-ray analyses.

Full text of DOI:10.1021/om0498807

Organometallics 2004, 23, 2469-2478
2469
Sid ea r m Effects. Syn th esis, Str u ctu r a l Ch a r a cter iza tion ,
a n d Rea ctivity of Ra r e Ea r th Com p lexes In cor p or a tin g a
Lin k ed Ca r bor a n yl-In d en yl Liga n d w ith a Teth er ed
Oxygen Atom §
Shaowu Wang,†,‡ Hung-Wing Li,† and Zuowei Xie*,†
Department of Chemistry, The Chinese University of Hong Kong,
Shatin, New Territories, Hong Kong, China, and Institute of Organic Chemistry, School of
Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, China
Received February 15, 2004
New ether-functionalized carboranyl-indenyl hybrid ligands were prepared. They can
prevent lanthanocene chlorides from ligand redistribution reactions and offer samarium(II)
complexes unusual reactivities. Treatment of Me2SiCl(C9H6CH2CH2OMe) with 1 equiv of
Li2C2B10H10 in toluene/Et2O afforded the monolithium salt [Me2Si(C9H5CH2CH2OMe)-
(C2B10H11)]Li(OEt2) (2). Interaction of 2 with 1 equiv of n-BuLi in Et2O produced the dilithium
salt [Me2Si(C9H5CH2CH2OMe)(C2B10H10)]Li2(OEt2)2 (3). Reaction of 3 with 1 equiv of LnCl3
at room temperature gave the complex salts of general formula [{[η5:σ-Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)]Ln(THF)(µ-Cl)3Ln[η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]}2{Li(THF)}]-
[Li(THF)4] (Ln ) Y (4), Yb (5)). Upon heating, 5 was converted into [η5:η1:σ-Me2Si(C9H5-
CH2CH2OMe)(C2B10H10)]Yb(THF)(µ-Cl)2Yb[η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)] (6) by
eliminating LiCl. Treatment of 4 or 5 with 2 equiv of group 1 metal amides gave organo-
rare-earth amide complexes [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]Y(NHC6H3-2,5-tBu2)-
(µ-Cl)Li(THF)3 (8) or [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]Yb(NHC6H3-2,6-iPr2)(µ-
Cl)Li(THF)3 (9). An equimolar reaction of SmI2 with 3 in THF generated, after addition of
LiCl, [{[η5:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]2Sm}{Li(THF)}]n (10) and [{η5:η1:η6-Me2-
Si(C9H5CH2CH2OMe)(C2B10H10)Sm}2(µ-Cl)][Li(THF)4] (11). In sharp contrast, a less reactive
YbI2 reacted with 3 in THF, producing only salt metathesis product [η5:η1:σ-Me2Si(C9H5-
CH2CH2OMe)(C2B10H10)]Yb(DME)(THF) (12). 12 reacted with 1 equiv of 3 to give the ionic
complex {[(µ-η5:η2):η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]2Yb}{Li(THF)2}2 (13). All com-
plexes were characterized by various spectroscopic techniques and elemental analyses. The
structures of 5, 6, and 8-13 were further confirmed by single-crystal X-ray analyses.
In tr od u ction
systems would be expected. In contrast, for those
substrates with a higher Lewis base strength, the
functionalized sidearm just serves as a protecting unit
and does not block the metal center, and increased
activity would be anticipated.4
Cyclopentadienyl or indenyl ligands with Lewis base
functionalities have found many applications in rare
earth chemistry.1 The tethered donors can coordinate
to the lanthanides, satisfying the steric requirement so
as to prevent lanthanocenes from ligand redistribution
reactions.2 Thus a large variety of metallocene deriva-
tives of the lanthanides have been prepared in the past
decade or so.1-4 On the other hand, the donor function-
ality has a strong influence on the activity of organo-
lanthanide complexes.4,5 If the substrates cannot com-
pete with the donor group of the ligand for the vacant
coordination site on the metal center, a decreased
catalytic activity in comparison to unfunctionalized
(3) (a) Qian, C.; Zou, G.; Sun, J . J . Chem. Soc., Dalton Trans. 1998,
1607. (b) Qian, C.; Zou, G.; Sun, J . J . Chem. Soc., Dalton Trans. 1999,
519. (c) Qian, C.; Zou, G.; Nie, W.; Sun, J .; Lemenovskii, D. A.; Borzov,
M. V. Polyhedron 2000, 19, 1955. (d) Qian, C.; Zou, G.; Sun, J . J .
Organomet. Chem. 1998, 566, 21. (e) Hultzsch, K. C.; Spaniol, T. P.;
Okuda, J . Organometallics 1997, 16, 4845. (f) Schumann, H.; Erbstein,
F.; Hermann, K.; Demtschuk, J .; Weimann, R. J . Organomet. Chem.
1998, 562, 255. (g) Deng, D.; Qian, C.; Song, F.; Wang, Z.; Wu, G.;
Zheng, P.; J in, S.; Lin, Y. J . Organomet. Chem. 1993, 458, 83. (h) Qian,
C.; Zheng, X.; Wang, B.; Deng, D.; Sun, J . J . Organomet. Chem. 1994,
466, 101. (i) Deng, D.; Qian, C.; Wu, G.; Zheng, P. J . Chem. Soc., Chem.
Commun. 1990, 880. (j) Van den Hende, J . R.; Hitchcock, P. B.;
Lappert, M. F.; Nile, T. A. J . Organomet. Chem. 1994, 472, 79. (k)
Vandeweghe, P.; Bied, C.; Collins, J .; Marcalo, J .; Santos, I. J .
Organomet. Chem. 1994, 475, 121. (l) Trifonov, A.; Ferri, F.; Collins,
J . J . Organomet. Chem. 1999, 582, 211. (m) Molander, G. A.; Schu-
mann, H.; Rosenthal, E. C. E.; Demtschuk, J . Organometallics 1996,
15, 3817. (n) Schumann, H.; Rosenthal, E. C. E.; Demtschuk, J .
Organometallics 1998, 17, 5324. (o) Cheung, M.-S.; Chan, H.-S.; Xie,
Z. Organometallics 2004, 23, 517.
§ Dedicated to Prof. Changtao Qian on the occasion of his 70th
birthday.
* Corresponding author. Fax: (852)26035057. Tel: (852)26096344.
E-mail: zxie@cuhk.edu.hk.
† The Chinese University of Hong Kong.
‡ Anhui Normal University.
(1) For recent reviews, see: (a) Arndt, S.; Okuda, J . Chem. Rev.
2002, 102, 1953. (b) Okuda, J . J . Chem. Soc., Dalton Trans. 2003, 2367.
(2) For reviews, see: (a) Schumann, H.; Messe-Markscheffel, J . A.;
Esser, L. Chem. Rev. 1995, 95, 865. (b) Edelmann, F. T. In Compre-
hensive Organometallic Chemistry II; Abel, E. W., Stone, F. A. G.,
Wilkinson, G., Eds.; Pergamon: New York, 1995; Vol. 4, p 11.
(4) Roesky, P. W.; Stern, C. L.; Marks, T. J . Organometallics 1997,
16, 4705.
(5) Xie, Z.; Qian, C.; Huang, Y.-Z. J . Organomet. Chem. 1991, 412,
61.
10.1021/om0498807 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/15/2004

2470 Organometallics, Vol. 23, No. 10, 2004
Wang et al.
(CH3)2). 13C NMR (CDCl3): δ 145.17, 144.01, 141.19, 129.48,
126.21, 125.05, 124.07, 119.86, 46.44 (C9H6), 72.16, 59.21, 28.77
(CH2CH2OCH3), 0.58, 0.24 (Si(CH3)2). MS (EI): 266 (M+).
Our previous work shows that linked carboranyl-
indenyl ligands [Me2A(C9H6)(C2B10H10)]2- (A ) C,6 Si7)
cannot stabilize half-sandwich rare earth complexes of
the type [η5:σ-Me2A(C9H6)(C2B10H10)]LnCl.8 Equimolar
reactions between M2[Me2A(C9H6)(C2B10H10)] (M ) Li,
Na) and LnCl3 always resulted in the formation of full-
sandwich complexes [η5:σ-Me2A(C9H6)(C2B10H10)]2Ln-,
which were also formed from the reaction of M2[Me2A-
(C9H6)(C2B10H10)] with SmI2.6,7 However, when a func-
tionalized sidearm MeOCH2CH2 was tethered to this
linked ligand, the novel samaracarborane [{η5:η1:η6-Me2-
Si(C9H5CH2CH2OMe)(C2B10H10)Sm}2(µ-Cl)][Li(THF)4]
was isolated from an equimolar reaction of [Me2Si(C9H5-
CH2CH2OMe)(C2B10H10)]Li2(OEt2)2‚LiCl with SmI2, as
shown in our preliminary communication.9 This result
demonstrated that functionalized sidearms have sig-
nificant effects on the reactivity of lanthanide com-
plexes. In this contribution, we report a full account on
the synthesis, structural characterization, and reactivity
of rare earth complexes with the donor-functionalized
carboranyl-indenyl ligand [Me2Si(C9H5CH2CH2OMe)-
P r ep a r a tion of [Me2Si(C9H5CH2CH2OMe)(C2B10H11)]Li-
(OEt2) (2). A 1.60 M solution of n-BuLi in hexane (34.7 mL,
55.6 mmol) was added dropwise with stirring to a solution of
o-C2B10H12 (4.00 g, 27.8 mmol) in a dry toluene/diethyl ether
(2:1, 45 mL) mixture at 0 °C. The reaction mixture was
warmed to room temperature and stirred for 0.5 h. The
resulting solution was then cooled to 0 °C, and Me2SiCl(C9H6-
CH2CH2OMe) (1; 7.41 g, 27.8 mmol) in a toluene/diethyl ether
(2:1, 10 mL) mixture was slowly added. The mixture was
stirred at room temperature for 20 h. Removal of the solvents
afforded a sticky solid, which was extracted with diethyl ether
(20 mL × 2). The solutions were combined and concentrated
to give a pale yellow sticky solid. Recrystallization from diethyl
ether/hexane produced 2 as a pale yellow crystalline solid (11.2
g, 88%). 1H NMR (pyridine-d5): δ 8.06 (d, J ) 7.2 Hz, 1H),
7.92 (d, J ) 7.8 Hz, 1H), 7.26 (s, 1H), 7.11 (m, 2H) (C9H5),
3.96 (t, J ) 7.8 Hz, 2H), 3.64 (t, J ) 7.8 Hz, 2H), 3.32 (s, 3H)
(CH2CH2OCH3), 3.74 (br s, 1H) (cage CH), 3.36 (q, J ) 6.9 Hz,
4H), 1.12 (t, J ) 6.9 Hz, 6H) (O(CH2CH3)2), 0.80 (s, 6H) (Si-
(CH3)2). 13C NMR (pyridine-d5): δ 139.51, 135.00, 128.22,
120.22, 117.71, 114.94, 113.86, 109.56, 86.82 (C9H5), 76.21,
58.45, 30.33 (CH2CH2OCH3), 74.45, 64.88 (C2B10H11), 66.15,
15.88 (O(CH2CH3)2), 0.34 (Si(CH3)2). 11B NMR (pyridine-d5):
δ -2.24 (2), -5.98 (1), -7.40 (2), -11.61 (3), -12.58 (2). IR
(KBr, cm-1): νBH 2563 (vs). Anal. Calcd for C20H39B10LiO2Si:
C, 52.83; H, 8.65. Found: C, 52.53; H, 8.51.
(C2B10H10)]2-
.
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were preformed
under an atmosphere of dry dinitrogen with the rigid exclusion
of air and moisture using standard Schlenk or cannula
techniques, or in a glovebox. All organic solvents were freshly
distilled from sodium benzophenone ketyl immediately prior
P r ep a r a tion of [Me2Si(C9H5CH2CH2OMe)(C2B10H10)]-
Li2(OEt2)2 (3). To a suspension of [Me2Si(C9H6CH2CH2OMe)-
(C2B10H11)]Li(OEt2) (2; 10.50 g, 23.1 mmol) in a mixed solvent
of n-hexane/diethyl ether (2:1, 60 mL) was slowly added a 1.60
M solution of n-BuLi in hexane (14.5 mL, 23.2 mmol) at 0 °C.
The mixture was stirred at 0 °C for 6 h and at room
temperature overnight. The precipitate was collected and
washed with n-hexane (3 × 15 mL), affording 3 as a pale yellow
to use. SmI2(THF)x,10 C9H7CH2CH2OMe,11 and Li2C2B10H10
8
were prepared according to literature methods. All other
chemicals were purchased from Aldrich Chemical Co. and used
as received unless otherwise noted. Infrared spectra were
obtained from KBr pellets prepared in the glovebox on a
Perkin-Elmer 1600 Fourier transform spectrometer. 1H and
13C NMR spectra were recorded on
a Bruker DPX 300
1
solid (10.30 g, 84%). H NMR (pyridine-d5): δ 8.22 (d, J ) 7.5
spectrometer at 300.13 and 75.47 MHz, respectively. 11B NMR
spectra were recorded on a Varian Inova 400 spectrometer at
128.32 MHz. All chemical shifts are reported in δ units with
reference to the residual protons of the deuterated solvents
for proton and carbon chemical shifts and to external BF3‚
OEt2 (0.00 ppm) for boron chemical shifts. Elemental analyses
were performed by MEDAC Ltd., U.K.
Hz, 1H), 7.76 (d, J ) 7.5 Hz, 1H), 7.23 (s, 1H), 7.02 (m, 2H)
(C9H5), 3.64 (t, J ) 7.8 Hz, 2H), 3.31 (t, J ) 7.8 Hz, 2H), 3.28
(s, 3H) (CH2CH2OCH3), 3.36 (q, J ) 6.9 Hz, 8H), 1.12 (t, J )
6.9 Hz, 12H) (O(CH2CH3)2), 0.92 (s, 6H) (Si(CH3)2). 13C NMR
(pyridine-d5): δ 137.91, 133.55, 126.60, 122.31, 118.01, 115.44,
114.38, 109.18, 89.08 (C9H5), 75.12, 58.19, 29.54 (CH2CH2OCH3),
77.98, 63.88 (C2B10H11), 66.15, 15.88 (O(CH2CH3)2), 1.97 (Si-
(CH3)2). 11B NMR (pyridine-d5): δ -1.75 (1), -5.12 (3), -8.07
(1), -9.48 (2), -10.48 (3). IR (KBr, cm-1): νBH 2555 (vs). Anal.
Calcd for C24H48B10Li2O3Si: C, 53.91; H, 9.05. Found: C, 54.27;
H, 8.87.
P r ep a r a tion of Me2SiCl(C9H6CH2CH2OMe) (1). A 1.60
M solution of n-BuLi in hexane (36.0 mL, 57.6 mmol) was
slowly added to a solution of MeOCH2CH2C9H7 (10.0 g, 57.4
mmol) in Et2O (200 mL) at 0 °C. The mixture was warmed to
room temperature and stirred overnight. The resulting solution
was then cooled to 0 °C, and Me2SiCl2 (30.0 mL, 230 mmol)
was added in one portion. The reaction mixture was stirred
at room temperature for 20 h. After removal of the precipitate,
the solvent and excess Me2SiCl2 were pumped off to give 1 as
a yellowish oil (14.0 g, 91%), which was pure enough for the
P r ep a r a tion of [{[η5:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
-
H
10)]Y(TH F )(µ-Cl)3Y[η5:η1:σ-Me 2Si(C9H 5CH 2CH 2OMe )-
(C2B10H10)]}2{Li(THF )}][Li(THF )4] (4). To a suspension of
YCl3 (0.20 g, 1.0 mmol) in THF (20 mL) was slowly added a
THF (15 mL) solution of 3 (0.53 g, 1.0 mmol) at room
temperature, and the mixture was stirred for 6 h. Removal of
the solvent gave a sticky solid, to which was added 15 mL of
toluene. The mixture was heated at reflux temperature for 0.5
h. After removal of the white precipitate, the solvent was
pumped off again, affording a white solid. Recrystallization
from a mixed solvent of n-hexane/toluene (1:5) produced 4 as
1
next step of the reaction. H NMR (CDCl3): δ 7.60 (d, J ) 7.2
Hz, 1H), 7.49 (d, J ) 7.5 Hz, 1H), 7.35 (dd, J ) 7.5 and 7.5
Hz, 1H), 7.26 (dd, J ) 7.5 and 7.2 Hz, 1H), 6.42 (s, 1H), 3.69
(s, 1H) (C9H6), 3.72 (t, J ) 7.2 Hz, 2H), 3.41 (s, 3H), 2.96 (t, J
) 7.2 Hz, 2H) (CH2CH2OCH3), 0.24 (s, 3H), 0.21 (s, 3H) (Si-
1
colorless crystals (0.49 g, 76%). H NMR (pyridine-d5): δ 8.06
(6) Wang, S.; Yang, Q.; Mak, T. C. W.; Xie, Z. Organometallics 2000,
19, 334.
(d, J ) 7.8 Hz, 4H), 7.91 (d, J ) 7.5 Hz, 4H), 7.21 (br s, 4H),
7.10 (m, 8H) (C9H5), 3.97 (t, J ) 7.8 Hz, 8H), 3.60 (t, J ) 7.8
Hz, 8H), 3.31 (s, 12H) (CH2CH2OCH3), 3.63 (m, 24H), 1.60 (m,
24H) (THF), 0.80 (s, 24H) (Si(CH3)2). 13C NMR (pyridine-d5):
δ 139.48, 134.98, 126.10, 121.74, 120.21, 117.71, 114.94,
113.86, 109.58 (C9H5), 76.20, 58.95, 30.31 (CH2CH2OCH3),
86.81, 64.86 (C2B10H11), 68.18, 26.16 (O(CH2CH2)2), 0.34 (Si-
(CH3)2). 11B NMR (pyridine-d5): δ -6.54 (4), -8.92 (8), -13.28
(20), -17.05 (8). IR (KBr, cm-1): νBH 2567 (vs). Anal. Calcd
(7) (a) Xie, Z.; Wang, S.; Yang, Q.; Mak, T. C. W. Organometallics
1999, 18, 2420. (b) Wang, S.; Yang, Q.; Mak, T. C. W.; Xie, Z.
Organometallics 1999, 18, 4478. (c) Xie, Z.; Wang, S.; Yang, Q.; Mak,
T. C. W. Organometallics 1999, 18, 1578. (d) Wang, S.; Yang, Q.; Mak,
T. C. W.; Xie, Z. Organometallics 1999, 18, 5511.
(8) Xie, Z. Acc. Chem. Res. 2003, 36, 1.
(9) Wang, S.; Li, H.-W.; Xie, Z. Organometallics 2001, 20, 3624.
(10) Girard, P.; Namy, J . L.; Kagan, H. B. J . Am. Chem. Soc. 1980,
102, 2693.
(11) Qian, C.; Zou, G., Sun, J . J . Organomet. Chem. 1998, 566, 21.

Sidearm Effects
Organometallics, Vol. 23, No. 10, 2004 2471
for C92H168B40Cl6Li2O11Si4Y4: C, 42.87; H, 6.57. Found: C,
42.65; H, 6.49.
using the procedure identical to that reported for 8: yield 0.31
g (65%). 1H NMR (pyridine-d5): δ 3.62 (s), 1.59 (s) (THF), plus
many broad, unresolved resonances. 11B NMR (pyridine-d5):
δ -1.46 (2), -5.96 (1), -7.01 (1), -11.18 (6). IR (KBr, cm-1):
νBH 2577 (vs). Anal. Calcd for C32H54B10ClLiNO2SiYb (9 -
2THF): C, 45.95; H, 6.51; N, 1.68. Found: C, 45.96; H, 6.74;
N, 1.80.
P r ep a r a tion of [{[η5:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
-
H10)]Yb(THF)(µ-Cl)3Yb[η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10-
10)]}2{Li(THF )}][Li(THF )4]‚C6H 5CH 3 (5‚C6H 5CH 3). This
H
complex was prepared as dark red crystals from YbCl3 (0.28
g, 1.0 mmol) and 3 (0.53 g, 1.0 mmol) in THF (30 mL) using
the procedure identical to that reported for 4: yield 0.55 g
P r ep a r a tion of [{[η5:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
10)]2Sm }{Li(THF )}]n (10). To a THF solution of SmI2(THF)x
-
1
(73%). H NMR (pyridine-d5): δ 3.50 (s), 1.46 (s) (THF), plus
H
many broad, unresolved resonances. 11B NMR (pyridine-d5):
δ -0.94 (8), -6.17 (16), -9.76 (8), -11.50 (8). IR (KBr, cm-1):
νBH 2571 (vs). Anal. Calcd for C99H176B40Cl6Li2O11Si4Yb4: C,
39.56; H, 5.90. Found: C, 39.21; H, 5.98.
(5.0 mL, 0.50 mmol) was slowly added a THF solution of 3
(0.27 g, 0.50 mmol) at room temperature, and the reaction
mixture was stirred overnight. The color of the solution slowly
changed from dark blue to dark red. After removal of THF,
toluene (15 mL) was added to the resulting sticky solid, and
the mixture was refluxed for 3 h. The solvent was then
removed, and the resulting orange-red solid was extracted with
a mixed solvent of toluene and THF (10:1, 3 × 10 mL). The
solutions were combined and concentrated to about 15 mL.
10 was isolated as orange-red crystals after this solution stood
at room temperature for 5 days (95 mg, 39% based on 3). After
addition of dry LiCl (0.10 g, 2.3 mmol) to the mother liquor
and the suspension was stirred at room temperature overnight,
the precipitate was filtered off, giving a clear dark red solution.
Dark red crystals, identified as [{η5:η1:η6-Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)Sm}2(µ-Cl)][Li(THF)4] (11) by a single-crystal
X-ray analysis, were isolated after this solution stood at room
temperature for a week (40 mg, 12%). For 10: 1H NMR
(pyridine-d5): δ 14.36 (br s, 2H), 10.74 (d, J ) 9.0 Hz, 2H),
7.35 (t, J ) 9.0 Hz, 2H), 7.16 (d, J ) 9.0 Hz, 2H), 6.53 (t, J )
9.0 Hz, 2H) (C9H5), 3.63 (br s, 4H), 1.59 (br s, 4H) (THF), 4.83
(br s, 4H), 3.75 (br s, 4H), 3.40 (s, 6H) (CH2CH2OCH3), 0.94
(s, 12H) (Si(CH3)2). 13C NMR (pyridine-d5): δ 138.37, 136.18,
129.00, 126.10, 121.21, 120.23, 119.52, 116.22, 103.55 (C9H5),
85.07 (C2B10H11), 76.21, 58.75, 30.91 (CH2CH2OCH3), 68.17,
26.15 (THF), 2.60, 0.37 (Si(CH3)2). 11B NMR (pyridine-d5):
32.50 (4), -5.15 (16). IR (KBr, cm-1): νBH 2572 (vs). Anal. Calcd
for C54H88B20LiO4Si2Sm: C, 44.37; H, 6.62. Found: C, 44.15;
H, 6.38.
P r epar ation of [{η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
-
H
B
10)}Yb(THF)(µ-Cl)2Yb{η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2-
10H10)}]‚C6H5CH3 (6‚C6H5CH3). A toluene/THF (10:1, 10
mL) solution of 5 (0.27 g, 0.18 mmol) was heated at 80 °C for
1 h. After removal of the precipitate, the clear solution was
slowly cooled to room temperature to give 6‚C6H5CH3 as dark
red crystals (0.16 g, 67%). 1H NMR (pyridine-d5): many broad,
unresolved resonances. 11B NMR (pyridine-d5): δ -0.48 (2),
-3.64 (4), -8.96 (8), -11.02 (4), -13.95 (2). IR (KBr, cm-1):
νBH 2548 (vs). Anal. Calcd for C43H72B20Cl2O3Si2Yb2: C, 38.94;
H, 5.47. Found: C, 38.84; H, 5.57.
P r ep a r a tion of [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
10)]Sm (THF )(µ-Cl)2Sm [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)-
-
H
(C2B10H10)] (7). To a suspension of SmCl3 (0.13 g, 0.50 mmol)
in THF (10 mL) was slowly added a THF (10 mL) solution of
3 (0.27 g, 0.50 mmol) at room temperature, and the mixture
was stirred overnight. The color of the solution gradually
changed from pale yellow to orange-red with disappearance
of SmCl3. After removal of THF under vacuum, toluene (15
mL) was added to the resulting orange-red solid. The mixture
was heated at reflux temperature for 1 h. The precipitate (LiCl)
was filtered off, and the resulting solution was concentrated
to dryness, affording an orange-red solid. Recrystallization
from a mixed toluene/THF (10:1) solution gave 7 as orange-
red crystals (0.24 g, 81%). 1H NMR (pyridine-d5): many broad,
unresolved resonances. 11B NMR (pyridine-d5): δ -0.01 (4),
-4.44 (4), -8.02 (6), -9.82 (2), -14.08 (4). IR (Kbr, cm-1): νBH
2568 (vs). Anal. Calcd for C36H64B20Cl2O3Si2Sm2: C, 36.37; H,
5.43. Found: C, 36.32; H, 5.57.
P r epar ation of [{η5:η1:η6-Me2Si(C9H5CH2CH2OMe)(C2B10
10)Sm }2(µ-Cl)][Li(THF )4] (11). To a THF solution of SmI2-
-
H
(THF)x (10.0 mL, 1.0 mmol) was slowly added a THF (20 mL)
solution of 3 (0.53 g, 1.0 mmol) at room temperature, to which
was added LiCl (0.10 g, 2.3 mmol). The reaction mixture was
stirred at room temperature overnight. The color of the
solution changed from dark blue to dark red. Workup using
the procedure identical to that reported for 10 gave 11 as dark
P r ep a r a tion of [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
10)]Y(NHC6H3-2,5-tBu 2)(µ-Cl)Li(THF )3 (8). To a THF (15
-
H
mL) solution of 4 (0.35 g, 0.27 mmol) was slowly added a THF
(10 mL) solution of KNHC6H3-2,5-But (0.13 g, 0.54 mmol) at
2
1
red crystals (0.30 g, 43%). H NMR (pyridine-d5): δ 13.89 (br
room temperature, and the mixture was stirred overnight.
After removal of THF, toluene (17 mL) was added to the
resulting solid. The mixture was heated at reflux temperature
for 1 h. The precipitate was filtered off. The clear solution was
slowly cooled to room temperature, affording 8 as colorless
s, 1H), 10.48 (d, J ) 9.0 Hz, 1H), 9.82 (d, J ) 9.0 Hz, 1H),
6.93 (br s, 1H), 6.52 (m, 1H), 6.20 (m, 1H), 5.91 (m, 1H), 5.12
(br s, 1H), 4.40 (br s, 1H), 4.03 (br s, 1H) (C9H5), 3.86 (s, 6H),
3.36 (br s, 4H), 3.17 (br s, 4H) (CH2CH2OCH3), 3.65 (m, 16H),
1.59 (m, 16H) (THF), -0.28 (s, 6H), -0.51 (s, 6H) (Si(CH3)2).
13C NMR (pyridine-d5): δ 129.35, 128.60, 125.70, 122.69,
121.33, 120.84, 119.98, 119.32 (C9H5), 69.50, 58.67, 31.65
(CH2CH2OCH3), 88.43, 65.73 (C2B10H11), 67.79, 22.78 (THF),
0.24, 0.08 (Si(CH3)2). 11B NMR (pyridine-d5): δ -3.5 (4), -9.8-
(4), -14.5(8), -15.0(4). IR (KBr, cm-1): νBH 2538 (vs), 2450
(m). Anal. Calcd for C48H88B20ClLiO6Si2Sm2: C, 41.87; H, 6.44.
Found: C, 41.66; H, 6.57.
1
crystals (0.36 g, 72%). H NMR (pyridine-d5): δ 8.36 (d, J )
8.1 Hz, 1H), 7.45 (dd, J ) 6.9 and 7.2 Hz, 1H), 7.33 (br s, 1H),
7.31 (dd, J ) 7.2 and 6.9 Hz, 1H), 7.27 (d, J ) 7.8 Hz, 1H),
7.00 (d, J ) 8.1 Hz, 1H), 6.45 (br s, 1H), 6.21 (d, J ) 7.8 Hz,
1H) (C9H5 and C6H3), 4.25 (br s, 1H) (NH), 3.55 (t, J ) 7.8 Hz,
2H), 3.15 (s, 3H), 3.07 (t, J ) 7.8 Hz, 2H) (CH2CH2OCH3), 3.65
(m, 12H), 1.60 (m, 12H) (THF), 1.53 (br s, 9H), 1.18 (br s, 9H)
(t-C4H9), 0.80 (s, 3H), 0.78 (s, 3H) (Si(CH3)2). 13C NMR
(pyridine-d5): δ 157.64, 149.83, 135.47, 131.30, 130.65, 129.38,
129.13, 127.05, 123.38, 123.30, 122.70, 117.66, 116.43, 109.75,
104.23 (C9H5 and C6H3), 77.50, 59.87, 31.47 (CH2CH2OCH3),
82.47, 63.49 (C2B10H10), 69.31, 27.29 (THF), 35.62, 35.52, 33.18,
31.93 (t-C4H9), 1.69, 1.16 (Si(CH3)2). 11B NMR (pyridine-d5):
δ -5.05 (4), -10.61 (6). IR (KBr, cm-1): νBH 2568 (vs). Anal.
Calcd for C34H58B10ClLiNO2SiY (8 - 2THF): C, 52.33; H, 7.49;
N, 1.80. Found: C, 52.54; H, 7.61; N, 1.63.
This complex was also obtained in 47% yield via the
equimolar reaction of SmI2(THF)x with [Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)]Li2(OEt2)2‚LiCl prepared directly from 1 and
C2B10H10Li2 followed by treatment with 1 equiv of n-BuLi.9
P r ep a r a tion of [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
10)]Yb(DME)(THF ) (12). To a THF solution of YbI2(THF)x
-
H
(19.0 mL, 1.0 mmol) was slowly added a THF solution of 3
(0.53 g, 1.0 mmol) at room temperature. The color of the
solution immediately changed from yellow to orange-red. The
reaction mixture was then stirred at room temperature
overnight. After removal of THF, the resulting solid was
washed with hot toluene (3 × 5 mL) to remove LiI. The orange-
P r ep a r a tion of [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10
10)]Yb(NHC6H3-2,6-iP r 2)(µ-Cl)Li(THF )3 (9). This complex
-
H
was prepared as dark red crystals from 5 (0.36 g, 0.24 mmol)
and NaNHC6H3-2,6-iPr2 (0.094 g, 0.48 mmol) in THF (25 mL)

2472 Organometallics, Vol. 23, No. 10, 2004
Wang et al.
Ta ble 1. Cr ysta l Da ta a n d Su m m a r y of Da ta Collection a n d Refin em en t for 5, 6, 8, a n d 9
5‚toluene
6‚toluene
8
9
formula
cryst size (mm)
fw
C
99H176B40Cl6Li2O11Si4Yb4
C
43H72B20Cl2O3Si2Yb2
C
42H74B10ClLiNO4SiY
C40H70B10ClLiNO4SiYb
0.66 × 0.13 × 0.05
0.50 × 0.40 × 0.25
0.60 × 0.25 × 0.17
0.52 × 0.20 × 0.06
3005.9
1326.4
924.5
980.6
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
monoclinic
C2/c
33.129(1)
11.238(1)
45.825(2)
90
105.61(1)
90
16431.8(11)
4
triclinic
P1h
triclinic
P1h
monoclinic
P21/c
21.775(3)
12.155(2)
19.751(3)
90
100.72(1)
90
5136.4(13)
4
9.918(1)
14.955(1)
21.076(1)
69.87(1)
84.99(1)
78.39(1)
2874.5(3)
2
10.104(2)
12.881(3)
21.254(4)
90.99(3)
100.25(3)
104.97(3)
2623.8(9)
2
Z
D
calcd, Mg/m3
1.215
1.532
1.170
1.268
radiation (λ), Å
2θ range, deg
µ, mm-1
Mo KR (0.71073)
2.6 to 50.0
2.424
Mo KR (0.71073)
2.0 to 50.0
3.405
Mo KR (0.71073)
3.2 to 50.0
1.222
Mo KR (0.71073)
3.8 to 52.0
1.932
F(000)
6008
1312
976
2012
no. of obsd reflns
no. of params refnd
goodness of fit
R1
10 626
672
0.937
0.056
13 550
649
0.969
0.028
4340
555
1.212
0.115
10 075
543
0.875
0.039
wR2
0.147
0.069
0.276
0.089
red solid was then extracted with a mixed solvent of toluene
and DME (10:1, 3 × 10 mL). The solutions were combined and
concentrated to 15 mL, from which orange crystals were
obtained after this solution stood at room temperature for 5
tropically for all non-hydrogen atoms by full-matrix least-
squares calculations on F2 using the SHELXTL program
package.13 For noncentrosymmetric structures, the appropriate
enantiomorph was chosen by refining Flack’s parameter x
toward zero.14 Most of the carborane hydrogen atoms were
located from difference Fourier syntheses. All other hydrogen
atoms were geometrically fixed using the riding model. Crystal
data and details of data collection and structure refinements
are given in Tables 1 and 2, respectively. Selected bond lengths
and angles are compiled in Table 3. Further details are
included in the Supporting Information.
1
days (0.51 g, 72%). H NMR (pyridine-d5): δ 8.15 (d, J ) 8.1
Hz, 1H), 7.30 (d, J ) 8.1 Hz, 1H), 7.00 (m, 2H), 6.80 (dd, J )
8.1 Hz, 1H) (C9H5), 3.66 (m, 4H) (THF), 3.47 (s, 4H) (DME),
3.25 (br s, 9H) (DME + CH2CH2OCH3), 3.18 (m, 4H) (CH2CH2-
OCH3), 1.62 (m, 4H) (THF), 0.84 (s, 3H), 0.70 (s, 3H),
(Si(CH3)2). 13C NMR (pyridine-d5): δ 144.43, 131.77, 127.98,
121.57, 120.21, 119.78, 114.52, 111.56, 98.29 (C9H5), 76.82,
73.51, 60.10, 60.62, 29.95, 27.28 (CH2CH2OCH3, THF, DME),
82.27, 69.31 (C2B10H11), 2.14, 1.52 (Si(CH3)2). 11B NMR (pyri-
dine-d5): δ -3.60 (2), -10.13 (2), -14.22 (6). IR (KBr, cm-1):
νBH 2562 (vs). Anal. Calcd for C20H38B10O3SiYb (12 - THF):
C, 37.78; H, 6.03. Found: C, 37.66; H, 6.33.
Resu lts a n d Discu ssion
Liga n d . Reaction of Li[C9H6CH2CH2OMe] with ex-
cess Me2SiCl2 in Et2O gave Me2SiCl(C9H6CH2CH2OMe)
(1) in 91% yield. Treatment of 1 with 1 equiv of
Li2C2B10H10 in toluene/Et2O afforded the monolithium
salt [Me2Si(C9H5CH2CH2OMe)(C2B10H11)]Li(OEt2) (2) in
88% yield. Interaction of 2 with 1 equiv of n-BuLi in
Et2O produced the dilithium salt [Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)]Li2(OEt2)2 (3) in 84% yield. 3 is in-
soluble in ether, whereas 2 is soluble. Therefore, they
were easily separated. These transformations are out-
lined in Scheme 1.
P r epar ation of {[(µ-η5:η2):η1:σ-Me2Si(C9H5CH2CH2OMe)-
(C2B10H10)]2Yb}{Li(THF )2}2‚C7H8 (13‚C7H8). To a THF (16
mL) solution of 12 (0.35 g, 0.50 mmol) was slowly added a THF
solution of 3 (0.26 g, 0.50 mmol) at room temperature. The
color of the solution immediately changed from orange to red.
The reaction mixture was then stirred at room temperature
overnight. Workup using the procedure identical to that
1
reported for 12 gave 13‚C7H8 as red crystals (0.45 g, 69%). H
NMR (pyridine-d5): δ 8.23 (d, J ) 7.5 Hz, 2H), 8.14 (d, J )
7.5 Hz, 2H), 8.09 (dd, J ) 7.5 Hz, 2H), 7.94 (br s, 2H), 7.76
(dd, J ) 7.5 Hz, 2H), 7.16 (m, 2H), 7.05 (m, 3H) (C9H5 and
C6H5CH3), 3.97 (m, 4H), 3.35 (m, 4H), 3.27 (s, 6H) (CH2CH2-
OCH3), 2.20 (s, 3H) (C6H5CH3), 3.64 (m, 16H), 1.59 (m, 16H)
(THF), 0.94 (s, 6H), 0.66 (s, 6H) (Si(CH3)2). 13C NMR (pyridine-
d5): δ 133.54, 129.76, 128.24, 126.61, 123.16, 122.33, 120.24,
118.97, 117.73, 115.45, 114.95, 114.38, 110.45 (C9H5 and C6H5-
CH3), 75.61, 58.46, 29.56 (CH2CH2OCH3), 68.19, 26.16 (THF),
80.76, 67.07 (C2B10H11), 23.19 (C6H5CH3), 1.99, 0.44 (Si(CH3)2).
11B NMR (pyridine-d5): δ -3.38 (8), -8.86 (12). IR (KBr, cm-1):
νBH 2565 (vs). Anal. Calcd for C55H96B20Li2O6Si2Yb: C, 50.32;
H, 7.37. Found: C, 50.55; H, 7.15.
The 1H NMR spectra of both 2 and 3 exhibit the same
splitting pattern with slightly different chemical shifts
and support one Et2O molecule per carboranyl in 2 and
two Et2O molecules per carboranyl in 3, respectively.
In addition, the 1H NMR spectrum of 2 displays a broad
singlet at δ ) 3.74 ppm attributable to the cage CH
proton, supporting that 2 is a monolithium salt. The 13
C
NMR data are in line with the results from the corre-
1
sponding H NMR spectra. The 11B NMR spectra show
a 2:1:2:3:2 splitting pattern for 2 and a 1:3:1:2:3 splitting
pattern for 3, respectively.
Rea ction w ith Ln Cl3. Treatment of 3 with 1 equiv
of LnCl3 at room temperature gave the complex salts of
This complex was also obtained in 65% yield from the
reaction of YbI2(THF)x with 2 equiv of 3 in THF, followed by
the same procedures used above.
X-r a y Str u ctu r e Deter m in a tion . All single crystals were
immersed in Paraton-N oil and sealed under N2 in thin-walled
glass capillaries. Data were collected at 293 K on a Bruker
SMART 1000 CCD diffractometer using Mo KR radiation. An
empirical absorption correction was applied using the SADABS
program.12 All structures were solved by direct methods and
subsequent Fourier difference techniques and refined aniso-
(12) Sheldrick, G. M. SADABS: Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Germany,
1996.
(13) SHELXTL V 5.03 Program Package; Siemens Analytical X-ray
Instruments, Inc.: Madison, WI, 1995.
(14) Flack, H. D. Acta Crystallogr. 1983, A39, 876.

Sidearm Effects
Organometallics, Vol. 23, No. 10, 2004 2473
Ta ble 2. Cr ysta l Da ta a n d Su m m a r y of Da ta Collection a n d Refin em en t for 10-13
10
11
12
13‚toluene
formula
cryst size (mm)
fw
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C
36H64B20LiO3Si2Sm
C48H88B20ClLiO6 Si2Sm2
C
24H46B10O4SiYb
C55H96B20Li2O6Si2Yb
0.54 × 0.46 × 0.30
0.10 × 0.03 × 0.02
1376.7
monoclinic
P21/c
10.18(1)
21.06(4)
33.39(6)
90
93.04(14)
90
7148(19)
4
0.43 × 0.43 × 0.08
0.50 × 0.37 × 0.13
1312.6
orthorhombic
Pbcn
15.946(1)
19.129(1)
22.969(1)
90
974.5
707.8
orthorhombic
Pnc2
9.322(1)
13.569(1)
23.332(1)
90
monoclinic
P21
9.402(1)
17.047(1)
10.350(1)
90
99.62(1)
90
1635.5(1)
2
90
90
90
90
2951.1(2)
2
1.097
7006.3(4)
4
1.244
Z
D
calcd, Mg/m3
1.279
1.437
radiation (λ), Å
2θ range, deg
µ, mm-1
Mo KR (0.71073)
3.5 to 50.0
1.064
Mo KR (0.71073)
4.1 to 50.0
1.737
Mo KR (0.71073)
4.0 to 56.0
2.924
Mo KR (0.71073)
3.3 to 52.0
1.413
F(000)
994
2784
712
2712
no. of obsd reflns
no. of params refnd
goodness of fit
R1
3962
290
1.090
0.033
9156
637
0.807
0.088
7563
361
0.997
0.029
6892
390
0.997
0.031
wR2
0.097
0.181
0.058
0.073
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles (d eg)a
5
6
8
9
10
11
12
(Yb)
13
(Yb)
(Ln)
(Yb)
(Yb)
(Y)
(Yb)
(Sm)
(Sm)
av Ln-C(ring)
av Ln-C(cage)
av Ln-Cl
av Ln-O (sidearm)
av Ln-O (THF)
av C(ring)-Si-C(cage)
av Cent-Ln-C(cage)
2.688(12)
2.527(12)
2.692(3)
2.387(7)
2.323(8)
107.4(6)
103.3
2.641(3)
2.494(3)
2.664(1)
2.439(3)
2.342(3)
105.9(1)
103.7
2.684(12)
2.540(10)
2.625(3)
2.466(9)
2.660(3)
2.488(2)
2.558(1)
2.463(2)
2.779(7)
2.635(7)
2.75(2)
2.814(7)
2.638(5)
2.845(4)
2.654(4)
2.645(4)
2.49(2)
2.631(4)
2.432(4)
109.8(2)
102.5
108.7(5)
105.5
107.9(1)
105.3
109.1(3)
104.1
111.5(2)
104.1
a
Cent: the centroid of the five-membered ring of the indenyl group.
Sch em e 1
(C2B10H10)] (7), was also prepared from the reaction of
3 with 1 equiv of SmCl3 at room temperature, followed
by extraction with hot toluene. These transformations
are summarized in Scheme 2.
Complexes 5-7 are paramagnetic species and do not
offer useful 1H and 13C NMR information. For the
1
diamagnetic yttrium complex 4, the H NMR spectrum
exhibits only one set of ligand proton signals, suggesting
a fluxional process may be present in the solution,
namely, the tethered sidearm can reversibly coordinate
to the central metal ion. As expected, both 3 and 4 show
very similar splitting patterns for the ligand protons.
The 13C NMR data are consistent with the 1H NMR
results. The 11B NMR spectrum of 4 displays a 1:2:2
splitting pattern, which is different from that of 3.
The molecular structure of 5, an analogue of 4, was
confirmed by single-crystal X-ray analyses. It consists
of well-separated, alternating layers of the discrete
tetrahedral cations [Li(THF)4]+ and the complex anions
[{[η5: σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]Yb(THF)(µ-
Cl)3Yb[η5:η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]}2-
{Li(THF)}]- and shows one toluene of solvation in the
crystal lattice. In the anion, the disordered Li(2) atom
links to two dimeric units of {[η5:σ-Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)]Yb(THF)(µ-Cl)3Yb[η5:η1:σ-Me2Si(C9H5-
CH2CH2OMe)(C2B10H10)]}- via the oxygen atom of one
of the sidearms from each unit, as shown in Figure 1.
Each Yb atom in the dimeric unit is η5-bound to one
five-membered ring of the indenyl group and σ-bound
to one cage carbon atom, three doubly bridging Cl
atoms, and one oxygen atom from either THF or the
sidearm in a distorted-octahedral coordination environ-
general formula [{[η5: σ-Me2Si(C9H5CH2CH2OMe)(C2B10-
H10)]-Ln(THF)(µ-Cl)3Ln[η5: η1:σ-Me2Si(C9H5CH2CH2OMe)-
(C2B10H10)]}2{Li(THF)}][Li(THF)4] (Ln ) Y (4), Yb (5))
in good yields. The coordinated LiCl was able to be
removed upon heating in toluene solution. For instance,
5 was converted into [η5: η1:σ-Me2Si(C9H5CH2CH2OMe)-
(C2B10H10)]Yb(THF)(µ-Cl)2Yb[η5: η1:σ-Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)] (6) by heating its toluene/THF
(10:1) solution at 80 °C for 1 h. The samarium analogue
of 6, [η5: η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]Sm-
(TH F )(µ-Cl)2Sm [η5:η1:σ-Me2Si(C9H 5CH 2CH 2OMe)-

2474 Organometallics, Vol. 23, No. 10, 2004
Wang et al.
Sch em e 2
ment (Figure 2). The other sidearm in the dimeric unit
does not coordinate to the Yb atom probably because of
steric reasons.
Figure 3 shows the dimeric structure of 6, which is a
neutral species generated by elimination of LiCl from
5. Unlike the structure of 5, both sidearm oxygen atoms
coordinate to the Yb atoms. In addition, each Yb atom
is also bound to either one THF or a B-H bond, leading
to an asymmetric structure. As expected, the average
Yb-Cl(µ2-Cl) distance of 2.664(1) Å in 6 is shorter than
the average Yb-Cl(µ3-Cl) distance of 2.692(3) Å in 5 and
is identical with the Yb-Cl(µ2-Cl) distance of 2.666(1)
Å found in [{η5: σ-Me2Si(C5Me4)(C2B10H10)}YbCl(µ-Cl)]2-
[Li(DME)3]2.15 The average Yb-C(ring) and Yb-C(cage)
distances in both 5 and 6 (Table 3) are comparable to
those observed in this family of complexes.2,8 The
average Yb-O(sidearm) distances are 2.387(7) in 5 and
2.439(3) Å in 6, respectively, which compare to the
2.468(9) Å in (η5:η1-C5H4CH2CH2OMe)2YbCl16 and the
2.450(12) Å in (η5:η1-C5H4CH2CH2OMe)2YbI.3g
F igu r e 1. Molecular structure of the anion [{[η5:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]Yb(THF)(µ-Cl)3Yb[η5:η1:σ-Me2Si-
(C9H5CH2CH2OMe)(C2B10H10)]}2{Li(THF)}]- in 5. Note that the Li2 atom is disordered over two sets of positions with
0.5:0.5 occupancies.

Sidearm Effects
Organometallics, Vol. 23, No. 10, 2004 2475
F igu r e 4. Molecular structure of [η5:η1:σ-Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)]Y(NHC6H3-2,5-tBu2)(µ-Cl)Li(THF)3 (8).
Selected bond distances (Å) and angles (deg): Y1-C1 )
2.540(10), Y1-N1 ) 2.222(9), Y1-Cl1 ) 2.625(3), Y1-O1
) 2.466(9), av Y1-C(ring) ) 2.684(12), Cent-Y1-C1 )
105.5.
F igu r e 2. Coordinating sphere around the Yb atoms in
5. Selected bond distances (Å) and angles (deg): Yb1-C1
) 2.519(12), Yb1′-C1′ ) 2.535(11), Yb1-Cl1 ) 2.704(3),
Yb1-Cl2 ) 2.700(3), Yb1-Cl3 ) 2.624(3), Yb1-O1 )
2.387(7), Yb1′-Cl1 ) 2.656(3), Yb1′-Cl2 ) 2.683(3), Yb1′-
Cl3 ) 2.787(3), Yb1′-O2 ) 2.323(8), av Yb1-C(ring) )
2.666(12), av Yb1′-C(ring) ) 2.689(12), Cent-Yb1-C1 )
103.1, Cent′-Yb1′-C1′ ) 103.5.
ligands18 cannot stabilize lanthanocene chlorides, and
only [{η5:σ-L(C9H6)(C2B10H10)}2Ln]- type of complexes
i
(L ) Me2C, Me2Si, Pr2NB) were isolated, regardless of
the molar ratios of the reactants and the sizes of the
lanthanides. Present examples indicate that modifica-
tion of these ligands with a Lewis-base-functionalized
sidearm leads to a new version of this type of ligands
which can efficiently stabilize lanthanocene chlorides.
Such sidearm effects were previously observed mainly
in early lanthanocene chloride complexes.2 The chlorine
atoms in these complexes are expected to be replaced
by other groups via salt metathesis reactions.
Treatment of 4 or 5 with 2 equiv of group 1 metal
amides gave organo-rare-earth amide complexes [η5:η1:
σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]Y(NHC6H3-2,5-
tBu2)(µ-Cl)Li(THF)3 (8) or [η5:η1:σ-Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)]Yb(NHC6H3-2,6-iPr2)(µ-Cl)Li(THF)3 (9)
in good yields, shown in Scheme 2. It is noted that
reactions of 4 with alkylating reagents such as CH3Li,
Me3SiCH2M (M ) Li, K), and Me3SiCH2MgCl were
complicated and no pure products were isolated. Unlike
complex 5, the coordinated LiCl cannot be removed by
recrystallization from hot toluene, suggesting very high
electron deficiency of the central metal ions.
The 1H NMR spectrum of the diamagnetic yttrium
complex 8 shows the presence of the hybrid ligand, the
2,5-tBu2C6H3NH unit, and THF in a molar ratio of 1:1:
3. The 11B NMR spectrum exhibits a 2:3 splitting
pattern, which is different from those of 3 and 4. These
data indicate that the splitting patterns of the 11B NMR
spectra of this type of complexes are very sensitive to
the coordination environments of central metal ions and
are hardly predictable.
F igu r e 3. Molecular structure of [η5:η1:σ-Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)]Yb(THF)(µ-Cl)2Yb[η5:η1:σ-Me2Si(C9H5-
CH2CH2OMe)(C2B10H10)] (6). Selected bond distances (Å)
and angles (deg): Yb1-C1 ) 2.460(3), Yb1-O1 ) 2.369-
(3), Yb1-Cl1 ) 2.642(1), Yb1-Cl2 ) 2.654(1), Yb1-H4′ )
2.62, av Yb1-C(ring) ) 2.627(3), Yb2-C1′ ) 2.528(3),
Yb2-O2 ) 2.509(2), Yb2-O3 ) 2.342(3), Yb2-Cl1 ) 2.692-
(1), Yb2-Cl2 ) 2.669(1), av Yb2-C(ring) ) 2.655(3), Yb1-
Cl1-Yb2 ) 103.39(3), Yb1-Cl2-Yb2 ) 103.67(3), Cent-
Yb1-C1 ) 104.1, Cent′-Yb2-C1′ ) 103.3.
Complexes 5, 6, [{η5:σ-Me2Si(C5Me4)(C2B10H10)}-
LnCl(µ-Cl)]2[Li(DME)3]2 (Ln ) Sm, Y, Yb),15 and
[{[η5:σ-iPr2NP(C9H6)(C2B10H10)]LnCl}2(µ-Cl)3Li(DME)]-
[Li(DME)3]2 (Ln ) Er, Y)17 represent new structure
types of contrained-geometry organo-rare-earth com-
plexes.1 The bridging atom, substituent on the cyclic
five-membered ring, and reaction condition have influ-
ences on the structures of the resulting metal complexes.
Our previous work shows that [Me2A(C9H6)(C2-
B10H10)]2- (A ) C, Si)7 and [iPr2NB(C9H6)(C2B10H10)]2-
Single-crystal X-ray analyses confirm the molecular
structures of both 8 and 9, shown in Figures 4 and 5,
respectively. Both exhibit a distorted-trigonal-bipyra-
midal arrangement of ligands with the cage carbon atom
and the tethered oxygen atom occupying the axial
positions. The average Yb-C(ring), Yb-C(cage), and
(15) Zi, G.; Yang, Q.; Mak, T. C. W.; Xie, Z. Organometallics 2001,
20, 2359.
(16) Qian, C.; Wang, B.; Deng, D.; Hu, J .; Chen, J .; Wu, G.; Zheng,
P. Inorg. Chem. 1994, 33, 3382.
(17) Wang, H.; Wang, H.; Li, H.-W.; Xie, Z. Organometallics 2004,
23, 875.
(18) Zi, G.; Li, H.-W.; Xie, Z. Organometallics 2002, 21, 1136.

2476 Organometallics, Vol. 23, No. 10, 2004
Wang et al.
Sch em e 3
Yb-O distances in 9 are comparable to those in 5 and
6 (Table 3). The Ln-Cl distances of 2.558(1) Å in 9 and
2.625(3) Å in 8 are close to the Er-Cl(µ) distance of
2.563(4) Å observed in [{η5:η6-Me2Si(C9H6)(C2B10H11)}-
Both 10 and 11 are the trivalent samarium complexes
as confirmed by single-crystal X-ray diffraction studies.
Complex 10 is a coordination polymer with Li(THF) as
a linkage connecting two [{η5:σ-Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)}2Sm]- fragments together via the teth-
ered oxygen atoms, shown in Figure 6. The coordination
geometry of this fragment (shown in Figure 7) is very
close to that of [{η5:σ-Me2Si(C9H6)(C2B10H10)}2Sm]-.7a
Slightly longer Sm-C(ring) and Sm-C(cage) distances
are observed in 10 in comparison with literature data
because of steric reasons.
Complex 11 consists of well-separated, alternating
layers of discrete tetrahedral cations [Li(THF)4]+ and
complex anions [{η5:η1:η6-Me2Si(C9H5CH2CH2OMe)-
(C2B10H10)Sm}2(µ-Cl)]-. In the anion, each Sm3+ ion is
η6-bound to the nido-C2B10H10 unit via a six-membered
C2B4 bonding face, η5-bound to the five-membered ring
of the indenyl group, and coordinated to a doubly
bridging Cl atom and one O atom from the appended
ether group of indenyl in a highly distorted-tetrahedral
geometry with the formal coordination number of eight
(Figure 8). The two nido-C2B10H10 units are connected
to each other through a C-C single bond at a distance
of 1.53(3) Å, and the dihedral angle between two six-
membered C2B4 rings is 69.6°. This complex represents
19
Er(THF)(µ-Cl)Na(THF)2]n and the Yb-Cl(µ) distance
20
of 2.552(2) Å found in [(Me3Si)2N]3Yb(µ-Cl)Li(THF)3
if the differences in Shannon’s ionic radii are taken into
account.21 The Yb-N distance of 2.157(2) Å com-
pares to the corresponding values of 2.188(5) Å in
{(iPr2C6H3N)(iPr2C6H3NH)Yb(µ-NC6H3 Pr2)}2{[Li(THF)]-
i
22
[Na(THF)}2 and 2.211(5) Å in [(Me3Si)2N]3Yb(µ-Cl)-
Li(THF)3.20 The Y-N distance of 2.222(9) Å falls in the
range 2.211-2.382 Å normally observed in organo-
yttrium amide complexes.3e
Rea ction w ith Ln I2. Treatment of SmI2 with 1 equiv
of 3 in THF at room temperature gave, after extraction
with hot toluene, [{[η5:σ-Me2Si(C9H5CH2CH2OMe)-
(C2B10H10)]2Sm}{Li(THF)}]n (10) as orange-red crystals
in 39% yield (based on 3). Addition of LiCl to the mother
liquor led to the isolation of [{η5:η1:η6-Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)Sm}2(µ-Cl)][Li(THF)4] (11) as dark
red crystals in 12% yield (based on 3). 11 was originally
isolated from an equimolar reaction of [Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)]Li2(OEt2)2‚LiCl with SmI2 in THF.9
These transformations are outlined in Scheme 3.
a very rare example of metallacarboranes bearing a
4-
(nido-RC2B10H10 2
)
tetraanion ligand.23
The average Sm-C(ring) and Sm-cage atom dis-
tances of 2.75(2) and 2.84(3) Å in 11 are very close to
the corresponding values of 2.751(4) and 2.823(4) Å
observed in [η5:η6-Me2Si(C9H6)(C2B10H11)]Sm(THF)2,7a
respectively. The average Sm-Cl(µ) distance of 2.645-
(4) Å in 11 is much shorter than the corresponding
values of 2.76(1) Å in [{(η5-C5Me5)2SmCl}2(µ-Cl)]- and
(19) Wang, S.; Wang, Y.; Cheung, M.-S.; Chan, H.-S.; Xie, Z.
Tetrahedron Sym.-in-Print 2003, 59, 10373.
(20) Sheng, E.; Wang, S.; Yang, G.; Zhou, S.; Cheng, L.; Zhang, K.;
Huang, Z. Organometallics 2003, 22, 684.
(21) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(22) Chan, H.-S.; Li, H.-W.; Xie, Z. Chem. Commun. 2002, 652.
(23) For reviews, see: (a) Xie, Z. Coord. Chem. Rev. 2002, 231, 23.
(b) Grimes, R. N. Coord. Chem. Rev. 2000, 200/ 202, 773. (c) Saxena,
A. K.; Maguire, J . A.; Hosmane, N. S. Chem. Rev. 1997, 97, 2421. (d)
Grimes, R. N. In Comprehensive Organometallic Chemistry II; Abel,
E. W., Stone, F. A. G., Wilkinson, G., Eds.; Pergamon: Oxford, 1995;
Vol. 1, p 371. (e) Saxena, A. K.; Hosmane, N. S. Chem. Rev. 1993, 93,
1081. (f) Grimes, R. N. Chem. Rev. 1992, 92, 251.
F igu r e 5. Molecular structure of [η5: η1:σ-Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)]Yb(NHC6H3-2,6-iPr2)(µ-Cl)Li(THF)3 (9).
Selected bond distances (Å) and angles (deg): Yb1-C1 )
2.488(2), Yb1-N1 ) 2.157(2), Yb1-Cl1 ) 2.558(1), Yb1-
O1 ) 2.463(2), av Yb1-C(ring) ) 2.660(3), Cent-Yb1-C1
) 105.3.

Sidearm Effects
Organometallics, Vol. 23, No. 10, 2004 2477
F igu r e 8. Molecular structure of the anion [{η5:η1:η6-Me2-
Si(C9H5CH2CH2OMe)(C2B10H10)Sm}2(µ-Cl)]- in 11. Se-
lected bond distances (Å) and angles (deg): C2-C2′ )
1.53(3), Sm1-Cl1 ) 2.643(4), Sm1′-Cl1 ) 2.647(5), Sm1-
O1 ) 2.49(2), Sm1′-O1′ ) 2.48(2), av Sm1-C(ring) ) 2.77-
(2), av Sm1-cage atom ) 2.82(2), av Sm1′-C(ring) )
2.74(2), av Sm1′-cage atom ) 2.84(2), Sm1-Cl1-Sm1′ )
107.4(2).
of the Sm-cage carbon and the cage C-C bonds;
coupling of the two cages via the formation of a C-C
single bond generates the nido-species (nido-RC2-
B10H10)2
4-, which bonds to the Sm3+ ions in a η6-fashion
to form complex 11. Addition of LiCl leads to the
substitution of an iodo with a chloro atom, facilitating
the crystallization of the product.
F igu r e 6. Perspective view of [{[η5:σ-Me2Si(C9H5CH2CH2-
OMe)(C2B10H10)]2Sm}{Li(THF)}]n (10) revealing a portion
of the infinite polymeric chain.
To get some insight into the reaction intermediates,
SmI2 was replaced by a less reactive YbI2. An equimolar
reaction of YbI2 with 3 in THF produced, after recrys-
tallization from a THF/DME solution, the divalent
ytterbium complex [η5:η1:σ-Me2Si(C9H5CH2CH2OMe)-
(C2B10H10)]Yb(DME)(THF) (12) in 72% yield. Treatment
of 12 with 1 equiv of 3 gave the ionic complex {[(µ-η5:
η2):η1:σ-Me2Si(C9H5CH2CH2OMe)(C2B10H10)]2Yb}{Li-
(THF)2}2 (13) in 69% yield. Complex 13 was also directly
prepared from the reaction of YbI2 with 2 equiv of 3 in
THF. These reactions are summarized in Scheme 4.
The isolation of 12 supports the above proposed
intermediate in the reaction of SmI2 with 3. In sharp
contrast to the SmI2 case, only the salt metathesis
product was isolated and no redox reactions were
detected in the case of YbI2, which offers useful infor-
mation of the reaction pathways.
1
The H NMR spectra show the presence of the hybrid
F igu r e 7. Coordinating sphere around the Sm atom in
10. Selected bond distances (Å) and angles (deg): Sm1-
C1 ) 2.635(7), av Sm1-C(ring) ) 2.779(7), Cent-Sm1-
C1 ) 104.1, Cent-Sm1-Cent ) 129.6.
ligand, THF, and DME in a molar ratio of 1:1:1 for 12
and support the molar ratio of two THF molecules per
hybrid ligand in 13, respectively. The splitting patterns
of the 11B NMR spectra are 1:1:3 in 12 and 2:3 in 13,
respectively. Their solid-state IR spectra display a
characteristic B-H absorption of a closo-carborane at
2.88(2) Å in [(η5-C5Me5)2Sm(µ-Cl)]3,24 implying that
steric repulsion plays an important role.
about 2562 cm-1
.
The formation of complexes 10 and 11 results from
the electron transfer from samarium(II) to the cage. It
may be suggested that the reaction of SmI2(THF)x with
3 gives the first intermediate [η5:η1:σ-Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)]SmII,7a followed by intermolecular
electron transfer and then ligand redistribution to afford
10. Either intermolecular or intramolecular electron
transfer from the SmII to the cage leads to the cleavage
The molecular structure of 12 is shown in Figure 9.
The Yb atom is η5-bound to the five-membered ring of
the indenyl group, σ-bound to the carborane cage carbon
atom, and coordinated to four oxygen atoms from the
sidearm, one DME, and one THF molecule, respectively,
in a distorted-octahedral geometry with a formal coor-
dination number of 8, which is similar to the eight-
coordinate [η5:σ-Me2C(C9H6)(C2B10H10)]Yb(DME)26 and
[η5:σ-iPr2NP(C9H6)(C2B10H10)]Yb(DME)2.17 The average
Yb-C(ring) distance of 2.814(7) Å, the average Yb-O
(24) Evans, W. J .; Drummond, D. K.; Grate, J . W.; Zhang, H.;
Atwood, J . L. J . Am. Chem. Soc. 1987, 109, 3928.

2478 Organometallics, Vol. 23, No. 10, 2004
Wang et al.
Sch em e 4
F igu r e 10. Molecular structure of {[(µ-η5:η2):η1:σ-Me2Si-
(C9H5CH2CH2OMe)(C2B10H10)]2Yb}{Li(THF)2}2 (13). Se-
lected bond distances (Å) and angles (deg): Yb1-C1 )
2.654(4), av Yb1-C(ring) ) 2.845(4), Li1-C12 ) 2.365(9),
Li1-C13 ) 2.611(9), Cent-Yb1-C1 ) 104.1, Cent-Yb1-
Cent ) 126.1.
distance of 2.529(4) Å, and the Yb-C(cage) distance of
2.638(5) Å are all longer than the corresponding values
of 2.790(8), 2.494(6), and 2.587(7) Å in [η5:σ-iPr2NP-
(C9H6)(C2B10H10)]Yb(DME)2 and 2.789(8), 2.445(5), and
2.561(6) Å observed in [η5:σ-Me2C(C9H6)(C2B10H10)]Yb-
(DME)2, probably because of steric reasons.
The Li-C distances are 2.365(9) and 2.611(9) Å, sug-
gesting a slip distortion from η2 to η1. These measured
values compare to the 2.332(8) Å in [{[(µ-η5):σ-Me2Si-
(C5Me4)(C2B10H10)]Li(THF)}2Li][Li(THF)4]15 and 2.318-
(4) Å in [(η5-C5H5)2Li][Ph4P].25
The solid-state structure of 13 was confirmed by
single-crystal X-ray analysis, shown in Figure 10. The
asymmetric unit contains one toluene of solvation. The
Yb atom is η5-bound to each of two five-membered rings
of the indenyl groups and σ-bound to each of two
carborane cage carbon atoms in a distorted-tetrahedral
geometry, which is similar to that of 10. The charge is
then compensated by two Li+ ions. Each Li atom is
asymmetrically η2-bound to the five-membered ring and
coordinated to three oxygen atoms from the sidearm and
two THF molecules, respectively. As expected, both Yb-
C(ring) and Yb-C(cage) distances in 13 are slightly
longer than the corresponding values observed in 12.
Con clu sion
The ether substituent on the five-membered ring of
the indenyl unit in linked carboranyl-indenyl hybrid
ligands has significant effects on the stability and
reactivity of the resulting organo-rare-earth complexes
via temporarily and reversibly coordinating to the metal
ion. For example, [Me2Si(C9H5CH2CH2OMe)(C2B10H10)]2-
can prevent lanthanocene chlorides from ligand redis-
tribution reactions by satisfying the steric requirements,
which offers opportunities for further studies on this
class of organolanthanide complexes.1,2 This ether-
functionalized ligand can offer divalent samarium com-
plexes unusual reactivities, resulting in the formation
of unexpected reduction/coupling products.
Ack n ow led gm en t. The work described in this paper
was supported by a grant from the Research Grants
Council of the Hong Kong Special Administration
Region (Project No. CUHK4026/02P). Z.X. acknowledges
the Croucher Foundation for a Senior Research Fellow-
ship Award. S.W. thanks the Excellent Young Scholars
Foundation of Anhui Province and the Postdoctoral
Fellowship of the Chinese University of Hong Kong.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data and data collection details, atomic coordinates, bond
distances and angles, anisotropic thermal parameters, and
hydrogen atom coordinates for complexes 5, 6, and 8-13. This
material is available free of charge via the Internet at
http:/pubs.acs.org.
F igu r e 9. Molecular structure of [η5:η1:σ-Me2Si(C9H5CH2-
CH2OMe)(C2B10H10)]Yb(DME)(THF) (12). Selected bond
distances (Å) and angles (deg): Yb1-C1 ) 2.638(5), Yb1-
O1 ) 2.631(4), Yb1-O2 ) 2.432(4), Yb1-O3 ) 2.546(4),
Yb1-O4 ) 2.506(3), av Yb1-C(ring) ) 2.814(7), Cent-
Yb1-C1 ) 102.5.
OM0498807
(25) Harder, S.; Prosenc, M. H. Angew. Chem., Int. Ed. Engl. 1994,
33, 1744.