Organometallic compounds of the lanthanides. 141. Synthesis, molecular structure, and solution behavior of some lanthanum(III) and ytterbium(II) complexes containing new tridentate 1,2-and 1,3-bis(2-dimethylamino)ethyl)cyclopentadienyl ligands

Article abstract of DOI:10.1021/om000409x

K[C₅H₄(CH₂CH₂NMe₂)] reacts with 2-dimethylamino)ethyl chloride in THF, forming an inseparable 1.5:1 mixture of isomeric 1,2- and 1,3-disubstituted bis(dimethylamino)ethyl)-cyclopentadiene, which on deprotonation with KH gives a mixture of the corresponding potassium salts K[1,2-C₅H₃(CH₂CH₂NMe₂)₂] (K[1,2-Do₂C₅H₃]; 1) and K[1,3-C₅H₃(CH₂CH₂-NMe₂)₂] (K[1,3-Do₂C₅H₃]; 2). Addition of LaI₃(THF)₃ to the mixture of 1 and 2 suspended in THF causes the formation of the half-sandwich complexes (η⁵:η¹:η¹-C₅H₃(CH₂CH₂ NMe₂)₂-1,2)LaI₂(THF) (3) and (η⁵:η¹:η¹-C₅H₃(CH₂CH₂ NMe₂)₂-1,3)LaI₂(THF) (4), which can successfully be separated because of their different crystal shapes. The analogous reaction with YbI₂(THF)₂ causes the precipitation of crystalline (η⁵:η¹:η¹-C₅H₃ (CH₂CH₂NMe₂)₂-1,2)YbI(THF)₂ (5). The noncrystallizing 1,3-isomer left in solution reacts with (C₅Me₅)Na, forming the polymeric mixed-metallocene ate complex {Na[μ₂-(η⁵:η¹:η¹-C₅ H₃(CH₂CH₂NMe₂)₂-1,3)(η⁵-C₅-Me₅) Yb(μ₂-I) Yb[μ₂-(η⁵:η¹:η¹-C₅ H₃(CH₂CH₂NMe₂)₂-1,3)(η⁵-C₅ Me₅}_n (6). The reaction of 5 with (C₅Me₅)K or (C₅H₄^tBu)Na results in the formation of the sandwich complexes (η⁵:η¹:η¹-C₅H₃(CH₂CH₂ NMe₂)₂-1,2)Yb(η⁵-C₅H₄^tBu) (7) and (η⁵:η¹:η¹-C₅H₃(CH₂CH₂ NMe₂)₂-1,2)Yb(η⁵-C₅Me₅), (8), respectively. The novel compounds have been characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. Additionally, X-ray structural analyses of 3-8 were performed.

Full text of DOI:10.1021/om000409x

4066
Organometallics 2000, 19, 4066-4076
Or ga n om eta llic Com p ou n d s of th e La n th a n id es. 141.1
Syn th esis, Molecu la r Str u ctu r e, a n d Solu tion Beh a vior of
Som e La n th a n u m (III) a n d Ytter biu m (II) Com p lexes
Con ta in in g New Tr id en ta te 1,2- a n d
1,3-Bis(2-(d im eth yla m in o)eth yl)cyclop en ta d ien yl
Liga n d s†
Igor L. Fedushkin
G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences,
Tropinina 49, 603600 Nizhny Novgorod GSP-445, Russian Federation
Sebastian Dechert and Herbert Schumann*
Institut fu¨r Anorganische und Analytische Chemie der Technischen Universita¨t Berlin,
Strasse des 17. J uni 135, D-10623 Berlin, Germany
Received May 15, 2000
K[C5H4(CH2CH2NMe2)] reacts with 2-(dimethylamino)ethyl chloride in THF, forming an
inseparable 1.5:1 mixture of isomeric 1,2- and 1,3-disubstituted bis((dimethylamino)ethyl)-
cyclopentadiene, which on deprotonation with KH gives a mixture of the corresponding
potassium salts K[1,2-C5H3(CH2CH2NMe2)2] (K[1,2-Do2C5H3]; 1) and K[1,3-C5H3(CH2CH2-
NMe2)2] (K[1,3-Do2C5H3]; 2). Addition of LaI3(THF)3 to the mixture of 1 and 2 suspended in
THF causes the formation of the half-sandwich complexes (η5:η1:η1-C5H3(CH2CH2NMe2)2-
1,2)LaI2(THF) (3) and (η5:η1:η1-C5H3(CH2CH2NMe2)2-1,3)LaI2(THF) (4), which can successfully
be separated because of their different crystal shapes. The analogous reaction with YbI2-
(THF)2 causes the precipitation of crystalline (η5:η1:η1-C5H3(CH2CH2NMe2)2-1,2)YbI(THF)2
(5). The noncrystallizing 1,3-isomer left in solution reacts with (C5Me5)Na, forming the
polymeric mixed-metallocene ate complex {Na[µ2-(η5:η1:η1-C5H3(CH2CH2NMe2)2-1,3)(η5-C5-
Me5)Yb(µ2-I)Yb[µ2-(η5:η1:η1-C5H3(CH2CH2NMe2)2-1,3)(η5-C5Me5)}n (6). The reaction of 5 with
t
(C5Me5)K or (C5H4 Bu)Na results in the formation of the sandwich complexes (η5:η1:η1-
t
C5H3(CH2CH2NMe2)2-1,2)Yb(η5-C5H4 Bu) (7) and (η5:η1:η1-C5H3(CH2CH2NMe2)2-1,2)Yb(η5-C5-
Me5) (8), respectively. The novel compounds have been characterized by elemental analysis,
NMR spectroscopy, and mass spectrometry. Additionally, X-ray structural analyses of 3-8
were performed.
In tr od u ction
oxidation in air compared to their nonfunctionalized
analogues. The synthesis of the first bis-functionalized
cyclopentadienyl ligand, 1,3-C5H3(SiMe2CH2PiPr2)2, and
of its zirconium complexes has been reported by Fryzuk
et al.3 Rhodium complexes containing both 1,2- and 1,3-
bis(phosphinopropyl)cyclopentadienyl ligands were re-
ported by Nelson et al.,4 and the rhodium complex [{1,3-
C5Me3[CH2C6F4P(C6F5)CH2]2}RhCl]BF4 was described
by Saunders et al.5 The only example of a complex with
a bis-oxygen-functionalized cyclopentadienyl ligand is
the zirconium complex [1,2-C5H3(CH2CH2OMe)2]ZrCl3.6
Scandium complexes with cyclopentadienyl ligands
incorporating both an amido and an amine function
have been synthesized by Piers et al.7
Metal complexes with donor-functionalized cyclopen-
tadienyl ligands have been studied intensively during
the past decade because of their potential application
as catalysts in polymerization processes.2 Recently we
reported on the synthesis and characterization of a
number of complexes of trivalent and divalent lan-
thanides with mono-N- and mono-O-functionalized cy-
clopentadienyl ligands.2p,t,u The additional intramolec-
ular coordination of the Lewis base function of the
cyclopentadienyl substituent to the metal center reduces
or even prevents the coordination of solvent molecules.
In general, such intramolecularly stabilized cyclopen-
tadienyl complexes are less sensitive to hydrolysis and
Since so far no bis-amino-functionalized cyclopenta-
dienyls have been used in complexation reactions and
lanthanide complexes of cyclopentadienyl systems con-
taining two donor-functionalized side chains are not
known at all, we started to prepare such a ligand system
in order to study its coordination behavior toward
lanthanum(III) and ytterbium(II) iodide, expecting in-
* To whom correspondence should be addressed. E-mail:
schumann@chem.tu-berlin.de.
† Dedicated to Professor Max Schmidt on the occasion of his 75th
birthday.
(1) Organometallic Compounds of the Lanthanides. Part 140: Tri-
fonov, A. A.; Kirillov, E. N.; Bochkarev, M. N.; Schumann, H.; Mu¨hle,
S. Izv. Akad. Nauk Ser. Khim. 1999, 384; Russ. Chem. Bull. (Engl.
Transl.) 1999, 48, 382.
10.1021/om000409x CCC: $19.00 © 2000 American Chemical Society
Publication on Web 08/31/2000

Organometallic Compounds of the Lanthanides
Ta ble 1. 1H a n d 13C{1H} NMR Da ta for 1-4
1H NMR
assignt
Organometallics, Vol. 19, No. 20, 2000 4067
13C{1H} NMR
solvent
δ (ppm)
J (Hz)
δ (ppm)
assignt
1
2
3
THF-d8
5.14 (d, 2H), 5.08 (t, 1H)
2.49-2.44 (m, 4H)
2.33-2.27 (m, 4H)
2.08 (s, 12H)
1,2-Do2CpH
NCH2CH2
NCH2CH2
(CH3)2N
3J (H,H) 2.2
118.2
103.7
102.2
64.1
45.6
29.5
CpCCH2
CpCH
Cp(CH)2
NCH2
(CH3)2NCH2
NCH2CH2
THF-d8
5.27 (t, 1H), 5.19 (d, 2H)
2.49-2.44 (m, 4H)
2.33-2.27 (m, 4H)
2.09 (s, 12H)
1,3-Do2CpH
NCH2CH2
NCH2CH2
(CH3)2N
4J (H,H) 3.0
115.4
104.0
102.8
63.5
45.8
27.3
CpCCH2
Cp(CH)2
CpCH
NCH2
(CH3)2NCH2
NCH2CH2
pyridine-d5
6.59 (d, 2H), 6.43(t, 1H)
3.64 (m, 4H)
3.27-2.93 (m, 2H)
2.99-2.85 (m, 2H)
2.81-2.61 (m, 4H)
2.44 (s, 12H)
1,2-Do2CpH
OCH2CH2
NCHHCH2
NCHHCH2
NCH2CH2
(CH3)2N
3J (H,H) 3.0
128.9
116.0
114.3
67.5, 25.5
63.5
CpCCH2
Cp(CH)2
CpCH
THF
NCH2
45.8
26.1
(CH3)2NCH2
NCH2CH2
1.59 (m, 4H)
OCH2CH2
4
pyridine-d5
6.95 (t, 1H), 6.53 (d, 2H)
3.64 (m, 4H)
3.39-3.15 (m, 2H)
2.95-2.70 (m, 2H)
2.62-2.45 (m, 4H)
2.36 (s, 12H)
1,3-Do2CpH
OCH2CH2
NCHHCH2
NCHHCH2
NCH2CH2
(CH3)2N
4J (H,H) 2.6
129.9
116.7
115.4
67.5, 25.5
63.0
CpCCH2
CpCH
Cp(CH)2
THF
NCH2
(CH3)2NCH2
NCH2CH2
45.6
26.6
1.59 (m, 4H)
OCH2CH2
sured on a hot-stage microscope in vacuum-sealed (0.01 mbar)
capillaries and are uncorrected. The NMR spectra were
recorded on a Bruker ARX 200 (1H, 200 MHz, 13C, 50.32 MHz)
spectrometer at room temperature. The NMR spectroscopic
data are cited in Tables 1 and 2. All chemical shifts are
reported in ppm relative to the 1H and 13C residues of the
deuterated solvents. Mass spectra (EI, 70 eV) were obtained
by using a Varian MAT 311A instrument. Only characteristic
fragments and isotopes of the highest abundance are listed.
Relative intensities in percent are given in parentheses.
Elemental analyses were performed on a Perkin-Elmer Series
II CHNS/O Analyzer 2400. Reasonably satisfactory analyses
could be obtained by using a special Schlenk tube and small
aluminum cans for weighing these extremely sensitive com-
pounds, but not in all cases, because of their especially high
sensitivity toward traces of moisture and air of some com-
pounds. 2-(Dimethylamino)ethyl chloride hydrochloride was
used as purchased from Aldrich. Free 2-(dimethylamino)ethyl
chloride was obtained by treatment of the hydrochloride with
sodium hydroxide prior to use. K[C5H4(CH2CH2NMe2)] was
prepared according to published procedures.8 Recrystallization
from THF resulted in the crystalline adduct [K(THF)]-
[{C5H4(CH2CH2NMe2)}], which was characterized by X-ray
diffraction. Its molecular structure will be published elsewhere.
[1,2-Bis(2-(d im et h yla m in o)et h yl)cyclop en t a d ien yl]-
p ota ssiu m (1) a n d [1,3-Bis(2-(d im eth yla m in o)eth yl)cy-
clop en ta d ien yl]p ota ssiu m (2). To a suspension of [K(THF)]-
[{C5H4(CH2CH2NMe2)}] (9.3 g, 37.6 mmol) in THF (140 mL)
was added dropwise 2-(dimethylamino)ethyl chloride (4.2 g,
39.0 mmol). The mixture was stirred for 0.5 h at room
temperature and then for 12 h at reflux temperature. Then,
water (250 mL) was added, the organic layer separated, dried
over Na2SO4, and concentrated at reduced pressure, and the
residual oil distilled under a vacuum (69-79 °C, 10-2 Torr),
yielding 6.73 g (86%) of a mixture of 1,2- and 1,3-bis(2-
(dimethylamino)ethyl)cyclopentadiene as a light-yellow trans-
parent liquid. A solution of this liquid (6.35 g, 30.4 mmol) in
teresting results concerning the mutual ring positions
of the two side chains and the fluxional behavior of the
complexes in solution.
Exp er im en ta l Section
All operations involving organometallic compounds were
carried out under an inert atmosphere of nitrogen using
standard Schlenk techniques in dry, oxygen-free solvents.
Melting points and decomposition temperatures were mea-
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Commun. 1990, 880. (b) Qian, C.; Zhu, D.; Li. D. J . Organomet. Chem.
1992, 430, 175. (c) Qian, C.; Wang, B.; Deng, D.; Wu, G.; Zheng, P. J .
Organomet. Chem. 1992, 427, C29. (d) Deng, D.; Song, F.; Wang, Z.;
Qian, C.; Wu, G.; Zheng, P. Polyhedron 1992, 11, 2883. (e) Deng, D.;
Qian, C.; Song, F.; Wang, Z.; Wu, G.; Zheng, G. J . Organomet. Chem.
1993, 443, 79. (f) Qian, C.; Zhu, D. J . Organomet. Chem. 1993, 445,
79. (g) Hermann, W. A.; Anwander, R.; Munck, F. C.; Scherer, W.
Chem. Ber. 1993, 126, 331. (h) J utzi, P.; Dahhaus, J .; Kristen, M. O.
J . Organomet. Chem. 1993, 450, C1. (i) Deng, D.; Qian, C.; Song, F.;
Wang, Z.; Wu, G.; Zheng, C.; J in, S.; Lin, Y. J . Organomet. Chem. 1993,
458, 83. (j) Laske, D. A.; Duchateu, R.; Teuben, J . H. J . Organomet.
Chem. 1993, 462, 149. (k) Anwander, R.; Hermann, W. A.; Scherer,
W.; Munck, F. C. J . Organomet. Chem. 1993, 462, 163. (l) Deng, D.;
Zheng, X.; Qian, C.; Sun, J .; Zhang, L. J . Organomet. Chem. 1994, 466,
95. (m) Qian, C.; Zheng, X.; Wang, B.; Deng, D.; Sun, J . J . Organomet.
Chem. 1994, 466, 101. (n) Van de Weghe, P.; Bied, C.; Collin, J .; Macalo,
J .; Santos, I. J . Organomet. Chem. 1994, 475, 79. (o) Van den Hende,
J . R.; Hitchcock, B. P.; Lappert, M. F.; Nile, T. A. J . Organomet. Chem.
1994, 472, 79. (p) Molander, G.; Schumann, H.; Rosenthal, E. C. E.;
Demtschuk, J . Organometallics 1996, 15, 3817. (q) Hultzsch, K. C.;
Spaniol, T. P.; Okuda, J . Organometallics 1997, 16, 4845. (r) Trifonov,
A. A.; Van de Wegh, P.; Collin, J .; Domingos, A.; Santos, J . J .
Organomet. Chem. 1997, 527, 225. (s) Hultzsch, K. C.; Spaniol, T. P.;
Okuda, J . Organometallics 1998, 17, 485. (t) Schumann, H.; Rosenthal,
E. C. E.; Demtschuk, J . Organometallics 1998, 17, 5324. (u) Schumann,
H.; Erbstein, F.; Fedushkin, I. L.; Demtschuk, J .; Girgsdies, F. Z.
Anorg. Allg. Chem. 1999, 625, 781.
(3) (a) Fryzuk, M. D.; Mao, S. S. H.; Zaworotko, M. J .; MacGillivray,
L. R. J . Am. Chem. Soc. 1993, 115, 5336. (b) Fryzuk, M. D.; Mao, S. S.
H.; Duval, P. B.; Rettig, S. J . Polyhedron 1995, 14, 11.
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(8) Herrmann, W. A.; Anwander, R.; Munck, F. C.; Scherer, W.
Chem. Ber. 1993, 126, 331.

4068 Organometallics, Vol. 19, No. 20, 2000
Ta ble 2. 1H a n d 13C{1H} NMR Da ta for 5-8
1H NMR
Fedushkin et al.
13C{1H} NMR
1J (171Yb,13C)
solvent
δ (ppm)
assignt
J (Hz)
δ (ppm)
assignt
(Hz)
5
6
7
THF-d8
5.67 (s, 1H), 5.54 (s, 2H)
3.59 (m, 8H)
2.54 (s, 8H)
2.33 (s, 12H)
1.71 (m, 8H)
1,2-Do2CpH
OCH2CH2
NCH2CH2
(CH3)2N
119.3
107.5
105.2
68.2
64.8
47.3
CpCCH2
CpCH
Cp(CH)2
THF
OCH2CH2
NCH2
(CH3)2NCH2
NCH2CH2
THF
26.3
27.2
THF-d8
5.52 (t, 1H), 5.45 (d, 2H)
2.59 (m, 2H)
2.49 (m, 2H)
2.29 (m, 4H)
2.23 (s, 12H)
1,3-Do2CpH
NCHHCH2
NCHHCH2
NCH2CH2
(CH3)2N
4J (H,H) 2.1
120.0
111.2
107.1
105.8
64.7
45.8
28.4
12.2
CpCCH2
CpCCH3
CpCH
Cp(CH)2
NCH2
(CH3)2NCH2
NCH2CH2
CpCCH3
1.93 (s, 15H)
CpCH3
2
C6D6
6.31 (t, 1H), 5.71 (d, 2H)
5.99 (t, 2H), 5.61 (t, 2H)
2.5-2.0 (m, 8H)
1.88 (s, 12H)
1.61 (s, 9H)
1,2-Do2CpH
tBu-CpH
NCH2CH2
(CH3)2N
3J (H,H) 3.2, J (Yb,H) 12.9, 7.7,
136.2
117.5
107.7
106.6
105.3
104.2
64.4
CpCC(CH3)3
CpCCH2
Cp(CH)2
tBu-CpC
CpCH
5.4
5.4
6.5
7.5
6.5
5.2
3J (H,H) 2.6, J (Yb,H) 10.3
2
(CH3)3C
tBu-CpC
NCH2
48.1
44.2
33.4
(CH3)2NCH2
(CH3)2NCH2
C(CH3)3
32.2
C(CH3)3
25.2
NCH2CH2
2
8
C6D6
6.25 (t, 1H), 5.38 (d, 2H)
2.5-1.7 (m, 8H)
2.15 (s, 15H)
1,2-Do2CpH
NCH2CH2
(CH3)Cp
3J (H,H) 3.4, J (Yb,H) 13.3, 8.2
116.7
111.8
108.2
107.5
64.7
CpCCH2
CpCCH3
Cp(CH)2
CpCH
5.4
6.4
6.4
7.5
1.89 (s, 12H)
(CH3)2N
NCH2
47.1
43.0
26.3
12.0
(CH3)2NCH2
(CH3)2NCH2
NCH2CH2
CpCH3
2
8
THF-d8
5.64 (t, 1H), 5.68 (d, 2H)
2.9-2.4 (m, 8H)
2.33 (s, 12H)
1,2-Do2CpH
NCH2CH2
(CH3)Cp
3J (H,H) 3.4, J (Yb,H) 12.9, 8.2
117.5
111.8
107.9
107.1
65.4
CpCCH2
CpCCH3
Cp(CH)2
CpCH
4.9
7.1
6.5
7.6
1.92 (s, 15H)
(CH3)2N
NCH2
45.9
25.9
11.9
(CH3)2NCH2
NCH2CH2
CpCH3
THF (50 mL) was added within 2 h with stirring to a
suspension of KH (1.1 g, 27.4 mmol) in THF (70 mL). The pale
yellow precipitate formed was filtered off and dried under a
vacuum, yielding 6.45 g (95%) of a mixture of 1 and 2 (1.5:1
ratio, demonstrated by 1H NMR spectroscopy). Anal. Calcd for
H, 5.39; N, 2.25. 4: MS (251 °C, 139La; m/z (%)) 599.8 (2) [M -
THF]+, 473.1 (100) [M - THF - I]+, 414.9 (5) [M - THF - I
- CH2NMe2]+, 58.1 (96) [Me2NCH2]+. Anal. Calcd for C17H31I2N2-
OLa (mol wt 672.15): C, 30.38; H, 4.65; N, 4.17. Found: C,
29.92; H, 5.02; N, 4.13.
C
13H23N2K (mol wt 246.44): C, 63.36; H, 9.41; N, 11.37.
Iodo[1,2-bis(2-(dim eth ylam in o)eth yl)cyclopen tadien yl]-
bis(tetr a h yd r ofu r a n )ytter biu m (II) (5). A mixture of 1 and
2 (1.55 g, 6.29 mmol) was added to a solution of YbI2(THF)2
(3.45 g, 6.03 mmol) in THF (50 mL). The mixture was stirred
for 3 h at room temperature; the red-orange solution that
formed was filtered off and reduced to a volume of 15 mL by
evaporation of the solvent under a vacuum at 50 °C. Cooling
to -28 °C caused precipitation of 1.49 g (38%) of 5 as orange
crystals, mp 212 °C dec. MS (271 °C, 174Yb; m/z (%)): 588.3
(4) [M - C5H3]+, 508.0 (10) [M - 2THF]+, 380.9 (4) [M - 2THF
- I]+, 300.8 (2) [YbI]+, 207.2 (7) [C5H3(CH2CH2NMe2)]+, 58.1
(100) [Me2NCH2]+. Anal. Calcd for C21H39N2O2IYb (mol wt):
C, 38.72; H, 6.03; N, 4.30; Yb, 26.56. Found: C, 37.14; H, 5.88;
N, 4.92; Yb, 26.34.
Found: C, 63.83; H, 8.79; N, 10.25.
D iio d o [1,2-b is (2-(d im e t h y la m in o )e t h y l)c y c lo p e n -
ta d ien yl](tetr a h yd r ofu r a n )la n th a n u m (III) (3) a n d Di-
iod o[1,3-bis(2-(d im eth yla m in o)eth yl)cyclop en ta d ien yl]-
(tetr a h yd r ofu r a n )la n th a n u m (III) (4). To a stirred suspen-
sion of a mixture of 1 and 2 (1.72 g, 6.97 mmol) in THF (40
mL) was added LaI3(THF)3 (5.05 g, 6.86 mmol). The mixture
was stirred for 30 min at room temperature. Then the solution
was separated from precipitated KI by filtration. After the
clear solution was concentrated under a vacuum to a volume
of 15 mL, 3.16 g (68.5%) of colorless crystals of 3 (elongated
blocks) and 4 (large cubic crystals) were isolated. Manual
separation of the crystals gave 1.34 g (29%) of 3 and 1.80 g
(39%) of 4; both 3 and 4 decomposed at ∼180 °C. 3: MS (195
°C, 139La; m/z (%)) 208.1 (0.7) [C5H3(CH2CH2NMe2)2]+, 58.1
(100) [Me2NCH2]+. Anal. Calcd for C17H31I2N2OLa‚1/2C4H8O
(mol wt 708.2): C, 32.22; H, 4.98; N, 3.96. Found: C, 31.38;
Sod iu m
Iod ob is{[1,3-b is(2-(d im et h yla m in o)et h yl)-
c y c lo p e n t a d ie n y l](p e n t a m e t h y lc y c lo p e n t a d ie n y l)}-
d iytter biu m (II) (6). The residual THF solution which is left
after isolation of 5 was added to a suspension of Cp*Na (0.59

Organometallic Compounds of the Lanthanides
Organometallics, Vol. 19, No. 20, 2000 4069
Ta ble 3. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for 3-5
3
4
5
empirical formula
fw
C
17H31I2LaN2O‚1/2C4H8O
C17H31I2LaN2O
672.15
C21H39N2O2IYb
651.48
708.20
cryst syst
space group
a (Å), R (deg)
b (Å), â (deg)
c (Å), γ (°)
V (Å3)
monoclinic
orthorhombic
P212121 (No. 19)
8.5876(1), 90
15.2281(2), 90
17.1304(2), 90
2240.19(5)
monoclinic
P21 (No. 4)
9.4725(1), 90
8.4049(2), 98.831(1)
15.1456(4), 90
1191.53(4)
P21/c (No. 14)
17.5679(3), 90
9.5385(1), 109.139(1)
15.4491(1), 90
2445.73(5)
Z
4
4
2
D(calcd) (g/cm3)
1.923
4.283
1352
1.993
4.669
1272
1.816
5.237
636
µ(Mo KR) (mm-1
F(000)
)
cryst size (mm3)
0.54 × 0.12 × 0.16
0.48 × 0.26 × 0.40
0.32 × 0.32 × 0.48
θ
min, θmax (deg)
1.13, 27.50
1.79, 27.50
1.36, 27.50
index ranges
-22 e h e 18, -12 e k e 8,
-19 e l e 20
18 239
5576 (R(int) ) 0.0577)
0.6883, 0.3644
5576, 0, 257
1.004
-11 e h e 9, -17 e k e 19,
-22 e l e 19
17 486
5141 (R(int) ) 0.0372)
0.4291, 0.2271
5141, 0, 212
1.059
-5 e h e 12, -9 e k e 10,
-19 e l e 17
5927
4635 (R(int) ) 0.0355)
0.3215, 0.2313
4635, 1, 249
1.007
no. of rflns collected
no. of indep rflns
max, min transmissn
no. of data, restraints, params
GOF on F2
R indices (I > 2σ(I))
R indices (all data)
abs structure param
max, min resid
R ) 0.0330, Rw ) 0.0610
R ) 0.0249, Rw ) 0.0496
R ) 0.0285, Rw ) 0.0509
0.01(2)
R ) 0.0468, Rw ) 0.0982
R ) 0.0591, Rw ) 0.1040
0.278(17)
R ) 0.0555, Rw ) 0.0679
1.051, -1.282
1.013, -0.645
2.181, -1.618
electron density (e/Å3)
g, 3.74 mmol) in THF (20 mL). The mixture turned dark purple
immediately. The solvent was removed under a vacuum, and
the residue was washed twice with toluene (15 mL) and was
then extracted with THF (30 mL). Again this THF extract was
treated with toluene (20 mL), resulting in the formation of 1.26
g (53%) of deep red crystals of 6, mp 240 °C dec. MS (242 °C,
174Yb; m/z (%)): 588.2 (4) [1,3-Do2C5H3YbI]+, 516.1 (22) [1,3-
Do2C5H3YbCp*]+, 381.0 (100) [1,3-Do2C5H3Yb]+, 308.0 (4)
[Cp*Yb]+, 58.1 (95) [Me2NCH2]+. Anal. Calcd for C46H76IN4-
NaYb2‚C7H8 (mol wt 1273.21): C, 50.00; H, 6.65; N, 4.40; Yb,
27.18. Found: C, 51.12; H, 5.93; N, 4.19; Yb, 27.11.
anisotropically. The carbon atoms of the disordered toluene
solvent molecules in 6 were refined isotropically; all other non-
hydrogen atoms were refined anisotropically. The hydrogen
atoms were placed in calculated positions and assigned to an
isotropic displacement parameter of 0.08 Å2. The idealized
methyl groups were allowed to rotate around their X-C bond.
Absolute structure parameters were determined using the
Flack parameters11 with SHELXL-97. SADABS12 was used to
perform area-detector scaling and absorption corrections. The
maximum and minimum transmission factors are summarized
in Tables 3 and 4. The geometrical aspects of the structures
were analyzed by using the PLATON program.13
(1,2-Bis(2-(d im et h yla m in o)et h yl)cyclop en t a d ien yl)-
(ter t-bu tylcyclop en ta d ien yl)ytter biu m (II) (7). A mixture
of 5 (0.9 g, 1.38 mmol) and tBuC5H4Na (0.2 g, 1.38 mmol)
turned immediately purple when 25 mL of THF was added.
The mixture was stirred for a few minutes, and the solvent
was removed under a vacuum. The residue was extracted with
diethyl ether (2 × 20 mL). Concentration of the clear solution
to 15 mL caused crystallization of 0.54 g (78%) of dark red 7,
mp 219 °C dec. MS (136 °C, 174Yb; m/z (%)): 502.1 (100) [M]+,
379.0 (59) [M - tBuCp]+, 321.0 (8) [M - tBuCp - CH2NMe2]+,
Resu lts a n d Discu ssion
Liga n d Syn th esis. In analogy to the synthetic ap-
proach to mono-N-donor-functionalized cyclopentadienyl
derivatives,2,14 the treatment of ((2-(dimethylamino)-
ethyl)cyclopentadienyl)potassium with 2-(dimethylami-
no)ethyl chloride in THF results in the formation of an
isomeric mixture of 1,2- and 1,3-bis(2-(dimethylamino)-
ethyl)cyclopentadiene (1,2-Do2C5H4 and 1,3-Do2C5H4)
along with additional isomers arising from prototropic
shifts. The introduction of the second N-functionalized
substituent to the cyclopentadienyl ring requires pro-
longed heating of the reaction mixture under reflux
conditions. Workup of the reaction mixture affords a
light yellow oil which distills continuously in a temper-
ature range of 69-79 °C/10-2 Torr, thus not allowing a
separation of the isomers (the temperatures necessary
to distill the product at pressures of 0.1-1 Torr cause
extensive decomposition). However, the ratio of the
t
295.0 (14) [(tBuCp)Yb]+, 279.0 (16) [M - BuCp - CH2NMe2
- CH2CH2]+, 58.1 (78) [Me2NCH2]+. Anal. Calcd for C22H36N2-
Yb (mol wt 501.57): C, 52.68; H, 7.23; N, 5.59; Yb, 34.50.
Found: C, 51.30; H, 6.17; N, 6.10; Yb, 34.57.
(1,2-Bis(2-(d im et h yla m in o)et h yl)cyclop en t a d ien yl)-
(p en ta m eth ylcyclop en ta d ien yl)ytter biu m (II) (8). In anal-
ogy to the synthesis of 7, complex 5 (1.1 g, 1.68 mmol) was
treated with Cp*K (0.28 g, 1.61 mmol) in 25 mL of THF.
Recrystallization from diethyl ether afforded 0.68 g (82%) of
deep purple crystals of 8: mp 195 °C dec. MS (193 °C, 174Yb;
m/z (%)): 516.1 (18) [M]+, 380.9 (68) [M - Cp*]+, 321.9 (8) [M
- Cp* - CH2NMe2]+, 306.8 (11) [Cp*Yb]+, 279.0 (3) [M -
tBuCp - CH2NMe2 - CH2CH2]+, 58.1 (100) [Me2NCH2]+. Anal.
Calcd for C23H38N2Yb (mol wt 515.59): C, 53.58; H, 7.43; N,
5.43; Yb, 33.56. Found: C, 52.95; H, 7.19; N, 5.98; Yb, 33.40.
X-r a y St r u ct u r e Det er m in a t ion . The crystal data and
details of data collection are given in Tables 3 and 4. The data
were collected on a Siemens SMART CCD diffractometer
(graphite-monochromated Mo KR radiation, λ ) 0.710 73 Å)
with an area detector by use of ω scans at 173 K. The
structures were solved by direct methods using SHELXS-979
and were refined on F2 using all reflections with SHELXL-
97.10 All non-hydrogen atoms in 3-5, 7, and 8 were refined
(9) Sheldrick, G. M. SHELXS-97 Program for the Solution of Crystal
Structures; Universita¨t Go¨ttingen, Go¨ttingen, Germany, 1990.
(10) Sheldrick, G. M. SHELXL-97 Program for the Refinement of
Crystal Structures; Universita¨t Go¨ttingen, Go¨ttingen, Germany, 1997.
(11) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
(12) Sheldrick, G. M. SADABS Program for Empirical Absorption
Correction of Area Detector Data; Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1996.
(13) Spek, A. L. Acta Crystallogr. 1990, A46, C-34.
(14) Rees, W. S., J r.; Dippel, K. A. Org. Prep. Proced. Int. 1992, 24,
527.

4070 Organometallics, Vol. 19, No. 20, 2000
Ta ble 4. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for 6-8
Fedushkin et al.
6
7
8
empirical formula
fw
C
46H76IN4NaYb2‚C7H8
C22H36N2Yb
501.57
C23H38N2Yb
515.59
1273.21
cryst syst
space group
a (Å), R (deg)
b (Å), â (deg)
c (Å), γ (°)
V (Å3)
orthorhombic
Pbcn (No. 60)
13.6957(1), 90
19.1068(1), 90
21.2924(1), 90
5571.82(6)
orthorhombic
P212121 (No. 19)
8.5441(2), 90
15.7446(3), 90
16.1012(3), 90
2165.99(8)
triclinic
P1h (No. 2)
10.4367(1), 103.334(1)
14.9603(2), 105.658(1)
15.3926(1), 93.699(1)
2231.06(4)
Z
4
4
4
D(calcd) (g/cm3)
1.518
3.933
2536
1.538
4.324
1008
1.535
4.200
1040
µ(Mo KR) (mm-1
F(000)
)
cryst size (mm3)
0.44 × 0.18 × 0.08
0.36 × 0.10 × 0.08
0.26 × 0.14 × 0.04
θ
min, θmax (deg)
1.91, 25.50
1.81, 27.50
1.41, 27.50
index ranges
-16 e h e 16, -23 e k e 23,
-25 e l e 16
34 172
5176 (R(int) ) 0.0960)
0.7934, 0.5760
5176, 35, 283
1.053
-11 e h e 9, -20 e k e 17,
-20 e l e 20
16 830
4967 (R(int) ) 0.0735)
0.7758, 0.5560
4967, 0, 233
1.092
-13 e h e 13, -15 e k e 19,
-19 e l e 14
17 149
10 100 (R(int) ) 0.0471)
0.5494, 0.4078
10 100, 0, 487
0.979
no. of rflns collected
no. of indep rflns
max, min transmissn
no. of data, restraints, params
GOF on F2
R indices (I > 2σ(I))
R indices (all data)
abs structure param
max, min resid
R ) 0.0421, Rw ) 0.0678
R ) 0.0454, Rw ) 0.0738
R ) 0.0635, Rw ) 0.0788
-0.020(19)
R ) 0.0419, Rw ) 0.0687
R ) 0.0771, Rw ) 0.0772
R ) 0.0832, Rw ) 0.0798
0.721, -0.665
2.167, -1.270
2.098, -0.888
electron density (e/Å3)
Sch em e 1
integral intensities of the resonances appearing in the
1H NMR spectrum of the distillate showing six distinct
N-methyl singlets and overlapping multiplets in the
“aromatic” region indicates that the product consists of
a 1.5:1 mixture of 1,2- and 1,3-Do2C5H4.
The 1H NMR spectrum of THF-d8 solutions of the
mixture containing 1 and 2 shows four well-resolved
resonances in the Cp region, two somewhat poorly
resolved signals for the CH2-CH2 bridges, and two
1
1
sharp NCH3 signals. H-1H and H-13C NMR COSY
measurements allow their unambiguous assignment.
On the basis of the fact that the molar amounts of 1
and 2 in the mixture are not equal (ca. 1.5:1), all 13C
NMR frequencies can be clearly assigned (Table 1).
Deprotonation of the mixture of the isomeric cyclo-
pentadienes with KH in THF gives the potassium salts
K[1,2-C5H3(CH2CH2NMe2)2] (1) and K[1,3-C5H3(CH2-
CH2NMe2)2] (2), which precipitate from the THF solu-
tion (Scheme 1). Both compounds are also only slightly
soluble in pyridine and insoluble in alkanes and aro-
matic hydrocarbons. 1 and 2 cannot be separated by
fractional extraction with THF but can be characterized
by NMR spectroscopic measurements.
La n th a n u m (III) Com p lexes. The metathetical re-
action of the mixture of 1 and 2 with the lanthanum-
(III) iodide LaI3(THF)3 in THF at room temperature
produces the two lanthanum(III) half-sandwich com-
plexes (1,2-Do2C5H3)LaI2(THF) (3) and (1,3-Do2C5H3)-

Organometallic Compounds of the Lanthanides
Organometallics, Vol. 19, No. 20, 2000 4071
Sch em e 2
LaI2(THF) (4) (Scheme 2). After separation of the
immediately formed potassium iodide and concentration
of the filtrate, the compounds 3 and 4 crystallize
simultaneously from the solution as colorless, well-
shaped crystals. Once being formed as crystals, the
complexes 3 and 4 lose their solubility. Fortunately, the
crystals of 3 and 4 are of different shape, thus allowing
a manual separation. Complex 3 crystallizes as elon-
gated blocks, whereas complex 4 forms cubic crystals.
Both compounds decompose without melting at tem-
peratures of about 180 °C.
F igu r e 1. ORTEP plot15 of the molecular structure and
numbering scheme of 3, with 30% probability thermal
ellipsoids. All hydrogen atoms are omitted for clarity.
1
The H NMR spectrum of pure 3 in pyridine shows
the expected two signals for the protons of the C5H3
fragment (δ 6.59 (d, 2H) and 6.43 (t, 1H)), only one
singlet signal for the NCH3 protons (δ 2.44, 12H), and
three sets of overlapping multiplets centered at δ 3.12
(2H), 2.92 (2H), and 2.71 (4H) for the methylene protons
1
of the side chains. A quite similar H NMR spectrum is
observed for pure 4 with two signals for the C5H3
protons (δ 6.95 (t, 1H) and 6.53 (d, 2H)), a singlet for
the NCH3 protons (δ 2.36 (12H)), and three multiplets
centered at δ 3.27 (2H), 2.78 (2H), and 2.54 (4H) for the
methylene protons. From the multiplet structure of the
CH2 resonances, which indicates the nonequivalence of
the methylene protons, it can be inferred that the N
atoms of both donor side arms coordinate the lanthanum
ion even in such a basic solvent such as pyridine. The
13C{1H} NMR spectra of 3 and 4 show six singlets, one
for the N-methyl groups, two for the methylene groups
of the side chains, and three for the ring carbon atoms
(Table 1).
It is noteworthy that the mass spectra of 3 and 4
recorded under EI conditions differ substantially.
Whereas for 3 no molecular fragments were detected
in the temperature range 20-260 °C, the mass spectrum
of 4 shows the unsolvated molecular fragments [(1,3-
Do2C5H3)LaI2]+ and [(1,3-Do2C5H3)LaI]+ with intensities
of 2 or 100%, respectively.
F igu r e 2. ORTEP plot15 of the molecular structure and
numbering scheme of 4, with 40% probability thermal
ellipsoids. All hydrogen atoms are omitted for clarity.
Table 3, the ORTEP drawings15 of the molecular struc-
tures of 3 and 4 are shown in Figures 1 and 2,
respectively, and selected bond lengths and angles are
presented in Table 5. Complex 3, containing the 1,2-
substituted cyclopentadienyl ligand, crystallizes in the
monoclinic space group P21/c. The asymmetric unit is
Molecu la r Str u ctu r es of th e La n th a n u m Com -
p lexes 3 a n d 4. The crystals of 3 and 4 separating
directly from the reaction solution can be used for single-
crystal X-ray diffraction analyses without further puri-
fication by recrystallization. Details of the crystal data
collections and the structure refinements are listed in
(15) Zsolnai, L.; Pritzkow, H. ZORTEP, ORTEP Program for PC;
Universita¨t Heidelberg, Heidelberg, Germany, 1994.

4072 Organometallics, Vol. 19, No. 20, 2000
Fedushkin et al.
Ta ble 5. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 3-5 w ith Estim a ted Sta n d a r d
Devia tion s
fragmentation of 4 observed in the mass spectrum under
EI conditions.
The La-N bonds in 3 (2.772 and 2.820 Å) are longer
than those in 4 (2.712 and 2.728 Å), probably caused
by steric strains between the cis-coordinated Me2N
groups in 3, and are comparable to those in Cp2La-
[C6H3(CH2NMe2)2-2,6] (2.788 and 2.755 Å).18 The La-N
bonds of both 3 and 4 are considerably shorter than
those in (Me2NCH2CH2C5H4)3La (2.898 Å).19 The La-
Cpcentroid distances are almost the same in both 3 and 4
(2.511 and 2.519 Å, respectively) and fairly close to those
in other monocyclopentadienyl lanthanum derivatives.20
Ytter biu m (II) Com p lexes. The treatment of mix-
tures of 1 and 2 with equimolar amounts of YbI2 in THF
affords only the 1,2-isomeric half-sandwich ytterbium-
(II) complex (1,2-Do2Cp)YbI(THF)2 (5) in ca. 40% yield
(Scheme 3). Compound 5 crystallizes from the filtered
and concentrated solution as large orange blocks. All
attempts to isolate the analogous complex containing
the 1,3-Do2Cp ligand did not succeed. However, addition
of (C5Me5)Na (Cp*Na) to the THF solution remaining
after the separation of 5, followed by treatment with
toluene, yields dark red crystals of a mixed ytterbium
complex containing both the 1,3-Do2Cp ligand and the
Cp* ligand, {Na[(1,3-Do2Cp)(Cp*)Yb]2(I)(C7H8)]n (6).
Also, compound 5 reacts with the cyclopentadienides
(tBuC5H4)Na and Cp*K in THF to give the mixed
complexes (1,2-Do2Cp)Yb(tBuC5H4) (7) and (1,2-Do2Cp)-
Yb(Cp*) (8), respectively (Scheme 3). 5 and 6 are soluble
in THF but insoluble in diethyl ether, toluene, and
hexane. Addition of 5 to pyridine (py) causes decomposi-
tion into YbI2(py)4 and unidentified products. 7 and 8
are readily soluble in THF, diethyl ether, and benzene.
5-8 melt with decomposition in the temperature range
195-240 °C, with the highest value observed for poly-
meric 6.
In the 1H NMR spectrum of the diamagnetic 5,
recorded in THF-d8 at 200-293 K, all signals are
significantly broadened, showing no spin-spin coupling
structure. The resonances of the ring protons show
chemical shifts of δ 5.67 (1H) and 5.54 (2H). The protons
of the methylene or the NCH3 groups give rise to broad
singlets at δ 2.54 (8H) or 2.33 (12H), respectively. The
appearance of the 13C{1H} NMR spectrum is rather
similar, with the exception that the resonances of the
methylene groups can be distinguished. These data
confirm two points: (i) both donor functions of the
cyclopentadienyl ligand are coordinated to the metal
even in THF solution; (ii) a mirror inversion of two
crown-type cycles Cp-CH2-CH2-(Me2)N-Yb forced by
limited rotation of the Cp ring around the Cpcentroid-Yb
axis takes place in solution. This is consistent with
published data21 and the data we obtained by structural
analysis. In the 1H NMR spectrum of 6, recorded in
THF-d8, the signals of the ring protons (t, δ 5.52, 1H;
d, δ 5.45, 2H) and of the methylene protons (m, δ 2.59,
3
4
5
Bond Distances and Angles
Ln-Cpa,b
Ln-I(1)
Ln-I(2)
Ln-N(1)
Ln-N(2)
Ln-O(1)
Ln-O(2)
2.511(2)
3.1974(4)
3.2287(4)
2.820(4)
2.772(3)
2.558(3)
2.519(2)
3.2681(4)
3.1696(4)
2.728(4)
2.712(4)
2.593(3)
2.466(5)
3.2529(8)
2.753(9)
2.762(9)
2.500(8)
2.522(8)
I(1)-Ln-Cp
I(2)-Ln-Cp
O(1)-Ln-Cp
O(2)-Ln-Cp
N(1)-Ln-Cp
N(2)-Ln-Cp
O(1)-Ln-N(1)
O(1)-Ln-N(2)
I(1)-Ln-I(2)
N(2)-Ln-N(1)
101.55(4)
167.05(5)
102.65(9)
100.66(4)
100.73(4)
176.62(8)
170.54(13)
103.8(2)
101.3(2)
91.4(2)
90.5(2)
163.5(3)
87.4(3)
89.97(9)
89.64(9)
167.10(11)
79.96(11)
88.346(10)
103.11(11)
89.69(11)
90.68(8)
93.65(12)
85.98(11)
157.990(13)
162.94(12)
98.9(3)
Ring Slippage
Ln-Cp
0.074
0.043
0.086
a
b
Ln ) La for 3 and 4 and Yb for 5. Cp defines the centroid of
the ring atoms C1-C5.
represented by one molecule of the complex and half of
a disordered THF molecule located on a center of
inversion. In contrast, complex 4, bearing the 1,3-
substituted cyclopentadienyl ligand, crystallizes in the
orthorhombic space group P212121. Both complexes 3
and 4 show similar molecular geometries. Two nitrogen
atoms, two iodine atoms, the oxygen atom of the
coordinated THF molecule, and the centroid position of
the Cp ring form a slightly distorded pseudo octahedron
around the lanthanum. However, the different coordi-
nation requirements of the cyclopentadienyl ligands lead
to different positions of the iodine atoms and of the THF
molecule relative to the metal center.
In complex 3, the equatorial plane is occupied by two
cis-arranged nitrogen atoms, the THF oxygen, and one
iodine atom, while the second iodine atom and the Cp
ring occupy the apical positions. The La-I bonds are
almost of equal length (3.1974 and 3.2287 Å). To the
best of our knowledge, this is the first example of a
complex of the type CpLnX2(L)3 in which the LnX2
fragment exhibits such a geometry.
In complex 4, the equatorial plane is occupied by the
two trans-positioned nitrogen atoms of the cyclopenta-
dienyl side arms and the two iodine atoms. The ring
centroid and the THF oxygen occupy the apical positions
of the distorted octahedron. The coordination environ-
ment of the metal in 4 corresponds to that in monocy-
clopentadienyl complexes of the type CpLnX2(THF)3 (Ln
) lanthanide, X ) Cl, Br, I)16 and is similar to that in
the naphthalene lanthanum complex [µ2-η4:η4-C10H8]-
[LaI2(THF)3]2,17 in which the halogen atoms are also
trans-positioned in the equatorial plane. Unexpectedly,
and in contrast to 3, the La-I bond lengths (3.1696 and
3.2681 Å) differ significantly, with the last value being
the longest Ln-I distance ever estimated in lanthanoid
iodine complexes. This fact agrees well with the kind of
(18) Hogerheide, M. P.; Boeresma, J .; Spek, A. L.; van Koten, G.
Organometallics 1996, 15, 1505.
(19) Anwander, R.; Herrmann, W. A.; Scherer, W.; Munck, F. C. J .
Organomet. Chem. 1993, 462, 163.
(20) (a) Suleimanov, G. Z.; Kurbanov, T. Kh.; Nuriev, Ya. A.;
Rybakova, L. F.; Beletskaya I. P. Dokl. Akad. Nauk SSSR 1982, 265,
896. (b) Hazin, P. N.; Huffman, J . C.; Bruno, J . W. Organometallics
1987, 6, 23.
(16) Schumann, H.; Meese-Marktscheffel, J . A.; Esser, L. Chem. Rev.
1995, 95, 865.
(17) Fedushkin, I. L.; Bochkarev, M. N.; Schumann, H.; Esser, L.;
Kociok-Ko¨hn, G. J . Organomet. Chem. 1995, 489, 145.
(21) Krut’ko, D. P.; Borisov, M. V.; Petrosyan, V. S.; Kuz’mina, L.
G.; Churakov, A. V. Russ. Chem. Bull. (Engl. Transl.) 1996, 45, 940.

Organometallic Compounds of the Lanthanides
Organometallics, Vol. 19, No. 20, 2000 4073
Sch em e 3
2H; m, δ 2.49, 2H; m, δ 2.29, 4H) are at least poorly
resolved, suggesting that in solution either both nitro-
gen atoms of the 1,3-Do2Cp ligand coordinate the Yb2+
ion or both are turned away from the metal center.
Taking into account that considerable steric problems
will arise if, along with the Cp* ligand and the Cp ring
of the 1,3-Do2Cp ligand, also the two side chains are
coordinated to the metal, the last case would be the most
probable one. The existence of a mono-N-coordinated
species in solution can be excluded, since in this case
an unambiguous assignment of the signals. The non-
equivalence of the NCH3 groups in solution can be
explained by a rigid coordination of the side chains to
the ytterbium ion, causing different positions of the
methyl groups relative to the metal. A careful inspection
of the 1H and 13C NMR spectra of 7 reveals small
additional couplings only for the Cp ring resonances,
thus excluding side rotation bands. It is possible to
suggest that 1H-171Yb and 13C-171Yb couplings cause
those additional spin-spin spectra, since the relative
intensities of the peaks observed are consistent with the
natural abundance of this ytterbium isotope (171Yb: spin
1/2, natural abundance 14.27%).22 Similar J (13C-171Yb)
couplings can be observed in the spectra of (C5Me5)2-
Yb(THF)2 in THF-d8, Cp*Yb[Si(SiMe3)3](THF)2 (10 Hz),23
and of dialkylytterbium compounds (158-265 Hz).24
1
three ring H signals of equal intensity should appear
in the spectrum. Since the low-temperature NMR
spectra of 6 do not differ significantly from its ambient-
temperature spectra, dynamic processes can also be
excluded.
1
The H NMR spectrum of 7 in benzene-d6 shows two
1
The H and 13C NMR spectra of 8 in benzene-d6 are
well-resolved signals for the disubstituted as well as for
the monosubstituted cyclopentadienyl ligand (Table 2),
a complex signal structure for the side chains of the 1,2-
Do2Cp ligand ranging from δ 2.5 to 2.0, a sharp signal
for the tert-butyl protons, and an extremely broad signal
for the NCH3 protons. The 13C NMR spectrum of 7
consists of 12 resonances, with the two CH3N signals
1
very similar to those of 7, including the H-171Yb and
13C-171Yb couplings of the resonances arising from the
Cp ring atoms, and show only the differences connected
(22) Avent, A. A.; Edelmann, M. A.; Lappert, M. F.; Lawless, G. A.
J . Am. Chem. Soc. 1998, 111, 3423.
(23) Corradi, M. M.; Frankland, A. D.; Hitchcock, P. B.; Lappert,
M. F.; Lawless, G. A. J . Chem. Soc., Chem. Commun. 1996, 2323.
(24) Eaborn, C.; Hitchcock, P. B.; Izod, K.; Lu, Zh.-R.; Smith, J . D.
Organometallics 1996, 15, 4783.
1
1
being also extremely broadened. H-1H, H-13C NMR
COSY, and 13C DEPT spectroscopic measurements allow

4074 Organometallics, Vol. 19, No. 20, 2000
Fedushkin et al.
Ta ble 6. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 6-8 w ith Estim a ted Sta n d a r d
Devia tion s
6
7
8
Bond Distances and Angles
Yb-Cp(1)a
Yb-Cp(2)a
Na-Cp(1)
Yb-N(1)b
Yb-I
Na-N(2)
Yb-N(2)c
Na-C(1)
Na-C(2)
Na-C(3)
Na-C(4)
Na-C(5)
2.440(3)
2.431(3)
2.545(3)
2.606(5)
3.1001(2)
2.495(5)
2.394(4)
2.451(5)
2.417(3)/2.415(3)
2.452(3)/2.456(3)
2.585(7)
2.623(5)
2.635(5)/2.627(5)
2.640(5)/2.636(6)
2.930(6)
2.776(6)
2.675(6)
2.757(6)
2.923(6)
Cp(1)-Yb-Cp(2)
I-Yb-Cp(1)
132.34(8)
106.06(6)
107.71(6)
93.31(15)
141.44(12) 133.10(12)/133.11(12)
I-Yb-Cp(2)
N(1)-Yb-Cp(1)
N(2)-Yb-Cp(1)
N(1)-Yb-Cp(2)
N(2)-Yb-Cp(2)
N(1)-Yb-N(2)
N(1)-Yb-I
93.90(19)
94.15(17)
93.36(14)/92.93(14)
92.40(14)/92.85(14)
118.40(14) 109.09(18) 116.13(15)/117.22(14)
111.62(19) 117.24(13)/116.57(15)
F igu r e 3. ORTEP plot15 of the molecular structure and
numbering scheme of 5, with 50% probability thermal
ellipsoids. All hydrogen atoms are omitted for clarity.
98.8(2)
96.79(15)/96.03(17)
91.11(13)
180
Yb-I-Yb′
Cp(1)-Na-Cp(1)′′ 127.16(13)
space group P21 with two molecules in the unit cell. The
calculation of the absolute structure parameter x indi-
cated a racemic twinning for the selected crystal. The
value of x was refined to 0.278(17); therefore, the ratio
of the two enantiomorphs is approximately 72:28. The
discrete molecules show a distorted-octahedral structure
(Figure 3) similar to that of the lanthanum(III) complex
3, except that the equatorial iodine in 3 is replaced by
a second THF. The cis-arranged Me2N donor units and
the THF molecules form the equatorial plane, while the
ring part of the 1,2-Do2Cp ligand and the iodine atom
occupy the axial positions (Cpcentroid-Yb-I ) 170.54°).
The monomeric structure of 5 is unique, because all
other ytterbium complexes of analogous empirical com-
position form halogen-bridged dimers [RYbX(L)n]2 (R )
alkyl,24 cyclopentadienyl;25 X ) halogen; L ) coordinat-
ing solvent such as THF or Et2O). In contrast to 3, there
is no mirror plane in 5 incorporating Cpcentroid-Yb-I,
since the R-carbon atoms of the cyclopentadienyl side
arms are turned clockwise around the Cpcentroid-Yb axis.
With regard to the difference in ionic radii of La(III)
and Yb(II), the Yb-I bond length in 5 (3.2529 Å) is
somewhat longer than the La-I distances in 3 (3.1974
and 3.2287 Å), while the distance Cpcentroid-Yb (2.466
Å) in 5 is somewhat shorter than the corresponding
value in 3 (2.511 Å). The smaller angle N-Yb-N (98.9°)
in 5 compared to that in 3 (N-La-N, 103.1°) is probably
the result of less repulsion of the two Me2N groups
caused by the clockwise turning of the R-carbon atoms
of the side chains. The distances Yb-N (2.753 and 2.762
Å) fall into the range found for the La-N distances in
3 (2.772 and 2.820 Å).
N(2)-Na-N(2)′′
Yb-Cp(1)-Na
Yb-Cp(1)*-Naa
102.4(3)
172.56(12)
157.53
Ring Slippage
0.079
Cp(1)-(Yb)
Cp(2)-(Yb)
Cp(1)-(Na)
0.082
0.064
0.319
0.046/0.063
0.070/0.088
0.104
a
Cp defines the centroid of the ring atoms Cp(1) (C(1)-C(5)
for 6 and 7 and C(101)-C(105)/C(201)-C(205) for 8), Cp(2) (C(14)-
C(18)), and Cp(1)* (C(2),C(3),C(4)). N(11)/N(21) for 8. c N(12)/
b
N(22) for 8. Symmetry transformations used to generate equiva-
lent atoms: (′) -x + 1, -y + 1, -z + 1; (′′) -x + 1, y, -z + 3/2.
with the exchange of tBuCp for Cp* as the second ligand
of the Yb2+ ion. As for 7, 1H-1H and 1H-13C NMR
COSY as well as 13C DEPT measurements were applied
to ensure the assignment of the signals of 8. If 8 is
dissolved in THF-d8, the signal associated with the
protons of the (CH3)2N groups becomes sharp and the
two very broad signals associated with the carbon atoms
of the (CH3)2N groups change into one broad signal, thus
indicating that in nonpolar solvents such as benzene
both donating side chains of the 1,2-Do2Cp ligand will
be fixed to the metal, whereas in polar solvents such as
THF the side chains compete with the solvent with
respect to their coordination to the metal.
The EI mass spectra of the complexes 5 and 6 show
no molecular ion peaks. The most intense metal-
containing fragments are [(1,2-Do2Cp)YbI]+ (10%) for
5 and [(1,3-Do2Cp)Yb]+ (100%) for 6. In the mass spectra
of 7 and 8 the molecular ion peaks appear at 136 or 193
°C with 100 or 18% intensity, respectively. The most
intense metal-containing fragment in the spectrum of
8, [1,3-Do2CpYb]+ (68%), corresponds to that in 6.
Molecu la r Str u ctu r es of th e Ytter biu m Com -
p lexes 5-8. The crystal data collection and structure
refinement data for 5 are given in Table 3 and those
for 6-8 in Table 4. Selected bond distances and angles
for 5 are given in Table 5 and those for 6-8 in Table 6.
The large well-shaped elongated blocks of 5 suitable
for single-crystal X-ray diffraction analysis were ob-
tained by crystallization from THF. The half-sandwich
ytterbium(II) complex 5 crystallizes in the monoclinic
X-ray-quality crystals of 6 were obtained from a THF/
toluene mixture. Complex 6 crystallizes in the orthor-
hombic space group Pbcn. 6 is a polymer consisting of
infinite chains formed by [Na{µ2-1,3-Do2Cp}Yb(µ2-I)Yb-
{µ2-1,3-Do2Cp}] units (Figure 4). Each ytterbium
atom is further η5-coordinated by a C5Me5 ligand. The
iodine atom is located on a center of inversion with
equal distances to the ytterbium atoms of the linear
(25) Constantine, S. P.; De Lima, G. M.; Hitchcock, P. B.; Keates,
J . M.; Lawless, G. A. J . Chem. Soc., Chem. Commun. 1996, 2421.

Organometallic Compounds of the Lanthanides
Organometallics, Vol. 19, No. 20, 2000 4075
F igu r e 4. ORTEP plot15 of the molecular structure and numbering scheme of 6, with 30% probability thermal ellipsoids.
All hydrogen atoms are omitted for clarity. Symmetry transformations used to generate equivalent atoms: (′) -x + 1, -y
3
+ 1, -z + 1; (′′) -x + 1, y, -z + /2.
Yb-I-Yb unit (180°). However, the unexpectedly large
thermal ellipsoid of the iodine atom suggests that in
different molecular units of the polymer the Yb-I-Yb
angle slightly deviates from 180°. Nevertheless, the
geometry of this fragment is rather rare in organolan-
thanide chemistry. The linear arrangement Yb-F-Yb,
but with different Yb-F distances (2.317 and 2.084 Å),
was established only for the mixed-valence ytterbium
complex Cp*2YbII(µ-F)YbIIICp*2.26 The Yb-I distances
in 6 (3.1001 Å each) are somewhat shorter than in the
complex [Cp*(THF)2Yb(µ-I)2YbCp*(THF)2] (3.134 and
3.175 Å)25 and remarkably shorter than in 5 (3.2529 Å).
The angle 1,3-Do2Cp-Yb-Cp* (132.34°) and the dis-
tances of the ytterbium atom to the ring centers (1,3-
Do2Cp-Yb, 2.440 Å; Cp*-Yb, 2.431 Å) fall into the
range found for {C5H4(CH2CH2NMe2)}2Yb27 and Cp*2-
Yb(py)2.28 Only one of the two N atoms of each 1,3-Do2-
Cp ligand is bonded to ytterbium, whereas the second
N atom coordinates a sodium atom. The bond length
Yb-N (2.606 Å) in 6 is much shorter than that in the
half-sandwich complex 5 (2.753 and 2.762 Å) but similar
to that in the ytterbium(II) complex {C5H4(CH2CH2-
NMe2)}2Yb (2.58 Å) containing mono-Me2N-functional-
ized Cp ligands.27 The Na-N bond length is 2.495 Å.
The distances of the sodium atom to the carbon atom
of the ring part of the 1,3-Do2Cp ligand range from 2.675
to 2.930 Å with the shortest contact to the carbon atom
bearing the side arm involved into the Na-N coordina-
tion. The angle Cpcentroid-Na-Cpcentroid is 127.16°. The
asymmetric unit of 6 contains a toluene molecule which
is disordered about a 2-fold rotation axis. All C-C
distances of the phenyl ring and all C-C-C angles
belonging to the phenyl and methyl groups were re-
strained to be equal. Furthermore, the carbon atoms of
the solvent molecule were restrained to lie on a common
plane.
Crystals of 7 and 8 suitable for single-crystal X-ray
analysis were grown from diethyl ether. 7 crystallizes
in the orthorhombic space group P212121 and 8 in the
triclinic space group P1h. The X-ray analysis of two
different crystals of 7 revealed two mirror isomers which
differ in the position of the tert-butyl substituent. The
asymmetric unit of 8 contains two crystallographically
independent molecules. In the monomeric and solvent-
free molecules of 7 (Figure 5) and 8 (Figure 6) the
ytterbium atoms are coordinated by both donor atoms
of the 1,2-Do2Cp ligand. The structures of 7 and 8
resemble the distorted-tetrahedral geometry of other
Cp2Yb(L)2 complexes with the formal coordination num-
ber 8.16 In comparison to complex 5, possessing the same
coordination number, the distances of the ytterbium
atoms to the ring center of the 1,2-Do2Cp ligand are
remarkably shorter (2.466 Å (5), 2.394 Å (7), 2.417/2.415
(26) Burns, C. J .; Andersen, R. A. J . Chem. Soc., Chem. Commun.
1989, 136.
(27) Bochkarev, M. N.; Fedushkin, I. L.; Nevodchikov, V. I.; Pro-
tchenko, A. V.; Schumann, H.; Girgsdies, F. Inorg. Chim. Acta 1998,
280, 138.
(28) Tilley, T. D.; Andersen, R. A.; Spencer, B.; Zalkin, A. Inorg.
Chem. 1982, 21, 2647.
t
Å (8)). The distances BuCpcentroid-Yb (2.451 Å) and
Cp*centroid-Yb (2.452/2.456 Å) in 7 or 8 are similar to

4076 Organometallics, Vol. 19, No. 20, 2000
Fedushkin et al.
(C5(iPr)5)2Eu (Cp-Eu-Cp ) 153.8°).30 The methyl groups
of the Cp* ring in 8 and the quaternary carbon atom of
t
the Bu group in 7 are bent out of the ring plane away
from the ytterbium atoms by up to 0.25(1) and 0.22(2)
Å, respectively. The R-carbon atoms of the side arms of
the 1,2-Do2Cp ligands deviate from the ring plane
toward the ytterbium atoms by up to 0.04(1) and
0.05(1) Å, respectively. In contrast to the ytterbium
complex 5, the geometry of the side chains in 7 and 8 is
symmetric relative to the plane containing the metal
atom and the centroids of the ligands. The N-Yb-N
angles in 7 (98.8°) and 8 (96.79/96.03°) are similar to
that in 5 (98.9°) but differ from that in {C5H4(CH2CH2-
NMe2)}2Yb (104.0°).28 However, the distances Yb-N in
7 (2.585, 2.623 Å) and 8 (2.635, 2.640/2.627, 2.636 Å)
are significantly shorter than in 5 (2.753, 2.762 Å) but
are somewhat longer than in {C5H4(CH2CH2NMe2)}2-
Yb (2.57, 2.58 Å).28
Con clu sion
We prepared half-sandwich and bent mixed-sandwich
complexes of lanthanum(III) and ytterbium(II) with the
novel 1,2- and 1,3-bis(2-(dimethylamino)ethyl)cyclopen-
tadienyl ligands by metathetic reactions of La(III) and
Yb(II) iodides with the potassium salts of the ligands.
The intramolecular coordination of the donor atoms of
the side chains was confirmed by X-ray structure
determination for all complexes 3-8. The different
coordination requirements of the 1,2- and the 1,3-donor-
functionalized ligands cause a specific coordination
geometry around the metal centers in the isomeric half-
sandwich lanthanum complexes 3 and 4. Using the
stabilizing influence of the 1,2-donor-functionalized
ligand, we were able to isolate the first monomeric
monocyclopentadienyl ytterbium(II) complex. The non-
equivalence of the 13C NMR signals of the N-methyl
groups in 7 and 8 in benzene solution confirms strong
Me2NfYb coordination. In contrast, the appearance of
a broadened singlet signal for these groups in THF
solution indicates that the N-donor atoms compete with
the coordinating solvent molecules. Investigations con-
cerning the catalytic activity of the complexes for the
block polymerization of styrene are in progress.
F igu r e 5. ORTEP plot15 of the molecular structure and
numbering scheme of 7, with 30% probability thermal
ellipsoids. All hydrogen atoms are omitted for clarity.
Ack n ow led gm en t. This work was financially sup-
ported by the Fonds der Chemischen Industrie and the
Deutsche Forschungsgemeinschaft as well as by the
Alexander von Humboldt Foundation (research fellow-
ship for I.L.F.). We thank also Dr. Zeigan and Dr.
Detlaff for recording the NMR spectra and Ms. M.
Borowski for assistance with carrying out the single-
crystal X-ray diffraction analyses. We are grateful to
Prof. M. N. Bochkarev for fruitful discussions.
F igu r e 6. ORTEP plot15 of the molecular structure and
numbering scheme of 8, with 30% probability thermal
ellipsoids. Only one of the two crystallographically inde-
pendent molecules is shown. All hydrogen atoms are
omitted for clarity
Su p p or tin g In for m a tion Ava ila ble: Full details of the
X-ray structures of complexes 3-8, including complete tables
of crystal data, atomic coordinates, bond lengths and angles,
and positional and anisotropical thermal parameters. This
material is available free of charge via the Internet at
http://pubs.acs.org.
29
those in (tBuC5H4)2Yb(THF)2 or Cp*2Yb(py)2,28 respec-
tively. While the 1,2-Do2Cp-Yb-Cp* angle in 8 (133.1°)
is typical for bent divalent lanthanidocenes, the 1,2-
Do2Cp-Yb-tBuCp angle of 141.44° in 7 shows a certain
tendency toward coplanarity, which is realized in
OM000409X
(29) Shen, Q.; Zheng, D.; Lin, L.; Lin, Y. J . Organomet. Chem. 1990,
391, 321.
(30) Sitzmann, H. Private communication.